In vitro study of the efficacy of Solanum nigrum against Leishmania major

Abstract

Leishmania parasites (Kinetoplastida: Trypanosomatidae) are obligate intracellular parasites of macrophages that causes visceral and cutaneous leishmaniases. Currently, there is inadequate therapeutic interventions to manage this endemic tropical disease, transmitted mainly by phlebotomine sandflies hence there is need to develop affordable and effective therapeutic measures. This study determined the in vitro efficacy of Solanum nigrum methanolic and aqueous plant extracts on Leishmania majo r parasites.  Cytotoxic effects of the extracts were determined using vero cells and reported as percentage viability of the cells. The promastigote parasites of Leishmania major were cultured and grown for 3 days in different concentrations of extracts to determine the MIC and IC 50 values. The in vitro antileishmanial efficacy was done on macrophages infected with L. major amastigote parasites and then treated with extracts in varying concentrations. The study revealed that all the test extracts had lower toxicity than control drugs, pentostam (IC 50 = 0.0 92 mg/ml) and amphotericin B (IC 50 =0.049 mg/ml).  The extracts tended to show a dose dependent cytotoxic effect which corresponded to high vero cells viability as their concentration increased.  Methanolic extract of S. nigrum from Kisii seemed to be more efficacious in vitro since it knocked out the promastigotes at a lower MIC level (0.5 mg/ml) when compared to all other extracts whose effective MIC level was ≥ 1 mg/ml. High concentrations of the test extracts and control drugs resulted to low infectivity and multiplication of L. major amastigotes. Findings from this study demonstrate that S. nigrum extracts have potential antileishmanial activities however; further investigation needs to be done on pure compound isolation, in vivo assays and clinical trials so as to use the promising compounds as effective antileishmanial agents.