In Vitro Antibacterial Activity of Selected Tanzania Medicinal Plants

Abstract

This study sought to give a scientific basis to plants already used for traditional purposes and also probe new antibacterial constituents from randomly selected plants whose anti-infective properties have not been evaluated. The antibacterial activity of ethanolic extracts from 19 Zimbabwean plants was assessed using the agar diffusion assay, minimum inhibitory concentration and minimum bactericidal using ampicillin as reference. Accumulation of rhodamine 6G in bacteria was used to determine the activity of extracts as drug efflux pump inhibitors (EPIs). Test bacteria were Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus and Bacillus subtilis. At least 8 extracts exhibited antibacterial activity against all bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determination of plant extracts ranged from 0.05 to 0.5 mg/ml and 0.06 mg/ml to > 1 mg/ml, respectively. Mangifera indica, Callistemon citrinus and Vernonia adoensis were bactericidal for all bacteria while the other extracts were bacteriostatic, and were thus the most potent. These 3 extracts were effective EPIs in the uptake of R6G with activity greater than the standard inhibitor reserpine. Hence, the compounds in these plants can serve as templates for the development of new antibacterial agents as well as efflux pump inhibitors.