Bioactivity and structure-activity relationship of cinnamic acid esters and their derivatives as potential antifungal agents for plant protection

Kun Zhou; Dongdong Chen; Bin Li; Bingyu Zhang; Fang Miao; Le Zhou

doi:10.1371/journal.pone.0176189

Abstract

A series of cinnamic acid esters and their derivatives were synthesized and evaluated for antifungal activities in vitro against four plant pathogenic fungi by using the mycelium growth rate method. Structure−activity relationship was derived also. Almost all of the compounds showed some inhibition activity on each of the fungi at 0.5 mM. Eight compounds showed the higher average activity with average EC₅₀ values of 17.4–28.6 μg/mL for the fungi than kresoxim-methyl, a commercial fungicide standard, and ten compounds were much more active than commercial fungicide standards carbendazim against P. grisea or kresoxim-methyl against both P. grisea and Valsa mali. Compounds C1 and C2 showed the higher activity with average EC₅₀ values of 17.4 and 18.5 μg/mL and great potential for development of new plant antifungal agents. The structure−activity relationship analysis showed that both the substitution pattern of the phenyl ring and the alkyl group in the alcohol moiety significantly influences the activity. There exists complexly comprehensive effect between the substituents on the phenyl ring and the alkyl group in the alcohol moiety on the activity. Thus, cinnamic acid esters showed great potential the development of new antifungal agents for plant protection due to high activity, natural compounds or natural compound framework, simple structure, easy preparation, low-cost and environmentally friendly.

Citation: Zhou K, Chen D, Li B, Zhang B, Miao F, Zhou L (2017) Bioactivity and structure-activity relationship of cinnamic acid esters and their derivatives as potential antifungal agents for plant protection. PLoS ONE 12(4): e0176189. https://doi.org/10.1371/journal.pone.0176189

Editor: Beom Seok Kim, Korea University, REPUBLIC OF KOREA

Received: February 3, 2017; Accepted: April 6, 2017; Published: April 19, 2017

Copyright: © 2017 Zhou 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 paper and its Supporting Information files.

Funding: This work was financially supported by the National Natural Science Foundation of China (31172365, 31572038), http://www.nsfc.gov.cn/, Zhou, Geng. This study was also supported by the Agricultural Science and Technology Innovation Project of Shaanxi Province (2016NY-171). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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

Introduction

Plant mycosis is an important problem of agricultural production worldwide [1] and often results in severe yield losses and quality decrease of agricultural products. Furthermore, many of the fungi can harm animal and human health due to their mycotoxins [2]. Therefore, various fungicides have been extensively used to control fungal plant diseases in current agriculture. However, the prolonged usage of some antifungal agents can lead to drug resistance, environmental problems and residue toxicity [3]. Thus, it is necessary to develop environmentally friendly plant fungicides. In the past decades, researchers have already put attention to natural product-based or -derived plant protectants due to lower environmental and mammalian toxicity of natural products [4].

Cinnamic acid esters and their derivatives are widely distributed in plants including cereals, legumes, oilseeds, fruits, vegetables and tea or coffee beverages[5]. Due to the common occurrence in plants and the low toxicity for humans, animals and environment [6,7], cinnamic acid derivatives have attracted much attention of many pharmacologists. In the past decades, cinnamic acid derivatives including natural and non-natural compounds had been proved to possess diverse pharmacological actions such as antimicrobial [8–11], anti-Mycobactrium tuberculosis [12], anticancer [13], anti-inflammatory [14], anti-human immunodeficiency virus (HIV) [15], antiparasitic [16,17], inducing neural progenitor cell proliferation [18] and so on. Athough cinnamic acid itself and its derivative cinnaldehyde had been found to have inhibition activity against some plant pathogenic fungi [19–21], few reports have been found on systematic investigation on the activity of cinnamic acid esters against plant pathogenic fungi. The purpose of the present research is to explore the bioactivity of a series of cinnamic acid esters and their derivatives against phyto-pathogenic fungi and structure-activity relationship (SAR), and meanwhile discover new potent antifungal compounds.

This study involves three series of the target compounds: ethyl cinnamates with various substituents on the phenyl ring (A), cinnamic acid esters with various alkyl groups in the alcohol moiety (B) and t-butyl or t-amyl cinnamates with various substituents on the phenyl ring (C).

Materials and methods

Chemicals

Kresoxim-methyl (>99%) and carbendazim (>99%) were purchased from Aladdin Co. Ltd. (Shanghai, China). Dimethyl sulfoxide (DMSO) was purchased from J&K Chemical Ltd. (Beijing, China). Other reagents and solvents were obtained locally and of analytical grade or purified according to standard methods before use. The water used was redistilled and ion-free.

Fungi

Plant pathogenic fungi, Fusarium solani, Pyricularia grisea, Valsa mali and Botryosphaeria dothidea, were provided by the Center of Pesticide Research, Northwest A&F University, China. The fungi were grown on potato dextrose agar (PDA) plates at 25°C and maintained at 4°C with periodic subculturing.

Instruments

Melting points were determined on an XT-4 micro-melting point apparatus. Nuclear magnetic resonance spectra (NMR) were performed on an Avance III 500 MHz instrument (Bruker, Karlsruhe, Germany). Chemical shifts (δ values) and coupling constants (J values) are given in ppm and Hz, respectively. High resolution mass spectra (HR-MS) were carried out with a microTOF-QⅡ instrument (Bruker, Karlsruhe, Germany).

Synthesis

Compounds A1−A7, A16, A19, A23−A28, C1−C4, C11 and C12 were prepared by our previously reported methods (method A in Fig 1) [16]. The general procedure is as follows. In brief, the solution of triphenylphosphanylidene acetate (Ph₃P = CHCO₂R, R = ethyl, t-butyl or t-amyl) (12 mmol) and aromatic aldehyde (10 mmol) in 50 mL toluene was refluxed for 1–4 h. After removal of the solvent, the resulting residue was subjected to a silica gel column chromatography (ϕ 40 mm×L 40 cm) using petroleum ether–ethyl acetate as eluent to yield the desired compounds.

Download:

Fig 1.

Synthetic routes of compounds A, B and C. Reagents and conditions. (a) Ph₃P = CHCO₂R³, EtOH or toluene, reflux, 1−4 h; (b) acetic anhydride, Et₃N, r.t., 1 h; (c) SOCl₂, reflux, 2 h; (d) R′OH, DCM, 0°C, 1 h.

https://doi.org/10.1371/journal.pone.0176189.g001

Compounds A1−A7, A16, A19, A25−A28.

The NMR data of the compounds were consistent with those previously reported by us [16].

Compounds A23, C1 and C3.

Ethyl 2,4-dihydroxycinnamate (A23) [22], t-butyl 2-hydroxycinnamate (C1) [23] and t-butyl 4-hydroxycinnamate (C3) [24] were confirmed by comparison of NMR data with those in literature.

Ethyl 2,5-dihydroxycinnamate (A24).

Yield: 54% yield; a pale brown crystal; mp: 118–120°C; ¹H NMR (500 MHz, CD₃OD): δ 7.91 (1H, d, J = 16.0 Hz), 6.90 (1H, s), 6.69 (2H, s), 6.46 (1H, d, J = 16.0 Hz), 4.20 (2H, q, J = 7.2 Hz), 1.30 (3H, t, J = 7.2 Hz); ¹³C NMR (125 MHz, CD₃OD): δ 169.5, 151.5, 151.3, 141.9, 122.9, 120.2, 118.1, 117.9, 114.6, 61.5, 14.6; Negative ESI-MS m/z: 206.9 [M-H]^-.

t-Amyl 2-hydroxycinnamate (C2).

Yield: 60%; a yellow oil; ¹H NMR (500 MHz, CDCl₃): δ 7.99 (1H, d, J = 16.1 Hz), 7.45 (1H, dd, J = 7.6, 1.2 Hz), 7.30 (1H, s, OH), 7.22 (1H, 2×t, J = 7.9, 1.4 Hz), 6.90 (2H, q, J = 7.6 Hz), 6.59 (1H, d, J = 16.1 Hz), 1.90 (2H, q, J = 7.4 Hz), 1.52 (6H, s), 0.95 (3H, t, J = 7.4 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 167.9, 155.6, 139.7, 131.1, 129.0, 121.9, 120.4, 118.3, 116.3, 83.2, 33.6, 25.7, 8.2; HR-ESI-MS [M+Na]⁺ calcd for C₁₄H₁₈NaO₃⁺, 257.1148, found 257.1157.

t-Amyl 4-hydroxycinnamate (C4).

Yield: 64%; a yellow oil; ¹H NMR (500 MHz, CDCl₃): δ 7.54 (1H, d, J = 15.9 Hz), 7.39 (2H, d, J = 8.6 Hz), 6.85 (2H, d, J = 8.5 Hz), 6.60 (1H, s, OH), 6.24 (1H, d, J = 15.9 Hz), 1.88 (2H, q, J = 7.4 Hz), 1.50 (6H, s), 0.94 (3H, t, J = 7.4 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 167.2, 158.0, 143.6, 129.8, 127.0, 115.8, 114.9, 83.1, 33.5, 25.7, 8.2; HR-ESI-MS [M+Na]⁺ calcd for C₁₄H₁₈NaO₃⁺, 257.1148, found 257.1159.

t-Butyl 2-hydroxy-3-methoxycinnamate (C11).

Yield: 79%; a yellow powder; mp: 76–77°C; ¹H NMR (500 MHz, CDCl₃): δ 7.87 (1H, d, J = 16.1 Hz), 7.07 (1H, dd, J = 6.9, 2.3 Hz), 6.82–6.83 (2H, m), 6.53 (1H, d, J = 16.1 Hz), 6.18 (1H, s, OH), 3.89 (3H, s), 1.53 (9H, s); ¹³C NMR (125 MHz, CDCl₃): δ 166.8, 146.8, 145.1, 138.4, 121.1, 121.0, 120.8, 119.5, 111.4, 80.2, 56.1, 28.2; HR-ESI-MS [M+Na]⁺ calcd for C₁₄H₁₈NaO₄⁺, 273.1097, found 273.1132.

t-Amyl 2-hydroxy-3-methoxycinnamate (C12).

Yield: 63%; a white powder; mp: 76.2–77°C; ¹H NMR (500 MHz, CDCl₃): δ 7.87 (1H, d, J = 16.1 Hz), 7.08 (1H, dd, J = 7.1, 2.1 Hz), 6.82–6.85 (2H, m), 6.53 (1H, d, J = 16.1 Hz), 6.15 (1H, s, OH), 3.90 (3H, s), 1.88 (2H, q, J = 7.4 Hz), 1.50 (6H, s), 0.94 (3H, t, J = 7.4 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 166.7, 146.8, 145.1, 138.3, 121.16, 121.11, 120.8, 119.5, 111.4, 82.6, 56.1, 33.5, 25.7, 8.2; HR-ESI-MS [M+Na]⁺ calcd for C₁₅H₂₀NaO₄⁺, 287.1254, found 287.1254.

Compounds A11−A15, A17, A18, A20−A22, B1−B12, C7−C10 and C13−C20 were prepared according to method B in Fig 1 by reaction of the corresponding acyl chloride and the corresponding alcohol. The general procedure was as follows. The mixture of cinnamic acid or cinnamic acids with substituents on the phenyl ring (0.10 mol) and 30 mL thionyl chloride was refluxed at 75°C for 2 h. The excess thionyl chloride was removed under reduced pressure. After the residue was dissolved in 10 mL DCM, the corresponding alcohol (10 mmol) was added at 0°C. The solution was stirred at 0°C for 1 h, and then washed with water (3 × 30 mL) followed by 5% Na₂CO₃ aqueous solution, and dried over anhydrous sodium sulfate. After filtration, the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography (ϕ 40 mm × L 40 cm) to afford the desired product.

Compounds A11-A15, A17, A18, A20-A22, B1-B5, B7-B12, C7, C9, C13, C15, C17 and C19.

Compounds ethyl ethyl 2-fluorocinnamate (A11) [25], ethyl 3-fluorocinnamate (A12) [26], ethyl 4-fluorocinnamate (A13) [27], ethyl 2-chlorocinnamate (A14) [28], ethyl 3-chlorocinnamate (A15) [29], 2-bromocinnamate (A17) [25], ethyl 3-Bromocinnamate (A18) [30], ethyl 2-trifluoromethylcinnamate (A20) [25], ethyl 3-trifluoromethylcinnamate (A21) [26], ethyl 4-trifluoromethylcinnamate (A22) [27], methyl cinnamate (B1) [25], n-propyl cinnamate (B2) [31], n-butyl cinnamate (B3) [31], t-butyl cinnamate (B4) [32], n-amyl cinnamate (B5) [33], n-hexyl cinnamate (B7) [34], n-heptyl cinnamate (B8) [35], n-octyl cinnamate (B9) [36], cyclohexyl cinnamate (B10) [32], benzyl cinnamate (B11) [37], phenyl cinnamate (B12) [37], t-butyl 2-methoxycinnamate (C7) [38], t-butyl 4-methoxycinnamate (C9) [38], t-butyl 4-fluorocinnamate (C13) [39], t-butyl 4-bromocinnamate (C15) [39], t-butyl 4-trifluoromethylcinnamate (C17) [39] and t-butyl 3,4-methylenedioxy cinnamate (C19) [40] were confirmed by comparison of NMR data with those in literature.

t-Amyl cinnamate (B6).

Yield: 72%; a colorless oil; ¹H NMR (500 MHz, CDCl₃): δ 7.59 (1H, d, J = 16.0 Hz), 7.50–7.52 (2H, m), 7.36–7.37 (3H, m), 6.38 (1H, d, J = 16.0 Hz), 1.86 (2H, q, J = 7.5 Hz), 1.50 (6H, s), 0.93 (3H, t, J = 7.5 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 166.3, 143.5, 134.7, 130.0, 128.8, 128.0, 120.2, 83.0, 33.6, 25.7, 8.3.

t-Amyl 2-methoxycinnamate (C8).

Yield: 76%; a yellow oil; ¹H NMR (500 MHz, DMSO-d₆): δ 7.82 (1H, d, J = 16.1 Hz), 7.68 (1H, dd, J = 7.7, 1.3 Hz), 7.38–7.42 (1H, m), 7.09 (1H, d, J = 8.3 Hz), 6.99 (1H, t, J = 7.4 Hz), 6.51 (1H, d, J = 16.1 Hz), 3.86 (3H, s), 1.82 (2H, q, J = 7.5 Hz), 1.44 (6H, s), 0.89 (3H, t, J = 7.4 Hz); ¹³C NMR (125 MHz, DMSO-d₆): δ 166.2, 158.2, 138.7, 132.2, 128.9, 122.8, 121.1, 120.3, 112.1, 82.5, 56.1, 33.2, 25.8, 8.5; HR-ESI-MS [M+Na]⁺ calcd for C₁₅H₂₀NaO₃⁺, 271.1305; found 271.1312.

t-Amyl 4-methoxycinnamate (C10).

Yield: 87%; a yellow oil; ¹H NMR (500 MHz, CDCl₃): δ 7.54 (1H, d, J = 16.0 Hz), 7.45 (2H, dt, J = 8.8, 1.9 Hz), 6.88 (2H, d, J = 8.8 Hz), 6.25 (1H, d, J = 16.0 Hz), 3.82 (3H, s), 1.86 (2H, q, J = 7.5 Hz), 1.49 (6H, s), 0.93 (3H, t, J = 7.5 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 166.6, 161.4, 143.2, 129.6, 127.4, 117.7, 114.3, 82.7, 55.3, 33.6, 25.7, 8.3; HR-ESI-MS [M+Na]⁺ calcd for C₁₅H₂₀NaO₃⁺, 271.1305, found 271.1310. [M+K]⁺ calcd for C₁₅H₂₀KO₃⁺, 287.1044; found 287.1048.

t-Amyl 4-fluorocinnamate (C14).

Yield: 93%; yellow oil; ¹H NMR (500 MHz, DMSO-d₆): δ 7.77–7.78 (2H, m), 7.58 (1H, d, J = 16.0 Hz), 7.22–7.25 (2H, m), 6.51 (1H, d, J = 16.0 Hz), 1.83 (2H, q, J = 7.4 Hz), 1.45 (6H, s), 0.90 (3H, t, J = 7.4); ¹³C NMR (125 MHz, CDCl₃): δ 166.1, 163.7 (d, J = 250.6 Hz), 142.2, 130.9 (d, J = 3.5 Hz), 129.8 (d, J = 8.3), 120.0 (d, J = 2.2. Hz), 116.0 (d, J = 21.9 Hz), 83.1, 33.5, 25.7, 8.3; HR-ESI-MS [M+Na]⁺ calcd for C₁₄H₁₇FNaO₂⁺, 259.1105; found 259.1113.

t-Amyl 4-bromocinnamate (C16).

Yield: 95%; a yellow oil; ¹H NMR (500 MHz, DMSO-d₆): δ 7.59–7.66 (4H, m), 7.55 (1H, d, J = 16.0 Hz), 6.58 (1H, d, J = 16.0 Hz), 1.83 (2H, q, J = 7.5 Hz), 1.45 (6H, s), 0.90 (3H, t, J = 7.5 Hz); ¹³C NMR (125 MHz, DMSO-d₆): δ 165.7, 142.6, 133.9, 132.2, 130.5, 124.0, 121.1, 82.8, 33.2, 25.8, 8.5; HR-ESI-MS [M+Na]⁺ calcd for C₁₄H₁₇⁷⁹BrNaO₂⁺, 319.0304, found 319.0302, calcd for C₁₄H₁₇⁸¹BrNaO₂⁺, 321.0284; found 321.0280.

t-Amyl 4-trifluoromethylcinnamate (C18).

Yield: 92%; a yellow oil; ¹H NMR (500 MHz, DMSO-d₆): δ 7.93 (2H, d, J = 8.2 Hz), 7.76 (2H, d, J = 8.3 Hz), 7.65 (1H, d, J = 16.0 Hz), 6.70 (1H, d, J = 16.0 Hz), 1.86 (2H, q, J = 7.5 Hz), 1.46 (6H, s), 0.91 (3H, t, J = 7.5 Hz); ¹³C NMR (125 MHz, DMSO-d₆): δ 165.5, 142.1, 138.6, 130.3 (q, J = 31.9 Hz), 129.3, 126.1 (q, J = 3.6 Hz), 124.5 (q, J = 271.8 Hz), 123.2, 83.1, 33.2, 25.8, 8.5; HR-ESI-MS [M+Na]⁺ calcd for C₁₅H₁₇F₃NaO₂⁺, 309.1073; found 309.1068.

t-Amyl 3,4-methylenedioxy cinnamate (C20).

Yield: 85%; a white powder; mp: 47–48°C; ¹H NMR (500 MHz, CDCl₃): δ 7.49 (1H, d, J = 15.9 Hz), 7.01 (1H, d, J = 1.6 Hz), 6.97 (1H, dd, J = 8.0, 1.6 Hz), 6.79 (1H, d, J = 8.0 Hz), 6.20 (1H, d, J = 15.9 Hz), 5.99 (2H, s), 1.85 (2H, q, J = 7.5 Hz), 1.49 (6H, s), 0.92 (3H, t, J = 7.5 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 166.5, 149.3, 148.3, 143.2, 129.1, 124.1, 118.2, 108.5, 106.5, 101.5, 82.8, 33.5, 25.7, 8.3; HR-ESI-MS [M+Na]⁺ calcd for C₁₅H₁₈NaO₄⁺, 285.1097, found 285.1099; [M+K]⁺ calcd for C₁₅H₁₈KO₄⁺, 301.0837; found 301.0841.

Synthesis of compounds A8-A10, C5 and C6.

According to our previously reported method [16], compounds A8−A10, C5 and C6 were prepared by acetylation reaction of the corresponding phenols. Briefly, the solution of compounds A2, A3, A4, C1 or C2 (2.1 mmol) and acetic anhydride (0.6 g, 6.2 mmol) in 20 mL triethylamine was stirred for 1 h at room temperature to provide the desired compounds.

Compounds A8-A10 and C5.

The NMR and MS data of compounds A8-A10 [26] and C5 [41] were consistent with those in the literature.

t-Amyl 2-acetoxyl cinnamate (C6).

Yield: 98%; a yellow oil; ¹H NMR (500 MHz, CDCl₃): δ 7.67 (2H, m), 7.39 (1H, 2×t, J = 8.0, 1.6 Hz), 7.24 (1H, d, J = 7.7 Hz), 7.11 (1H, dd, J = 8.1, 0.9 Hz), 6.40 (1H, d, J = 16.0 Hz), 2.36 (3H, s), 1.86 (2H, q, J = 7.5 Hz), 1.49 (6H, s), 0.94 (3H, t, J = 7.4 Hz); ¹³C NMR (125 MHz, CDCl₃): δ 169.1, 165.9, 149.2, 136.6, 130.8, 127.4, 127.3, 126.3, 123.0, 122.1, 83.1, 33.6, 25.6, 20.9, 8.2; HR-ESI-MS [M+Na]⁺ calcd for C₁₆H₂₀NaO₄⁺, 299.1254; found 299.1260.

Antifungal assay

The mycelium linear growth rate method was used to screen the antifungal activities in vitro of compounds against four strains of plant pathogenic fungi [42]. Commercial fungicide standards kresoxim-methyl or carbendazim were used as positive controls.

Briefly, the solution of the test compound (50 μmol) in 0.5 mL of DMSO was added to 9.5 mL of sterile water. The resulting solution was added to 90 mL of melted PDA agar at 50°C and quickly and completely mixed to provide the mixture containing 0.5 mM of the compounds and 0.5% (v/v) DMSO. The mixture was poured into a sterilized Petri dish (ca. 15 mL each plate) in a laminar flow chamber. The culture medium containing only 0.5% DMSO was used as a blank without observable effect on the growth of the fungi. When the medium in the plate was partially solidified, a fungus disk (d = 5 mm) cut beforehand from subcultured Petri dishes was placed at the center of the medium. The dishes were kept in an incubator at 25°C for 72 h. Each experiment was carried out in triplicate. The diameters (in mm) of a fungal colony were measured in three different directions, and the growth inhibition rates were calculated according to the method reported previously [42].

The compounds with higher initial activities were further assayed for median effective concentrations (EC₅₀) according to the method described above. A set of stock solutions of test compounds in 5% DMSO aqueous solution was prepared by double-fold dilution method. Each stock solution (10 mL) was mixed with autoclaved liquid PDA medium (190 mL) to provide a series of mediums with various concentrations of the test compound. The culture medium containing only 0.5% DMSO was used as a blank control. Each test was performed in triplicate. The probit value of the average inhibition rate for each test concentration and the corresponding lg[concentration (μg/mL)] were used to establish antifungal toxicity regression equation by the linear least-square fitting method. The EC₅₀ value of each compound and its confidence intervals at 95% probability were calculated from the corresponding toxicity regression equation by using PRISM software ver. 5.0 (GraphPad Software Inc., San Diego, CA,USA) [42].

Duncan multiple comparison test was used to evaluate significant difference between the average inhibition rates or EC₅₀ values of various compounds by using PRISM software ver. 5.0 [42].

Results

Design of compounds

In order to know the effect of substitution patterns of the phenyl ring and the type of alkyl groups in the alcohol moiety on the activity, we firstly designed both A and B series of target compounds. A series consisting of 28 compounds is a class of ethyl cinnamate derivatives containing various substituents on the phenyl ring. B series including 12 compounds is a class of cinnamic acid esters formed by cinnamic acid and various alcohols or phenol. Next, under the guidance of SAR of compounds A and B, we further designed C series including 20 compounds by combination of preponderant active groups in order to further explore the comprehensive effect of the substituents on the phenyl ring and the alkyl groups in the alcohol moiety on the activity and find more potential compounds. Compounds C are a class of t-butyl or t-amyl cinnamates with various substituents on the phenyl ring (Fig 1).

Synthesis of compounds

Compounds A1–A7, A16, A19, A23–A28, C1-C4, C11 and C12 were prepared by Wittig reaction of triphenylphosphanylidene acetate [Ph₃P = CHCO₂R′] and aromatic aldehyde in ethanol or toluene. Compounds A2–A4, C1 and C2 were acetylated with acetic anhydride to afford compounds A8–A10, C5 and C6, respectively. Substituted cinnamoyl chlorides reacted with the corresponding alcohols to obtain compounds A11–A15, A17, A18, A20–22, B1–12, C7–C10 and C13–C20. The synthetic route of compounds A, B and C is outlined in Fig 1. The substitution patterns of the compounds are listed in Tables 1, 2 and 3.

Download:

Table 1. Substitution patterns of compounds A1-A28 and initial antifungal activity at 0.5 mM (72 h).

https://doi.org/10.1371/journal.pone.0176189.t001

Download:

Table 2. Substitution patterns of compounds B1−B12 and initial antifungal activity at 0.5 mM.

https://doi.org/10.1371/journal.pone.0176189.t002

Download:

Table 3. Substitution patterns of compounds C1−C20 and initial antifungal activity at 0.5 mM.

https://doi.org/10.1371/journal.pone.0176189.t003

The synthesized compounds include 11 new compounds and 49 known compounds. The known compounds were confirmed by comparison of NMR data and those reported in literature. The new compounds (C2, C4, C6, C8, C10–C12, C14, C16, C18, C20) were identified by ¹H NMR, ¹³C NMR and HRMS analysis. In positive or negative ESI-MS spectra, each of the compounds showed its corresponding pseudo-molecular ion peak [M+Na]⁺. In ¹H and ¹³C NMR spectra, all the compounds revealed two doublet signals in the ranges of 7.5 to 8.1 and δ_H 6.2 to 6.7 ppm due to the protons of the ethylene moiety and one signal in the range of δ_C 165 to 167 ppm due to C (= O). The coupling constant of ca. 16 Hz between the protons of the ethylene moiety showed E configuration of the compounds. The NMR data of the known compounds were agreement with the corresponding literature data.

Antifungal activity

According to the mycelium linear growth rate method [39], the synthesized compounds were screened for antifungal activity in vitro at 0.5 mM (ca.100 μg/mL) against four plant pathogenic fungi. Kresoxim-methyl and carbendazim, two commercial fungicide standards, were used as positive controls.

The results listed in Tables 1, 2 and 3 showed that all the compounds displayed some inhibition activity against each of the fungi at 0.5 mM (around 100 μg/mL). Among A and B series, compounds A2, A5, A8, A22, A25, B4 and B6 showed the higher activity with average inhibition rates of 73‒84% for four tested fungi, superior to kresoxim-methyl and carbendazim (70.2%, 72.4%). For A series, A2 showed the highest average activity (84.6%), followed by A25 and A5 (83.1%, 80.7%). Among B series, B6 gave the highest average activity (81.1%) followed by B4 (73.0%). For C series, all the compounds showed the average inhibition rates of >50% except for 18. Especially, C1-C6 exhibited the very high average inhibition rates of 85–91% for all the fungi, obviously superior to all compounds A, B, kresoxim-methyl or carbendazim.

In order to explore the antifungal potential in more detail and SAR, some of the compounds (A2, A4, A8, A25, C1−C6) with the higher initial activity were further determined for median effective concentrations (EC₅₀) against each of the fungi. The results are listed in Table 4. Seventy percent of all the test items (28/40) revealed good to excellent activity with EC₅₀ values of 9.9−30 μg/mL. Compounds A4, A25 and C2 showed the highest activity against F. solani with EC₅₀ values of 17.8−19.8 μg/mL (P<0.05). For P grisea, C1 and C2 showed the highest activity (EC₅₀ = 15.4, 17.0 μg/mL) (P<0.05), followed by A2 (EC₅₀ = 18.3 μg/mL). Compounds A25, C1 and C3 displayed the strongest activity against V mali (EC₅₀ = 18.4, 18.6, 21.1 μg/mL) (P<0.05). For B. dothidea, C1, C1 and C5 showed the highest activity with EC₅₀ values of 11.4, 9.9 and 13.7 μg/mL (P<0.05), followed by A2 with EC₅₀ values of 17.5 μg/mL. As far as the average EC₅₀ value of each compound for all the fungi was concerned, C1 had the highest activity (average EC₅₀ = 17.4 μg/mL), followed by C2 (average EC₅₀ = 18.5 μg/mL). It was worth noting that all the test compounds were much more active on P. grisea and V. mali than kresoxim-methyl (EC₅₀ = 58.7, 98.5 μg/mL) or on P. grisea than carbendazim (EC₅₀ > 100 μg/mL).

Download:

Table 4. EC₅₀ values of the compounds with higher initial activity against four strains of fungi.

https://doi.org/10.1371/journal.pone.0176189.t004

Discussion—Structure-activity relationship

Comparison of the activities and structures of the compounds in Tables 1 and 2 showed that both substitution patterns of the benzene ring and the type of alkyl groups in the alcohol moiety significantly influence the activity of cinnamic esters. For ethyl cinnamate derivatives (A series), in most cases, the introduction of substituents to the benzene ring leads to increase of the activity. For electron-donating groups like OH, OMe, and OAc, the order of the activity of various position isomers is o-substituted isomer > p-substituted isomer > m-substituted isomer, whereas for electron-withdrawing groups like halogen atoms and trifluoromethyl, p-substituted isomers generally have the highest activity. 2,4-Dihydroxy or 2,5-dihydroxy compounds (A23, A24) are less active than the corresponding single hydroxyl compounds (A23 vs A2 or A4; A24 vs A2 or A3). For 2-OH-substituted compound (A2), the presence of additional 3-OMe has little effect on the activity (A2 vs A25), whereas for 4-OH- or 4-OMe-substituted compounds, introduction of 3-OMe leads to significant decrease of the activity (A4 vs A26; A7 vs A27). Additionally, compared with 3,4-dimethoxy, 3,4-methylenedioxy can improve the activity (A27 vs A28).

For B series, the activity of the linear alkyl esters (A1, B1−B3, B5, B7−B9) showed an obvious trend of increase at first and then decrease with elongation of the linear alkyl chain in the alcohol moiety (Table 2). The n-butyl ester (B3) showed the highest activity with an average inhibition rates of 46.8% for all the fungi, followed by the n-propyl ester (B2, 39.4%), n-amyl ester (B5, 35.4%) and n-hexyl ester (B7, 35.8%). Compared with linear alkyl groups, the corresponding tertiary alkyl groups can significantly increase the activity (B3 vs B4; B5 vs B6), showing that the steric hindrance near the ester group is helpful to improvement of the activity. The same trend was also observed by comparison of the activity of B7 and B10. Replacement of the cyclohexyl with phenyl leads to decrease of the activity (B12 vs B10), whereas replacement of the linear alkyl with benzyl (B11) causes slight increase of the activity.

By comparison of the activity of compounds C in Table 3 and that of the corresponding compounds A in Table 1 or B in Table 2, it was found that there exists a complex comprehensive effect between the substituent on the phenyl ring and the alkyl group in the alcohol moiety on the activity. The combinations of “2-OH, 4-OH or 2-OAc + t-butyl or t-amyl” (C1-C6) are able to create significantly synergistic enhancement effect on the activity. On the contrary, the combinations of “2-OMe, 4-OMe, 2-OH-3-OMe, 4-F, 4-Br, 4-CF₃ or 3,4-OCH₂O + t-butyl or t-amyl” (C7-C20) generally decrease the activity, compared with t-butyl or t-amyl cinnamates (B4, B6), or the corresponding substituted cinnamic acid ethyl esters (A5, A7, A13, A19, A22, A25, A28).

From the EC₅₀ values in Table 4, it was further found that the comprehensive effect between the substituent on the phenyl ring and the alkyl group in the alcohol moiety on the activity varies with the species of the test fungi. The combinations of both “2-OH + t-butyl” (C1) and “2-OH + t-amyl” (C2) can significantly improve the activity against each of the fungi, relative to “2-OH + ethyl” (A2). By contrast, the combinations of “4-OH or 2-OAc + t-butyl or t-amyl” (C1−C6) can increase the activity on P grisea, V mali and B. dothidea, but decrease the activity on F. solani (C3, C4 vs A4; C5, C6 vs A8).

Although the activity of the compounds against some of the fungi is inferior to carbendazim, this class of compounds showed some attractive advantages, such as natural compounds or natural compound framework, simple structure, easy synthesis, low-cost as well as environmentally friendly [6,7]. Therefore, cinnamic acid esters possess great potential as new antifungal agents or promising lead compounds for development of new environmentally friendly plant fungicides. The results of this study can provide direction for the further optimal design of the structure. Furthermore, it is necessary to determine the in vivo activity and action mechanism of these compounds.

Supporting information

S1 File. ¹H NMR, ¹³C NMR, LRMS and HRMS data and spectra of the compounds and their toxicity regression equations against four fungi.

https://doi.org/10.1371/journal.pone.0176189.s001

(PDF)

Acknowledgments

We sincerely thank Hongli Zhang (Northwest A&F University) for the NMR determination of the compounds and Professor Zhenghui guan (Northwest University, China) the HRMS determination of NMR.

Author Contributions

Conceptualization: LZ FM.
Data curation: KZ DDC.
Formal analysis: BL.
Funding acquisition: LZ.
Investigation: KZ DDC BL BYZ FM.
Methodology: LZ FM.
Project administration: LZ FM.
Resources: LZ.
Supervision: LZ FM.
Validation: LZ KZ.
Visualization: LZ KZ.
Writing – original draft: LZ KZ FM.
Writing – review & editing: LZ KZ.

References

1. Savary S, Teng PS. Willocquet L, Nutter FW Jr. Quantification and modeling of crop losses: a review of purposes. Annu Rev Phytopathol. 2006; 44: 89–112. pmid:16480337
- View Article
- PubMed/NCBI
- Google Scholar
2. Bräse S, Encinas A, Keck J, Nising CF. Chemistry and biology of mycotoxins and related fungal metabolites. Chem Rev. 2009; 109: 3903–3990. pmid:19534495
- View Article
- PubMed/NCBI
- Google Scholar
3. Delp CJ. Coping with resistance to plant disease. Plant Dis. 1980; 64: 652–657.
- View Article
- Google Scholar
4. Wedge DE, Camper ND. Biologically active natural products in agrochemicals and pharmaceuticals. Cutler HG, Cutler SJ, editors. CRC Press: Boca Raton, FL, USA; 2000. Pp. 1−15.
5. Clifford NM. Chlorogenic acids and other cinnamates—nature, occurrence, dietary burden, absorption and metabolism. J Sci Food Agric. 2000; 80: 1033–1043.
- View Article
- Google Scholar
6. Lafay S, Gil-Izquierdo A. Bioavailability of phenolic acids. Phytochem Rev. 2008; 7: 301–311.
- View Article
- Google Scholar
7. Hoskins JA. The occurrence, metabolism and toxicity of cinnamic acid and related compounds. J Appl Toxicol. 1984; 4: 283–292. pmid:6394637
- View Article
- PubMed/NCBI
- Google Scholar
8. De Vita D, Friggeri L, D'Auria F D, Pandolfi F, Piccoli F, Panella S, et al. Activity of caffeic acid derivatives against Candida albicans biofilm. Bioorg Med Chem Lett. 2014; 24: 1502–1505. pmid:24582984
- View Article
- PubMed/NCBI
- Google Scholar
9. Fu J, Cheng K, Zhang Z, Fang R, Zhu H. Synthesis, structure and structure-activity relationship analysis of caffeic acid amides as potential antimicrobials. Eur J Med Chem. 2010; 45: 2638–2643. pmid:20181415
- View Article
- PubMed/NCBI
- Google Scholar
10. Sova M. Antioxidant and antimicrobial activities of cinnamic acid derivatives. Mini Rev Med Chem. 2012; 12: 749–767. pmid:22512578
- View Article
- PubMed/NCBI
- Google Scholar
11. Fabricio B, Laura M, Cecilia S, Francisco G, Fernando G, Marcela K-S, et al. Structure-antifungal activity relationship of cinnamic acid derivatives. J Agric Food Chem. 2007; 55: 10635–10640. pmid:18038998
- View Article
- PubMed/NCBI
- Google Scholar
12. Guzman JD, Mortazavi PN, Munshi T, Evangelopoulos D, McHugh TD, Gibbons S, et al. 2-Hydroxy-substituted cinnamic acids and acetanilides are selective growth inhibitors of Mycobacterium tuberculosis. MedChemComm. 2014; 5: 47–50.
- View Article
- Google Scholar
13. De P, Baltas M, Bedos-Belval F. Cinnamic acid derivatives as anticancer agents-a review. Curr Med Chem. 2011; 18: 1672–1703. pmid:21434850
- View Article
- PubMed/NCBI
- Google Scholar
14. Debnath B, Samanta S, Roy K, Jha T. QSAR study on some p-arylthio cinnamides as antagonists of biochemical ICAM-1/LFA-1 interaction and ICAM-1/JY-8 cell adhesion in relation to anti-inflammatory activity. Bioorg Med Chem. 2003; 11: 1615–1619. pmid:12659746
- View Article
- PubMed/NCBI
- Google Scholar
15. Lee SU, Shin CG, Lee CK, Lee YS. Caffeoylglycolic and caffeoylamino acid derivatives, halfmers of L-chicoric acid, as new HIV-1 integrase inhibitors. Eur J Med Chem. 2007; 42: 1309–1315. pmid:17434650
- View Article
- PubMed/NCBI
- Google Scholar
16. Zhang B-Y, Lv C, Li WB, Cui Z-M, Chen D-D, Cao F-J, et al. Ethyl cinnamate derivatives as promising high-efficient acaricides against Psoroptes cuniculi: synthesis, bioactivity and structure-activity relationship, Chem Pharm Bull. 2015; 63: 255–262. pmid:25739666
- View Article
- PubMed/NCBI
- Google Scholar
17. Otero E, Robledo SM, Díaz S, Carda M, Muñoz D, Paños J, et al. Synthesis and leishmanicidal activity of cinnamic acid esters: structure-activity relationship. Med Chem Res. 2014; 23: 1378–1386.
- View Article
- Google Scholar
18. Yabe T, Hirahara H, Harada N, Ito N, Nagai T, Sanagi T, et al. Ferulic acid induces neural progenitor cell proliferation in vitro and in vivo. Neuroscience. 2010; 165: 515–524. pmid:19837139
- View Article
- PubMed/NCBI
- Google Scholar
19. Hazir S, Shapiro-Ilan D I, Bock C H, Hazir C, Leite L G, Hotchkiss M W. Relative potency of culture supernatants of Xenorhabdus and Photorhabdus spp. on growth of some fungal phytopathogens. Eur J Plant Pathol. 2016; 146: 369–381.
- View Article
- Google Scholar
20. Lu M, Han Z, Yao L. In vitro and in vivo antimicrobial efficacy of essential oils and individual compounds against Phytophthora parasitica var. nicotianae. J. Applied Microbiol. 2013; 115: 187–198.
- View Article
- Google Scholar
21. Bock H C, Shapiro-Ilan D I, Wedge D E, Cantrell C L. Identification of the antifungal compound, trans-cinnamic acid, produced by Photorhabdus luminescens, a potential biopesticide against pecan scab. J. Pest Sci. 2014; 87: 155–162;
- View Article
- Google Scholar
22. Gagey N, Neveu P, Benbrahim C, Goetz B, Aujard I, Baudin J-B, et al. Two-photon uncaging with fluorescence reporting: evaluation of the o-hydroxycinnamic platform. J Am Chem Soc. 2007; 129: 9986–9998. pmid:17658803
- View Article
- PubMed/NCBI
- Google Scholar
23. Frimer AA, Aljadeff G, Gilinsky-Sharon P. Reaction of coumarins with superoxide anion radical (O2-.): facile entry to o-coumarinic acid systems. Israel J Chem. 1986; 27: 39–44.
- View Article
- Google Scholar
24. Ouimet MA, Stebbins ND, Uhrich KE. Biodegradable coumaric acid-based poly(anhydride-ester) synthesis and subsequent controlled release. Macromol Rapid Commun. 2013; 34: 1231–1236. pmid:23836606
- View Article
- PubMed/NCBI
- Google Scholar
25. Chatterjee AK, Choi T-L., Sanders DP, Grubbs RH. A general model for selectivity in olefin cross metathesis. J Am Chem Soc. 2003; 125: 11360–11370. pmid:16220959
- View Article
- PubMed/NCBI
- Google Scholar
26. Fan X, Zhang H-S, Chen L, Long Y-Q. Efficient synthesis and identification of novel propane-1,3-diamino bridged CCR5 antagonists with variation on the basic center carrier. Eur J Med Chem. 2010; 45: 2827–2840. pmid:20347189
- View Article
- PubMed/NCBI
- Google Scholar
27. Cao P, Li C-Y, Kang Y-B, Xie Z, Sun X-L, Tang Y. Ph₃As-catalyzed Wittig-type olefination of aldehydes with diazoacetate in the presence of Na₂S₂O₄. J Org Chem. 2007; 72: 6628–6630. pmid:17655362
- View Article
- PubMed/NCBI
- Google Scholar
28. Huang Z-Z, Tang Y. Unexpected catalyst for Wittig-type and dehalogenation reactions. J Org Chem. 2002; 67: 5320–5326. pmid:12126422
- View Article
- PubMed/NCBI
- Google Scholar
29. Penafiel I, Pastor IM, Yus M. Heck-matsuda reactions catalyzed by a hydroxyalkyl-functionalized NHC and palladium acetate. Eur J Org Chem. 2012; 43: 3151–3156.
- View Article
- Google Scholar
30. Fontan N, Garcia-Dominguez P, Alvarez R, de Lera AR. Novel symmetrical ureas as modulators of protein arginine methyl transferases. Bioorg Med Chem. 2013; 21: 2056–2067. pmid:23395110
- View Article
- PubMed/NCBI
- Google Scholar
31. Yang W, Chen H, Li J, Li C, Wu W, Jiang H. Palladium-catalyzed aerobic oxidative double allylic C-H oxygenation of alkenes: a novel and straightforward route to α,β-unsaturated esters. Chem Comm. (Cambridge, United Kingdom) 2015; 51: 9575–9578.
- View Article
- Google Scholar
32. Tyagi V, Fasan R. Myoglobin-catalyzed olefination of aldehydes. Angew Chem Int Ed. 2016; 55: 2512–2516.
- View Article
- Google Scholar
33. Liu J, Shao C, Zhang Y, Shi G, Pan S. Copper-catalyzed highly efficient ester formation from carboxylic acids/esters and formates. Org Biomol Chem. 2014; 12: 2637–2640. pmid:24668215
- View Article
- PubMed/NCBI
- Google Scholar
34. Zhan S, Tao X, Cai L, Liu X, Liu T. The carbon material functionalized with NH2+ and SO₃H groups catalyzed esterification with high activity and selectivity. Green Chem. 2014; 16: 4649–4653.
- View Article
- Google Scholar
35. Xin Y-C, Shi S-H, Xie D-D, Hui X-P, Xu P-F. N-heterocyclic carbene-catalyzed oxidative esterification reaction of aldehydes with alkyl halides under aerobic conditions. Eur J Org Chem. 2011; 2011: 6527–6531.
- View Article
- Google Scholar
36. Sinha AK, Sharma A, Swaroop A, Kumar V. Single step green process for the preparation of substituted cinnamic esters with trans-selectivity. U.S. Pat. Appl. Publ. US 20080045742 A1 20080221, 2008.
37. Sova M, Perdih A, Kotnik M, Kristan K, Rizner T L, Solmajer T, et al. Flavonoids and cinnamic acid esters as inhibitors of fungal 17β-hydroxysteroid dehydrogenase: A synthesis, QSAR and modelling study. 2006; 14: 7404–7418. pmid:16891119
- View Article
- PubMed/NCBI
- Google Scholar
38. Davies SG, Mulvaney AW, Russell AJ, Smith AD. Synthesis of homochiral β-amino acids. Tetrahedron: Asymmetry. 2007; 18: 1554–1566.
- View Article
- Google Scholar
39. Zhu M-K, Zhao J-F, Loh T-P. Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage. Org. Lett. 2011; 13: 6308–6311. pmid:22054076
- View Article
- PubMed/NCBI
- Google Scholar
40. El-Batta A, Jiang C, Zhao W, Anness R, Cooksy AL, Bergdahl M. Wittig reactions in water media employing stabilized ylides with aldehydes. Synthesis of α,β-unsaturated esters from mixing aldehydes, α-bromoesters, and Ph₃P in aqueous NaHCO3. J Org Chem. 2007; 72: 5244–5259. pmid:17559278
- View Article
- PubMed/NCBI
- Google Scholar
41. Wong CTT, Lam HY, Song T, Chen G, Li X. Synthesis of constrained head-to-tail cyclic tetrapeptides by an imine-induced ring-closing/contraction strategy. Angew Chem Int Ed. 2013; 52: 10212–10215.
- View Article
- Google Scholar
42. Hou Z, Zhu L-F, Yu X-C, Sun M-Q, Miao F, Zhou L. Design, synthesis, and structure-activity relationship of new 2-aryl-3,4-dihydro-β-carbolin-2-ium salts as antifungal agents, J Agric Food Chem. 2016; 64: 2847–2854. pmid:27004437
- View Article
- PubMed/NCBI
- Google Scholar

[ref1] 1. Savary S, Teng PS. Willocquet L, Nutter FW Jr. Quantification and modeling of crop losses: a review of purposes. Annu Rev Phytopathol. 2006; 44: 89–112. pmid:16480337
View Article
PubMed/NCBI
Google Scholar

[2] View Article

[3] PubMed/NCBI

[4] Google Scholar

[ref2] 2. Bräse S, Encinas A, Keck J, Nising CF. Chemistry and biology of mycotoxins and related fungal metabolites. Chem Rev. 2009; 109: 3903–3990. pmid:19534495
View Article
PubMed/NCBI
Google Scholar

[6] View Article

[7] PubMed/NCBI

[8] Google Scholar

[ref3] 3. Delp CJ. Coping with resistance to plant disease. Plant Dis. 1980; 64: 652–657.
View Article
Google Scholar

[10] View Article

[11] Google Scholar

[ref4] 4. Wedge DE, Camper ND. Biologically active natural products in agrochemicals and pharmaceuticals. Cutler HG, Cutler SJ, editors. CRC Press: Boca Raton, FL, USA; 2000. Pp. 1−15.

[ref5] 5. Clifford NM. Chlorogenic acids and other cinnamates—nature, occurrence, dietary burden, absorption and metabolism. J Sci Food Agric. 2000; 80: 1033–1043.
View Article
Google Scholar

[14] View Article

[15] Google Scholar

[ref6] 6. Lafay S, Gil-Izquierdo A. Bioavailability of phenolic acids. Phytochem Rev. 2008; 7: 301–311.
View Article
Google Scholar

[17] View Article

[18] Google Scholar

[ref7] 7. Hoskins JA. The occurrence, metabolism and toxicity of cinnamic acid and related compounds. J Appl Toxicol. 1984; 4: 283–292. pmid:6394637
View Article
PubMed/NCBI
Google Scholar

[20] View Article

[21] PubMed/NCBI

[22] Google Scholar

[ref8] 8. De Vita D, Friggeri L, D'Auria F D, Pandolfi F, Piccoli F, Panella S, et al. Activity of caffeic acid derivatives against Candida albicans biofilm. Bioorg Med Chem Lett. 2014; 24: 1502–1505. pmid:24582984
View Article
PubMed/NCBI
Google Scholar

[24] View Article

[25] PubMed/NCBI

[26] Google Scholar

[ref9] 9. Fu J, Cheng K, Zhang Z, Fang R, Zhu H. Synthesis, structure and structure-activity relationship analysis of caffeic acid amides as potential antimicrobials. Eur J Med Chem. 2010; 45: 2638–2643. pmid:20181415
View Article
PubMed/NCBI
Google Scholar

[28] View Article

[29] PubMed/NCBI

[30] Google Scholar

[ref10] 10. Sova M. Antioxidant and antimicrobial activities of cinnamic acid derivatives. Mini Rev Med Chem. 2012; 12: 749–767. pmid:22512578
View Article
PubMed/NCBI
Google Scholar

[32] View Article

[33] PubMed/NCBI

[34] Google Scholar

[ref11] 11. Fabricio B, Laura M, Cecilia S, Francisco G, Fernando G, Marcela K-S, et al. Structure-antifungal activity relationship of cinnamic acid derivatives. J Agric Food Chem. 2007; 55: 10635–10640. pmid:18038998
View Article
PubMed/NCBI
Google Scholar

[36] View Article

[37] PubMed/NCBI

[38] Google Scholar

[ref12] 12. Guzman JD, Mortazavi PN, Munshi T, Evangelopoulos D, McHugh TD, Gibbons S, et al. 2-Hydroxy-substituted cinnamic acids and acetanilides are selective growth inhibitors of Mycobacterium tuberculosis. MedChemComm. 2014; 5: 47–50.
View Article
Google Scholar

[40] View Article

[41] Google Scholar

[ref13] 13. De P, Baltas M, Bedos-Belval F. Cinnamic acid derivatives as anticancer agents-a review. Curr Med Chem. 2011; 18: 1672–1703. pmid:21434850
View Article
PubMed/NCBI
Google Scholar

[43] View Article

[44] PubMed/NCBI

[45] Google Scholar

[ref14] 14. Debnath B, Samanta S, Roy K, Jha T. QSAR study on some p-arylthio cinnamides as antagonists of biochemical ICAM-1/LFA-1 interaction and ICAM-1/JY-8 cell adhesion in relation to anti-inflammatory activity. Bioorg Med Chem. 2003; 11: 1615–1619. pmid:12659746
View Article
PubMed/NCBI
Google Scholar

[47] View Article

[48] PubMed/NCBI

[49] Google Scholar

[ref15] 15. Lee SU, Shin CG, Lee CK, Lee YS. Caffeoylglycolic and caffeoylamino acid derivatives, halfmers of L-chicoric acid, as new HIV-1 integrase inhibitors. Eur J Med Chem. 2007; 42: 1309–1315. pmid:17434650
View Article
PubMed/NCBI
Google Scholar

[51] View Article

[52] PubMed/NCBI

[53] Google Scholar

[ref16] 16. Zhang B-Y, Lv C, Li WB, Cui Z-M, Chen D-D, Cao F-J, et al. Ethyl cinnamate derivatives as promising high-efficient acaricides against Psoroptes cuniculi: synthesis, bioactivity and structure-activity relationship, Chem Pharm Bull. 2015; 63: 255–262. pmid:25739666
View Article
PubMed/NCBI
Google Scholar

[55] View Article

[56] PubMed/NCBI

[57] Google Scholar

[ref17] 17. Otero E, Robledo SM, Díaz S, Carda M, Muñoz D, Paños J, et al. Synthesis and leishmanicidal activity of cinnamic acid esters: structure-activity relationship. Med Chem Res. 2014; 23: 1378–1386.
View Article
Google Scholar

[59] View Article

[60] Google Scholar

[ref18] 18. Yabe T, Hirahara H, Harada N, Ito N, Nagai T, Sanagi T, et al. Ferulic acid induces neural progenitor cell proliferation in vitro and in vivo. Neuroscience. 2010; 165: 515–524. pmid:19837139
View Article
PubMed/NCBI
Google Scholar

[62] View Article

[63] PubMed/NCBI

[64] Google Scholar

[ref19] 19. Hazir S, Shapiro-Ilan D I, Bock C H, Hazir C, Leite L G, Hotchkiss M W. Relative potency of culture supernatants of Xenorhabdus and Photorhabdus spp. on growth of some fungal phytopathogens. Eur J Plant Pathol. 2016; 146: 369–381.
View Article
Google Scholar

[66] View Article

[67] Google Scholar

[ref20] 20. Lu M, Han Z, Yao L. In vitro and in vivo antimicrobial efficacy of essential oils and individual compounds against Phytophthora parasitica var. nicotianae. J. Applied Microbiol. 2013; 115: 187–198.
View Article
Google Scholar

[69] View Article

[70] Google Scholar

[ref21] 21. Bock H C, Shapiro-Ilan D I, Wedge D E, Cantrell C L. Identification of the antifungal compound, trans-cinnamic acid, produced by Photorhabdus luminescens, a potential biopesticide against pecan scab. J. Pest Sci. 2014; 87: 155–162;
View Article
Google Scholar

[72] View Article

[73] Google Scholar

[ref22] 22. Gagey N, Neveu P, Benbrahim C, Goetz B, Aujard I, Baudin J-B, et al. Two-photon uncaging with fluorescence reporting: evaluation of the o-hydroxycinnamic platform. J Am Chem Soc. 2007; 129: 9986–9998. pmid:17658803
View Article
PubMed/NCBI
Google Scholar

[75] View Article

[76] PubMed/NCBI

[77] Google Scholar

[ref23] 23. Frimer AA, Aljadeff G, Gilinsky-Sharon P. Reaction of coumarins with superoxide anion radical (O2-.): facile entry to o-coumarinic acid systems. Israel J Chem. 1986; 27: 39–44.
View Article
Google Scholar

[79] View Article

[80] Google Scholar

[ref24] 24. Ouimet MA, Stebbins ND, Uhrich KE. Biodegradable coumaric acid-based poly(anhydride-ester) synthesis and subsequent controlled release. Macromol Rapid Commun. 2013; 34: 1231–1236. pmid:23836606
View Article
PubMed/NCBI
Google Scholar

[82] View Article

[83] PubMed/NCBI

[84] Google Scholar

[ref25] 25. Chatterjee AK, Choi T-L., Sanders DP, Grubbs RH. A general model for selectivity in olefin cross metathesis. J Am Chem Soc. 2003; 125: 11360–11370. pmid:16220959
View Article
PubMed/NCBI
Google Scholar

[86] View Article

[87] PubMed/NCBI

[88] Google Scholar

[ref26] 26. Fan X, Zhang H-S, Chen L, Long Y-Q. Efficient synthesis and identification of novel propane-1,3-diamino bridged CCR5 antagonists with variation on the basic center carrier. Eur J Med Chem. 2010; 45: 2827–2840. pmid:20347189
View Article
PubMed/NCBI
Google Scholar

[90] View Article

[91] PubMed/NCBI

[92] Google Scholar

[ref27] 27. Cao P, Li C-Y, Kang Y-B, Xie Z, Sun X-L, Tang Y. Ph₃As-catalyzed Wittig-type olefination of aldehydes with diazoacetate in the presence of Na₂S₂O₄. J Org Chem. 2007; 72: 6628–6630. pmid:17655362
View Article
PubMed/NCBI
Google Scholar

[94] View Article

[95] PubMed/NCBI

[96] Google Scholar

[ref28] 28. Huang Z-Z, Tang Y. Unexpected catalyst for Wittig-type and dehalogenation reactions. J Org Chem. 2002; 67: 5320–5326. pmid:12126422
View Article
PubMed/NCBI
Google Scholar

[98] View Article

[99] PubMed/NCBI

[100] Google Scholar

[ref29] 29. Penafiel I, Pastor IM, Yus M. Heck-matsuda reactions catalyzed by a hydroxyalkyl-functionalized NHC and palladium acetate. Eur J Org Chem. 2012; 43: 3151–3156.
View Article
Google Scholar

[102] View Article

[103] Google Scholar

[ref30] 30. Fontan N, Garcia-Dominguez P, Alvarez R, de Lera AR. Novel symmetrical ureas as modulators of protein arginine methyl transferases. Bioorg Med Chem. 2013; 21: 2056–2067. pmid:23395110
View Article
PubMed/NCBI
Google Scholar

[105] View Article

[106] PubMed/NCBI

[107] Google Scholar

[ref31] 31. Yang W, Chen H, Li J, Li C, Wu W, Jiang H. Palladium-catalyzed aerobic oxidative double allylic C-H oxygenation of alkenes: a novel and straightforward route to α,β-unsaturated esters. Chem Comm. (Cambridge, United Kingdom) 2015; 51: 9575–9578.
View Article
Google Scholar

[109] View Article

[110] Google Scholar

[ref32] 32. Tyagi V, Fasan R. Myoglobin-catalyzed olefination of aldehydes. Angew Chem Int Ed. 2016; 55: 2512–2516.
View Article
Google Scholar

[112] View Article

[113] Google Scholar

[ref33] 33. Liu J, Shao C, Zhang Y, Shi G, Pan S. Copper-catalyzed highly efficient ester formation from carboxylic acids/esters and formates. Org Biomol Chem. 2014; 12: 2637–2640. pmid:24668215
View Article
PubMed/NCBI
Google Scholar

[115] View Article

[116] PubMed/NCBI

[117] Google Scholar

[ref34] 34. Zhan S, Tao X, Cai L, Liu X, Liu T. The carbon material functionalized with NH2+ and SO₃H groups catalyzed esterification with high activity and selectivity. Green Chem. 2014; 16: 4649–4653.
View Article
Google Scholar

[119] View Article

[120] Google Scholar

[ref35] 35. Xin Y-C, Shi S-H, Xie D-D, Hui X-P, Xu P-F. N-heterocyclic carbene-catalyzed oxidative esterification reaction of aldehydes with alkyl halides under aerobic conditions. Eur J Org Chem. 2011; 2011: 6527–6531.
View Article
Google Scholar

[122] View Article

[123] Google Scholar

[ref36] 36. Sinha AK, Sharma A, Swaroop A, Kumar V. Single step green process for the preparation of substituted cinnamic esters with trans-selectivity. U.S. Pat. Appl. Publ. US 20080045742 A1 20080221, 2008.

[ref37] 37. Sova M, Perdih A, Kotnik M, Kristan K, Rizner T L, Solmajer T, et al. Flavonoids and cinnamic acid esters as inhibitors of fungal 17β-hydroxysteroid dehydrogenase: A synthesis, QSAR and modelling study. 2006; 14: 7404–7418. pmid:16891119
View Article
PubMed/NCBI
Google Scholar

[126] View Article

[127] PubMed/NCBI

[128] Google Scholar

[ref38] 38. Davies SG, Mulvaney AW, Russell AJ, Smith AD. Synthesis of homochiral β-amino acids. Tetrahedron: Asymmetry. 2007; 18: 1554–1566.
View Article
Google Scholar

[130] View Article

[131] Google Scholar

[ref39] 39. Zhu M-K, Zhao J-F, Loh T-P. Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage. Org. Lett. 2011; 13: 6308–6311. pmid:22054076
View Article
PubMed/NCBI
Google Scholar

[133] View Article

[134] PubMed/NCBI

[135] Google Scholar

[ref40] 40. El-Batta A, Jiang C, Zhao W, Anness R, Cooksy AL, Bergdahl M. Wittig reactions in water media employing stabilized ylides with aldehydes. Synthesis of α,β-unsaturated esters from mixing aldehydes, α-bromoesters, and Ph₃P in aqueous NaHCO3. J Org Chem. 2007; 72: 5244–5259. pmid:17559278
View Article
PubMed/NCBI
Google Scholar

[137] View Article

[138] PubMed/NCBI

[139] Google Scholar

[ref41] 41. Wong CTT, Lam HY, Song T, Chen G, Li X. Synthesis of constrained head-to-tail cyclic tetrapeptides by an imine-induced ring-closing/contraction strategy. Angew Chem Int Ed. 2013; 52: 10212–10215.
View Article
Google Scholar

[141] View Article

[142] Google Scholar

[ref42] 42. Hou Z, Zhu L-F, Yu X-C, Sun M-Q, Miao F, Zhou L. Design, synthesis, and structure-activity relationship of new 2-aryl-3,4-dihydro-β-carbolin-2-ium salts as antifungal agents, J Agric Food Chem. 2016; 64: 2847–2854. pmid:27004437
View Article
PubMed/NCBI
Google Scholar

[144] View Article

[145] PubMed/NCBI

[146] Google Scholar

Figures

Abstract

Introduction

Materials and methods

Chemicals

Fungi

Instruments

Synthesis

Compounds A1−A7, A16, A19, A25−A28.

Compounds A23, C1 and C3.

Ethyl 2,5-dihydroxycinnamate (A24).

t-Amyl 2-hydroxycinnamate (C2).

t-Amyl 4-hydroxycinnamate (C4).

t-Butyl 2-hydroxy-3-methoxycinnamate (C11).

t-Amyl 2-hydroxy-3-methoxycinnamate (C12).

Compounds A11-A15, A17, A18, A20-A22, B1-B5, B7-B12, C7, C9, C13, C15, C17 and C19.

t-Amyl cinnamate (B6).

t-Amyl 2-methoxycinnamate (C8).

t-Amyl 4-methoxycinnamate (C10).

t-Amyl 4-fluorocinnamate (C14).

t-Amyl 4-bromocinnamate (C16).

t-Amyl 4-trifluoromethylcinnamate (C18).

t-Amyl 3,4-methylenedioxy cinnamate (C20).

Synthesis of compounds A8-A10, C5 and C6.

Compounds A8-A10 and C5.

t-Amyl 2-acetoxyl cinnamate (C6).

Antifungal assay

Results

Design of compounds

Synthesis of compounds

Antifungal activity

Discussion—Structure-activity relationship

Supporting information

S1 File. 1H NMR, 13C NMR, LRMS and HRMS data and spectra of the compounds and their toxicity regression equations against four fungi.

Acknowledgments

Author Contributions

References

S1 File. ¹H NMR, ¹³C NMR, LRMS and HRMS data and spectra of the compounds and their toxicity regression equations against four fungi.