Methods for the Evaluation of Polyphenolic Content in “Uva Di Troia Canosina” Grape and Seeds at the Different Maceration Stages

Abstract

Seeds and skins derived from the small berries of “uva di Troia canosina” grape, a Vitis vinifera variety autochthonous of Apulia region (South Italy), collected at four different stages (“Tesi” 1–4) of the fermentation process were extracted by means of a maceration. The extracts were purified and analyzed, in order to study the influence of fermentation over grape seed and skin polyphenolic content. Seed extraction was performed by a multistep maceration with two solvents: ethanol and acetone, the former giving the best results; moreover, the extracts were purified with pure ethyl acetate in order to enrich their polyphenolic content. On the other hand, skin extraction was achieved by a single-step maceration in methanol and a purification with a brominated synthetic adsorbent resin. The evaluation of the extraction yield and polyphenolic content was carried out by TLC, UV/VIS, and LC/DAD analyses. In the seed extracts, the characteristic polyphenols (catechin, epicatechin, and procyanidin B1 and B2) useful for the development of a nutraceutical product, endowed with antioxidant properties, were present, while no resveratrol was detected in “uva di Troia canosina” grape skin extracts, even in an LC/MS-MS analysis.