Broad-spectrum antimicrobial activity of a novel phenyl ester and extracts from Nelsonia canescens

Nelsonia canescens is traditionally used to treat infections. This study evaluated its phytochemical composition and antimicrobial activity to validate these ethnomedicinal claims. The methanol extract, its fractions (hexane, chloroform, ethyl acetate, and butanol), and the isolated compound (A1) were screened for phytochemicals and tested against Staphylococcus aureus, Escherichia coli, Salmonella typhi, Candida albicans, and Aspergillus niger using agar diffusion and broth dilution methods, with ciprofloxacin and fluconazole as controls. Phytochemical analysis revealed the presence of flavonoids, saponins, tannins, alkaloids, and cardiac glycosides, which may contribute to the observed bioactivity. Antimicrobial assays showed that the butanol fraction and A1 exhibited strong activity, with zones of inhibition of 30–36 mm (S. aureus) and 28–30 mm (E. coli). The ethyl acetate fraction displayed moderate antifungal effects (17 mm against C. albicans). A1 had the lowest minimum inhibitory concentrations (MIC: 2.5–10 mg/mL) and was bactericidal (MBC: 5–50 mg/mL), comparable to ciprofloxacin (MIC: 1.25–2.5 µg/mL). Non-polar fractions were inactive, while fluconazole was effective only against fungi (MIC/MFC: 1.25–2.5 µg/mL). Overall, polar fractions and A1 showed promising activity against Gram-positive bacteria and C. albicans, although standard drugs were more potent. These findings support the traditional use of N. canescens and highlight its potential as a source of natural antimicrobial agents, with further optimization potentially enhancing its efficacy.