https://orcid.org/0000-0001-7008-7453
Correction
4 Dec 2025: Tiwa BN, Fankam AG, Sonfack CB, Mouozong R, Kengne MF, et al. (2025) Correction: Anti-staphylococcal activity, antibiotic-resistance modulation effects and action of Harungana madagascariensis (Hypericaceae) fruit extracts on the antioxidant system of multidrug-resistant Staphylococcus aureus. PLOS ONE 20(12): e0338020. https://doi.org/10.1371/journal.pone.0338020 View correction
Figures
Abstract
Global public health is facing a real challenge due to infections caused by multidrug-resistant bacteria. Among these bacteria, Staphylococcus aureus is known to rapidly develops antibiotic resistance. This study aimed to evaluate the antibacterial potential of Harungana madagascariensis fruit extracts and their effects on the antioxidant system of multidrug-resistant Staphylococcus aureus. Moreover, the extracts were evaluated for their antibiotic-resistance modulation effects against some multidrug-resistant Staphylococcus aureus. The antibacterial activity of the extracts and their effect in combination with antibiotics were assessed using the micro-dilution method. The catalase activity was assessed by measuring the height of foam, whereas the lipid peroxidation was carried out through spectrophotometric quantification of malondialdehyde. The phytochemical analysis of extracts was carried out using qualitative and quantitative standard assays. The tested extracts showed antibacterial activities, with minimum inhibitory concentrations ranging from 32 to 2048 μg/mL. The most active extract (hexane extract) has inhibited the catalase activity and induced the lipid peroxidation in S. aureus DO18SA, indicating its ability to interact with the antioxidant system of the bacteria. Moreover, the dichloromethane/methanol extract increased by 2–128-fold the activity of levofloxacin, ampicillin, and cefotaxime against selected multidrug-resistant S. aureus. It also showed synergistic effect with cefotaxime against D051SA. Alkaloids, triterpenes, and phenols were detected in all the extracts, whereas the other phytochemical classes were selectively distributed. The methanol extract had the highest phenolic content (142.20 ± 16.75 mg GAE/g of extract). Overall, the findings of this study suggest that extracts of Harungana madagascariensis fruits could be valuable sources of new agents for treating multidrug-resistant Staphylococcus aureus infections.
Citation: Tiwa BN, Fankam AG, Sonfack CB, Mouozong R, Kengne MF, Mbaveng AT, et al. (2025) Anti-staphylococcal activity, antibiotic-resistance modulation effects and action of Harungana madagascariensis (Hypericaceae) fruit extracts on the antioxidant system of multidrug-resistant Staphylococcus aureus. PLoS One 20(8): e0329771. https://doi.org/10.1371/journal.pone.0329771
Editor: Armel Jackson Seukep, University of Buea, CAMEROON
Received: May 12, 2025; Accepted: July 20, 2025; Published: August 7, 2025
Copyright: © 2025 Ngueffo 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
One of the greatest advances made in medicine was the discovery of antibiotics, which has led to the saving of millions of lives [1]. Therefore, the overuse and misuse of these antibiotics make bacteria develop resistance to them, leading to an increase in nosocomial infections and therapeutic failures [2]. In the United States, antibiotic resistance causes around 2.8 million infections and 35,000 deaths a year [3]. The prevalence of multidrug-resistant (MDR) bacteria in Africa is high, with some studies reporting rates of up to 70% in hospitalised patients [4].
Staphylococcus aureus (S. aureus) is a human bacterial pathogen belonging to the genus Staphylococcus and characterized as Gram-positive cocci [5]. It is an opportunistic bacterium that is responsible for the majority of community and hospital-acquired infections such as, septicemia, endocarditis, and cutaneous infections [5,6]. Under pathogenic conditions, S. aureus is very difficult to treat due to its strong ability to produce virulence factors, to rapidly colonize the host, and to develop drug resistance mechanisms [7]. S. aureus infections caused approximately 1.1 million deaths globally in 2019 [8]. This is mainly attributed to its ability to develop resistance to multiple antibiotics such as β-lactams, aminoglycosides, macrolides, lincosamides, fluoroquinolones, chloramphenicol, sulfonamides, streptomycin, and tetracycline [9,10]. This is possible through multiple means, such as overexpression of efflux pumps, β- lactamases’ production, reduced porin expression, and mutation of quinolone targets [11,12]. Consequently, S. aureus has been placed on the World Health Organization (WHO) priority class bacteria list for the development of new antimicrobial agents. It is therefore very important to find new strategies to fight infections due to MDR S. aureus.
Reactive oxygen species (ROS) such as superoxide anion (O2-), hydroxyl radical (OH·), and hydrogen peroxide (H2O2) induce oxidative damage to the cellular macromolecule and may lead to cellular metabolic dysfunction. As one of the defence mechanisms, bacteria use enzymes such as catalases, which play a significant role in protecting bacteria from oxidative stress caused by hydrogen peroxide [13]. Moreover, ROS induce lipid peroxidation that causes changes in the membrane structure by altering its fluidity and damaging the membrane integrity [14]. So, botanicals or phytochemicals targeting the antioxidant system of the bacteria may serve as good candidates against MDR bacteria.
Medicinal plants, which are used by around 80% of the world’s population to treat various health problems, can be a good candidate for the discovery of new treatment options of microbial infections [15]. In fact, plants synthesize a wide variety of secondary metabolites, such as phenols, flavonoids, terpenoids, tannins, and alkaloids, endowed with antimicrobial properties [16,17].
Harungana madagascariensis Lam. ex Poir., belongs to the Hypericaceae family and is widely distributed in Africa [18]. It is used in African traditional medicine to treat many human diseases, including diarrhoea, dysentery, gonorrhoea, typhoid fever, jaundice, haemorrhoids, leprosy, anaemia, postpartum bleeding, and skin and heart problems. Its chemical evaluation has shown that different organs of H. madagascariensis contained phytochemicals such as anthranoids, anthraquinones, xanthones, flavonoids, triterpenoids, steroids, and alkaloids [18,19]. Moreover, botanicals and phytochemicals from H. madagascariensis have been reported to have many pharmacological properties, including antimicrobial, antioxidant, anti-sickling, and antiproliferative activities [20–25]. The leaf, bark, and root extracts of H. madagascariensis have been reported for their in vitro antibacterial activities against various pathogens. Therefore, no related activities reported for its fruits are accessible in the literature. So, this work aimed to evaluate the antibacterial potential of H. madagascariensis fruit extracts and their effects on the antioxidant system of MDR S. aureus. Moreover, these extracts were evaluated for their antibiotic-resistance modulation effects against some MDR S. aureus isolates.
Materials and methods
Plant material and extraction
H. madagascariensis (Hypericaceae) was collected in January 2024 at Dschang, West Cameroon. The plant sample was identified at the National Herbarium of Yaoundé, Cameroon, where the voucher has been deposited under the registration number 43848/HNC.
Air-dried fruits of H. madagascariensis were powdered and macerated in hexane, methanol, and the mixture dichloromethane/methanol (1:1) for 48 h at room temperature. After filtration on Whatman filter paper No. 1, each organic filtrate was concentrated using a rotary evaporator under reduced pressure to obtain the crude extracts. The residual solvent was removed by drying the crude extracts at 40°C in an oven. The extracts were then kept at 4°C until further use.
Preliminary phytochemical screening of the extracts
Qualitative phytochemical screening.
In order to detect the different classes of secondary metabolites that were most likely to be responsible for the biological activities, a qualitative phytochemical screening was performed on the extracts as previously described [26,27].
Determination of the total phenolic content.
The total phenolic content (TPC) of the extracts was determined spectrophotometrically using the Folin-Ciocalteu reagent [28]. The reaction mixture consisted of 0.02 mL extract (2 mg/mL), 1 mL Folin-Ciocalteu reagent, and 0.8 mL 20% sodium carbonate solution. The mixture was stirred and incubated at 37°C for 30 min, then the absorbance was measured at 765 nm. The extract was replaced with distilled water in the control tubes. Results were expressed as milligrams of gallic acid equivalents per gram of extract (mg GAE/g). Each sample was assayed three times.
Evaluation of the antibacterial activity of extracts
Bacteria and culture conditions.
In this study, fourteen clinical MDR isolates (D009SA, D018SA, D020SA, D021SA, D031SA, D047SA, D049SA, D050SA, D051SA, D052SA, D057SA, D060SA, D074SA, and D094SA) and a reference strain (ATCC25923) of S. aureus were utilized. The reference strain (ATCC25923) was from American Type Culture Collection. The features of these pathogenic bacteria are presented in the supporting information (S1 Table). Mueller-Hinton agar (ReadyMED®, USA) was used to culture and maintain the bacteria, whereas Mueller Hinton broth (MHB) (ReadyMED®, USA) was used for the preparation of the bacterial inoculum and to carry out the antibacterial assays.
Determination of the minimum inhibitory and bactericidal concentrations.
The minimum inhibitory concentration (MIC) of extracts was determined using INT colorimetric assay [29] with slight modifications [30]. Briefly, 100 µL of extract or reference antibacterial drug, dissolved in 10% dimethyl sulfoxide (DMSO, BDH Chemicals Ltd, Poole, England)/MHB, were serially diluted two-fold in a 96-well sterile microplate. Thereafter, 100 μL of inoculum (1.5 × 106 CFU/mL) were added in each well, and the plates were covered with a sterile plate sealer and incubated at 37°C for 18 h. Wells containing inoculum without extract served as growth control. The MIC, defined as the lowest sample concentration that prevented the growth of the bacteria, was then detected after the addition of 30 μL of 0.2 mg/mL p-iodonitrotetrazolium chloride (INT, Loba Chemie Pvt Ltd, Mumbai, India) in each well of the plates, followed by incubation at 37°C for 30 min. Viable bacteria reduced the yellow dye to pink. The minimum bactericidal concentrations (MBC) of each extract was determined by adding 50 μL aliquots of the preparations which did not show any growth after incubation during MIC determination, to 150 μL of MHB in a new 96-well microplate. These preparations were incubated at 37°C for 48 h. MBC was considered as the lowest concentration of sample that prevented the color change of the medium after the addition of INT [30]. Each experiment was carried out in duplicate and repeated three times.
The antibacterial activity of extracts was interpreted as followed based on the most recent cut-off values: Outstanding activity if MIC < 8 μg/mL; excellent activity if 8 < MIC ≤ 40 μg/mL; Very good activity if 40 < MIC ≤ 128 μg/mL; good activity if 128 < MIC ≤ 320 μg/mL; average activity if 320 < MIC ≤ 625 μg/mL; weak activity if 625 < MIC ≤ 1024 μg/mL and not active if MIC >1024 μg/mL [31]. Moreover, extract was considered bactericidal, if MBC/MIC ≤ 4 and bacteriostatic if MBC/MIC > 4 [32].
Assessment of the antibiotic-resistance modifying effects of extracts.
The antibiotic modulation effect of extracts was performed as previously described [33,34]. The MICs of ciprofloxacin, levofloxacin, streptomycin, ampicillin, ceftriaxone, cefotaxime, and vancomycin (Sigma-Aldrich) were determined in the presence and absence of a sub-inhibitory concentration (MIC/8) of different extracts. The modulation factor (MF), defined as the ratio between the MIC of the antibiotic alone and that of the antibiotic in the presence of the extract, was calculated. MF ≥ 2 has been set as the threshold for biological significance of the antibiotic modulation effect [35,36]. Each assay was performed in duplicate and repeated thrice.
Synergy assay.
The synergy effect of the combination of antibiotics (ampicillin and cefotaxime) and Cl2CH2/ MeOH extract was investigated using the checkerboard broth micro-dilution method [37]. In a 96-well sterile microplate, 100 µL of antibiotic were introduced in the first well of each column followed by two-fold serial dilutions of the antibiotic from row A to G. Then, 100 µL of extract were introduced in the first well of each row, followed by two-fold serial dilutions from column 1–10. One hundred (100) µL of inoculum were then added to all wells except the last four wells of colon 12 and the last well of column 11, which were used as controls. The microplates were then incubated at 37°C, and MIC was determined after 18 h of incubation as previously described. The fractional inhibitory concentration index (ƩFIC) for all the combinations was determined using the following formula:
The interaction was considered as: synergy (ƩFIC ≤ 0.5); additivity (0.5 < ƩFIC ≤ 1); indifferent if (ΣFIC >1–2); and antagonism (ƩFIC > 2) [38].
Evaluation of the effect of the hexane extract on the antioxidant system S. aureus
Effect of the hexane extract on catalase activity of S. aureus.
The effect of the most active extract (hexane extract) on catalase activity of S. aureus (D018SA) was carried out as previously described [39]. Briefly, fresh colonies of S. aureus were inoculated in 5 mL of sterile MHB and incubated at 37°C for the whole night. Likewise, overnight cultures of S. aureus were cultured in a medium containing 1 mL of hexane extract (MIC and 2xMIC) or polymyxin B (MIC) and 4 mL of MHB. Then, 100 µL of each sample’s aliquot were put into a test tube in addition to 100 µL of 1% Triton X-100 and 100 µL of 30% (v/v) H2O2. Once the tubes were well mixed, they were kept at room temperature for 5 minutes. The foam’s height unchanged for fifteen minutes, was then measured in cm with a ruler and compared to the untreated D018SA.
Lipid peroxidation assay.
The level of lipid peroxidation was performed by measuring the concentration of malondialdehyde (MDA) using thiobarbituric acid [40]. Briefly, fresh colonies of S. aureus aureus (D018SA) were cultured overnight in 4 mL of MHB containing 1 mL of hexane extract (MIC and 2xMIC) or polymyxin B (MIC). Thereafter, 1 mL of the test culture, 1 mL of thiobarbituric acid, and 1 mL of trichloroacetic acid were introduced in a screw-cap test tube, mixed well, and heated to 100°C for 10 minutes in a water bath. After the test tubes were allowed to cool, they were centrifuged for 20 minutes at 5000 rpm. The supernatants were collected, and their absorbances were measured at 535 nm against the control. The MDA concentration (nM) was calculated based on the millimolar absorbance coefficient (E0 = 156 cm−1.mM−1) using the equation shown below:
Statistical analysis
The data for TPC, catalase activity, and the MDA concentration were presented as the mean with the standard deviation (Mean ± SD) from three replicates. One-way analysis of variance (ANOVA) followed by Tukey’s multiple comparison test was employed to compare the means. The statistical analysis and graphs were done with GraphPad Prism for Windows, version 5.0.1. Results were considered significant if p < 0.05.
Results
Phytochemical composition of extracts
Qualitative phytochemical composition.
The results of the phytochemical screening showed that all the tested extracts contain alkaloids, triterpenes, and phenols. Moreover, flavonoids, saponins, and anthraquinones were detected in dichloromethane/methanol (Cl2CH2/MeOH) and methanol (MeOH) extracts. All the seeking phytochemicals were present in the MeOH extract (Table 1).
Total phenolic content of extracts.
This study evaluated the TPC of the tested extracts. The results showed that the MeOH extract of H. madagascariensis fruits presented the highest TPC (142.20 ± 16.75 mg GAE/g extract), followed by Cl2CH2/MeOH extract (103.27 ± 6.03 mg GAE/g). Indeed, the hexane extract showed the lowest phenolic content (2.40 ± 0.42 mg GAE/g of extract) (Fig 1).
TPC: Total phenolic content; GAE: gallic acid equivalents. Cl2CH2/MeOH: Dichloromethane/methanol. MeOH: Methanol.
Antibacterial activity of H. madagascariensis fruit extracts
MIC and MBC of extracts.
The data summarized in Table 2 present the MIC and MBC of the tested extracts against pathogenic S. aureus. The results showed that these extracts had antibacterial activity with MIC ranging from 32 to 2048 µg/mL. The MeOH extract displayed inhibitory activity on all the tested isolates (100%), whereas the hexane and Cl2CH2/MeOH extracts have inhibited the growth of 14/15 (93.33%) of the tested bacteria. The hexane extract appears as the most active extract. It displayed excellent activity against S. aureus D018SA (MIC = 32 µg/mL) ATCC25923, and D020SA (MIC = 64 µg/mL). It was more active on S. aureus D018SA (MIC = 32 µg/mL) than streptomycin, which was used as reference antibacterial drug (MIC > 256 µg/mL). Globally, MBCs of the tested extracts were above 2048, and those ≤ 2048 µg/mL were detected on at least 4/15 of the tested bacteria. The MBC/MIC ratio of all the tested extracts was less than 4 on at least one strain. This was mostly observed with Cl2CH2/MeOH extract (7/15 of the tested S. aureus). Therefore, the MBC/MIC ratio was more than 4 for the hexane extract on the most sensitive strains (ATCC25923, D018S, and D020SA).
Antibiotic-resistance modulation effects of extracts
In order to select the extracts likely to potentiate the antibiotic activity, a preliminary experiment carried out against D094SA (S2 Table) has allowed us to select the CH2Cl2/MeOH extract as a potential antibiotic modulator. This extract improved by 2–128-fold the activity of the tested antibiotics on MDR S. aureus. This was observed with cefotaxime (80%), vancomycin and levofloxacin (60%), ceftriaxone and streptomycin (40%), and ciprofloxacin and ampicillin (20%) in the presence of CH2Cl2/MeOH extract (Table 3).
Interactions between antibiotics and CH2Cl2/MeOH extract
The interaction effects between antibiotics and CH2Cl2/MeOH extract were evaluated through the determination of the fractional inhibitory concentration index (ΣFIC). The results showed synergy (ΣFIC = 0.375) for the combination of cefotaxime with CH2Cl2/MeOH extract and additivity (ΣFIC = 0.56) for the combination of ampicillin with CH2Cl2/MeOH extract (Table 4).
Effect of the active extract on the antioxidant system S. aureus
Effect of the hexane extract on catalase activity of D018SA.
The catalase activity of D018SA was determined by measuring the height of foam. In untreated cells, the height of foam was 1.05 ± 0.07 cm, whereas in extract-treated D018SA, it was 0.70 ± 0.14 cm and 0.65 ± 0.07 cm at MIC and 2xMIC, respectively (Fig 2). These results indicate a significant (p < 0.05) inhibition of the catalase activity of D018SA by the hexane extract.
MIC: Minimal inhibitory concentration. The MIC of polymyxin B and extract against D018SA were 16 and 32 µg/mL, respectively. ** (p < 0.01); *** (p < 0.001).
Effect of the active extracts on D018SA lipid peroxidation
The lipid peroxidation activity (expressed in terms of malondialdehyde concentration) was evaluated in extract-treated D018SA. The MDA concentration was 189.27 ± 13.35 nM for control, 704.85 ± 35.86 nM and 2101.30 ± 70.74 nM in extract-treated S. aureus D018SA, at MIC and 2xMIC, respectively. Moreover, the effect of extract (2xMIC) was high compared to that of polymyxin B (1639.86 ± 46.97 nM) used as standard (Fig 3). These results show that this extract has significantly (p < 0.05) induced the lipid peroxidation in D018SA.
MIC: Minimal inhibitory concentration; The MIC of polymyxin B and extract against D018SA were 16 and 32 µg/mL, respectively. ** (p < 0.01); *** (p < 0.001).
Discussion
The global spread of MDR pathogens is leading to the reduction in the arsenal of antibiotics, and therefore to the need for the development of new drugs with novel target mechanisms [41,42]. This study was aimed at investigating the antibacterial potential of Harungana madagascariensis fruit extracts and their effects on the antioxidant system of multidrug-resistant S. aureus. Moreover, the extracts were evaluated for their antibiotic-resistance modulation effects against some MDR isolates.
Medicinal plants may contain antimicrobial compounds that are used to treat infectious disorders [16,43]. In the first part of this study, we have evaluated the anti-staphylococcal activity of H. madagascariensis fruit extracts against some clinical MDR isolates. The findings have shown that the tested extracts presented varied antibacterial potentials. This could be attributed to the difference in phytochemical composition observed between the extracts [44]. The difference observed may also be due to the different solvent used for the extraction [45]. According to the cut-off points of MICs established by Wamba et al. [31], the hexane fruits’ extract showed excellent activity (8 < MIC ≤ 64 µg/mL) against some of the tested bacteria. Moreover, its MBC/MIC ratio was more than 4 on the most sensitive strains (ATCC25923, D018S, and D020SA), suggesting that it has a bacteriostatic effect [32]. The result of this work is in agreement with previous studies that have demonstrated the antibacterial activity of leaves, bark, and roots of H. madagascariensis against other bacteria species [20,21]. For instance, Tankeo et al. (2016) have shown that the methanol extract of H. madagascariensis bark had excellent activity (MIC ≤ 8 µg/mL) against some Gram-negative strains, including Escherichia coli ATCC10536 and W3110. They have identified ferruginin A, an anthranoid, as the possible active ingredient of that extract [20]. Moreover, Tegaboue et al. (2021) have shown that leaves, bark, and roots of H. madagascariensis have excellent to moderate activity on some clinical bacteria, including S. aureus [21]. Astilbin, a flavone isolated from the ethyl acetate extract of H. madagascacriensis leaves, was also shown to have strong activity against Staphylococcus epidermidis, Micrococcus luteus, Acinetobacter sp., and Moraxella sp. [46]. In this study, the hexane extract has presented the best activity, with MIC = 32 µg/mL on S. aureus D018 SA, and with MIC = 64 µg/mL against ATCC10536 and D020SA. This may be attributed to the presence of nonpolar compounds such as triterpenes or simple phenols detected in this extract. Taken together our findings, this study highlights the potential of H. madagascariensis, and especially its hexane fruit extract, as a candidate for the discovery of an anti-staphylococcal drug.
The discovery of innovative drugs with new modes of action could represent a promising solution to counteract the ongoing emergence and spread of resistant infections. These new drugs should be designed to escape preexisting mechanisms of resistance [42]. Herein, the effect of the hexane extract has been assessed on the D018SA antioxidant system. Many pathogens are known to produce catalase enzymes to protect themselves from hydrogen peroxide, a defense mechanism commonly used by the host’s immunity. Previous studies have reported that catalase-deficient mutant pathogens are more sensitive to oxidative stress and attack by the host immune system [47]. There is no literature available describing the mechanism of extracts of H. madagascariensis upon bacterial catalase activity. In this study, the hexane extract of H. madagascariensis fruits has inhibited the catalase activity of S. aureus D018SA. This could be due to the presence of simple phenols, such as thymol, carvacrol and other phenolic acids known to possess antibacterial properties and to inactivate bacterial enzyme systems as one of their potential modes of action [39]. The hexane extract has induced lipid peroxidation in S. aureus D018SA. This may be a consequence of the inhibition of catalase activity causing an increase of ROS, which may induce lipid peroxidation. In fact, it is known that catalase produced under oxidative stress conditions can prevent lipid peroxidation [48]. Therefore, when the catalase is nonfunctional or inhibited, ROS induce lipid peroxidation, which causes changes in the cell membrane structure by altering its fluidity and damaging the membrane integrity [14,49]. Moreover, the presence of triterpenes in the hexane extract may also explain these results. In fact, many reports have shown that triterpenes induce oxidative stress by reacting with bacterial membrane components such as lipids to produce ROS, which causes lipid peroxidation [50]. Inhibiting multidrug resistance mechanisms such as efflux pump expression, β-lactamase production, and biofilm formation is currently considered as a potential strategy to reduce the spread of resistance in bacteria [51–53]. Among the existing approaches, many researchers have reported that the combination of plant extracts with antibiotics could exhibit synergy effects against MDR bacteria, including S. aureus [35,54–56]. In this study, we have evaluated the combination effects of H. madagascariensis fruit extracts with eight commonly used antibiotics. It appeared that CH2Cl2/MeOH extract of H. madagascariensis fruit has increased by 2–128-fold the efficacy of levofloxacin, ampicillin, and cefotaxime on MDR S. aureus. It also showed a synergy effect (ƩFIC = 0.375) with cefotaxime against the S. aureus DO51SA. This may be attributed to the presence of secondary metabolites such as alkaloids, terpenoids, and flavonoids, which were detected in high proportions in this extract during this study. It has been demonstrated that these phytochemicals could inhibit the expression of efflux pumps [57,58] or β-lactamases [59,60], known as important resistance mechanisms in S. aureus [11,12].
Conclusions
The findings of this study gave valuable insight into the potential usage of H. madagascariensis fruit extracts for treating microbial infections, especially those due to MDR Staphylococcus aureus. The study provided the first evidence of the antimicrobial-resistance modulation effect and the inhibition of the antioxidant system of H. madagascariensis fruit extracts against Staphylococcus aureus. It also provides scientific credence to the traditional uses of H. madagascariensis for managing microbial infections. So, these extracts could be considered as important sources of new agents to treat infections due to MDR Staphylococcus aureus. Therefore, more research on these extracts may be done regarding the identification of their active ingredients as well as their safety investigations.
Supporting information
S2 Table. Results of the preliminary modulation essay of extracts at its sub-inhibitory concentration (MIC/8) against S. aureus D094SA.
https://doi.org/10.1371/journal.pone.0329771.s002
(PDF)
Acknowledgments
The authors thank the National Herbarium of Cameroon, Yaoundé Cameroon for the identification of the studied plant.
References
- 1. Aminov RI. A brief history of the antibiotic era: lessons learned and challenges for the future. Front Microbiol. 2010;1:134. pmid:21687759
- 2. Ye J, Chen X. Current Promising Strategies against Antibiotic-Resistant Bacterial Infections. Antibiotics (Basel). 2022;12(1):67. pmid:36671268
- 3. Orosz L, Lengyel G, Ánosi N, Lakatos L, Burián K. Changes in resistance pattern of ESKAPE pathogens between 2010 and 2020 in the clinical center of University of Szeged, Hungary. Acta Microbiol Immunol Hung. 2022;:10.1556/030.2022.01640. pmid:35084364
- 4. Mohd Asri NA, Ahmad S, Mohamud R, Mohd Hanafi N, Mohd Zaidi NF, Irekeola AA, et al. Global Prevalence of Nosocomial Multidrug-Resistant Klebsiella pneumoniae: A Systematic Review and Meta-Analysis. Antibiotics (Basel). 2021;10(12):1508. pmid:34943720
- 5. Reddy PN, Srirama K, Dirisala VR. An Update on Clinical Burden, Diagnostic Tools, and Therapeutic Options of Staphylococcus aureus. Infect Dis (Auckl). 2017;10:1179916117703999. pmid:28579798
- 6. Pantosti A. Methicillin-Resistant Staphylococcus aureus Associated with Animals and Its Relevance to Human Health. Front Microbiol. 2012;3:127. pmid:22509176
- 7. Akanbi OE, Njom HA, Fri J, Otigbu AC, Clarke AM. Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Recreational Waters and Beach Sand in Eastern Cape Province of South Africa. Int J Environ Res Public Health. 2017;14(9):1001. pmid:28862669
- 8. GBD 2019 Antimicrobial Resistance Collaborators. Global mortality associated with 33 bacterial pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet. 2022;400(10369):2221–48. pmid:36423648
- 9. Schindler BD, Jacinto P, Kaatz GW. Inhibition of drug efflux pumps in Staphylococcus aureus: current status of potentiating existing antibiotics. Future Microbiol. 2013;8(4):491–507. pmid:23534361
- 10. Alabbosh KF, Zmantar T, Bazaid AS, Snoussi M, Noumi E. Antibiotics Resistance and Adhesive Properties of Clinical Staphylococcus aureus Isolated from Wound Infections. Microorganisms. 2023;11(5):1353. pmid:37317326
- 11. Foster TJ. Antibiotic resistance in Staphylococcus aureus. Current status and future prospects. FEMS Microbiol Rev. 2017;41(3):430–49. pmid:28419231
- 12. Martínez JL. Mechanisms of Action and of Resistance to Quinolones. Antibiotic Drug Resistance. Wiley. 2019. 39–55.
- 13. Johnson LA, Hug LA. Distribution of reactive oxygen species defense mechanisms across domain bacteria. Free Radic Biol Med. 2019;140:93–102. pmid:30930298
- 14. Juan CA, Pérez de la Lastra JM, Plou FJ, Pérez-Lebeña E. The Chemistry of Reactive Oxygen Species (ROS) Revisited: Outlining Their Role in Biological Macromolecules (DNA, Lipids and Proteins) and Induced Pathologies. Int J Mol Sci. 2021;22(9):4642. pmid:33924958
- 15.
World Health Organization. The World health report: 2003: shaping the future. World Health Organization. 2003. https://iris.who.int/handle/10665/42789
- 16. Cowan MM. Plant products as antimicrobial agents. Clin Microbiol Rev. 1999;12(4):564–82. pmid:10515903
- 17.
Kuete V. African flora to fight bacterial resistance, part I: standards for the activity of plant-derived products. 1st ed. Academic Press. 2023.
- 18.
Iwu MM. Handbook of African Medicinal Plants. CRC Press, 1994.
- 19. Happi GM, Tiani GLM, Gbetnkom BYM, Hussain H, Green IR, Ngadjui BT, et al. Phytochemistry and pharmacology of Harungana madagascariensis: mini review. Phytochemistry Letters. 2020;35:103–12.
- 20. Tankeo SB, Damen F, Sandjo LP, Celik I, Tane P, Kuete V. Antibacterial activities of the methanol extracts, fractions and compounds from Harungana madagascariensis Lam. ex Poir. (Hypericaceae). J Ethnopharmacol. 2016;190:100–5. pmid:27267830
- 21. Deutou Tégaboué D, Cidjeu Pouaha CL, Ebelle Etame RM, K G S, Ngo Hagbe D, Moussa I, et al. Parts, Period, and Extraction Solvents as Parameters Influencing Harungana madagascariensis Lam. ex Poir. (Hypericaceae) Antibacterial Activity. Evid Based Complement Alternat Med. 2021;2021:6615596. pmid:33777157
- 22. Kuete V, Seukep AJ. Harungana madagascariensis as a source of antibacterial agents. Advances in Botanical Research. Elsevier. 2023. p. 177–91.
- 23. Kouam SF, Ngadjui BT, Krohn K, Wafo P, Ajaz A, Choudhary MI. Prenylated anthronoid antioxidants from the stem bark of Harungana madagascariensis. Phytochemistry. 2005;66(10):1174–9. pmid:15924922
- 24. Biapa PCN, Matei H, Bâlici Ş, Oben JE, Ngogang JY. Protective effects of stem bark of Harungana madgascariensis on the red blood cell membrane. BMC Complement Altern Med. 2013;13:98. pmid:23663227
- 25. Kuete V, Efferth T. Pharmacogenomics of Cameroonian traditional herbal medicine for cancer therapy. J Ethnopharmacol. 2011;137(1):752–66. pmid:21763411
- 26.
Harbone J. Phytochemical Methods: A Guide to Modern Techniques of Plant Analysis. London: Chapman & Hall. 1973.
- 27.
Bruneton J. Pharmacognosie: phytochimie, plantes medicinales. 3 ed. Paris: Tec & Doc. 1999.
- 28. Ramde-Tiendrebeogo A, Tibiri A, Hilou A, Lompo M, Millogo-Kone H, Nacoulma O, et al. Antioxidative and antibacterial activities of phenolic compounds from <em>Ficus sur Forssk</em>. and <em>Ficus sycomorus</em> L. (Moraceae) : potential for sickle cell disease treatment in Burkina Faso. Int J Bio Chem Sci. 2012;6(1).
- 29. Eloff JN. A sensitive and quick microplate method to determine the minimal inhibitory concentration of plant extracts for bacteria. Planta Med. 1998;64(8):711–3. pmid:9933989
- 30. Kuete V, Ngameni B, Simo CCF, Tankeu RK, Ngadjui BT, Meyer JJM, et al. Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae). J Ethnopharmacol. 2008;120(1):17–24. pmid:18718518
- 31. Wamba BE, Mbaveng AT, Kuete V. Fighting Gram-positive bacteria with African medicinal plants: Cut-off values for the classification of the activity of natural products. In: Kuete V, Editor. African flora to fight bacterial resistance, part I: standards for the activity of plant-derived products. Advances in Botanical Research, 106:413–522; 2023.
- 32. Levison ME. Pharmacodynamics of antimicrobial drugs. Infectious Disease Clinics of North America. 2004;18(3):451–65.
- 33. Coutinho HDM, Costa JGM, Lima EO, Falcão-Silva VS, Siqueira-Júnior JP. Enhancement of the antibiotic activity against a multiresistant Escherichia coli by Mentha arvensis L. and chlorpromazine. Chemotherapy. 2008;54(4):328–30. pmid:18698137
- 34. Fankam AG, Kuiate J-R, Kuete V. Antibacterial and antibiotic resistance modulatory activities of leaves and bark extracts of Recinodindron heudelotii (Euphorbiaceae) against multidrug-resistant Gram-negative bacteria. BMC Complement Altern Med. 2017;17(1):168. pmid:28340621
- 35. Kovač J, Gavarić N, Bucar F, Smole Možina S. Antimicrobial and resistance modulatory activity of Alpinia katsumadai seed phenolic extract, essential oil and post-distillation extract. Food Technol Biotech. 2014;52(2):248–54.
- 36. Prasch S, Duran AG, Chinchilla N, Molinillo JMG, Macías FA, Bucar F. Resistance modulatory and efflux-inhibitory activities of capsaicinoids and capsinoids. Bioorg Chem. 2019;82:378–84. pmid:30428416
- 37. Daly SM, Sturge CR, Greenberg DE. Inhibition of Bacterial Growth by Peptide-Conjugated Morpholino Oligomers. Methods Mol Biol. 2017;1565:115–22. pmid:28364238
- 38. European Committee for Antimicrobial Susceptibility Testing (EUCAST) of the European Society of Clinical Microbiology and Infectious Dieases (ESCMID). EUCAST Definitive Document E.Def 1.2, May 2000: Terminology relating to methods for the determination of susceptibility of bacteria to antimicrobial agents. Clin Microbiol Infect. 2000;6(9):503–8. pmid:11168186
- 39. Sawant S, Baldwin TC, Metryka O, Rahman A. Evaluation of the Effect of Plectranthus amboinicus L. Leaf Extracts on the Bacterial Antioxidant System and Cell Membrane Integrity of Pseudomonas aeruginosa PA01 and Staphylococcus aureus NCTC8325. Pathogens. 2023;12(6):853. pmid:37375543
- 40. Tsaturyan V, Poghosyan A, Toczyłowski M, Pepoyan A. Evaluation of Malondialdehyde Levels, Oxidative Stress and Host-Bacteria Interactions: Escherichia coli and Salmonella Derby. Cells. 2022;11(19):2989. pmid:36230950
- 41. Miethke M, Pieroni M, Weber T, Brönstrup M, Hammann P, Halby L, et al. Towards the sustainable discovery and development of new antibiotics. Nat Rev Chem. 2021;5(10):726–49.
- 42. Tondi D. Novel Targets and Mechanisms in Antimicrobial Drug Discovery. Antibiotics. 2021;10(2):141.
- 43.
Kuete V. Medicinal plant research in Africa: pharmacology and chemistry. London, England: Elsevier. 2013.
- 44. Farzaei MH, Rahimi R, Attar F, Siavoshi F, Saniee P, Hajimahmoodi M, et al. Chemical composition, antioxidant and antimicrobial activity of essential oil and extracts of Tragopogon graminifolius, a medicinal herb from Iran. Nat Prod Commun. 2014;9(1):121–4. pmid:24660479
- 45. Eloff JN. Avoiding pitfalls in determining antimicrobial activity of plant extracts and publishing the results. BMC Complement Altern Med. 2019;19(1):106. pmid:31113428
- 46. Moulari B, Pellequer Y, Lboutounne H, Girard C, Chaumont J-P, Millet J, et al. Isolation and in vitro antibacterial activity of astilbin, the bioactive flavanone from the leaves of Harungana madagascariensis Lam. ex Poir. (Hypericaceae). J Ethnopharmacol. 2006;106(2):272–8. pmid:16483735
- 47. Iwase T, Tajima A, Sugimoto S, Okuda K, Hironaka I, Kamata Y, et al. A Simple Assay for Measuring Catalase Activity: A Visual Approach. Sci Rep. 2013;3(1).
- 48. Noonpakdee W, Sitthimonchai S, Panyim S, Lertsiri S. Expression of the catalase gene katA in starter culture Lactobacillus plantarum TISTR850 tolerates oxidative stress and reduces lipid oxidation in fermented meat product. Int J Food Microbiol. 2004;95(2):127–35. pmid:15282125
- 49. Nandi A, Yan L-J, Jana CK, Das N. Role of Catalase in Oxidative Stress- and Age-Associated Degenerative Diseases. Oxid Med Cell Longev. 2019;2019:9613090. pmid:31827713
- 50. Yang S-K, Yusoff K, Ajat M, Yap W-S, Lim S-HE, Lai K-S. Antimicrobial activity and mode of action of terpene linalyl anthranilate against carbapenemase-producing Klebsiella pneumoniae. J Pharm Anal. 2021;11(2):210–9. pmid:34012697
- 51. Baym M, Stone LK, Kishony R. Multidrug evolutionary strategies to reverse antibiotic resistance. Science. 2016;351(6268):aad3292. pmid:26722002
- 52. Douglas EJA, Wulandari SW, Lovell SD, Laabei M. Novel antimicrobial strategies to treat multi-drug resistant Staphylococcus aureus infections. Microb Biotechnol. 2023;16(7):1456–74. pmid:37178319
- 53. Elshobary ME, Badawy NK, Ashraf Y, Zatioun AA, Masriya HH, Ammar MM, et al. Combating Antibiotic Resistance: Mechanisms, Multidrug-Resistant Pathogens, and Novel Therapeutic Approaches: An Updated Review. Pharmaceuticals (Basel). 2025;18(3):402. pmid:40143178
- 54. Wamba BEN, Mbaveng AT, Nayim P, Dzotam JK, Ngalani OJT, Kuete V. Antistaphylococcal and Antibiotic Resistance Modulatory Activities of Thirteen Cameroonian Edible Plants against Resistant Phenotypes. Int J Microbiol. 2018;2018:1920198. pmid:30057614
- 55. Ranjutha V, Chen Y, Al-Keridis LA, Patel M, Alshammari N, Adnan M, et al. Synergistic Antimicrobial Activity of Ceftriaxone and Polyalthia longifolia Methanol (MEPL) Leaf Extract against Methicillin-Resistant Staphylococcus aureus and Modulation of mecA Gene Presence. Antibiotics (Basel). 2023;12(3):477. pmid:36978344
- 56. Limboo KH, Singh B. Antibiotic potentiating effect of Bauhinia purpurea L. against multidrug resistant Staphylococcus aureus. Front Microbiol. 2024;15:1385268. pmid:38694794
- 57. Prasch S, Bucar F. Plant derived inhibitors of bacterial efflux pumps: an update. Phytochem Rev. 2015;14(6):961–74.
- 58. Zhang S, Wang J, Ahn J. Advances in the Discovery of Efflux Pump Inhibitors as Novel Potentiators to Control Antimicrobial-Resistant Pathogens. Antibiotics (Basel). 2023;12(9):1417. pmid:37760714
- 59. Liu S, Zhou Y, Niu X, Wang T, Li J, Liu Z, et al. Magnolol restores the activity of meropenem against NDM-1-producing Escherichia coli by inhibiting the activity of metallo-beta-lactamase. Cell Death Discov. 2018;4:28. pmid:29531825
- 60. Dettweiler M, Melander RJ, Porras G, Risener C, Marquez L, Samarakoon T, et al. A Clerodane Diterpene from Callicarpa americana Resensitizes Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics. ACS Infect Dis. 2020;6(7):1667–73. pmid:32579326