Constituents of grape pomace from the Sicilian cultivar `Nerello Mascaleseʹ

A chemical study of grape (Vitis vinifera) pomace, from the red Sicilian cultivar `Nerello Mascaleseʹ, has been carried out. The methanolic extract was further fractionated and analysed by HPLC–UV–DAD and HPLC–MS–ESI, allowing identification of 16 flavonols or flavonol glucosides (1–16), the flavan-3-ols catechin (17) and epicatechin (18), as well as their gallate esters 19 and 20, 10 anthocyanins (21–30), 5 pyranoanthocyanins (31–35), and 3 low-molecular weight proanthocyanins (36–38). The pyranoanthocyanins cyanidin 3-O-glucoside acetaldehyde (31), peonidin 3-O-glucoside acetaldehyde (32), petunidin 3-O-glucoside acetaldehyde (33) and malvidin 3-O-glucoside acetaldehyde (34) have been identified for the first time in grape pomace. From quantitative analysis of the main constituents, quercetin 3-O-glucoside (5) and quercetin 3-O-glucuronide (9) proved to be the most abundant flavonol glycosides, and malvidin 3-O-glucoside (27) the main anthocyanin. Flash-chromatography of the EtOAc extract allowed isolation and spectral identification of lupeol (39), oleanoic acid (40), quercetin (3) and β-sitosterol glucoside (41).