Antiparasitic activity of chalcones analogue against Trichomonas vaginalis: biochemical, molecular and in silico aspects

Trichomonas vaginalis is the etiologic agent of trichomoniasis, a worldwide distributed sexually transmitted infection (STI) that affects the genitourinary tract. Even though this disease already has a treatment in the prescription of drugs of the 5-nitroimidazole class, described low treatments adhesion, adverse side effects and cases of resistant isolates demonstrate the need for new formulations. With this in mind, chalcones emerge as a potential alternative to be tested, being compounds widely distributed in nature, easy to chemically synthesize and presenting several biological activities already reported. In this experiment, we evaluated the antiparasitic activity of 10 chalcone at a concentration of 100 µM against ATCC 30236 T. vaginalis isolates, considering negative (live trophozoites), positive (Metronidazole 100 µM) and vehicle (DMSO 0.6%) controls. Compounds 3a, 3c, 3g and 3i showed promising results, with MICs set at 70 µM, 80 µM, 90 µM and 90 µM, respectively (p < 0,05). Cytotoxicity assays were performed on VERO and HMVII cell lines and revealed low inhibition rates at concentrations bellow 20 µM. To elucidate a possible mechanism of action for these molecules, the DPPH, ABTS and FRAP assays were performed, in which none of the four compounds presented antioxidant activity. Assays to verify ROS and lipid peroxidation in the parasite membrane were performed. None of the tested compounds identified ROS accumulation after incubation with trophozoites. 3g molecule promoted an increase in MDA production after incubation. Results presented in this paper demonstrate the promising trichomonicidal profile, although further tests are still needed to optimize their performance and better elucidate the mechanisms of action involved.