Study on antimalarial activity of Capsicum frutescens L. fruit extracts during early and established Plasmodium infection in mice

Abstract

Resistance has been a major battle confronting researchers since the first synthetic antimalarials were developed, prompting endemic regions to seek alternate remedy. Capsicum frutescens L. (CFL) fruit is one of such plants used locally to treat fever and malaria. However, there is dearth of information on the most promising in vivo antiplasmodial candidate between crude and solvent-partitioned extractions in animal models. Water, ethyl acetate, and n-hexane were used to extract, assess, and compare the in vivo antiplasmodial activity of CFL crude extracts and solvent-partitioned extracts in chloroquine-sensitive Plasmodium berghei (NK-65)-infected mice. 368 adult albino mice (both sexes) were used; 56 females for toxicity tests, 136 for three extracts and 176 for four fractions using suppressive and curative models. Mice were randomly grouped into five (n = 4) for treatment, while a group for control and a group for choroquine were separately maintained throughout for the crudes and fractions. Group A= 0.2 ml normal saline, group B= 10 mg/kg body weight chloroquine, while groups C-G= 0.5, 1.0, 2.0, 4.0, 8.0 mg/kg body weight CFL respectively for each extract and fraction. All experiments were performed using standard methods. LD₅₀ for both crude extracts and solvent fractions was > 20 mg/kg. Aqueous extract had better antiplasmodial performance among the three extracts while residual fraction did among the four fractions, for both suppressive and curative models. Aqueous fractions had higher concentrations of metabolites, better in vivo antiplasmodial activities, and more prolonged lifespan than crude extracts. CFL administration significantly resisted body weight loss, drop in packed cell volume, and fall in rectal temperature caused by the parasites. This action was more prominent in the fractions than in extracts, especially at 2.0 mg/kg. Therefore, this study established that aqueous extraction is preferable for Capsicum and that crude extraction is not sufficient to harness the in vivo antiplasmodial potential, hence justifying use of water for the preparation in local communities as alternative medicine.