Phytochemical analysis and antimicrobial activities of methanolic stem extracts of Ochna schweinfurthiana F. Hoffm.

Context: Medicinal plants are an enormous source of alternative antimicrobial therapy, particularly in this era of emerging resistance against orthodox antimicrobial agents. Aims: To evaluate the phytochemical and antimicrobial activities of methanolic stem extracts of Ochna schweinfurthiana F. Hoffm. and various fractions (chloroform, n-hexane, ethyl acetate, and n-butanol) obtained through liquid-liquid partition. Methods: The basic phytochemistry assay and disc diffusion/broth dilution techniques were used. The microorganisms tested were pure isolates of Methicillin Resistance Staphylococcus aureus, Staphylococcus aureus, Streptococcus pyogenes, Salmonella typhi, Shigella dysenteriae, Klebsiella pneumonia, Neisseria gonnorhea, Pseudomonas aeruginosa, Corynebacterium ulcerans, Bacillus subtilis, Escherichia coli, Proteus mirabilis, Candida albicans, Candida tropicalis, Candida stellatoidea and Candida krusei. Results: Thin layer chromatography results showed 13 prominent coloured spots from chloroform extract using dichloromethane/methanol 10: 1 as the solvent system. The crude extract revealed the presence of flavonoids, saponins, tannins, glycosides and steroids/terpenes. Antimicrobial susceptibilities and zones of inhibition (ZI) findings showed that stem extracts inhibited growth of all microbes at ZI range of 22 - 29 mm except C. ulcerans, B. subtilis, E. coli, P. mirabilis, C. stellatoidea and C. krusei. It was observed that chloroform fraction had the highest antimicrobial activities with minimum inhibitory concentration of 1.25 mg/mL against all susceptible pathogens except P. aeruginosa (2.5 mg/mL). Conclusions: Ochna schweinfurthiana F. Hoffm. stem contains bioactive constituents with potent antimicrobial activities at low MIC, especially in the chloroform soluble fraction. This study validates and encourages the ethnomedicinal use of this plant in treating infections caused by these susceptible microbes.