Avaliação da atividade tricomonicida de compostos originários do café: um estudo in silico e in vitro

Abstract

Trichomoniasis is a Sexually Transmitted Infection (STI) that affects annually more than 270 million people in the globe, whose etiological agent is the protozoan Trichomonas vaginalis. Recently, the growing observation of clinical isolates resistance to the standard treatment (metronidazole, MTZ) is worrisome and welcomes studies regarding the development of new therapeutic options. The aim of this work was to evaluate compounds commonly isolated from coffee leaves as an alternative to trichomoniasis treatment. For this, in vitro assays were conducted to evaluate caffeine, caffeic acid, chlorogenic acid, quinic acid and mangiferin’s anti-T. vaginalis activity against two strains with different susceptibility to MTZ. As a mean to understand their mechanism of action, ultrastructural evaluation of treated trophozoites was conducted through transmission electronic microscopy (TEM) and molecular docking with the enzyme lactate dehydrogenase assays were carried out. Cytotoxicity of the compounds was evaluated against human and vaginal microbiome bacterial isolate. Three compounds were highlighted for their anti-T. vaginalis activity against MTZresistant strain: caffeine, chlorogenic acid and quinic acid, with IC50 of 4.83 µM, 10.01 µM and 12.73 µM, respectively. Curiously, no compound presented activity against the sensitive strain, indicating that the mechanism of action may reside in specific pathways. TEM analysis showed hydrogenosome’s alterations in the treatment of both organic acids. Caffeine presented enhanced mobilization of endoplasmic reticulum and autophagosomes were observed. In molecular docking all compounds presented strong interactions with the aminoacids residues important to LDH’s catalytic site of T. vaginalis, highlighting chlorogenic and quinic acids and mangiferin with the best score values (respectively, 35.2062, 27.1713 and 26.7005). The three promising compounds didn’t present toxicity against human cells in vitro and were selective to the parasite’s cells (selectivity index >10). No compound presented cytotoxic activity against bacteria commonly isolated from vaginal microbiome at the maximal concentration of 400 µM. In that way, caffeine and chlorogenic and quinic acids showed themselves as candidates as new drugs. As perspectives, enzymatic in vitro and in vivo studies are needed to further characterize the compounds’ mechanism of action and their behavior in more complex biological media.