THE EFFECT OF SOIL AND CLIMATIC FACTORS ON ANTIMICROBIAL AND PHYTOCHEMICAL COMPOSITION OF STINGING NETTLE (Urtica massaica)

Abstract

Emerging multidrug resistance by many microorganisms callsfor exploration of new sources of drug alternatives. Plants are largely unexplored source of drug repository. Medicinal plants have great potential for providing novel drug leads with novel mechanism of action. Ecological and environmental factors have been reported to affect plant phytochemical contents. Soil and climate are some of these factors that are considered in the current study in the efficacy of Urtica massaica against some pathogenic bacteria.Therefore, the present study aimed at determining the antimicrobial activity and phytochemical profile of Urtica massaica.The study was conducted atthe Centre for Microbiology Research, Kenya Medical Research Institute. Plant samples were collected from Eldoret, Kericho, Kitale and Marigat;Kenya. The plants were dried in an oven to moisture content of 13%, and ground into fine powder, weighed and stored.Crude extracts from the stored fine powder were prepared using hot water and methanol.Reference (ATCC) strains and clinical isolates of Staphylococcus aureus, Escherichia coli, Aspergillus flavus and Candida albicans were used in bioassay testing of crude extracts at different concentrations.The antimicrobial activity of the extracts was determined by measuring the zones of inhibition using the disc diffusion method. The minimum inhibitory concentration for the extracts against each microorganism was determined and phytochemical screening was done on the crude extracts to determine the phytochemicals present. Analysis of variance was done to determine the difference in inhibition zones between methanolic and aqueous extracts of U. massaica. Significant differences (p<0.05) in inhibition zones between the crude extracts of U. massaica and positive control (Gentamycin and Ciprofloxacin) were reported against the selected group of microorganisms. However, non-significant differences (P>0.05) in inhibition zones between aqueous and methanolic crude extracts of U. massaica were reported among the four groups of microorganisms used in the study.Inhibition zones of aqueous crude extracts of U. massaica arraigned between 6.50 and 6.67mm while those of methanolic extracts were between 6.33 and 8.42mm.The aqueous crude extracts of U.massaica did not show any antimicrobial activity (6.00mm) against E. coli. There were no significant differences (p>0.05) in inhibition zones among the test plants from the four regions of the study. Inhibition zones of U. massaica crude extracts sampled from Kericho, Kitale, Marigat and Eldoret ranged between 13.08-14.75mm, 13.17-13.83mm, 13.17-14.00mm and 13.08-14.67mm respectively.The methanolic extract of the U. massaica from Eldoret showed presence of saponins, tarpenoids, steroids and flavonoids. Extracts from Kitale and Kericho recorded the presence of alkaloids, steroids and flavonoids, while those from Marigat reported the presence of saponins, tarpenoids, steroids and tannins. It was concluded that themethanolic extracts of U. massaica could bepotential source of drug formulation against the bacterial microorganisms (S. aureus and E. coli) and fungi (C. albicans and A. flavus).