Evaluation of in vitro leishmanicidal activity of tea tree oil (Melaleuca alternifolia)

Leishmania is a trypanosomatid protozoan which is transmitted by the female Phlebotomus sand fly. Leishmaniasis is prevalent in four continents and is considered to be endemic in 88 countries, 72 of which are developing countries. It is estimated that it’s global prevalence and incidence is 12 millions and 500 thousands respectively. The recommended drugs used for the treatment of this disease are mainly ineffective, toxic and exhibit many side effects. Based on some studies,tea tree oil that is a yellow color liquid with spicy odor exhibit antibacterial and antifungal activity, so, we evaluated it’s anti-leishmanial effect. Tea tree oil was purchased from Dr Jahangiri pharmaceutical company and it’s various concentrations (mg/ml800, mg/ml400, mg/ml200, mg/ml100) were prepared in 1ml volume of TSB solvent in 15ml test tubes, then 9 ml of RPMI-1640 medium and 1×106 promastigotes was added to each tube, as a final volume of 10 ml. These tubes were incubated at 23o c for 72 hours and number of parasites in the first 6 hours once every hour and after that every 24 hours were counted by hemocytometer. Lethal dose of tea tree oil for 50% of promastigotes (IC50) is 337 mg/ml, while the 800 mg/ml of this extract can killed 95% of the parasites after 24 hours of incubation, and it’s lower concentrations of this extract showed dose-dependent leishmanicidal activity. Glucantime as positive control drug at concentration of 300 mg/ml killed all the promastigotes, while the number of promastigotes in negative control tubes was increase during the incubation period. Anti-Leishmanial activity of tea tree oil with IC50 of 337 mg/ml and 95% lethality of 800 mg/ml is promising and further study for analyse the active ingredients of this oil and evaluation of it’s anti-leishmanial effect, particularly in laboratory animal is recommended.