Efficacy of the combination of crude extracts of Solanum nigrum and Plumbago capensis on Leishmania major

Background: Leishmaniasis is an endemic tropical disease caused by Leishmania parasites, 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 the in vitro antileishmanial effects of blends of crude extracts of Solanum nigrum and Plumbago capensis against Leishmania majo r . Methods: : The promastigote parasites of Leishmania major were cultured and grown for 3 days in different concentrations of the individual extracts to determine minimum inhibitory concentrations (MIC). The in vitro antileishmanial efficacy was determined by exposing promastigotes and macrophages infected with L. major to the blends of extracts in ratios of 2000:250, 1000:500, 500:1000 and 250:2000. Finally, nitric oxide released by L. major infected 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 using S. nigrum and P. capensis extracts is effective in treating Leishmania majo r infection. Based on our findings we recommend in vivo studies to be conducted to determine the efficacy of these combined therapies against Leishmania major .