Objective: The aim of this study was to investigate phytochemical composition and antileishmanial activities of Thymus carmanicus different extracts individually and in combination with meglumine antimoniate (Glucantime®; MA) to introduce possible complementary drugs against Leishmania major using experimental methods.
Materials and methods: The aerial parts of T. caramanicus were extracted by maceration using a series of solvents, including petroleum ether, chloroform, ethyl acetate, 80% methanol, and water. Total phenolic and flavonoid content was determined using colorimetry and thymol content was determined by HPLC method. Experiments assessed in vitro antileishmanial activity and cytotoxicity.
Results: Although the combination of the petroleum ether extract with meglumine antimoniate exhibited the strongest raw antileishmanial activity against L. major promastigotes (IC₅₀ = 236.5 µg/mL, p<0.001) and amastigotes (IC₅₀ = 43.15 µg/mL, p<0.001), the combination index (CI) value of 1.23 indicated an antagonistic interaction. In contrast, the methanolic extract combined with MA proved to be the most effective candidate for combination therapy, as demonstrated by a CI of 0.92 (suggesting moderate synergism), a satisfactory selectivity index (SI) of 7.04, and a high amastigote mortality rate.
Conclusion: The methanolic extract with compounds like polyphenolics, flavonoids, and thymol, shows high anti-leishmanial activity and safety, making it a good option for combination therapy.