Determination of polyphenols and antioxidant activity of Vitis labrusca cv. baile berries

Grape juice and grape skin extracts are important commercial source of polyphenolic compounds which exert different functional properties such as color potential, antimicrobial, antioxidant activity, and health benefits. In this paper we describe a sensitive and specific assay for determination of bioactive polyphenolic compounds in Campbell Early (Vitis labrusca cv. baile). Five polyphenolic components were separated on an Agilent Zorbax Extend C18 Column (250 mm x 4.6 mm x 5 μm) and detected by a diode array detector. The mobile phase was composed of (a) aqueous phosphoric acid (0.2%, v/v); and (b) acetonitrile using a gradient elution. Analytes were performed at 25 degrees C with a flow rate of 0.8 ml/min and UV detection at 280, 360, and 520 nm. All calibration curves showed good linear regression (r2 ≥ 0.9999) within tested ranges. Overall intra- and inter-day variations were less than 1.90%, and the average recoveries were 95.5-105% for analytes. The antioxidant activity determined by DPPH radical assay, ranged from 86-105 for extracts, and 165-252 for studied standards (μM trolox/100 g dry wt.). The proposed method would be sensitive enough and reliable for quality control in functional food and modernization of Campbell Early (Vitis labrusca cv. baile) as potent antioxidant agents.