Antimicrobial Activity of Bridelia micrantha and Grewia plagiophylla Leaf Extracts

Escalation in occurrences of resistant microorganisms especially to synthetic drugs, has obliged the need to search for new bioactive compounds having natural origin. Bridelia micrantha and Grewia plagiophylla are medicinal plants whose roots, bark and leaves have been used by traditional herbalists to treat various diseases, but the antibacterial activity of the Kenyan ecotype has not been determined. Among the diseases treated by extracts of these plant parts are bacterial diseases such as gonorrhea, syphilis, leprosy etc. Use of herbal medicine has been with disbelief and fear since people are not sure of their effect. This reserach sought to determine the antibacterial activity of crude leaf extracts of Bridelia micrantha and Grewia plagiophylla. The phytochemicals present in ethyl acetate and methanol extracts was also determined. Escherichia coli, Salmonella typhi and Staphylococcus aureus were used as the test organisms. Extraction of crude extracts was done by cold extraction. Test organisms were inoculated in Muller Hilton media and disks impregnated with sample placed on the surface of the media. The diameter of zone of inhibition was measured in mm for every treatment using a ruler. The methanol and ethyl acetate leaf extracts from the test plant had considerable antibacterial effects on S. aureus. Most of the extracts tested positive for tannins, terpenoids, flavonoids and carotenoids. Alkaloids were absent in all the plants extracts. All the plant extracts showed no inhibition against E. coli, Methanol extract of Bridelia micrantha and, Grewia plagiophylla exhibited a zone of inhibition of 19 mm and 20 mm against Staphylococcus aureus and Salmonella typhi respectively. Ethanol extracts was inactive against all test organisms at various concentrations. Antibacterial activity difference was based on type of solvent used for extraction. The results gives scientific validity for the use of the plant as a medicine source.