In vitro antimicrobial activity of Albizia amaraleaves from Lindi region, Tanzania.

Ethnopharmacological relevance: Aqueous Albizia amara leaf extract is used by traditional healers for treatment of diarrheal diseases. Aim of study: To evaluate the antimicrobial activity of chromatographic fractions obtained from Albizia amara leaf extract on microorganisms. Materials and methods: Chloroform and chloroform-methanol fractions were eluted from silica gel column chromatography, monitored by TLC and evaluated for antimicrobial activity using the disk diffusion method on the following microorganisms; Escherichia coli, Salmonella typhi, Klebsiella pneumoniae, Bacillus cereus, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans. Diameters of zones of inhibition were used to indicate antimicrobial activity. Results: Antimicrobial activity was observed to increase with polarity of eluting solvent system. Fractions eluted by less polar solvent systems did not show antimicrobial activity against any of the tested microorganisms. Fractions eluted with the mobile phase with higher methanol concentration showed the broadest antimicrobial spectrum by inhibiting all the tested microorganisms. The most susceptible bacteria were E.coli and S. typhi, and the least susceptible was K. pneumoniae while the most susceptible of the fungi was C. neoformans. Conclusion: Polar fractions displayed broadest antimicrobial activity; hence, aqueous leaf extracts of the plant reported to be used in traditional medicine is supported by the findings of this study. Importance of fractionating crude extracts to obtain full picture of biological activity is emphasized and cytotoxic studies to determine toxicity of the fractions and isolation of the active compound(s) are recommended