Bioactive constituents of Moringa stenopetala leaves associated with antioxidant antimicrobial and nutritional properties
摘要
Moringa stenopetala is widely consumed as a nutritious food source and has long been utilized in traditional medicine for the management of various ailments. This study aimed to conduct a comprehensive evaluation of the phytochemical composition and biological activities of M. stenopetala leaves using different solvent extracts. Antioxidant activity (ABTS and FRAP assays), antimicrobial activity, phytochemical quantification, vitamin analysis, phenolic and flavonoid profiling using HPLC, and volatile compound identification using GC–MS were performed. Antioxidant capacity revealed marked solvent-dependent variations. The methanolic extract exhibited the strongest radical-scavenging activity in ABTS, achieving an IC₅₀ of 15.85 µg/mL, approaching the potency of ascorbic acid. Ethanol and water extracts also displayed notable activity, whereas non-polar fractions showed considerably weak effects. Similar trends were observed in the FRAP assay, where methanol again demonstrated the highest reducing power (IC₅₀ = 39.08 µg/mL), followed by ethanol and water, indicating that antioxidant activity is largely associated with polar phytoconstituents. Antimicrobial screening using the agar diffusion method showed selective inhibition patterns among the tested microorganisms. Ethanolic extract produced the strongest antibacterial activity, particularly against Bacillus subtilis, comparable to the standard gentamycin. Moderate activity was also observed with acetone, chloroform, and ethyl acetate fractions against Staphylococcus aureus. Conversely, all extracts failed to inhibit Escherichia coli, Proteus vulgaris, Aspergillus niger, and Candida albicans, suggesting that the antimicrobial constituents of M. stenopetala are more effectual against Gram-positive rather than Gram-negative or fungal pathogens. Phytochemical quantification of the methanolic extract demonstrated a rich profile of secondary metabolites, including considerable levels of alkaloids (53.56 mg/g) and phenolics (38.23 mg/g). HPLC profiling further confirmed the dominance of several potent phenolic and flavonoid compounds, with gallic acid, chlorogenic acid, coumaric acid, and rutin representing the major peaks. These compounds are well—known for strong antioxidant and therapeutic properties, supporting the high radical-scavenging performance observed. The vitamin composition analysis identified both water- and fat-soluble micronutrients. Riboflavin (B₂) and α-tocopherol were detected at relatively high concentrations, indicating additional nutritional and antioxidant contributions. GC–MS analysis of volatile constituents revealed six major components, with 13-docosenamide (Z) and 1,2-benzenedicarboxylic acid derivatives as dominant peaks. These volatiles are known for antimicrobial, anti-inflammatory, and bioactive properties, further enriching the biochemical profile of the extract. These results indicate that the leaves of M. stenopetala are a promising source of bioactive compounds with antioxidant and antimicrobial properties.