Chemical characterization of commercial dietary ingredients from Vitis vinifera L. Original Research Article

In recent years a large number of commercial products containing ingredients from winery byproducts have proliferated in the market. However, little research has focused on studying the phenolic composition of these products and there is still no legislation concerning their commercialization. In this work, a wide range of commercial ingredients derived from Vitis vinifera L. grape seeds (n = 16) and skins (n = 4), grape pomace (n = 6) and leaves (n = 3) as well as different production batches of some of them, have been analyzed. Gallic acid, monomeric flavan-3-ols ((+)-catechin, (−)-epicatechin and epicatechin-3-O-gallate), procyanidins dimers (B3, B1, B4, B2, B3′-3-O-gallate), and trimers (T2 and C1) were identified in ingredients derived from grape seeds. These ingredients were comprised of fractions enriched either in monomeric, oligomeric or polymeric flavan-3-ols, with a mean degree of polymerization (mDP) ranging from 2.1 to 11.2. Grape anthocyanins (delphinidin, cyanidin, petunidin, peonidin and malvidin-3-glucosides, -3-(6-acetyl)-glucosides and -3-(6-p-coumaroyl)-glucosides, and peonidin and malvidin-3-(6-caffeoyl)-glucosides) were identified in ingredients derived from non-processed grape skins whereas grape pomace ingredients also contained anthocyanin-derived pigments (the pyruvate, vinylcatechol, vinylepicatechin, vinylphenol and vinylguaiacol derivatives of malvidin-3-glucoside, and malvidin-3-(6-acetyl)-glucoside-vinylepicatechin). In the case of the ingredients of leaves, anthocyanins (delphinidin, cyanidin, petunidin, peonidin and malvidin-3-glucosides and -3-(6-p-coumaroyl)-glucosides, and cyanidin and peonidin-3-(6-acetyl)-glucosides), and non-anthocyanin compounds (trans-caftaric acid, and the -3-O-galactoside, -glucuronide and -glucoside derivatives of quercetin and kaempherol, and quercetin aglycone) were identified; the relationship between the two types of compounds (anthocyanin/flavonol) differed in the distinct ingredients studied. Despite the large variability found between the different brands of ingredients derived from a particular byproduct, all of the ingredients studied were authentically derived from the V. vinifera L. spp.