Abstract
Background and aims: The search for naturally derived drugs with higher efficacy and fewer side effects for treating leishmaniasis, a zoonotic infectious disease, has become a significant focus in research. This study aimed to evaluate the inhibitory and lethal effects of the natural alkaloid trigonelline compared to the synthetic drug glucantime, as well as to assess their potential synergistic effects on the promastigote and amastigote stages of Leishmania major (MRHO/IR/75/ER) under in vitro conditions. Methods: In this experimental study, L. major promastigotes and amastigotes, along with mouse macrophages (J774), were cultured and treated with the compounds under investigation. Cell viability was determined using the trypan blue exclusion test, metabolic activity was measured with the MTT colorimetric assay, and inhibition of amastigotes within macrophages was evaluated using Giemsa staining. Results: Trigonelline[PK1] , as a natural compound, at concentrations of 25, 50, 100, and 200 µg/mL significantly reduced the survival rate of promastigotes (P<0.001). Additionally, trigonelline enhanced the anti-leishmanial efficacy of glucantime against both promastigote and amastigote stages at lower doses (P<0.001). The cytotoxicity (CC50) for macrophages treated with[PK2] glucantime was 349.1 µg/mL, with trigonelline it was 1863.3 µg/mL, and for the combination treatment, it was 476.3 µg/mL. Conclusion: Trigonelline exhibited a synergistic effect with glucantime, improving its anti-leishmanial activity. Due to its antioxidant properties, lower cytotoxicity to macrophage cells, and the potential for reducing glucantime dosage in combination therapy, trigonelline presents a promising option for the treatment of leishmaniasis. [PK1]Comment of the Second Reviewer: Compounds Trigonelline, as a natural compound [PK2]Comment of the Second Reviewer: Compounds We have described it in the background.