Abstract
Cutaneous leishmaniasis, a neglected tropical disease (NTD) caused by Leishmania tropica, Leishmania major and other members of the same species, poses significant challenges in the public health sector, especially in developing countries. The limitations of current treatments, including toxicity, resistance, availability, and cost effectiveness, necessitate the development of novel therapeutics. This study investigated the leishmanicidal potential of five Thiadiazine thione derivatives (THTT) against L. tropica, at a dose range of 25-426 µM using an MTT assay. Compounds T9, T24, T25 (tris-THTT) and PG (mono-THTT) exhibited notable IC(50) values of 20.01, 26.94, 27.71, and 82.79 µM, respectively. Moreover, the same compounds demonstrated promising docking scores against critical leishmanial enzymes, such as Trypanothione reductase, Trypanothione synthetase, Leishmanolysin, and C24-sterol methyl transferase. Hemolytic assay revealed that all the compounds are non-toxic at lower concentrations. Mono-THTTs (PG and BG) showed higher CC(50) values i.e., 401.65, 375.68 as compared to tris-THTTs (T9, T24, T25) which is 104.61, 104.51 and 89.73 µM respectively. All derivatives showed high selectivity indices (SI) compared to the standard drug Amphotericin-B. Furthermore, in-silico investigations targeting COX1 and COX2 enzymes unveiled a high affinity of the tested compounds towards these enzymes, indicating their potential involvement as anti-inflammatory agents. Subsequent in-vitro HRBC membrane stabilization and egg albumin denaturation assays confirmed the anti-inflammatory potential of all the compounds. These findings validate THTT derivatives as an effective and novel class of anti-leishmanial agents against L. tropica with a favorable safety profile and potential anti-inflammatory properties. Further research is recommended to elucidate their mechanisms of action and in-vivo efficacy.