Effects of S-Allyl-Cysteine on Survival, Apoptosis, and Proliferation of Leishmania Major in Vitro

Background: Many studies have suggested the benefits of garlic oil extracts against Leishmania parasites. Recent research has proved that these derivatives (such as allicin) are cytotoxic and therapeutic effects of garlic are in fact due to an odorless compound (S-allyl-cysteine). Considering the small number of studies in this field, we evaluated the effectiveness of S-allyl-cysteine on survival, apoptosis, and proliferation of Leishmania major promastigotes in vitro. Methods: In this study Leishmania major promastigotes (MRHO/IR/75/ER) were used. The parasites were first cultured and then treated with S-allyl-cysteine at end concentrations of 2.5, 5.0, 10.0, 20.0, 40.0, and 50.0 mM. Their survival, apoptosis, and proliferation was assessed after 72 hours. Findings: None of the concentrations of S-allyl-cysteine could induce apoptosis in parasite promastigotes. Lower concentrations (5.0 and 10.0 mM) of S-allyl-cysteine had greatest effect on proliferation. On the other hand, direct observation showed that cultures comprising S-allyl-cysteine at end concentration of 20.0, 40.0, and 50.0 mM formed more rosettes. Conclusion: The antioxidant effects of S-allyl-cysteine have been previously proved. Similarly, this study showed that some concentrations of S-allyl-cysteine could affect the survival and growth of promastigotes in culture medium. Therefore, this substance seems to be a good stimulating factor for growth of parasite promastigotes in culture media.