In vitro activity of aqueous and methanol extracts of Callistemon citrinus (Family Myrtaceae) against Leishmania major.

Abstract

Leishmania major is a protozoan parasite that causes cutaneous leishmaniasis and the standard drugs are expensive and toxic. Cheaper and safer natural drugs are therefore needed. In this study, the in vitro efficacy of crude extracts of callistemon citrinus were tested against l. Major. Controls were anti leishmanial drugs pentostam and liposomal amphotericin b. The minimum inhibitory concentrations of c. Citrinus crude aqueous and methanolic extracts were 5mg/ml and 1mg/ml respectively compared to 12.5µg/ml and 6.25µg/ml for pentostam and liposomal amphotericin b respectively. The ic50 for c. Citrinus extracts against promastigotes ranged from 297.75 to 572.69µg/ml compared to 0.26 and 0.82µg/ml for pentostam and liposomal amphotericin b. The ic50 for c. Citrinus extracts against vero cells ranged from 467µg/ml to 1314.65µg/ml. The promastigotes’ viability after treatment with aqueous and methanolic extracts was 69.58% and 75.74% respectively. At 125µg/ml, the aqueous and methanolic c. Citrinus extracts had in vitro amastigotes’ infection rates (irs) of 77.0±2.50 % and 77.5±3.50% respectively. The multiplication indices (mis) and irs of amastigotes treated with c. Citrinus crude aqueous extracts and those treated with crude methanolic extracts differed insignificantly (p > 0.05). C. Citrinus methanolic extracts stimulated production of about 20µm nitric oxide in balb/c mice peritoneal macrophages suggesting immuno-modulatory role of the extracts. The crude aqueous and methanolic extracts of c. Citrinus were therefore concluded to be relatively less toxic and possessed in vitro anti-leishmanial activity against l. Major promastigotes and amastigotes.