Compostos fenólicos de mirtilo (Vaccinium sp.): com solventes eutéticos profundos naturais e avaliação da atividade em modelo de úlcera gástrica

Abstract

Gastric ulcer is a chronic gastrointestinal disorder that promotes the excessive generation of reactive oxygen species, which results in oxidative stress and subsequent worsening of the clinical picture of the disease. Thus, the introduction of antioxidants into the diet may be an alternative for prevention and treatment of the disease. Blueberry is a fruit rich in polyphenols and the extraction of these compounds in a safe and eco-friendly manner have become very attractive. In this context, the objective of this study was to develop an eco-friendly extraction method using deep natural eutectic solvents (NADES), to obtain bioactive compounds from blueberry and to evaluate the biological activity of the extract in the gastric ulcer model in rats. First, a NADES-based method for extracting blueberry anthocyanins was optimized using a multivariate experimental design to find the best solvent molar ratio. In this study, all possible proportions (0-100%) were evaluated for ternary mixtures composed by choline chloride:glycerol:citric acid. Choline chloride:glycerol:citric acid at the molar ratio 0.5:2:0.5 (NADES 9) was the ideal NADES for extracting blueberry anthocyanins. NADES 9 was as efficient as the organic solvent (methanol:water:formic acid) when compared at the same sample:solvent ratio and yielded about 76% of blueberry anthocyanins compared to an exhaustive extraction with organic solvent. NADES 9 yielded higher proportion of arabinoside anthocyanins and lower proportion of galactoside and glucoside anthocyanins than the organic solvent. The antioxidant capacity (ORAC and FRAP assays) of the purified anthocyanin fraction obtained using NADES 9 was greater than or equal to the fractions extracted using organic solvent. Considering the promising effect of NADES, the second part of this study was aimed to investigate the gastroprotective effect of crude blueberry NADES-based extract (CE) and its fractions anthocyanin-rich fraction (ARF) and non-anthocyanin phenolic fraction (NAPF) in a gastric ulcer model in rats. The animals were treated for 14 days with water, vehicle NADES, CE (10.0 mg/kg b.w.), ARF (4.2 mg/kg b.w.), NAPF (5.8 mg/kg b.w.) or lansoprazole (30.0 mg/kg b.w.) (intragastric) and after a 12-hour fasting received 75% ethanol (2 mL/kg) to induce gastric ulcer. EB decreased ulcer index and preserved the integrity of gastric mucosa, as well as reduced glutathione depletion and inflammatory response. All treatments reduced protein oxidation and NO overproduction in ethanol-treated rats. The NADES vehicle also contributed to the effect of CE in reducing the oxidative stress. ARF increased fecal acetate levels, an important short-chain fatty acid, and seems to be sole responsible for the prevention of GSH depletion. Taken together, the results of this study indicate that NADES is a promising solvent for eco-friendly extraction of polyphenols and can be used to obtain biocompatible extracts of blueberry that exhibit protective effects against gastric ulcer.