Antioxidant activity and phenolics content of selected Brazilian wines

The levels of total phenolics, resveratrol (cis- and trans-isomers), quercetin, monomeric anthocyanin and the antioxidant activity of monovarietal northeastern Brazilian wines were investigated. Antioxidant activities of wine samples were determined after extraction using ethyl acetate at different pH values, yielding three fractions for each sample assayed. The most active fraction against DPPH radical was from a Tannat wine sample (CE50 = 3.4 ± 0.1 μg/mL), while the most active fraction at the ABTS+ assay was from a Shyraz sample (CE50 = 1.6 ± 0.03 μg/mL), which was more active than Trolox (CE50 = 2.9 ± 0.05 μg/mL). The total phenolic content of some of the wine samples studied was considerably higher than the values reported in literature for red wines. Levels of trans-resveratrol (determined by HPLC) varied from 0.04 to 1.26 mg/L and were considerably lower than the levels of cis-resveratrol (0.72–5.49 mg/L, average of 2.7 mg/L) and quercetin (average of 2.5 mg/L). Total monomeric anthocyanin content ranged from 5.1 to 20.7 mg monomeric anthocyanin/L. Our results confirm previously published reports showing that the levels of cis-resveratrol are considerably higher than those of trans-resveratrol in some Brazilian wines.