Antibacterial activity of East African medicinal plants

In an ethnopharmacological survey, extracts of the six East African medicinal plants Entada abyssinica (stem bark), Terminalia spinosa (young branches), Harrisonia abyssinica (roots), Ximenia caffra (roots), Azadirachta indica (stem bark and leaves), and Spilanthes mauritiana (roots and flowers) were tested against 105 strains of bacteria from seven genera (Staphylococcus, Enterococcus, Pseudomonas, Escherichia, Klebsiella, Salmonella, Mycobacterium). The minimum inhibitory concentration reached by 50% (MIC50%) and 90% (MIC90%) of the strains for the extracts of E. abyssinica, T. spinosa, X. caffra, and A. indica (stem bark) ranged from 0.13-8 mg/ml and from 0.5 to > 8 mg/ml, respectively. Their minimum bactericidal concentration by 50% (MBC50%) and MBC90% were all between 0.5 and > 8 mg/ml. H. abyssinica, A. indica (leaves), and S. mauritiana (roots and flowers) had MIC and MBC values greater than or equal to 8 mg/ml. Mycobacteria were not inhibited at extract concentrations of 0.5-2 mg/ml. It is concluded that plant extracts with low MIC and MBC values may serve as sources for compounds with therapeutic potency. (C) 1998 Elsevier Science Ireland Ltd.