Efficacy of the combination of crude extracts of Solanum nigrum and Plumbago capensis on Leishmania major
Background:Leishmaniasis is an endemic tropical disease caused byLeishmaniaparasites, transmitted mainly by phlebotomine sandflies, impacting both health and socioeconomic wellbeing. Currently there are inadequate therapeutic measures to manage the disease thus indicating the need for the development of affordable and effective therapeutic interventions from herbal plants as alternative medicine. This study investigated theinvitroantileishmanial effects of blends of crude extracts ofSolanum nigrumandPlumbago capensisagainstLeishmania major.Methods:The promastigote parasites ofLeishmania majorwere cultured and grown for 3 days in different concentrations of the individual extracts to determine minimum inhibitory concentrations (MIC). Thein vitroantileishmanial efficacy was determined by exposing promastigotes and macrophages infected withL. majorto the blends of extracts in ratios of 2000:250, 1000:500, 500:1000 and 250:2000. Finally, nitric oxide released byL. majorinfected macrophages that were treated with the plant extracts at ratio of 125:125 was quantified using a standard nitrite curve.Results:The individual methanol extracts were most effective in inhibiting the growth of promastigotes with MIC values between 0.25 mg/ml and 1.0 mg/ml as compared to aqueous extracts. The most active ratios for the blends were 250:2000 and 2000:250 for methanolic and aqueous blends respectively. The infection rates and multiplication indices associated with all the combined extracts were significantly different (P< 0.05) from those of pentostam and amphotericin B at all the concentrations studied. The OD for the combined test extracts ranged between 0.034 and 0.041 and these corresponded to < 5 µM of NO.Conclusion:Findings from this study demonstrate that combination therapy usingS. nigrumandP. capensisextracts is effective in treatingLeishmania major infection. Based on our findings we recommendin vivostudies to be conducted to determine the efficacy of these combined therapies againstLeishmaniamajor.