Phytochemical investigation, in-vitro antiplasmodial assessment and cytotoxic effect of ethanol extract of whole plant of Crotalaria arenaria (Benth)

Crotataria arenaria (Benth) is a native plant from Northern part of Nigeria which is employed as antimalarial herb in traditional medicine in the communities where it grows. The phytochemical composition, In-vitro antiplasmodial activity and in-vitro cytotoxic effect of the extract and fractions of the whole plant of Crotalaria arenaria were investigated. The mature and fresh whole plant of C. arenaria were collected, air dried and pulverized. The pulverized form of the plant were soaked in ethanol for two weeks and later decanted, filtered and concentrated using rotatory evaporator at 40oC and evaporated to dryness and labeled CRA-1. The dried ethanol solid extract (CRA-1) was patitioned/fractionated using water, chloroform, ethyl acetate, 18% aqueous methanol, n-hexane which afforded chloroform fraction (CRA-1-01), water fraction (CRA-1-02), ethyl acetate fraction (CRA-1-03) aqueous methanol fraction (CRA-1-04) and n-hexane (CRA - 1- 05) and they were dried and tested for their photochemicals and In-vitro antiplasmdial activity against Plasmodium falciparum strain (K1). The ethanol extract and its fractions were found to significantly inhibited/suppressed multi-drug resistant strain of P. falciparium (K1) in the range of 86.73% - 65.31% at varied concentrations of 5000 µg/ml, 2000 µg/ml, 1000 µg/ml and 500 µg/ml. The ethanol extract and its fractions showed the presence of tannins, saponins and alkaloids which could be responsible for the In-vitro antiplasmodial activity of the whole plant extract of C. arenaria and each of its fractions. Ethanol crude extracts of whole plant of Crotalaria arenaria and its fractions were investigated for cytotoxicity in Brine shrimp lethality Test (BSLT). Larvicidal activities were noticed with dosage concentration from 1000 µg/ml down to 10 µg/ml of the plant extract and all its fractions. The relative cytotoxic effects of extract and fractions obtained from whole plant of Crotalaria arenaria were found to be dose-dependent because higher dosage brought about an increase in mortality of Artemia salina Leach. Sea salty water of the crude ethanol extract and its fractions served as the negative control. The chloroform fraction was observed to be most cytotoxic killing 30% of brine shrimp larvae at lowest concentration of 10 µg/ml with average percentage lethality of 46.67%. Aqueous methanol and ethanol crude extract appears to show similar and closely related activities against brine shrimp larvae at highest concentration of 1000 µg/ml. The ethanol crude extract and aqueous methanol fractions are toxic at higher dosage as they were found to induce significant mortality effect (In-vitro) against Artemia salina Leach particularly at concentration of 1000 µg/ml and therefore not safe for oral consumption especially at higher uncontrolled doses but at relatively low/moderate doses. The findings in this present study demonstrated that the extract of C. arenaria (whole plant) and fractions have significant in vitro antiplasmodial activity and this has justified the traditional use of the whole plant extract of Crotaria arenaria in the folklore medicine to cure malaria related illness. The results obtained in this study may serve as key data for utilization of Crotalaria arenaria in the development of bioactive agents which could be used as antimalarial, anticancer, pesticidal, insecticidal and anti-proliferation agents. The study recommended in-vivo antiplasmodial assay of the extract of the whole plant of Crotalaria arenaria to further substantiate the findings of this present study.