Quantification of Polyphenols in Grape-Derived Samples

Gallic acid (1), caffeic acid (2), E-resveratrol (3), E-piceatannol (4), catechin (5), epicatechin (6), gallocatechin (7), E-piceid (8), astilbin (10), quercetin-3-O-glucoside (16), and quercetin-3-O-glucuronide (23) were purchased from Sigma-Aldrich standards (St. Louis, MI, USA). Procyanidins B1 (24), B2 (25), and B3 (27) were purchased from Extrasynthèse (Genay, France). E-ε-viniferin (13), E-δ-viniferin (15), ampelopsin A (17), E-miyabenol C (32), hopeaphenol (36), isohopeaphenol (37), and Z/E-vitisin B (41) were obtained as previously described [2 (link)]. Acetonitrile, methanol, and formic acid were purchased from ThermoFisher Scientific (Courtaboeuf, France). Ultra-pure water was prepared with a Milli-Q water purification system (Merck Millipore, Molsheim, France).