Isolation and Characterisation of Anti-plasmodial Compounds from Selected Medicinal Plants from South Nyanza Region

Abstract

Malariacaused by Plasmodium parasites, still has an overwhelming impact on public health in developing nations. Due to its prevalence, virulence and drug resistance, it remainsone of the most serious and widespread parasitic disease in sub-Saharan Africa. The fight against malaria has been hampered by inadequate drug supply, high costs of drugsandlack of an effective vaccine. Consequently there is need for continued research on the discovery and development of new more efficacious anti-malarial drugs. In this work, bio-evaluation of three Kenyan medicinal plants used in treatment of malaria in westernKenya:Clerodendrum myricoides (Oliv.), Clerodendrum rotundifolia (Hochst.), and Hypoestesforskolei (Vahl.), was undertaken. The root extracts were sequentially extractedstarting with hexane, DCM, EtOAc and MeOH. Isolation of compounds was doneby column,preparative and thin layer chromatography. Identification of compounds was done by IH NMR, COSY, I3C NMR, DEPT, HMBC, IR, mass spectroscopy and comparisonwith published data. Preliminary activity and cytotoxicity studies were done on vero cells 199. Extracts were screened against Plasmodium falciparum chloroquine sensitivestrain (D6) and the following results noted: C. myricoides (hexane 8.72±1.81, DCM IOl±1.56, EtOAc <3.91 and MeOH 19.73 ug/ml.), C. rotundifolia (hexane 4.65±O.64,DCM 9.6l±O.lI, EtOAc 5.81±0.47 and MeOH 8.06±O.35 ug/ml.) and H. forskolei (hexane 14.l2±3.75, DCM 4.00±1.25, EtOAc 20.l0±14.03 and MeOH 4.92±0.44 ug/ml.). Hypoetesforskolei DCM extract yielded 3,4a,7,7,10a-pentamethyl-3- vinyl dodeca hydrobenzo [f] chromene(93) and 3,4a,7,7,10a-pentamethyl-3-vinyl dodeca hydrobenzo [f] chromen-Bsol (94) and kaur-16-ene-19-oic acid (95); Clerodendrum myricoidesEtOAc fraction afforded stigmasterol (89), lupeol (90), and p-hydroxy benzyl octaeicosanoate (91) while Clerodendrum rotundifolia DCMlEtOAc fractions realized oleanolicacid (92). p-hydroxyhe~l octaeicosanoate (91) is being reported for the first time from Clerodendrum myricoides, while, 3,4a,7,7,10a-pentamethyl-3-vinyl dodeca hydrobenzo[f]chromene(93) and 3,4a,7, 7,1Oa-pentamethyl-3-vinyl dodeca hydrobenzo [f]chromen-8-01(94) and kaur-16-ene-19-oic acid (95) are also reported for the first time from Hypoetes forskolei. The isolated compounds exhibited mild to moderate antiplasmodial activity against chloroquine sensitive Plasmodium falciparum strain (D6). The results obtained form a good basis for further investigation of the isolated compounds for possible synergism and structure activity studies to improve their antiplasmodial activity. The isolated compounds can be good leads for development into anti-malarial compounds.There is need therefore to preserve the plants as well as the .extractedcompounds for further structure-activity studies