EVALUATION OF METHANOLIC EXTRACTS OF SIX MEDICINAL PLANTS USED BY HERBAL PRACTITIONERS IN CENTRAL PROVINCE- KENYA

The antimicrobial effects of selected medicinal plants commonly used by herbal practitioners in central province Kenya was evaluated on different bacterial strains- Staphylococcus aureus (Gram +ve cocci) – ATCC 20591, Salmonella typhi (Gram –ve rod) – ATCC 2202, Escherichia coli (Gram-ve rod) – STD. 25922, Klebsiella pneumoniae (clinical isolate) and Pseudomonas aeroginosa (Gram-ve rod) – ATCC 25852. Also Candida albicans ATCC EK138 was used as a fungal isolate. Methanol was used as the only solvent in the extraction. The in vitro antimicrobial activity was performed by agar disc diffusion method. The most susceptible Gram-positive bacteria was S. aureus (between 19.33-23.33mm), while the most susceptible Gram-negative bacteria was P.  aeruginosa (14.66-19.33mm). All the extracts showed sufficient inhibitory activity to the test strains. The Gram positive strain (S. aureus) was more sensitive to the extracts (range 23.33-19.33mm) than the Gram negative strains (range 21.00-14.66mm). The mean inhibition value was between 15.997mm and 19.995mm. Statistical analysis revealed that Hyptis spicigera and Crotalaria quartiniana produced significantly different (P≤0.05) zones of inhibition in all the test strains. Other extracts average zones of inhibition showed no significant difference among the test strains. The significant antibacterial activity of active extracts was compared with the standard antimicrobials (Fluconazole for C. albicans, and amoxicillin for bacterial isolates) and dried methanol discs, giving a pooled SD of 2.349mm. The results obtained in the present study suggest that the extracts can be used in treating diseases caused by the test organisms.