PHYTOCHEMICAL PROFILES AND ANTIMALARIAL ACTIVITY OF MEDICINAL PLANT EXTRACTS USED BY THE MARAKWET COMMUNITY IN KENYA

Abstract

Malaria continues to have a devastating impact on public health. Resistance to antimalarial drugs is a threat to treatment of malaria. Globally, medicinal plants have been used to treat malaria for a long time. This study aims to establish the medicinal plants used to treat malaria in Marakwet East Sub County and to determine their efficacy and safety. Ethno-botanical survey was conducted through oral interviews using a semi structured questionnaire. The plant materials reported by the traditional health practitioners as medicine used to treat malaria were collected, taxonomically identified, voucher specimens deposited at the University of Eldoret herbarium and processed for phytochemical extraction using ethanol and water solvents. Antimalarial activity was assessed in vivo using Plasmodium berghei ANKA strain- infected female Swiss albino mice (20±2g), for each extract the mice received a daily oral dose of 400mg/kg body weight for 4 days. The positive control received Artemisinine/Lumefantrine combination at 5 mg/kg/day orally, while the negative control group received placebo treatment of 10% Tween 80. Percentage chemo suppression was calculated from the percentage parasitaemia of the negative control and the test drugs. Effects of the plant extracts on change in body weight and improvements on survival time were determined. Cytotoxicity was assessed in vitro using Thiazolyl Blue Tetrazolium Bromide (MTT) assay on VERO E6 cell lines at 100µg/ml. Acute toxicity of the extracts was tested in Swiss albino mice up to a dosage of 2000mg/kg body weight. The results showed that thirty-one medicinal plants belonging to twenty-four botanical families were used to treat malaria in Marakwet East Sub County. Capparaceae and Rutaceae (9.7 %) were the most used families, and Ximenia americana (39.3%) and Boscia coriacea (32.1 %) were the most frequently used plant species to treat malaria in the study area. Most of the medicinal plants were shrubs (41.9 %) and leaves were the most frequently used plant parts (39.13%). All the extracts were active in vivo at 400mg/kg body weight, with chemo suppression ranging from 31.55 ± 1.28 % to 68.77 ± 2.44 %. There was significant (P≤ 0.05) parasite density reduction in mice that received the test extracts compared to the negative control. Ethanol and water extracts of Ximenia americana were the most active plant extracts with chemo suppression of 68.77 ± 2.44 % and 64.09 ± 1.34 % respectively. Ethanol extract of Adenia gummifera was slightly cytotoxic with a CC50 of 87.92 μg/ml when tested up to 100µg/ml. The other tested plant extracts passed the safety test with CC50 ≥100µg/ml. Eight ethanol and water medicinal plants extracts tested for acute toxicity did not cause mortality at the high dose of 2000mg/kg body weight, thus confirming their safety to mammals. This study validates the traditional use of the evaluated medicinal plants to treat malaria. It was recommended that the most active plant extracts Ximenia americana, Boscia coriacea and Capparis cartileginea can be targeted for further exploration, formulation and promoted for conventional use to treat malaria. Further research on the toxocity of the remaining medicinal plants is also recommended.