Atividades antioxidante e antimicrobiana de Connarus favosus Planch. e seu papel bloqueador da atividade hemorrágica do veneno de Bothrops atrox, de acordo com o uso tradicional

Abstract

Envenomings resulting from snakebites were classified, in 2009, by the World Health Organization as a neglected tropical disease. In Brazil, the genus Bothrops sp. is responsible for most of these accidents and, in the Amazon region, the majority of snakebite reports is attributed to the species Bothrops atrox. The venom from snakes of the genus Bothrops sp. is composed by proteins such as phospholipase A2, metalloproteinases, among others. The hemorrhagic activity is caused by metalloproteinase which induce vascular damage and ischemic zones which contribute to the appearance of necrosis in the local tissue. The treatment recommended by the Ministry of Health of Brazil against snakebites is the antivenom administration, however, this treatment does not neutralize the local effects satisfactorily. The coastal communities of Northern Brazil, due to long distances from health centers, have limited access to serumtherapy treatment and use plants of folk medicine to block the actions induced by snake venoms. This study investigated the potential of the aqueous extract of Connarus favosus (AECf) to inhibit hemorrhagic and phospholipase A2 activities induced by Bothrops atrox venom (BaV) and to determine the antioxidant and antimicrobial potentials of the extract. AECf was analyzed phytochemically for secondary metabolites and phenolics (condensed tannins and hydrolyzable tannins) by colorimetry. Antioxidant activity was evaluated by quantitative assays using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Fe3+/phenanthroline. Antimicrobial activity was evaluated by the disk diffusion and minimal inhibitory concentration test, and cytotoxicity was evaluated using human fibroblast cells (MRC-5). Inhibition of BaV-induced hemorrhagic activity was assessed after oral administration of the extract using pre-treatment, post-treatment and combined (BA plus AECf) treatment protocols. Inhibition of indirect hemolysis caused by phospholipase A2 (PLA2) was investigated in vitro. Interaction between AECf and BaV was investigated by SDS-PAGE electrophoresis, Western blot (Wb) and zymography. The phytochemical profile of AECf revealed ten secondary metabolite classes, and colorimetry showed high total phenolic and total (condensed and hydrolyzable) tannin content. AECf exhibited high antioxidant and antimicrobial potentials. The IC50 for the cytotoxic effect was 51.91 (46.86 - 57.50) μg/mL. Inhibition of BaV-induced hemorrhagic activity was significant in all the protocols, and inhibition of PLA2 activity was significant with the two highest concentrations. The BaV/AECf mixture produced the same bands as BaV by itself in SDS-PAGE and Wb although the bands were much fainter. Zymography confirmed the proteolytic activity of BaV, but when the venom was pre-incubated with AECf this activity was blocked. AECf was effective in reducing BaV-induced hemorrhagic activity when administered by the same route as that used in folk medicine.