Anti-leishmanial activity of acacia mellifera (leguminosae: momosoideae) against leishmania Major

Leishmaniasis is a major group of parasitic diseases in the tropical regions. Their public health importance requires integrated measures in order to ensure effective control of the disease. Chemotherapy is the mainstay of control with pentavalent antimonial agents still widely used as the drugs of choice. However, these drugs are associated with many undesired effects, which include renal and cardiac toxicity, myalgia, anthralgia, pancreatitis, gastrointestinal problems, cardiac arrhythmia and sudden death. The antimonials are also very expensive, and require a long period of administration. Subsequently, the search for compounds with possible antileishmanial activity is growing. A lot of focus is currently being given to natural products. It has long been known that plants are a rich source of compounds with potential medicinal uses. Acacia mellifera subsp. mellifera is a recognized medicinal plant used for conditions such as malaria, pneumonia, sterility, stomach problems and primary stages of syphilis. However, limited information is available on its isolated metabolites. The main objective of this study was to determine whether A. mellifera has any antileishmanial activities. To achieve this the stem bark and leaves of A. mellifera were extracted using methanol and dichloromethane then extracts evaluated against Leishmania major promastigotes and amastigotes in vitro. Further fractionation on dichloromethane extracts yielded nine fractions designated as fractions I-IX. The effects of extracts as well as fractions were evaluated both in cell free media and using infected macrophages. To evaluate the immunostimulatory activities of the extracts, production of nitric oxide in supernatants from macrophages stimulated with extracts was detected by Griess test. All tests were done in triplicate. Statistical analyses of the results obtained were done by analysis of variance, chi-square and Kruskal- Wallis test. Results revealed that extracts containing a combination of methanol and dichloromethane had the highest activity against L major promastigotes in cell-free culture. 100% mortaJity was observed on promastigotes cultured with 5mg/ml of the methanol and dichloromethane crude extracts. The methanol and dichloromethane stem bark extracts, however, did not inhibit the transformation of L major amastigotes into promastigotes (P>0.05). The stem bark methanol extract had the lowest infection rate of 41.35%. Infection rates of the extracts compared to a positive control had a difference (X2 =13.89; df=9; P>0.05). The fractions of dichloromethane had a statistically significant difference in their infection rates (F=6.827; df=4,15; P0.05). These results suggest another possibJe mechanism of action of the fractions other than through stimulation of nitric oxide production. A comparison of the immunostimulatory effects between the methanol and dichloromethane indicated production of nitric oxide by the methanol extract. There was a difference (H4444= 14.04; P<0.05). The results from this study demonstrate that Acacia mellifera indeed has activity against Leishmania major parasites. This is a major contribution toward attainment of the Millenium Development Goal that seeks to combat disease.