Efeito antioxidante in vitro e in vivo do extrato aquoso da casca do caule de Tapirira guianensis

Abstract

Tapirira guianensis is a medium-sized tree found throughout Latin America. In folk medicine, it is used to treat problems such as inflammation, wounds, and sexually transmitted diseases such as syphilis, however, there are few records in the literature about its biological effects. In this context, the aim of this study was to evaluate the chemical composition, the toxicity described popularly and the antioxidant activity, in vitro and in vivo, of the stem bark of T. guianensis. For this, an aqueous extract of the bark of T. guianensis stem (EATg) was prepared using 100g of bark powder in 1 liter of water per infusion. The quantification of phenolic compounds was performed using a standard curve of gallic acid by the Folin-Ciocalteu method, and the quantification of flavonoids was performed using a standard curve of quercetin, evaluated by the method of aluminum chloride. The in vitro antioxidant activity was evaluated by free radical scavenging assays 2,2-Diphenyl-1-picrylhydrazyl (DPPH•+ ); 2,2'-azino-bis(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) and protection against protein degradation (BSA) induced by the oxidizing agent 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH); and the protection from plasmid DNA degradation of bacteria exposed to hydrogen peroxide and ultraviolet light. The toxicity of EATg was evaluated in nematodes Canorhabditis elegans, and protection from oxidative stress in vivo was evaluated through the induction of oxidative stress by the oxidizing agent Juglone. The chemical composition analysis of EATg showed 122.41 ± 3.45 EAG/g of phenolic compounds and non-quantifiable levels of flavonoids. Antioxidant potential analysis revealed an IC50 of 2.80 ± 1.20 µg/mL, with a maximum inhibition of 88.14% ± 1.47 at a concentration of 10 µg/mL for DPPH•+ radical capture and an IC50 of 5.41 ± 0.07 µg/mL, with a maximum inhibition of 99.64% ± 0.09 at a concentration of 25 µg/mL for ABTS•+ radical capture. The protective effect against BSA-induced oxidative stress occurred at all concentrations (5 a 250 µg/mL), and protection against DNA fragmentation occurred from a concentration of 25 to 250 µg/mL. The data obtained in the toxicity test proved the safe use of the extract at concentrations below 200 µg/mL, at these concentrations the EATg also protected the nematode against the oxidative stress induced by Juglone. Our data revealed that EATg has phenolic compounds in its chemical composition, in addition to presenting an antioxidant effect in vitro in the capture of free radicals, and in protection against oxidative stress induced in macromolecules, and in vivo, it presented low acute toxicity and protection against Juglone-induced oxidative stress effect in C. elegans nematodes. These results open perspectives for new tests based on chemical characterization and evaluation of the antioxidant potential of EATg.