Antiplasmodial activity of methanol leaf extract of <i>Cryptolepis oblongifolia</i> (Apocynaceae) (MEISN) SCHLTR in mice infected with <i>Plasmodium berghei-berghei</i>

Abstract

Malaria remains a major public health problem in Sub-saharan Africa, where 85-90% of all global burden of the disease exist. In traditional medicine, Cryptolepis oblongifolia is used to cure cough, malaria, stomachache and diarrhoea. The aim of this study is to evaluate the antiplasmodial activity of the methanol leaf extract of Cryptolepis oblongifolia in mice infected with Plasmodium berghei. Oral median lethal dose (LD₅₀) and phytochemical screening of the extract were carried out using OECD 425 guidelines and method of Trease and Evans respectively. The antiplasmodial activity of the plant was studied using chloroquine-sensitive Plasmodium berghei-berghei in three rodent malaria models: Curative, suppressive and prophylactic. Data were analyzed using one way ANOVA followed by Dunnett’s post hoc test. The oral median lethal dose (LD₅₀) of the extract was found to be > 5000 mg/kg. The extract  contained alkaloid, saponin, flavonoid, phenol, cardiac glycosides, steroids, terpenoids and tannins. The extract at the doses tested (375, 750 and 1500 mg/kg) produced significant (p < 0.001) curative effect with percentage parasite clearance of 15.8, 40.3 and 57.9, respectively. The extract also produced significant (p < 0.001) suppressive antiplasmodial effect with percentage chemosuppression of 24.9, 41.2 and 55.5 respectively. A significant prophylactic (p < 0.001) effect was recorded with percentage chemoprophylaxis of 5.7, 20.1 and 44.8, respectively. The extract at the highest dose (1500 mg/kg) prolonged the survival time of the treated mice, in the curative group, to 28 days compared to those in the negative control group that survived for 7.8 days. The results of this study indicate that the methanol leaf extract of Cryptolepis oblongifolia has significant antiplasmodial activity in mice.