EVALUATION OF PRIORITIZED MEDICINAL PLANTS FOR THEIR BIOACTIVITY IN KAIMOSI AREA OF NANDI AND VIHIGA COUNTIES OF KENYA

Abstract

The use of traditional plant medicine in treatment relies on presence of biologically active compounds that aid in combating diseases. In Kenya different plant species are used to treat several diseases especially among the population where modern medicine is either not accessible or affordable. Drawbacks facing traditional medicine include issues pertaining to safety, efficacy, quality, access and rational use of traditional herbal medicine, and training in herbal medicine. This study was undertaken to evaluate the prioritized medicinal plants in Kaimosi area of Nandi and Vihiga counties for bioactivity of plant extracts for validity of efficacy against disease causing microorganisms. Ethnomedicinal knowledge was documented using lead questions on a questionnaire from herbal practitioners and claims of efficacy of some of the plants as antimicrobial agents by herbal practitioners investigated. Various plants were select by ranking methods to be used for antimicrobial tests. The disc diffusion method was used to ascertain the efficacy of plant extracts and to detect those that were active so as to subsequently determine their minimum inhibitory concentrations using the microdilution method. One hundred and seven species belonging to 94 genera distributed in 44 families were documented with the highest number of species belonging to the Asteraceae (21.5%), followed by the Euphorbiaceae and Fabaceae (7.5%). Taxonomic keys were prepared for all the species collected. The leaves comprised the plant part most frequently used for medicinal purposes (78%) followed by the roots (34%) and the whole plant (21%). The methods commonly used to prepare the ethnomedicines included infusions (49.7%) and decoctions (21.7%), and the most common route of drug administration was oral (63.1%) followed by topical application (23%). Crude extracts of increasing polarity i.e. petroleum ether, chloroform, methanol and water from eleven selected plants; were tested against thirteen test microbes to evaluate their efficacy. The extracts from Lantana trifolia were the most active against bacteria (14 extracts out of 28) and those of Fuerstia africana (10 extracts out of 24) against fungal isolated with activity in the range of 1mm to 7 mm(6 mm subtracted from gross measure) for the former and from 1mm to 2 mm for the latter. The isolates most susceptible to the extracts were Shigella sp. (Shigella flexneri, 39 extracts and Sh. sonnei, 22 extracts), Bacillus subtilis (26 extracts) and Staphylococcus aureus (13 extracts) each out of 44 extracts. Chloroform and methanol extracts of L. trifolia had the largest inhibition zone of 7mm diameter against Sh. flexneri and 6.5mm against S. aureus. Isolates of Pseudomonas aeruginosa, Salmonella typhi and Trichophyton mentagrophyte were resistant to all plant extracts with no clearance zone on the agar plates. Fuerstia africana produced the most promising results on both fungal and bacterial isolates, giving a MIC value of 0.051 mg/ml against Shigella flexneri and 0.102 mg/ml against Staphylococcus aureus. The results of the documentation of medicinal plant in Kaimosi are significant in aiding in the production of the countries’ pharmacopoeia and in overall, the study support the use of medicinal plants in the management of infectious diseases in the study area.