Anti-malarial activity and phytochemical studies of cissampelos mucronata and Stephania Abyssinica
Omole, Ruth Anyango
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Malaria remains the most important public health problem in the tropics. Each year, about 500,000,000 and 2,700,000 malaria cases and related deaths, respectively, are reported globally with Africa accounting for 90%. In Kenya, more than 4 million people are infected annually, the majority being children under five years and pregnant women. The disease is caused by parasites in the genus Plasmodium and is transmitted through bites of infected female anopheline mosquito. It is the most serious disease due to its prevalence, virulence and drug resistance. Chemotherapy remains the main strategy in malaria control but has become less effective due to widespread drug resistance, high cost and inadequate armory of drugs for treatment of malaria. Consequently there is need for research and the discovery of new more effective anti-malarial agents with different mode of action. Plants are considered as important sources of lead compounds in drug development owing to their successful use in treatment of various human ailments since antiquity. In search for new anti-malarial principles, bio-evaluation of Cissampelos mucro nata and Stephania abyssinica which are used in treatment of malaria by people living in southern Nyanza was undertaken. The crude extracts were sequentially extracted starting with hexane, DCM, EtOAc and MeOH. Isolation of the compounds was done using TLC, CC and PTLC. Identification of the compounds was done by IH NMR, COSY, l3C NMR, DEPT, HMQC, HMBC, mass and IR spectroscopy. Preliminary activity and cytotoxicity studies were done on Vero cells 199. Extracts were screened against Plasmodium Jalciparum D6 strain and the following anti-plasmodial activity noted: C. mucronata (hexane: ICso 8.73±1.8l ug/ml, DCM: ICso 1O.09±l.S6 ug/ml, EtOAc: ICso <3.91 ug/ml and MeOH: ICso 19.78±2.38 ug/ml) and S. abyssinica (DCM: ICso <3.91 ug/m, EtOAc: ICso S.09±0.041 ug/m and MeOH: ICso 9.61±0.1lllg/m). Cytotoxicity bioassay of crude extracts was done using vero cells 199 and S. abyssinica hexane extracts, DCM, EtOAc and MeOH (CCso 82.12 ug/ml, 100 ug/ml, 100 ug/ml and 100 ug/ml, respectively) were not toxic to vero cells 199. Ethyl acetate extract of C. mucronata exhibited toxicity to vero cells 199 (CCso 10.34 ug/ml) although it was the most active extract against P. Jalciparum (D6) while hexane: (CCso 90.34 ug/ml) , DCM (CCso 100.00 ug/ml) and MeOH (CCso 66.33 ug/ml) extracts were not toxic. (-)-Stigmasterol (204) and (- )-curine (205) were isolated from C. mucronata while (+ )-nonacosan-1 0-01 (206), (- )-S-oxoaknadinine (207), (-)pseudocurine (208) and (- )-isocurine (209) were reported from S. abyssinica for the first time. Anti-plasmodial activity was exhibited by (- )-curine (205): ICso 0.24±0.03 ug/ml, 0.22±0.06 ug/ml), (+)-nonacosan-10-ol (206) (lCso 13.79±1.02, 4.3S±2.4S ug/ml), (-)-S-oxoaknadinine (207) (ICso 10.2S±1.84, 3.4S±2.22 ug/ml), (-)-pseudocurine (208): ICso 0.29±0.00 ug/ml, O.3l±0.Ol ug/ml) and (-)-isocurine (209) (lCso 0.7S±0.11 ug/ml, 1.6S±O.03 ug/ml) against D6 and W2 strains, respectively. It was confirmed that some of the compounds isolated from the two plants had strong anti-malarial activity making them good candidates for further scientific research on anti-plasmodial drug discovery and development. The results thus validate the ethnobotanical medicinal use of the two plants for the treatment of malaria despite potential toxicity exhibited by organic extracts.