Antiplasmodial Activity Cytotoxicity and Phytochemical Composition of Justicia Betonica Vernonia Dumicola and Rotheca Myricoides and Their Combinations

ABSTRACT

Malaria, a disease caused by Plasmodium species is currently the main cause of human sickness and death in the world, more so in the tropics. It mostly affects pregnant mothers and children below five years of age. The parasites develop resistance to antiplasmodial drugs and this has been a challenge in control and treatment of the disease through chemotherapy, something that necessitates the continuous search for alternative antiplasmodial agents. The use of plants to treat malaria and other ailments has been there since time immemorial. The plants: J. betonica, V. dumicola and R. myricoides are among the many that are used traditionally to treat malaria. In spite of this use, their antiplasmodial activity and toxicity has neither been scientifically confirmed nor evaluated. The World Health Organization suggests scientific evaluation of the safety of medicinal plants though they are generally regarded as safe. There are no reports on the scientific evaluation of the safe and effective concentraton of these extracts.This study aimed at determining the antiplasmodial activity, cytotoxicity and qualitative phytochemical composition of aqueous extracts of J. betonica aerial parts, and leaves of V. dumicola and R. myricoides. The plant materials were collected from Gucha region, Kisii County and transported to Kenyatta University. In vivo antiplasmodial activity of the aqueous extracts of the plants was tested in a four day suppressive assay using Plasmodium berghei in mice. In vitro antiplasmodial activity was done using the D6 strain of Plasmodium falciparum. Cytotoxic evaluation was doneusing the vero cell-line in vitro using the MTT assay. Qualitative phytochemical screening was done according to standard protocols. The aqueous extract of R. myricoides leaves had the highest chemosuppression with an IC50 value of 1.32±0.03μg/ml while lowest chemosuppression was in the combined aqueous extract of J. betonica aerial parts and leaves of V. dumicola. This recorded an IC50 value of 11.03±1.18μg/ml. For cytotoxicity studies, aqueous extract of J. betonica aerial parts recorded the lowest cytotoxic activity with IC50 value of 690±11.00μg/ml whereas aqueous extract of R. myricoides leaves recorded highest cytotoxic activity with IC50 value of 106.00±8.00μg/ml. According to the selectivity index (SI) criteria, all the extracts showed SI value above 3 indicating the plant extracts were selective. All the plant extracts tested contained anthraquinones, phenols and tannins. They all showed antiplasmodial activity which could be attributed to the phytochemicals observed. The three plants analysed in this study are recommended for development of antimalarial agents.