Impact of traditional cooking methods on total phenolics, flavonoids, and antioxidant capacities of dark green leafy vegetables

Bahar Yalçın Çeliktaş; Muazzez Garipağaoğlu; Şeyda Karaman Ersoy

doi:10.1371/journal.pone.0358478

Abstract

This study evaluated the effects of four domestic cooking methods—steaming, microwaving, low-water boiling and high-water boiling—on the phenolic composition and antioxidant capacities of five dark green leafy vegetables (sorrel, stinging nettle, spinach, Swiss chard and purslane). Total phenolics, phenolic acids, flavonoids and tannins were quantified spectrophotometrically, while antioxidant capacities were assessed by DPPH, ABTS and CUPRAC assays. Cooking induced species- and method-dependent changes in phenolic profiles. Total phenolic content significantly decreased in sorrel (p = 0.005), whereas other vegetables showed stable or slightly increased values. Phenolic acids increased markedly in stinging nettle and purslane, particularly after low-water boiling (+279.3% and +275.0%) and steaming (+153.2% and +159.5%). Flavonoid levels declined mainly under high-water boiling but remained stable in purslane. Tannin-associated phenolic compounds decreased in nettle and sorrel during boiling, whereas purslane exhibited increases across several treatments. Antioxidant capacities generally decreased with high-water boiling, while steaming and microwaving preserved or enhanced DPPH and CUPRAC activity in purslane. Strong correlations were observed between total phenolic content and antioxidant assays (r = 0.853–0.956). Overall, steaming and microwaving were identified as the most effective techniques for retaining phenolic compounds and antioxidant capacity, whereas high-water boiling caused the greatest losses. These findings highlight the importance of selecting appropriate cooking methods to preserve the nutritional quality of leafy vegetables.

Citation: Yalçın Çeliktaş B, Garipağaoğlu M, Karaman Ersoy Ş (2026) Impact of traditional cooking methods on total phenolics, flavonoids, and antioxidant capacities of dark green leafy vegetables. PLoS One 21(9): e0358478. https://doi.org/10.1371/journal.pone.0358478

Editor: Marcello Iriti, University of Milan, ITALY

Received: March 17, 2026; Accepted: September 1, 2026; Published: September 17, 2026

Copyright: © 2026 Yalçın Çeliktaş et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Green leafy vegetables are widely recognized as “protective foods” due to their richness in vitamins, minerals, dietary fibre and phenolic compounds [1]. Their abundant bioactive constituents—including polyphenols, carotenoids and glucosinolates—have been associated with improved insulin sensitivity, reduced cardiovascular risk, antihypertensive effects and protection against several cancer types [2,3]. Current dietary guidelines recommend at least five servings (400 g/day) of fruits and vegetables, with two servings specifically derived from green leafy varieties [4].

Dark green leafy vegetables, in particular, exhibit strong biological activity owing to their diverse phytochemical profiles, including phenolic compounds, flavonoids, carotenoids, vitamins, minerals and essential fatty acids [5]. These profiles vary across species, contributing to different health-promoting properties. For instance, nettle

(Urtica dioica) contains high levels of phenolics and flavonoids- predominantly chlorogenic acid, caffeic acid derivatives, and rutin- that underpin its antioxidant activity [6], while spinach (Spinacia oleracea) provides lutein, β-carotene and phenolic acids — principally p-coumaric acid derivatives — alongside a unique flavonoid fraction dominated by patuletin and spinacetin glycosides-supporting immune and metabolic functions [7]. Swiss chard (Beta vulgaris subsp. vulgaris) demonstrates benefits for metabolic syndrome due to its betalain and phenolic content including syringic acid and vitexin-derived apigenin flavonoids- [8], and purslane (Portulaca oleracea)—rich in α-linolenic acid and vitamins E and C, caffeic acid, quercetin, kaempferol, and luteolin—exhibits anti-inflammatory and hypolipidemic effects [9]. Sorrel (Rumex acetosa) also shows high antioxidant potential attributable to its flavonoid and phenolic acid composition — particularly quercetin derivatives, chlorogenic acid, caffeic acid, and rutin — [10]. However, the levels of these bioactive compounds are highly influenced not only by species and genotype but also by cultivation conditions, post-harvest handling and particularly home cooking practices [11].

In everyday nutrition, most vegetables are consumed cooked, with boiling, steaming and microwaving being the most common household methods [12]. These thermal treatments can markedly influence the physical attributes, sensory quality and bioactive compounds of vegetables [13]. Depending on the species, raw material quality and applied method, heating may produce both beneficial and adverse outcomes [14]. Nutrient losses, tissue softening and colour changes often occur during cooking, yet bioavailability of certain bioactive components may increase and anti-nutritional factors may be reduced. Such changes are largely attributable to the disruption of the vegetable matrix, through which low molecular weight compounds released during heating can interact with nutrients, either reducing or enhancing their accessibility [15].

Although previous studies have examined the influence of individual cooking methods on total phenolic content and antioxidant activity, the findings remain inconsistent across species and experimental conditions [16–18]. Recent comprehensive reviews also highlight substantial variability in reported outcomes and emphasize the lack of a standardized methodology, making it difficult to identify the most beneficial cooking technique [19]. Moreover, limited research has simultaneously quantified key phenolic subclasses—phenolic acids, flavonoids and tannins—and linked them to multiple antioxidant assays within a unified experimental design. Evidence is particularly scarce for dark green leafy vegetables commonly consumed in Türkiye, such as nettle, spinach, sorrel, Swiss chard and purslane, especially under standardized domestic cooking conditions. To address these gaps, this study assessed the effects of four traditional cooking methods—steaming, microwaving, low-water boiling and high-water boiling—on total phenolic content, phenolic acids, flavonoids, tannins and antioxidant capacities (DPPH, ABTS, CUPRAC) in these vegetables. The three antioxidant assays were selected because they operate through distinct reaction mechanisms: DPPH and ABTS measure hydrogen atom transfer (HAT) and single electron transfer (SET)-based radical scavenging activity, while CUPRAC assesses electron transfer capacity via cupric ion reduction. Their combined use provides a more comprehensive and mechanistically diverse evaluation of antioxidant capacity than any single assay alone [20]. By integrating detailed phenolic characterisation with multiple antioxidant assays and correlation analysis, the study offers method- and species-specific insights that advance current understanding and inform practical dietary and culinary recommendations for optimising the nutritional quality of cooked leafy vegetables.

Materials and methods

Chemicals

All chemicals were of analytical grade and purchased from Merck (Darmstadt, Germany) and Sigma-Aldrich (St. Louis, USA). The reagents included Folin-Ciocalteu reagent, sodium carbonate (Na₂CO₃), sodium hydroxide (NaOH), sodium potassium tartrate (NaKC₄H₄O₆), copper(II) sulfate pentahydrate (CuSO₄·5H₂O), gallic acid, ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt], potassium persulfate (K₂S₂O₈), DPPH [1,1-diphenyl-2-picrylhydrazyl], copper(II) chloride (CuCl₂), neocuproine (Nc), ammonium acetate (NH₄Ac), aluminum chloride (AlCl₃), quercetin, sodium acetate (CH₃COONa), sodium molybdate (Na₂MoO4), sodium nitrite (NaNO2), hydrochloric acid (HCl) and Trolox [6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid], and caffeic acid.

Instruments

Analyses were performed using a UV–Vis spectrophotometer (PG Instruments T80 + , UK), incubator (Elektromag Lab., M6040 BP, Türkiye), analytical balance (Weightlab Instruments, WSA-224, Türkiye), centrifuge (Elektromag, M4812M, Türkiye), shaking water bath (Nükleon Laboratuvar, TT107–30 L, Türkiye), and vortex mixer (Dizgi Analitik, Türkiye). Micropipettes (10–100 µL and 100–1000 µL, Ertick, Türkiye) were used for precise liquid handling. Laboratory glassware (beakers, tubes, glass pipettes; ISOLAB, Germany) was employed in all assays. For sample preparation, a microwave oven (Arçelik MD 574, Türkiye), hand blender (Sinbo SHB 3107, Türkiye), and stainless-steel cooking pot (Karaca Galaxy Series, Türkiye) were utilized.

Plant material and sample preparation

Fresh samples of five dark green leafy vegetables-Nettle (Urtica dioica), Spinach (Spinacia oleracea), Sorrel (Rumex acetosa), Swiss chard (Beta vulgaris subsp. cicla), and Purslane (Portulaca oleracea)—were purchased from local farmers’ markets in Istanbul, Türkiye. Approximately 3 kg of each vegetable was procured. Immediately after purchase, all samples were cleaned, washed under running tap water, and gently dried with paper towels. To prevent nutrient loss, no storage was applied; samples were processed directly. Vegetables were chopped into uniform pieces and weighed into 100 g portions using an analytical balance to ensure consistency across experimental replicates. Each vegetable was divided into three independent sample portions, which were subjected separately to each cooking treatment, representing biological replicates. Subsequently, for each biological replicate, all chemical and antioxidant measurements were carried out in analytical triplicate to ensure measurement precision. The overall experimental workflow is illustrated in Fig 1.

Download:

Fig 1. Graphical overview of the experimental study design.

https://doi.org/10.1371/journal.pone.0358478.g001

Cooking procedures

Cooking conditions were standardized according to previously published protocols with minor modifications [21–23]. The two boiling conditions were selected to reflect contrasting domestic practices commonly reported in the literature: low-water boiling (50 mL per 100 g) simulates minimal-water cooking as described by Turkmen et al. [21] and Şengül et al. [22], while high-water boiling (250 mL per 100 g) represents conventional excess-water boiling widely used in household settings [23]. These conditions were deliberately chosen to represent the full range of water-contact cooking, enabling assessment of the role of water volume as an independent variable in phenolic retention.

Low-water boiling: 100 g of vegetable samples were added to 50 mL of boiling distilled water in a stainless-steel pot, covered, and simmered for 5 min.

High-water boiling: 100 g of samples were cooked in 250 mL boiling distilled water for 5 min.

Steaming: 100 g of samples were placed in a metal strainer over 300 mL boiling distilled water, covered, and steamed for 5 min.

Microwave cooking: 100 g of vegetables with 15 mL distilled water were placed in a porcelain dish (25 cm diameter, 5 cm depth) and microwaved at 600 W for 3 min.

Cooking times of 3–5 min were selected to reflect typical household culinary practices reported in the literature for leafy vegetables [21,22], and to ensure visual and textural doneness without excessive heat exposure. These durations are consistent with times previously applied in comparative cooking studies on similar plant matrices [23]. It is acknowledged that optimal cooking time may vary among species; however, a standardised duration was applied across all vegetables to enable direct comparison of cooking method effects independent of time variables. After cooking, samples were cooled to room temperature, homogenized with a hand blender for 30 s and processed for further analysis.

Dry matter determination

To eliminate the influence of variable moisture content among samples, all analytical data were expressed on a dry weight (DW) basis. Following each cooking treatment, homogenized samples were placed in pre-weighed aluminum dishes and dried in an incubator at 70 °C until a constant weight was achieved (approximately 48 h). Dry matter content was then calculated from the difference between the initial and final sample weights. Dry matter content was calculated using the following equation 1:

(1)

where W₁ is the fresh weight of the homogenized sample (g) and W₂ is the weight of the sample after drying to constant mass (g).

The dried samples were subsequently used for extraction and further analyses; therefore, the results reflect the combined effects of cooking and subsequent drying.

Preparation of extracts

The extraction procedure was adapted from Türkmen et al. [21] with minor modifications. Approximately 2 g of dried and homogenized raw or cooked vegetable samples were extracted with 10 mL of 70% methanol in a shaking water bath at 25 °C for 2 h. Extracts were centrifuged (5000 rpm, 15 min), and the supernatants were collected. The residues were re-extracted under the same conditions, and pooled supernatants were filtered through Whatman No. 1 filter paper. The clarified extracts were stored at −18 °C until analysis.

Determination of total phenolic content

Total phenolic content (TPC) was determined using the Folin–Ciocalteu method described by Singleton et al. [24], implemented via a modified protocol incorporating copper-alkaline reagent solutions (Lowry A, B, and C). This modification is based on the principle originally described by Lowry et al. [25]. In this approach, an alkaline copper pre-treatment is applied prior to the addition of the Folin–Ciocalteu reagent. Although this modification may yield values that differ quantitatively from those obtained using the conventional Folin–Ciocalteu procedure [26], all samples and calibration standards were processed under identical analytical conditions, ensuring internal consistency for comparative purposes.

Three solutions were prepared: Lowry A solution: 2% (w/v) Na₂CO₃ dissolved in 0.1 M NaOH. Lowry B solution: 1% (w/v) NaKC₄H₄O₆ and 0.5% (w/v) CuSO₄. Lowry C solution: prepared by mixing 50 mL Lowry A with 1 mL Lowry B. Briefly, 0.1 mL of sample extract, 1.9 mL distilled water, and 2.5 mL Lowry C solution were added to test tubes and incubated at room temperature for 10 min. Subsequently, 0.25 mL of Folin-Ciocalteu reagent diluted 1:3 with distilled water was added. After 30 min incubation, absorbance was measured at 750 nm using the UV-Vis spectrophotometer against a blank. Gallic acid standards (6.00 × 10 ⁻ ⁵–3.00 × 10 ⁻ ⁴ mol/L) were subjected to the same analytical procedure, including the Lowry C pre-treatment, and were used to construct the calibration curve (y = 6100x + 0.0158, R² = 0.9984). Results were calculated from the calibration curve and expressed as µmol gallic acid equivalents per gram dry weight (µmol GAE/g DW) according to Equation 2.

(2)

Determination of total flavonoid content

Total flavonoid content (TFC) was determined according to the spectrophotometric method developed by Chang et al. [27], with minor modifications. In brief, 0.5 mL of vegetable extract was mixed with 1.5 mL methanol, 0.1 mL of 10% aluminum chloride (AlCl₃) solution, 0.1 mL of 1 M sodium acetate (CH₃COONa), and 2.8 mL distilled water. The mixture was thoroughly vortexed and incubated at room temperature for 30 min. Following incubation, the absorbance was measured at 427 nm. Calibration was performed with quercetin standards (5.00 × 10 ⁻ ⁶-3.00 × 10 ⁻ ⁵ mol/L) (y = 21600x + 0.0056, R² = 0.998). Results were expressed as µmol QE/g DW (QE: Quercetin equivalent) with equation 3.

(3)

Determination of total phenolic acid content (Arnow Assay)

Total phenolic acids (TPA) were determined using the Arnow assay as described by Gawlik-Dziki et al. [28]. It should be noted that the Arnow assay selectively detects ortho-dihydroxy phenolic compounds — primarily caffeic acid, chlorogenic acid, and related catechol-type derivatives — through their reaction with molybdate-nitrite reagent under alkaline conditions. Phenolic acids lacking the ortho-dihydroxy (catechol) structural motif, such as gallic acid, ferulic acid, and p-coumaric acid, do not yield a chromogenic response in this assay. Therefore, the values reported here represent ortho-dihydroxy phenolic acid fractions rather than total phenolic acids in the broadest sense, and should be interpreted accordingly. Reaction mixtures contained 0.5 mL extract, 2.5 mL distilled water, 0.5 mL 0.5 M HCl, 0.5 mL Arnow reagent (10% (w/v) sodium molybdate and 10% (w/v) sodium nitrite), 0.5 mL 10% NaNO₂, and 0.5 mL 1 M NaOH, adjusted to 5.0 mL with distilled water. Absorbance was measured at 490 nm. Caffeic acid standards (2.0 × 10 ⁻ ⁵-2.4 × 10 ⁻ ⁴ mol/L) were used for calibration (y = 3642x + 0.0451, R² = 0.9985). Results were expressed as µmol CAE/g DW (CAE: caffeic acid equivalent) by using the following equation 4.

(4)

Determination of tannin-associated phenolic compounds

Effects on tannin-associated phenolic compounds (TAPC) were determined following Zargar et al. [29] using the Folin–Ciocalteu method. A 0.1 mL extract was diluted with 7.5 mL distilled water, then mixed with 0.5 mL Folin reagent and 1.0 mL 35% Na₂CO₃. After vortexing, dilution to 10 mL and incubation for 30 min, absorbance was measured at 725 nm. Gallic acid standards (5.00 × 10 ⁻ ⁶–3.00 × 10 ⁻ ⁵ mol/L) were used for calibration (y = 291497x – 0.0158, R² = 0.9998). Results were expressed as µmol GAE/g DW according to equation 5. It should be noted that the Folin–Ciocalteu reagent reacts non-specifically with a broad range of reducing compounds, including non-tannin phenolics, ascorbic acid, reducing sugars, and amino acids [20]. In the absence of a prior tannin-specific isolation step – such as PVPP adsorption, protein precipitation, or condensed tannin-specific methods (e.g., vanillin–HCl or butanol–HCl assays) –the values reported here do not selectively quantify tannins; they are therefore designated as tannin-associated phenolic compounds (TAPC) and should be interpreted as operational Folin-reactive estimates within a comparative analytical framework. Furthermore, it is acknowledged that the Folin–Ciocalteu, AlCl₃ (flavonoid), and Arnow (phenolic acid) assays employed in this study exhibit overlapping reactivity toward certain phenolic compound classes; consequently, the four parameters reported– TPC, TPA, TFC, and TAPC – represent operationally defined spectrophotometric fractions rather than strictly isolated biochemical categories. This limitation is inherent to colorimetric phenolic analysis and has been widely recognized in the literature [20]. Chromatographic approaches such as HPLC-DAD or LC-MS/MS would be required for definitive subgroup separation and are recommended for future studies.

(5)

ABTS radical scavenging assay

ABTS radical scavenging activity was evaluated according to Re et al. [30]. A 7 mM ABTS solution was prepared by dissolving 0.1920 g ABTS in distilled water and mixing with 0.0331 g K₂S₂O₈ to obtain a 2.45 mM solution, kept in the dark for 12–16 h. The ABTS ⁺ · solution was diluted with methanol (1:10, v/v). For analysis, 2.9 mL methanol, 0.1 mL extract, and 1 mL ABTS ⁺ · solutions were mixed and incubated at room temperature for 6 min. Absorbance was recorded at 734 nm. Trolox standards (5.00 × 10 ⁻ ⁶-2.50 × 10 ⁻ ⁵ mol/L) were used for calibration (y = 26000x-0.0322, R² = 0.9965), and results were expressed as µmol Trolox equivalents per g dry weight (µmol TE/g DW) according to equation 6.

(6)

DPPH radical scavenging assay

The DPPH assay was performed according to Çelik et al. [31]. A 0.5 mM methanolic DPPH solution was prepared by dissolving 11.71 mg DPPH in 100 mL methanol and stored in the dark. Reaction mixtures contained 0.5 mL DPPH solution, 0.15 mL extract, and 1.85 mL methanol. Samples were incubated at room temperature for 30 min, and absorbance was measured at 525 nm. Trolox standards (1.00 × 10 ⁻ ⁵–6.00 × 10 ⁻ ⁵ mol/L) were used for calibration (y = 12400x + 0.5828, R² = 0.9901). Results were expressed as µmol TE/g DW by using the following equation 7.

(7)

CUPRAC assay

CUPRAC (cupric ion reducing antioxidant capacity) was measured following Apak et al. [32]. The assay mixture contained 1.0 mL CuCl₂ (1.0 × 10 ⁻ ² M), 1.0 mL Nc (7.5 × 10 ⁻ ³ M), and 1.0 mL NH₄Ac buffer (1.0 M, pH 7.0), followed by 0.1 mL extract and 0.9 mL methanol. After vortexing and incubation for 30 min at room temperature, absorbance was measured at 450 nm. Trolox standards (1.00 × 10 ⁻ ⁵- 6.00 × 10 ⁻ ⁵ mol/L) were used for calibration (y = 15400x-0.0326, R² = 0.9970). Results were expressed as µmol TE/g DW according to equation 8.

(8)

For reference and comparison with literature values commonly expressed in mg/g, the µmol values reported in this study can be converted using the respective molecular weights of the reference standards: gallic acid (MW = 170.12 g/mol) for TPC and TAPC, caffeic acid (MW = 180.16 g/mol) for TPA, quercetin (MW = 302.24 g/mol) for TFC, and trolox (MW = 250.29 g/mol) for antioxidant capacity assays. For example, TPC values of 53.55 µmol GAE/g DW and 12.12 µmol GAE/g DW for raw sorrel and spinach correspond to approximately 9.11 mg GAE/g DW and 2.06 mg GAE/g DW, respectively.

The calibration curves and graphical summaries of cooking-induced changes are presented in Supplementary File 1.

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics for Windows, Version 29.0 (IBM Corp., Armonk, NY, USA). Prior to analysis, the normality of the data distribution was assessed using skewness and kurtosis coefficients, and homogeneity of variances was evaluated using Levene’s test. One-way analysis of variance (ANOVA) was conducted to determine significant differences among groups. When a significant effect was observed, Tukey’s Honestly Significant Difference (HSD) post hoc test was applied for multiple comparisons. Relationships between continuous variables were examined using Pearson’s correlation analysis. A p-value < 0.05 was considered statistically significant for all analyses. The raw experimental data used for these statistical analyses are provided in S2 File.

Results and discussion

Dry matter content

The dry matter contents of raw and cooked samples are presented in Table 1. Among the uncooked vegetables, nettle showed the numerically highest dry matter content (9.56 ± 0.38%), while the remaining species ranged between 3.54% and 6.05%. These values are consistent with previously reported ranges of 7.2–14.6% for wild species [23] and 7.39–19.83% for cultivated leafy vegetables [33]. Variations in dry matter content were observed among cooking methods, with steaming and microwaving generally associated with higher values in some vegetables, while high-water boiling tended to yield lower values. The decreases observed during boiling are attributable to the leaching of water-soluble constituents into the cooking medium, including sugars, organic acids, soluble dietary fibre, soluble proteins, minerals, and low-molecular-weight phenolic compounds. Such losses can substantially reduce dry matter yield and may simultaneously alter the apparent concentration and proportional contribution of phenolic compounds in the extracts — independently of any direct effect of heat on phenolic stability. Species-specific variations in the magnitude of these losses likely reflect differences in cell wall architecture, tissue porosity, and the relative abundance of soluble solids.

Download:

Table 1. Dry matter (%) of raw and cooked vegetables.

https://doi.org/10.1371/journal.pone.0358478.t001

Effects on total phenolic content

The effects of different cooking methods on total phenolic content (TPC), phenolic acids, flavonoids and tannin-associated phenolic compounds are presented in Table 2. Among the raw samples, sorrel exhibited the highest TPC (53.55 ± 1.00 µmol GAE/g DW), followed by spinach, purslane, nettle and Swiss chard. Overall, cooking tended to reduce TPC; however, these changes were statistically significant only in sorrel (p = 0.005). No significant differences among cooking methods were observed for nettle, spinach, Swiss chard or purslane (p > 0.05).

Download:

Table 2. Effects of cooking methods on TPC, TPA, TFC, and TAPC of vegetables.

https://doi.org/10.1371/journal.pone.0358478.t002

The greatest numerical reductions in TPC were observed following high-water boiling, ranging from 0.7% to 74.1% depending on the vegetable species. Microwaving also reduced TPC in several vegetables, particularly in sorrel (−56.2%) and nettle (−40.6%); however, except for sorrel, these changes were not statistically significant. Similar species-dependent responses to thermal processing have been reported previously, indicating that phenolic stability is strongly influenced by both plant characteristics and cooking conditions [34–37].

At the mechanistic level, the reductions in total phenolic content observed during cooking may be attributed to thermal degradation and oxidation of phenolic compounds induced by heat treatment [38]. Heat can also alter phenolic–matrix interactions by disrupting ester and glycosidic linkages that bind phenolic compounds to cell wall components, thereby increasing the release and extractability of bound phenolic fractions [39]. However, prolonged heating may promote degradation of phenolic compounds, resulting in lower measurable TPC values [38]. The differing responses among vegetable species suggest that the impact of cooking on TPC is influenced by the composition and distribution of phenolic compounds within the plant matrix. The comparatively greater stability observed in purslane relative to sorrel may therefore reflect species-specific differences in phenolic composition and tissue structure.

Beyond the nature of thermal degradation itself, the magnitude of phenolic loss is further modulated by the water volume used during cooking. The substantially greater water volume in high-water boiling (250 mL vs 50 mL per 100 g sample) creates a larger concentration gradient between the vegetable matrix and the surrounding medium, potentially intensifying leaching of water-soluble phenolics into the cooking liquid independent of heat exposure. Consequently, the greater losses observed under high-water boiling likely represent the combined effect of thermal degradation and solvent-mediated extraction rather than thermal effects alone. This is consistent with previous reports showing that water volume is a primary determinant of phenolic loss during boiling [40] and underscores the importance of water-to-vegetable ratio as an independent variable in cooking studies. It should also be noted that the cooking water was not collected or analysed in this study; therefore, the reductions observed under boiling conditions cannot be attributed solely to thermal degradation, as migration of water-soluble phenolics into the cooking medium may have contributed to the apparent losses.

Effects on phenolic acids

Phenolic acid content followed a similarly species-dependent response. Sorrel contained the highest levels in the raw state (13.98 ± 8.17 µmol CAE/g DM), followed by spinach, purslane, Swiss chard and nettle. Although steaming resulted in a numerical increase in phenolic acids in sorrel (+43.5%) and high-water boiling caused a numerical decrease (−34.7%), neither change was statistically significant (p > 0.05). Similarly, the apparent decreases in Swiss chard and the large numerical increases in nettle and purslane under low-water boiling (+279.3% and +275.0%, respectively) and steaming (+153.2% and +159.5%) did not reach statistical significance (p > 0.05), likely due to the high variability within groups.

The numerical increases observed in some vegetables may be associated with heat-induced release of previously bound phenolic compounds [41]. Thermal processing can alter phenolic–matrix interactions by disrupting ester and glycosidic linkages that bind phenolic compounds to cell wall components, thereby increasing the extractability of phenolic acids [42]. Conversely, reductions observed under boiling conditions may reflect the migration of water-soluble phenolic compounds into the cooking medium, particularly when larger volumes of water are used [38]. Similar shifts between bound and soluble phenolic fractions following thermal processing have been reported in other plant-based foods, including legumes and leafy vegetables [41,43]. Because the cooking water was not collected or analysed in the present study, the relative contributions of enhanced extractability, thermal degradation and leaching could not be distinguished. Overall, steaming and low-water boiling tended to better preserve phenolic acids than high-water boiling, although these differences were not statistically significant.

Effects on total flavonoids

Flavonoid content also varied according to vegetable type and cooking method. Raw spinach exhibited the highest levels (5.27 ± 0.10 µmol QE/g DW), followed by sorrel, purslane, Swiss chard and nettle (p < 0.001). Swiss chard experienced significant reductions across all cooking methods (34–38%; p < 0.001), while purslane largely retained its flavonoids, with small numerical increases under some conditions. In spinach, steaming and high-water boiling resulted in significant reductions of 18–19% compared with raw samples (p < 0.05), whereas microwaving produced values that were not significantly different from the raw state. Nettle also exhibited reductions across all cooking methods, with the greatest loss observed following high-water boiling (p = 0.034).

These findings are consistent with previous studies showing that flavonoid retention during cooking is influenced by both processing conditions and the characteristics of the plant matrix [13,38,42,44,45]. Thermal treatment may affect the stability and extractability of flavonoid compounds through structural modifications of plant tissues and changes in flavonoid–matrix interactions [38]. Differences in the magnitude and direction of flavonoid changes among vegetable species therefore likely reflect variations in tissue structure and flavonoid composition. Overall, steaming appeared to preserve flavonoids more effectively than boiling, whereas the effects of microwaving varied among vegetable species [40].

Effects on tannin-associated phenolic compounds

As noted in the Methods section, the values reported for tannin-associated phenolic compounds represent Folin-reactive reducing substances rather than analytically isolated tannin fractions and should therefore be interpreted within a comparative framework. Among the raw samples, sorrel exhibited the highest levels (1.87 µmol GAE/g DW), followed by Swiss chard, spinach, purslane and nettle.

Numerically, high-water boiling was associated with the greatest reductions in tannin-associated phenolic compounds, resulting in decreases of 46% in sorrel, 64% in spinach, 89% in nettle and 35% in Swiss chard. However, these changes were statistically significant only in nettle (p < 0.05). Sorrel largely maintained its tannin-associated phenolic content following steaming and microwaving, whereas purslane showed numerical increases under all cooking methods, although these changes did not reach statistical significance (p > 0.05).

Previous studies have similarly reported substantial reductions in tannin content following boiling and other thermal treatments [46–49]. The observed decreases may be associated with thermal degradation and the migration of water-soluble Folin-reactive compounds into the cooking medium, whereas apparent increases may reflect enhanced extractability of previously bound phenolic constituents during heat treatment. Because no tannin-specific isolation step was applied and cooking water was not analysed, the relative contributions of degradation, leaching and changes in extractability could not be distinguished in the present study.

Changes in antioxidant capacities (DPPH, ABTS, CUPRAC)

The effects of different cooking methods on DPPH, ABTS and CUPRAC antioxidant capacities are presented in Table 3. In raw form, sorrel exhibited the highest DPPH activity (58.47 µmol TE/g DW), whereas the remaining vegetables ranged from 1.55 to 31.56 µmol TE/g DW, consistent with previously reported values of 2.3–77.2 µmol TE/g DW in leafy vegetables [50]. Cooking produced species-dependent responses. In purslane, steaming produced a statistically significant increase compared with raw samples (+60.2%; p < 0.05), while the increases observed with microwaving (+14.5%) and low-water boiling (+81.0%) did not reach statistical significance (p > 0.05). In sorrel, Swiss chard and nettle, the observed reductions across cooking methods were not statistically significant (p > 0.05). In spinach, high-water boiling resulted in a significant decrease compared with raw (p < 0.05), while other methods did not differ significantly. Such variability aligns with earlier findings indicating that thermal processes may either enhance or reduce DPPH activity depending on vegetable matrix and heat exposure [22,51–53]. For example, substantial increases (99–111%) have been reported after boiling tropical greens [51], while prolonged boiling has been shown to either improve or drastically reduce antioxidant capacity depending on the species [22]. Meta-analytic evidence similarly suggests that steaming generally increases DPPH activity, whereas boiling and microwaving often lead to declines [53,54]. Overall, these results demonstrate that thermal processing can both enhance and diminish DPPH capacity, largely due to structural and compositional changes affecting the release and stability of antioxidant compounds.

Download:

Table 3. Effects of different cooking methods on the antioxidant capacities of vegetables.

https://doi.org/10.1371/journal.pone.0358478.t003

For ABTS, sorrel again showed the highest antioxidant capacity in the raw state (55.79 µmol TE/g DW), with other vegetables ranging between 5.03 and 32.45 µmol TE/g DW—like previous values reported for wild edible plants [54,55]. Cooking generally reduced ABTS capacity, with significant decreases observed in nettle, spinach and Swiss chard (p < 0.01). High-water boiling was associated with the greatest numerical losses (46–77%); however, statistically significant reductions were observed only in nettle, spinach and Swiss chard (p < 0.05). In sorrel and purslane, no significant differences were detected among cooking methods (p > 0.05). Steaming and microwaving resulted in comparatively lower declines and helped preserve activity in purslane. Prior studies similarly reported 16–25% losses in steamed and microwaved broccoli [45], 10–30% reductions in boiled spinach and zucchini [55], and mixed effects—including both decreases and modest increases—depending on cooking method and vegetable type [56]. Collectively, these findings indicate that ABTS responses vary with species and processing conditions, with high water-contact methods intensifying losses, while microwaving and occasionally steaming better preserve antioxidant capacity.

CUPRAC values showed comparable trends. Sorrel exhibited the highest activity in raw form (106.61 ± 0.91 µmol TE/g DW), followed by purslane, spinach, Swiss chard and nettle. Cooking reduced CUPRAC capacity in nettle, spinach and Swiss chard, with statistically significant decreases observed across most methods (p < 0.05). In sorrel and purslane, no statistically significant differences were detected among cooking methods (p > 0.05), despite large numerical variations. The greatest numerical losses were observed under high-water boiling (−59.2% in sorrel; −54.9% in spinach), and under microwaving in nettle (−62%) and Swiss chard (−57%), the latter two being statistically significant. These trends are consistent with earlier studies showing that CUPRAC responses vary widely depending on vegetable type, heating time and cellular structure [18, 57, 58]. Reported increases of several hundred percent after boiling or microwaving artichoke [57] contrast with large losses in onions under similar treatments [58]. Increases—such as those observed in purslane—likely result from heat-induced disruption of cell walls and subsequent release of bound phenolic compounds that enhance measurable antioxidant capacity.

The relationships between phenolic compounds and antioxidant capacities under different cooking methods are shown in Table 4. In raw vegetables, total phenolic content exhibited very strong correlations with all antioxidant assays (DPPH, ABTS and CUPRAC; r = 0.911–0.920). Phenolic acids also showed similarly strong associations (r = 0.883–0.902), while tannin-associated phenolic compounds were significantly correlated with both phenolic compounds and antioxidant capacity. However, given that both tannin-associated phenolic compounds and TPC were estimated using Folin–Ciocalteu chemistry, this relationship should be interpreted with caution, as it may partly reflect shared analytical reactivity rather than independent biological associations. Flavonoids, in contrast, showed only moderate correlations.

Download:

Table 4. Correlations between phenolic compounds and antioxidant capacity according to cooking methods.

https://doi.org/10.1371/journal.pone.0358478.t004

Similar patterns were observed under steaming and microwaving, whereas correlations weakened under high-water boiling, possibly due to reduced extractability or loss of compounds. The dominant antioxidant mechanism in raw and mildly processed samples — reflected by the strong correlations between TPC and DPPH, ABTS, and CUPRAC (r = 0.911–0.920) — is consistent with hydrogen atom transfer (HAT) and single electron transfer (SET) pathways mediated by phenolic hydroxyl groups. However, the partial weakening of these correlations under high-water boiling conditions may indicate an increasing contribution of thermally-derived antioxidant compounds, including Maillard reaction products such as reductones and melanoidins, which are known to exhibit DPPH and ABTS radical scavenging activity independently of native phenolic content [12]. Such thermally-generated antioxidants may partly compensate for phenolic losses in boiled samples, obscuring a direct structure-activity relationship between TPC and measured antioxidant capacity. Overall, these findings suggest that phenolic compounds are major contributors to antioxidant capacity under the present conditions; however, these associations should be interpreted with caution, as other compounds and assay-specific responses may also influence the results. These observations are consistent with previous studies reporting strong associations between phenolic content and antioxidant activity in leafy vegetables [50, 59, 60].

This study has several limitations that should be considered when interpreting the findings. First, plant samples were obtained from a single source and did not account for potential seasonal or batch-related variability, which may limit the generalizability of the results. Second, samples were subjected to oven drying prior to extraction; therefore, the observed changes reflect the combined effects of cooking and subsequent drying, rather than cooking alone. In addition, the use of spectrophotometric assays provided overall estimates of phenolic content and antioxidant capacity, but did not allow for compound-specific identification. Finally, although biological and analytical replicates were applied, the relatively high variability observed in some parameters may reflect inherent heterogeneity in plant matrices. The spectrophotometric assay used for tannin-associated phenolic compound determination was based on Folin–Ciocalteu chemistry without prior tannin-specific precipitation (e.g., PVPP treatment) and therefore lacked selectivity for true tannin fractions. More broadly, the Folin–Ciocalteu, AlCl₃ and Arnow methods used for TPC, TFC and TPA determination are known to exhibit overlapping reactivity toward shared phenolic substrates. Consequently, the reported parameters should be interpreted as operationally defined spectrophotometric fractions rather than biochemically distinct compound classes [20]. Additionally, cooking water was not retained or analysed. Therefore, the reductions observed under boiling conditions may partly reflect migration of soluble phenolic compounds into the cooking medium rather than true chemical degradation. In culinary applications where the cooking liquid is consumed, such as soups and stews, these apparent losses may represent redistribution rather than elimination of bioactive compounds.

Conclusion

This study demonstrated that dark green leafy vegetables are important sources of phenolic compounds, flavonoids, tannin-associated phenolic compounds and antioxidant activity, and that their retention is influenced by the cooking method applied. Among the evaluated techniques, steaming and microwaving generally resulted in better preservation of phenolic compounds and antioxidant capacity, whereas high-water boiling was associated with greater reductions in most bioactive parameters. In some vegetables, low-water boiling was associated with higher measured phenolic acid values, suggesting that processing conditions may influence the availability of specific phenolic constituents. Overall, cooking methods involving limited water contact and shorter heating times appeared more favourable for preserving the bioactive properties of leafy vegetables. Together with evidence from previous studies indicating improved retention of sensory attributes under these conditions, the present findings support steaming and microwaving as favourable cooking methods for dark green leafy vegetables. However, the observed changes reflect the combined effects of cooking and the subsequent drying step applied prior to analysis. In addition, cooking water was not collected or analysed; therefore, apparent reductions observed under boiling conditions may partly reflect migration of soluble compounds into the cooking medium rather than true degradation. Despite these limitations, the findings provide practical insights for both household food preparation and institutional catering settings, where the preservation of bioactive compounds is an important consideration. Future studies incorporating different cooking durations, alternative processing techniques, cooking-water analysis and compound-specific analytical approaches are warranted to further elucidate the mechanisms underlying these changes and to support evidence-based dietary recommendations.

Supporting information

S1 File. Calibration curves for all spectrophotometric assays and graphical summaries of cooking-induced changes in phenolic compounds and antioxidant capacities.

https://doi.org/10.1371/journal.pone.0358478.s001

(DOCX)

S2 File. Raw experimental data used for statistical analyses, including all replicate measurements for phenolic compounds and antioxidant capacity assays.

https://doi.org/10.1371/journal.pone.0358478.s002

(XLSX)

References

1. Kumar D, Kumar S, Shekhar C. Nutritional components in green leafy vegetables: a review. J Pharmacogn Phytochem. 2020;9(5):2498–502.
- View Article
- Google Scholar
2. Aslam T, Maqsood M, Jamshaid I, Ashraf K, Zaidi F, Khalid S, et al. Health benefits and therapeutic importance of green leafy vegetables (GLVs). Eur Acad Res. 2020;8:4213–29.
- View Article
- Google Scholar
3. Ansari P, Khan JT, Chowdhury S, Reberio AD, Kumar S, Seidel V, et al. Plant-based diets and phytochemicals in the management of diabetes mellitus and prevention of its complications: a review. Nutrients. 2024;16(21):3709. pmid:39519546
- View Article
- PubMed/NCBI
- Google Scholar
4. Türkiye beslenme rehberi. Ankara: T.C. Sağlık Bakanlığı. 2022.
5. Thakur V, Mal D, Soga K, Gandhi A. A review on nutritional quality of green leafy vegetables. Ecol Environ Conserv. 2022;28(Suppl):S351–6.
- View Article
- Google Scholar
6. Devkota HP, Paudel KR, Khanal S, Baral A, Panth N, Adhikari-Devkota A, et al. Stinging Nettle (Urtica dioica L.): Nutritional Composition, Bioactive Compounds, and Food Functional Properties. Molecules. 2022;27(16):5219. pmid:36014458
- View Article
- PubMed/NCBI
- Google Scholar
7. Cho MJ, Howard LR, Prior RL, Morelock T. Flavonoid content and antioxidant capacity of spinach genotypes determined by high‐performance liquid chromatography/mass spectrometry. J Sci Food Agric. 2008;88(6):1099–106.
- View Article
- Google Scholar
8. Gamba M, Raguindin PF, Asllanaj E, Merlo F, Glisic M, Minder B, et al. Bioactive compounds and nutritional composition of Swiss chard (Beta vulgaris L. var. cicla and flavescens): a systematic review. Crit Rev Food Sci Nutr. 2021;61(20):3465–80. pmid:32746613
- View Article
- PubMed/NCBI
- Google Scholar
9. Mitroi C. Purslane (Portulaca oleracea) – nutritional value and food uses. J Agroaliment Process Technol. 2025;30:357–65.
- View Article
- Google Scholar
10. Irtegün Kandemir S, Aktepe N, Baran A, Baran MF, Atalar MN, Keskin C. Determination of chemical composition and antioxidant, cytotoxic, antimicrobial, and enzyme inhibition activities of Rumex acetosella L. plant extract. Chem Pap. 2024;78(10):4583–92.
- View Article
- Google Scholar
11. Amagloh FC, Kaaya AN, Tumuhimbise GA, Katungisa A, Amagloh FK, Yada B. Household Processing Methods and Their Impact on Bioactive Compounds and Antioxidant Activities of Sweetpotato Genotypes of Varying Storage Root Flesh Colours. Antioxidants (Basel). 2022;11(10):1867. pmid:36290590
- View Article
- PubMed/NCBI
- Google Scholar
12. Zhao C, Liu Y, Lai S, Cao H, Guan Y, San Cheang W, et al. Effects of domestic cooking process on the chemical and biological properties of dietary phytochemicals. Trends in Food Science & Technology. 2019;85:55–66.
- View Article
- Google Scholar
13. Rana MdR, Ahmad H, Sayem ASM, Jothi JS, Hoque MdM, Rahman M. Effects of Different Cooking Methods on Physicochemical and Bioactive Compounds of Selected Green Vegetables in North Eastern Region, Bangladesh. Curr Res Nutr Food Sci. 2021;9(2):628–38.
- View Article
- Google Scholar
14. Razzak A, Mahjabin T, Khan MRM, Hossain M, Sadia U, Zzaman W. Effect of cooking methods on the nutritional quality of selected vegetables at Sylhet City. Heliyon. 2023;9(11):e21709. pmid:38027907
- View Article
- PubMed/NCBI
- Google Scholar
15. Yalçın B, Garipağaoğlu M. Yeşil yapraklı sebzeler ve sağlık: pişirme yöntemlerinin besin değeri üzerindeki etkileri. Beslenme ve diyetetik alanında güncel yaklaşımlar. Platanus Publishing. 2025. p. 21–41.
16. Geetha K, Hulamani S, Shivaleela HB. Effect of cooking on total antioxidant activity, polyphenols and flavonoid content in commonly consumed vegetables. Int J Curr Microbiol Appl Sci. 2018;7(2):1459–66.
- View Article
- Google Scholar
17. Deyalage ST, Wickramasinghe I, Amarasinghe N, Thilakarathna G. Influence of cooking methods on antioxidant activities of selected leafy vegetables gymnema lactiferum, wattakaka volubilis, and argyreia populifolia in Sri Lanka. Int J Food Sci. 2021;2021:6660308. pmid:34124235
- View Article
- PubMed/NCBI
- Google Scholar
18. Demirel Ozbek Y, Saral O, Turker PF. Modern and traditional cooking methods affect the antioxidant activity and phenolic compounds content of Trachystemon Orientalis (L.) G. Don. PLoS One. 2024;19(2):e0299037. pmid:38394328
- View Article
- PubMed/NCBI
- Google Scholar
19. Kosewski G, Kowalówka M, Drzymała-Czyż S, Przysławski J. The Impact of Culinary Processing, including Sous-Vide, on Polyphenols, Vitamin C Content and Antioxidant Status in Selected Vegetables-Methods and Results: A Critical Review. Foods. 2023;12(11):2121. pmid:37297363
- View Article
- PubMed/NCBI
- Google Scholar
20. Prior RL, Wu X, Schaich K. Standardized methods for the determination of antioxidant capacity and phenolics in foods and dietary supplements. J Agric Food Chem. 2005;53(10):4290–302. pmid:15884874
- View Article
- PubMed/NCBI
- Google Scholar
21. Turkmen N, Sari F, Velioglu Y. The effect of cooking methods on total phenolics and antioxidant activity of selected green vegetables. Food Chemistry. 2005;93(4):713–8.
- View Article
- Google Scholar
22. Şengül M, Yildiz H, Kavaz A. The Effect of Cooking on Total Polyphenolic Content and Antioxidant Activity of Selected Vegetables. International Journal of Food Properties. 2013;17(3):481–90.
- View Article
- Google Scholar
23. Sergio L, Boari F, Pieralice M, Linsalata V, Cantore V, Di Venere D. Bioactive phenolics and antioxidant capacity of some wild edible greens as affected by different cooking treatments. Foods. 2020;9(9):1320. pmid:32962154
- View Article
- PubMed/NCBI
- Google Scholar
24. Singleton VL, Orthofer R, Lamuela-Raventós RM. [14] Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent. Methods in Enzymology. Elsevier. 1999. p. 152–78. https://doi.org/10.1016/s0076-6879(99)99017-1
25. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951;193(1):265–75. pmid:14907713
- View Article
- PubMed/NCBI
- Google Scholar
26. Singleton VL, Rossi JAJ. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. Am J Enol Vitic. 1965;16(3):144–58.
- View Article
- Google Scholar
27. Chang C-C, Yang M-H, Wen H-M, Chern J-C. Estimation of total flavonoid content in propolis by two complementary colometric methods. Journal of Food and Drug Analysis. 2020;10(3).
- View Article
- Google Scholar
28. Gawlik-Dziki U, Dziki D, Baraniak B, Lin R. The effect of simulated digestion in vitro on bioactivity of wheat bread with Tartary buckwheat flavones addition. LWT - Food Science and Technology. 2009;42(1):137–43.
- View Article
- Google Scholar
29. Zargar B, Majeed D, Ganai SA, Mir SA, Dar BN. Effect of different processing parameters on antioxidant activity of tea. Food Measure. 2017;12(1):527–34.
- View Article
- Google Scholar
30. Re R, Pellegrini N, Proteggente A, Pannala A, Yang M, Rice-Evans C. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic Biol Med. 1999;26(9–10):1231–7. pmid:10381194
- View Article
- PubMed/NCBI
- Google Scholar
31. Çelik SE, Tufan AN, Bekdeser B, Özyürek M, Güçlü K, Apak R. Identification and Determination of Phenolics in Lamiaceae Species by UPLC-DAD-ESI-MS/MS. J Chromatogr Sci. 2017;55(3):291–300. pmid:27884875
- View Article
- PubMed/NCBI
- Google Scholar
32. Apak R, Güçlü K, Ozyürek M, Karademir SE. Novel total antioxidant capacity index for dietary polyphenols and vitamins C and E, using their cupric ion reducing capability in the presence of neocuproine: CUPRAC method. J Agric Food Chem. 2004;52(26):7970–81. pmid:15612784
- View Article
- PubMed/NCBI
- Google Scholar
33. Zor M, Sengul M, Karakütük İA, Odunkıran A. Changes caused by different cooking methods in some physicochemical properties, antioxidant activity, and mineral composition of various vegetables. Food Processing Preservation. 2022;46(11).
- View Article
- Google Scholar
34. Sabuncu M, Konak M, Şahan Y. Rumex acetosella L’nin biyoalınabilir antioksidan özelliklerinin belirlenmesi. Bursa Uludag Univ J Agric Fac. 2019;33(2):197–207.
- View Article
- Google Scholar
35. Mehić E, Kazazić M. Influence of processing on antioxidant activity and phenolic content of Swiss chard (Beta vulgaris L. subsp. cicla). Educa. 2021;14:21–4.
- View Article
- Google Scholar
36. Melini F, Lisciani S, Camilli E, Marconi S, Melini V. Effect of Cooking on Phenolic Compound Content and In Vitro Bioaccessibility in Sustainable Foods: A Case Study on Black Beans. Sustainability. 2023;16(1):279.
- View Article
- Google Scholar
37. Meral R. Yuzuncu Yil Univ Fen Bilimleri Enstitusu Dergisi. 2016;21(1):55–67.
- View Article
- Google Scholar
38. Gao Y, Xia W, Shao P, Wu W, Chen H, Fang X, et al. Impact of thermal processing on dietary flavonoids. Current Opinion in Food Science. 2022;48:100915.
- View Article
- Google Scholar
39. Călinoiu LF, Vodnar DC. Whole Grains and Phenolic Acids: A Review on Bioactivity, Functionality, Health Benefits and Bioavailability. Nutrients. 2018;10(11):1615. pmid:30388881
- View Article
- PubMed/NCBI
- Google Scholar
40. Wu X, Zhao Y, Haytowitz DB, Chen P, Pehrsson PR. Effects of domestic cooking on flavonoids in broccoli and calculation of retention factors. Heliyon. 2019;5(3):e01310.
- View Article
- Google Scholar
41. Obayiuwana OA, Behrends V, Calle-Patino Y, Costabile A, Corona G. The impact of cooking and digestion on the phenolic acid content of selected Nigerian and UK grown wholegrains. Proc Nutr Soc. 2021;80(OCE1):E39.
- View Article
- Google Scholar
42. Kurniawan A, Hidayat C, Rahayu ES. Effect of cooking methods on total phenolic, flavonoid contents and antioxidant activity of red spinach (Amaranthus tricolor L.). In: IOP Conf Ser Earth Environ Sci. 2021; 012040. https://doi.org/10.1088/1755-1315/762/1/012040
43. Teixeira-Guedes CI, Oppolzer D, Barros AI, Pereira-Wilson C. Impact of cooking method on phenolic composition and antioxidant potential of four varieties of Phaseolus vulgaris L. and Glycine max L. LWT. 2019;103:238–46.
- View Article
- Google Scholar
44. Kouassi LVS, N’gbo MLK, Sinh JN, Disseka WK, Faulet MBA. Effect of boiling times on polyphenol, flavonoid, tannin, vitamin C and β-carotene contents of African asparagus (Laccosperma secundiflorum). Int J Biochem Res Rev. 2021;30(10):35–44.
- View Article
- Google Scholar
45. Kim HY, Ediriweera MK, Boo K-H, Kim CS, Cho SK. Effects of Cooking and Processing Methods on Phenolic Contents and Antioxidant and Anti-Proliferative Activities of Broccoli Florets. Antioxidants (Basel). 2021;10(5):641. pmid:33922092
- View Article
- PubMed/NCBI
- Google Scholar
46. Boua Boua B, Ouattara DC, Traoré L, Mamyrbekova-Békro JA, Békro YA. Effect of domestic cooking on the total phenolic, flavonoid and condensed tannin content from plantain of Côte d’Ivoire. J Mater Environ Sci. 2020;11(3):396–403.
- View Article
- Google Scholar
47. Managa MG, Shai J, Thi Phan AD, Sultanbawa Y, Sivakumar D. Impact of Household Cooking Techniques on African Nightshade and Chinese Cabbage on Phenolic Compounds, Antinutrients, in vitro Antioxidant, and β-Glucosidase Activity. Front Nutr. 2020;7:580550. pmid:33409289
- View Article
- PubMed/NCBI
- Google Scholar
48. Issa JY, Onyango A, Makokha AO, Okoth J. Effect of Boiling and Wet Frying on Nutritional and Antinutrients Content of Traditional Vegetables Commonly Consumed in Malawi. JFR. 2019;9(1):19.
- View Article
- Google Scholar
49. Maqbool N, Sofi SA, Makroo HA, Mir SA, Majid D, Dar BN. Cooking methods affect eating quality, bio-functional components, antinutritional compounds and sensory attributes of selected vegetables. Ital J Food Sci. 2021;33(SP1):150–62.
- View Article
- Google Scholar
50. Tiveron AP, Melo PS, Bergamaschi KB, Vieira TMFS, Regitano-d’Arce MAB, Alencar SM. Antioxidant activity of Brazilian vegetables and its relation with phenolic composition. Int J Mol Sci. 2012;13(7):8943–57. pmid:22942744
- View Article
- PubMed/NCBI
- Google Scholar
51. Hossain A, Khatun MA, Islam M, Huque R. Enhancement of Antioxidant Quality of Green Leafy Vegetables upon Different Cooking Method. Prev Nutr Food Sci. 2017;22(3):216–22. pmid:29043220
- View Article
- PubMed/NCBI
- Google Scholar
52. İduğ T, Hizli Güldemi̇r H, Şen A, Güldemi̇r O. Investigation on the effects of cooking methods on anti-inflammatory and antioxidant activities of five mostly consumed vegetables in winter. International Journal of Agriculture Environment and Food Sciences. 2022;6(1):182–8.
- View Article
- Google Scholar
53. Murador D, Braga AR, Da Cunha D, De Rosso V. Alterations in phenolic compound levels and antioxidant activity in response to cooking technique effects: A meta-analytic investigation. Crit Rev Food Sci Nutr. 2018;58(2):169–77. pmid:26858038
- View Article
- PubMed/NCBI
- Google Scholar
54. Yalçın S, Kasnak C, Palamutoğlu R, Ünlü Ü. Antioxidant Activity and Phytochemical Profile of Eight Wild Edible Plants Grown in Afyonkarahisar, Türkiye. Akademik Gıda. 2025;23(1):12–9.
- View Article
- Google Scholar
55. Jiménez-Monreal AM, García-Diz L, Martínez-Tomé M, Mariscal M, Murcia MA. Influence of cooking methods on antioxidant activity of vegetables. J Food Sci. 2009;74(3):H97–103. pmid:19397724
- View Article
- PubMed/NCBI
- Google Scholar
56. Seal T, Pillai B, Chaudhuri K. Effect of cooking methods on total phenolics and antioxidant activity of selected wild edible plants. Int J Pharm Pharm Sci. 2023;15(7):20–6.
- View Article
- Google Scholar
57. Kayahan S, Saloglu D. Comparison of Phenolic Compounds and Antioxidant Activities of Raw and Cooked Turkish Artichoke Cultivars. Front Sustain Food Syst. 2021;5.
- View Article
- Google Scholar
58. Ozyurt D, Goc B, Demirata B, Apak R. Effect of Oven and Microwave Heating on the Total Antioxidant Capacity of Dietary Onions Grown in Turkey. International J Food Properties. 2013;16(3):536–48.
- View Article
- Google Scholar
59. George J, Edwards D, Pun S, Williams D. Evaluation of Antioxidant Capacity (ABTS and CUPRAC) and Total Phenolic Content (Folin-Ciocalteu) Assays of Selected Fruit, Vegetables, and Spices. Int J Food Sci. 2022;2022:2581470. pmid:36506706
- View Article
- PubMed/NCBI
- Google Scholar
60. Nhu-Trang T-T, Nguyen Q-D, Cong-Hau N, Anh-Dao L-T, Behra P. Characteristics and Relationships between Total Polyphenol and Flavonoid Contents, Antioxidant Capacities, and the Content of Caffeine, Gallic Acid, and Major Catechins in Wild/Ancient and Cultivated Teas in Vietnam. Molecules. 2023;28(8):3470. pmid:37110703
- View Article
- PubMed/NCBI
- Google Scholar

[ref1] 1. Kumar D, Kumar S, Shekhar C. Nutritional components in green leafy vegetables: a review. J Pharmacogn Phytochem. 2020;9(5):2498–502.
View Article
Google Scholar

[2] View Article

[3] Google Scholar

[ref2] 2. Aslam T, Maqsood M, Jamshaid I, Ashraf K, Zaidi F, Khalid S, et al. Health benefits and therapeutic importance of green leafy vegetables (GLVs). Eur Acad Res. 2020;8:4213–29.
View Article
Google Scholar

[5] View Article

[6] Google Scholar

[ref3] 3. Ansari P, Khan JT, Chowdhury S, Reberio AD, Kumar S, Seidel V, et al. Plant-based diets and phytochemicals in the management of diabetes mellitus and prevention of its complications: a review. Nutrients. 2024;16(21):3709. pmid:39519546
View Article
PubMed/NCBI
Google Scholar

[8] View Article

[9] PubMed/NCBI

[10] Google Scholar

[ref4] 4. Türkiye beslenme rehberi. Ankara: T.C. Sağlık Bakanlığı. 2022.

[ref5] 5. Thakur V, Mal D, Soga K, Gandhi A. A review on nutritional quality of green leafy vegetables. Ecol Environ Conserv. 2022;28(Suppl):S351–6.
View Article
Google Scholar

[13] View Article

[14] Google Scholar

[ref6] 6. Devkota HP, Paudel KR, Khanal S, Baral A, Panth N, Adhikari-Devkota A, et al. Stinging Nettle (Urtica dioica L.): Nutritional Composition, Bioactive Compounds, and Food Functional Properties. Molecules. 2022;27(16):5219. pmid:36014458
View Article
PubMed/NCBI
Google Scholar

[16] View Article

[17] PubMed/NCBI

[18] Google Scholar

[ref7] 7. Cho MJ, Howard LR, Prior RL, Morelock T. Flavonoid content and antioxidant capacity of spinach genotypes determined by high‐performance liquid chromatography/mass spectrometry. J Sci Food Agric. 2008;88(6):1099–106.
View Article
Google Scholar

[20] View Article

[21] Google Scholar

[ref8] 8. Gamba M, Raguindin PF, Asllanaj E, Merlo F, Glisic M, Minder B, et al. Bioactive compounds and nutritional composition of Swiss chard (Beta vulgaris L. var. cicla and flavescens): a systematic review. Crit Rev Food Sci Nutr. 2021;61(20):3465–80. pmid:32746613
View Article
PubMed/NCBI
Google Scholar

[23] View Article

[24] PubMed/NCBI

[25] Google Scholar

[ref9] 9. Mitroi C. Purslane (Portulaca oleracea) – nutritional value and food uses. J Agroaliment Process Technol. 2025;30:357–65.
View Article
Google Scholar

[27] View Article

[28] Google Scholar

[ref10] 10. Irtegün Kandemir S, Aktepe N, Baran A, Baran MF, Atalar MN, Keskin C. Determination of chemical composition and antioxidant, cytotoxic, antimicrobial, and enzyme inhibition activities of Rumex acetosella L. plant extract. Chem Pap. 2024;78(10):4583–92.
View Article
Google Scholar

[30] View Article

[31] Google Scholar

[ref11] 11. Amagloh FC, Kaaya AN, Tumuhimbise GA, Katungisa A, Amagloh FK, Yada B. Household Processing Methods and Their Impact on Bioactive Compounds and Antioxidant Activities of Sweetpotato Genotypes of Varying Storage Root Flesh Colours. Antioxidants (Basel). 2022;11(10):1867. pmid:36290590
View Article
PubMed/NCBI
Google Scholar

[33] View Article

[34] PubMed/NCBI

[35] Google Scholar

[ref12] 12. Zhao C, Liu Y, Lai S, Cao H, Guan Y, San Cheang W, et al. Effects of domestic cooking process on the chemical and biological properties of dietary phytochemicals. Trends in Food Science & Technology. 2019;85:55–66.
View Article
Google Scholar

[37] View Article

[38] Google Scholar

[ref13] 13. Rana MdR, Ahmad H, Sayem ASM, Jothi JS, Hoque MdM, Rahman M. Effects of Different Cooking Methods on Physicochemical and Bioactive Compounds of Selected Green Vegetables in North Eastern Region, Bangladesh. Curr Res Nutr Food Sci. 2021;9(2):628–38.
View Article
Google Scholar

[40] View Article

[41] Google Scholar

[ref14] 14. Razzak A, Mahjabin T, Khan MRM, Hossain M, Sadia U, Zzaman W. Effect of cooking methods on the nutritional quality of selected vegetables at Sylhet City. Heliyon. 2023;9(11):e21709. pmid:38027907
View Article
PubMed/NCBI
Google Scholar

[43] View Article

[44] PubMed/NCBI

[45] Google Scholar

[ref15] 15. Yalçın B, Garipağaoğlu M. Yeşil yapraklı sebzeler ve sağlık: pişirme yöntemlerinin besin değeri üzerindeki etkileri. Beslenme ve diyetetik alanında güncel yaklaşımlar. Platanus Publishing. 2025. p. 21–41.

[ref16] 16. Geetha K, Hulamani S, Shivaleela HB. Effect of cooking on total antioxidant activity, polyphenols and flavonoid content in commonly consumed vegetables. Int J Curr Microbiol Appl Sci. 2018;7(2):1459–66.
View Article
Google Scholar

[48] View Article

[49] Google Scholar

[ref17] 17. Deyalage ST, Wickramasinghe I, Amarasinghe N, Thilakarathna G. Influence of cooking methods on antioxidant activities of selected leafy vegetables gymnema lactiferum, wattakaka volubilis, and argyreia populifolia in Sri Lanka. Int J Food Sci. 2021;2021:6660308. pmid:34124235
View Article
PubMed/NCBI
Google Scholar

[51] View Article

[52] PubMed/NCBI

[53] Google Scholar

[ref18] 18. Demirel Ozbek Y, Saral O, Turker PF. Modern and traditional cooking methods affect the antioxidant activity and phenolic compounds content of Trachystemon Orientalis (L.) G. Don. PLoS One. 2024;19(2):e0299037. pmid:38394328
View Article
PubMed/NCBI
Google Scholar

[55] View Article

[56] PubMed/NCBI

[57] Google Scholar

[ref19] 19. Kosewski G, Kowalówka M, Drzymała-Czyż S, Przysławski J. The Impact of Culinary Processing, including Sous-Vide, on Polyphenols, Vitamin C Content and Antioxidant Status in Selected Vegetables-Methods and Results: A Critical Review. Foods. 2023;12(11):2121. pmid:37297363
View Article
PubMed/NCBI
Google Scholar

[59] View Article

[60] PubMed/NCBI

[61] Google Scholar

[ref20] 20. Prior RL, Wu X, Schaich K. Standardized methods for the determination of antioxidant capacity and phenolics in foods and dietary supplements. J Agric Food Chem. 2005;53(10):4290–302. pmid:15884874
View Article
PubMed/NCBI
Google Scholar

[63] View Article

[64] PubMed/NCBI

[65] Google Scholar

[ref21] 21. Turkmen N, Sari F, Velioglu Y. The effect of cooking methods on total phenolics and antioxidant activity of selected green vegetables. Food Chemistry. 2005;93(4):713–8.
View Article
Google Scholar

[67] View Article

[68] Google Scholar

[ref22] 22. Şengül M, Yildiz H, Kavaz A. The Effect of Cooking on Total Polyphenolic Content and Antioxidant Activity of Selected Vegetables. International Journal of Food Properties. 2013;17(3):481–90.
View Article
Google Scholar

[70] View Article

[71] Google Scholar

[ref23] 23. Sergio L, Boari F, Pieralice M, Linsalata V, Cantore V, Di Venere D. Bioactive phenolics and antioxidant capacity of some wild edible greens as affected by different cooking treatments. Foods. 2020;9(9):1320. pmid:32962154
View Article
PubMed/NCBI
Google Scholar

[73] View Article

[74] PubMed/NCBI

[75] Google Scholar

[ref24] 24. Singleton VL, Orthofer R, Lamuela-Raventós RM. [14] Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent. Methods in Enzymology. Elsevier. 1999. p. 152–78. https://doi.org/10.1016/s0076-6879(99)99017-1

[ref25] 25. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951;193(1):265–75. pmid:14907713
View Article
PubMed/NCBI
Google Scholar

[78] View Article

[79] PubMed/NCBI

[80] Google Scholar

[ref26] 26. Singleton VL, Rossi JAJ. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. Am J Enol Vitic. 1965;16(3):144–58.
View Article
Google Scholar

[82] View Article

[83] Google Scholar

[ref27] 27. Chang C-C, Yang M-H, Wen H-M, Chern J-C. Estimation of total flavonoid content in propolis by two complementary colometric methods. Journal of Food and Drug Analysis. 2020;10(3).
View Article
Google Scholar

[85] View Article

[86] Google Scholar

[ref28] 28. Gawlik-Dziki U, Dziki D, Baraniak B, Lin R. The effect of simulated digestion in vitro on bioactivity of wheat bread with Tartary buckwheat flavones addition. LWT - Food Science and Technology. 2009;42(1):137–43.
View Article
Google Scholar

[88] View Article

[89] Google Scholar

[ref29] 29. Zargar B, Majeed D, Ganai SA, Mir SA, Dar BN. Effect of different processing parameters on antioxidant activity of tea. Food Measure. 2017;12(1):527–34.
View Article
Google Scholar

[91] View Article

[92] Google Scholar

[ref30] 30. Re R, Pellegrini N, Proteggente A, Pannala A, Yang M, Rice-Evans C. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic Biol Med. 1999;26(9–10):1231–7. pmid:10381194
View Article
PubMed/NCBI
Google Scholar

[94] View Article

[95] PubMed/NCBI

[96] Google Scholar

[ref31] 31. Çelik SE, Tufan AN, Bekdeser B, Özyürek M, Güçlü K, Apak R. Identification and Determination of Phenolics in Lamiaceae Species by UPLC-DAD-ESI-MS/MS. J Chromatogr Sci. 2017;55(3):291–300. pmid:27884875
View Article
PubMed/NCBI
Google Scholar

[98] View Article

[99] PubMed/NCBI

[100] Google Scholar

[ref32] 32. Apak R, Güçlü K, Ozyürek M, Karademir SE. Novel total antioxidant capacity index for dietary polyphenols and vitamins C and E, using their cupric ion reducing capability in the presence of neocuproine: CUPRAC method. J Agric Food Chem. 2004;52(26):7970–81. pmid:15612784
View Article
PubMed/NCBI
Google Scholar

[102] View Article

[103] PubMed/NCBI

[104] Google Scholar

[ref33] 33. Zor M, Sengul M, Karakütük İA, Odunkıran A. Changes caused by different cooking methods in some physicochemical properties, antioxidant activity, and mineral composition of various vegetables. Food Processing Preservation. 2022;46(11).
View Article
Google Scholar

[106] View Article

[107] Google Scholar

[ref34] 34. Sabuncu M, Konak M, Şahan Y. Rumex acetosella L’nin biyoalınabilir antioksidan özelliklerinin belirlenmesi. Bursa Uludag Univ J Agric Fac. 2019;33(2):197–207.
View Article
Google Scholar

[109] View Article

[110] Google Scholar

[ref35] 35. Mehić E, Kazazić M. Influence of processing on antioxidant activity and phenolic content of Swiss chard (Beta vulgaris L. subsp. cicla). Educa. 2021;14:21–4.
View Article
Google Scholar

[112] View Article

[113] Google Scholar

[ref36] 36. Melini F, Lisciani S, Camilli E, Marconi S, Melini V. Effect of Cooking on Phenolic Compound Content and In Vitro Bioaccessibility in Sustainable Foods: A Case Study on Black Beans. Sustainability. 2023;16(1):279.
View Article
Google Scholar

[115] View Article

[116] Google Scholar

[ref37] 37. Meral R. Yuzuncu Yil Univ Fen Bilimleri Enstitusu Dergisi. 2016;21(1):55–67.
View Article
Google Scholar

[118] View Article

[119] Google Scholar

[ref38] 38. Gao Y, Xia W, Shao P, Wu W, Chen H, Fang X, et al. Impact of thermal processing on dietary flavonoids. Current Opinion in Food Science. 2022;48:100915.
View Article
Google Scholar

[121] View Article

[122] Google Scholar

[ref39] 39. Călinoiu LF, Vodnar DC. Whole Grains and Phenolic Acids: A Review on Bioactivity, Functionality, Health Benefits and Bioavailability. Nutrients. 2018;10(11):1615. pmid:30388881
View Article
PubMed/NCBI
Google Scholar

[124] View Article

[125] PubMed/NCBI

[126] Google Scholar

[ref40] 40. Wu X, Zhao Y, Haytowitz DB, Chen P, Pehrsson PR. Effects of domestic cooking on flavonoids in broccoli and calculation of retention factors. Heliyon. 2019;5(3):e01310.
View Article
Google Scholar

[128] View Article

[129] Google Scholar

[ref41] 41. Obayiuwana OA, Behrends V, Calle-Patino Y, Costabile A, Corona G. The impact of cooking and digestion on the phenolic acid content of selected Nigerian and UK grown wholegrains. Proc Nutr Soc. 2021;80(OCE1):E39.
View Article
Google Scholar

[131] View Article

[132] Google Scholar

[ref42] 42. Kurniawan A, Hidayat C, Rahayu ES. Effect of cooking methods on total phenolic, flavonoid contents and antioxidant activity of red spinach (Amaranthus tricolor L.). In: IOP Conf Ser Earth Environ Sci. 2021; 012040. https://doi.org/10.1088/1755-1315/762/1/012040

[ref43] 43. Teixeira-Guedes CI, Oppolzer D, Barros AI, Pereira-Wilson C. Impact of cooking method on phenolic composition and antioxidant potential of four varieties of Phaseolus vulgaris L. and Glycine max L. LWT. 2019;103:238–46.
View Article
Google Scholar

[135] View Article

[136] Google Scholar

[ref44] 44. Kouassi LVS, N’gbo MLK, Sinh JN, Disseka WK, Faulet MBA. Effect of boiling times on polyphenol, flavonoid, tannin, vitamin C and β-carotene contents of African asparagus (Laccosperma secundiflorum). Int J Biochem Res Rev. 2021;30(10):35–44.
View Article
Google Scholar

[138] View Article

[139] Google Scholar

[ref45] 45. Kim HY, Ediriweera MK, Boo K-H, Kim CS, Cho SK. Effects of Cooking and Processing Methods on Phenolic Contents and Antioxidant and Anti-Proliferative Activities of Broccoli Florets. Antioxidants (Basel). 2021;10(5):641. pmid:33922092
View Article
PubMed/NCBI
Google Scholar

[141] View Article

[142] PubMed/NCBI

[143] Google Scholar

[ref46] 46. Boua Boua B, Ouattara DC, Traoré L, Mamyrbekova-Békro JA, Békro YA. Effect of domestic cooking on the total phenolic, flavonoid and condensed tannin content from plantain of Côte d’Ivoire. J Mater Environ Sci. 2020;11(3):396–403.
View Article
Google Scholar

[145] View Article

[146] Google Scholar

[ref47] 47. Managa MG, Shai J, Thi Phan AD, Sultanbawa Y, Sivakumar D. Impact of Household Cooking Techniques on African Nightshade and Chinese Cabbage on Phenolic Compounds, Antinutrients, in vitro Antioxidant, and β-Glucosidase Activity. Front Nutr. 2020;7:580550. pmid:33409289
View Article
PubMed/NCBI
Google Scholar

[148] View Article

[149] PubMed/NCBI

[150] Google Scholar

[ref48] 48. Issa JY, Onyango A, Makokha AO, Okoth J. Effect of Boiling and Wet Frying on Nutritional and Antinutrients Content of Traditional Vegetables Commonly Consumed in Malawi. JFR. 2019;9(1):19.
View Article
Google Scholar

[152] View Article

[153] Google Scholar

[ref49] 49. Maqbool N, Sofi SA, Makroo HA, Mir SA, Majid D, Dar BN. Cooking methods affect eating quality, bio-functional components, antinutritional compounds and sensory attributes of selected vegetables. Ital J Food Sci. 2021;33(SP1):150–62.
View Article
Google Scholar

[155] View Article

[156] Google Scholar

[ref50] 50. Tiveron AP, Melo PS, Bergamaschi KB, Vieira TMFS, Regitano-d’Arce MAB, Alencar SM. Antioxidant activity of Brazilian vegetables and its relation with phenolic composition. Int J Mol Sci. 2012;13(7):8943–57. pmid:22942744
View Article
PubMed/NCBI
Google Scholar

[158] View Article

[159] PubMed/NCBI

[160] Google Scholar

[ref51] 51. Hossain A, Khatun MA, Islam M, Huque R. Enhancement of Antioxidant Quality of Green Leafy Vegetables upon Different Cooking Method. Prev Nutr Food Sci. 2017;22(3):216–22. pmid:29043220
View Article
PubMed/NCBI
Google Scholar

[162] View Article

[163] PubMed/NCBI

[164] Google Scholar

[ref52] 52. İduğ T, Hizli Güldemi̇r H, Şen A, Güldemi̇r O. Investigation on the effects of cooking methods on anti-inflammatory and antioxidant activities of five mostly consumed vegetables in winter. International Journal of Agriculture Environment and Food Sciences. 2022;6(1):182–8.
View Article
Google Scholar

[166] View Article

[167] Google Scholar

[ref53] 53. Murador D, Braga AR, Da Cunha D, De Rosso V. Alterations in phenolic compound levels and antioxidant activity in response to cooking technique effects: A meta-analytic investigation. Crit Rev Food Sci Nutr. 2018;58(2):169–77. pmid:26858038
View Article
PubMed/NCBI
Google Scholar

[169] View Article

[170] PubMed/NCBI

[171] Google Scholar

[ref54] 54. Yalçın S, Kasnak C, Palamutoğlu R, Ünlü Ü. Antioxidant Activity and Phytochemical Profile of Eight Wild Edible Plants Grown in Afyonkarahisar, Türkiye. Akademik Gıda. 2025;23(1):12–9.
View Article
Google Scholar

[173] View Article

[174] Google Scholar

[ref55] 55. Jiménez-Monreal AM, García-Diz L, Martínez-Tomé M, Mariscal M, Murcia MA. Influence of cooking methods on antioxidant activity of vegetables. J Food Sci. 2009;74(3):H97–103. pmid:19397724
View Article
PubMed/NCBI
Google Scholar

[176] View Article

[177] PubMed/NCBI

[178] Google Scholar

[ref56] 56. Seal T, Pillai B, Chaudhuri K. Effect of cooking methods on total phenolics and antioxidant activity of selected wild edible plants. Int J Pharm Pharm Sci. 2023;15(7):20–6.
View Article
Google Scholar

[180] View Article

[181] Google Scholar

[ref57] 57. Kayahan S, Saloglu D. Comparison of Phenolic Compounds and Antioxidant Activities of Raw and Cooked Turkish Artichoke Cultivars. Front Sustain Food Syst. 2021;5.
View Article
Google Scholar

[183] View Article

[184] Google Scholar

[ref58] 58. Ozyurt D, Goc B, Demirata B, Apak R. Effect of Oven and Microwave Heating on the Total Antioxidant Capacity of Dietary Onions Grown in Turkey. International J Food Properties. 2013;16(3):536–48.
View Article
Google Scholar

[186] View Article

[187] Google Scholar

[ref59] 59. George J, Edwards D, Pun S, Williams D. Evaluation of Antioxidant Capacity (ABTS and CUPRAC) and Total Phenolic Content (Folin-Ciocalteu) Assays of Selected Fruit, Vegetables, and Spices. Int J Food Sci. 2022;2022:2581470. pmid:36506706
View Article
PubMed/NCBI
Google Scholar

[189] View Article

[190] PubMed/NCBI

[191] Google Scholar

[ref60] 60. Nhu-Trang T-T, Nguyen Q-D, Cong-Hau N, Anh-Dao L-T, Behra P. Characteristics and Relationships between Total Polyphenol and Flavonoid Contents, Antioxidant Capacities, and the Content of Caffeine, Gallic Acid, and Major Catechins in Wild/Ancient and Cultivated Teas in Vietnam. Molecules. 2023;28(8):3470. pmid:37110703
View Article
PubMed/NCBI
Google Scholar

[193] View Article

[194] PubMed/NCBI

[195] Google Scholar

Figures

Abstract

Introduction

Materials and methods

Chemicals

Instruments

Plant material and sample preparation

Cooking procedures

Dry matter determination

Preparation of extracts

Determination of total phenolic content

Determination of total flavonoid content

Determination of total phenolic acid content (Arnow Assay)

Determination of tannin-associated phenolic compounds

ABTS radical scavenging assay

DPPH radical scavenging assay

CUPRAC assay

Statistical analysis

Results and discussion

Dry matter content

Effects on total phenolic content

Effects on phenolic acids

Effects on total flavonoids

Effects on tannin-associated phenolic compounds

Changes in antioxidant capacities (DPPH, ABTS, CUPRAC)

Conclusion

Supporting information

S1 File. Calibration curves for all spectrophotometric assays and graphical summaries of cooking-induced changes in phenolic compounds and antioxidant capacities.

S2 File. Raw experimental data used for statistical analyses, including all replicate measurements for phenolic compounds and antioxidant capacity assays.

References