Ethnopharmacology of Antimalarial Plants Used Among the Luhya Community in Kakamega East Sub-county

Abstract

Malaria remains a major disease in Kenya responsible for high mortality especially in the children aged under five years and pregnant women. Many communities in Kenya still use plants for the management of malaria. An ethnobotanical survey was conducted among 21 herbal practitioners in Kakamega East sub-County in Western Kenya to identify antimalarial plants used by the Luhya community. Two plants, Leucas calostachys Oliv. and Justicia betonica L. were selected after the ethnobotanical survey for evaluation of their antimalarial activities and phytochemical constituents. Most of the herbal practitioners interviewed were aged more than 50 years old and had a low level of formal education. A total of 42 plant species in 24 plant families were identified for the management of malaria. Two plants, Rumex steudelii Hochst.ex A. Rich and Phyllanthus sepialis Müll. Arg are reported for the first time for the management of malaria. The Lamiaceae family was the most frequently encountered for treatment for malaria in this community. Melia azedarach L, Aloe spp, Ajuga integrifolia Buch. Ham, Vernonia amygdalina Del., Rotheca myricoides (Hochst.) Steane and Mabb, Fuerstia africana T.C.E.Fr., Zanthoxylum gilletii (De Wild.) P.G. Waterman and Leucas calostachys Oliv. were the most commonly used plants for treatment of malaria. Leucas calostachys Oliv. and Justicia betonica L., were selected for antimalarial activity testing and phytochemical evaluation. Extracts of Leucas calostachys and Justicia betonica were studied for activity against chloroquine-sensitive 3D7 Plasmodium falciparum and β-hematin inhibition. The methanol extract and ethylacetate extract of Leucas calostachys and Justicia betonica respectively showed the best antiplasmodial activity and β-hematin inhibition activity. This is the first report of β-hematin inhibition activities of these plants. Bio-assay guided fractionation led to the tentative identification of compounds from active fractions of Leucas calostachys and Justicia betonica using LCMS/MS. Eight flavonoidal compounds and 12 phenylethanoid were identified from the methanol fraction of Leucas calostachys. The flavonoids were: isorhamnetin, luteolin-7-O-glucoside, luteolin-4́́ -O-glucoside, luteolin diglucoside, apigenin-O-glucoside, genistein-O-glucoside, chrysoeriol-7-O-glucoside, and chrysoeriol-7-O-glucuronide. Seven phenylethanoid compounds were identified and included acteoside, isoactoeside, hydroxyacteoside, forthsoside B, samioside, alyssonoside and leucoseptoside A. Five other phenyethanoids could not be identified. This is the first report of any phytochemicals from Leucas calostachys. Similarly, 13 compounds were identified from active fraction of J. betonica and these included five carotenoids and nine indoloquinolines. Four of the carotenoids were lutein/zeaxanthin, anhydrolutein I, anhydrolutein II and lutein 5, 6-epoxide. On the other hand, five of the indoloquinolines identified were 5H, 6H quinindolin-11-one, 10H indolo [3,2-b] quinoline, 6H indolo [2,3-b] quinoline, 11H indolo [3,2-c] quinoline and 7H indolo [2,3-c] quinoline. The rest of the compounds could not be identified using the LCMSMS. This is the first time carotenoids, 11H indolo [3, 2-c] quinoline and 7H indolo [2, 3-c] quinoline have been identified in this plant. The results of this study supports the use of Leucas calostachys Oliv. and Justicia betonica L. in the treatment of malaria among the Luhya community in Kenya. It therefore justifies the continued search of antimalarial medicine from natural sources based on folkloric information.