Anti-Staphylococcus aureus activity of methanol extracts of 12 plants used in Cameroonian folk medicine

Spilanthes filicaulis (Schumach. &Thonn.) C. D. Adams: An insights into ethnopharmacologically important but scientifically understudied species

Spilanthes filicaulis (Schumach. & Thonn.) C. D. Adams is synonymous to Acmella caulirhiza Delile. The plant, also known as cock's eye or African cress, is a medicinal herb that belongs to the Asteraceae family. In this paper, the holistic and current applications of S. filicaulis were synthesized and critically discussed by summarizing, for the first time, its botany, traditional medicinal uses, active components, and pharmacological properties. We employed the databases of ScienceDirect, Scopus, Online Wiley library, PubMed, and Google Scholar to retrieve data on S. filicaulis from inception till February 2024, resulting in more than 70 electronic references. Based on literature reports, S. filicaulis has rich ethnopharmacological uses in different disease areas but their scientific validations are still in early stage, or not verified yet. In general, 16 phytochemicals have been identified so far. They include spilanthol, piperine, erucic acid, and isoquinoline derivative among others. The plant extracts possess anticancer, antioxidant, antimicrobial, anti-inflammatory, hepato-protective, anthelminthic, and analgesic activities. In the future, the phytochemical components, and biological activities of S. filicaulis need to be further investigated. Similarly, mechanistic studies need to be incorporated to the biological testing, to uncover the modes of actions of the species extracts and active components. Considering the species' rich ethnopharmacological applications, and the dearth of robust and established toxicity reports, the study on the safety of S. filicaulis would be an interesting and rewarding approach for further research.

In Silico Method for the Screening of Phytochemicals against Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved resistance even against the last resort β-lactam antibiotics. This is because of the acquisition of an additional penicillin-binding protein 2a (PBP2a) which is a resistance determinant in MRSA. Currently, available PBP2a inhibitors are ineffective against life-threatening and fatal infections caused by microorganisms. Therefore, there is an urgent need to screen natural compounds that could overpass the resistance issue alone or in combination with antibacterial drugs. We studied the interactions of different phytochemicals with PBP2a so that crosslinking of peptidoglycans could be inhibited. In structure-based drug designing, in silico approach plays a key role in determining phytochemical interactions with PBP2a. In this study, a total of 284 antimicrobial phytochemicals were screened using the molecular docking approach. The binding affinity of methicillin, -11.241 kcal/mol, was used as the threshold value. The phytochemicals having binding affinities with PBP2a stronger than methicillin were identified, and the drug-likeness properties and toxicities of the screened phytochemicals were calculated. Out of the multiple phytochemicals screened, nine were found as good inhibitors to be PBP2a, among which cyanidin, tetrandrine, cyclomorusin, lipomycin, and morusin showed strong binding potential with the receptor protein. These best-selected phytochemicals were also docked to the allosteric site of PBP2a, and most of the compounds revealed strong interactions with the allosteric site. These compounds were safe to be used as drugs because they did not show any toxicity and had good bioactivity scores. Cyanidin had the highest binding affinity (S-score of -16.061 kcal/mol) with PBP2a and with high gastrointestinal (GI) absorption. Our findings suggest that cyanidin can be used as a drug against MRSA infection either in purified form or that its structure can lead to the development of more potent anti-MRSA medicines. However, experimental studies are required to evaluate the inhibitory potential of these phytochemicals against MRSA.

Phytochemical Screening and Antimicrobial Activity Evaluation of Selected Medicinal Plants in Ethiopia

Background

The emergence and spread of resistant microbes continue to be a major public health concern. Effective treatment alternatives, particularly from traditionally used medicinal plants, are needed.

Objective

The main objective of this study was to conduct phytochemical screening and antimicrobial activity evaluation of selected traditionally used medicinal plants in Ethiopia.

Methods

The ethnomedicinal use value frequency index (FI) was used to select twelve medicinal plants. Phytochemical classes of compounds were screened using different standard methods. Anti-microbial activities of plant extracts were evaluated against Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Candida albicans. Minimum inhibitory concentrations were measured using the broth micro-dilution method. The data were analyzed using Statistical Package for the Social Sciences (SPSS) version 21.0 and the findings were presented descriptively and using non parametric one-way ANOVA analysis (Kruskal-Wallis/Ddunn's test).

Results

The phytochemical constituents identified were flavonoids, alkaloids, glycosides, phenols, saponins, steroids, and terpenoids, with flavonoids, alkaloids, and phenols being the most abundant. The crude extracts and chloroform fractions of the extracts showed an activity against the tested strains. The crude extract of Thalictrum rhynchocarpum Quart.-Dill. and A.Rich root demonstrated superior activity against all the tested strains with the lowest minimum inhibitory concentrations of 0.48 μg/mL against Staphylococcus aureus and Escherichia coli; 0.98 μg/mL against Klebsiella pneumoniae, Pseudomonas aeruginosa; and 3.90 μg/mL against Candida albicans, which are even better than the reference drug, gentamicin and clotrimazole.

Conclusion

The majority of evaluated medicinal plants demonstrated remarkable activity against tested microbial strains, which can be attributed to the presence of secondary metabolites of different classes of compounds. The finding provided scientific evidence for the use of these traditionally used medicinal plants.

Antibacterial potential of Malaysian ethnomedicinal plants against methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA)

This study aimed to evaluate the antibacterial activities of 61 plant extracts from 49 Malaysian ethnomedicinal plants and to investigate the interaction of the active plant extracts in combination with synthetic antibiotics against the MSSA and MRSA strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the plant extracts were determined using a microdilution method against MSSA and MRSA strains. The interaction between active plant extracts and the antibiotics was assessed using the checkerboard method. The total fractional inhibitory concentration (∑FIC) indices from the combination were calculated to determine the nature of the interaction. Out of the 61 plant extracts tested against the MSSA strain, 7 plant extracts (~ 11%) showed MIC values of less than 200 μg/mL, 17 extracts (~ 28%) showed MIC between 200 and 800 µg/mL and seed extracts of Areca catechu showed MBC values of 400 μg/mL. The seed extract of A. catechu showed MIC and MBC of 400 μg/mL against the MRSA strains while leaf extract of Cocos nucifera showed MIC of 400 μg/mL against MRSA NCTC 12493. When the active plant extracts (MIC ≤ 200 µg/mL for MSSA, and ≤ 400 µg/mL for MRSA) were tested in combination with vancomycin and ciprofloxacin, they showed no interaction against both MSSA and MRSA with ∑FIC between 1.06 and 2.03. These findings provide a preliminary overview of the anti-MSSA and anti-MRSA properties of Malaysian ethnobotanical plants to combat Staphylococcal infections. Further research is needed to establish an antibacterial profile of the tested plant extracts.