Quercetin 3 glucuronide

Methanol, formic acid, water, acetonitrile (all HPLC-grade purity), sodium dihydrogen phosphate, disodium hydrogen phosphate, trans-caftaric acid, caffeic acid, syringic acid, quercetin hydrate, quercetin-3-glucoside trans-piceid, and vitamin standards were purchased from Sigma-Aldrich (St. Louis, MO, USA). Gallic acid, protocatechuic acid, p-coumaric acid, ferulic acid, and taxifolin were purchased from Fluka (Buchs, Switzerland). Quercetin-3-glucuronide, procyanidins, (+)-catechin, (−)-epicatechin, piceatannol, and resveratrol were purchased from Extrasyn-these (Genay, France); p-hydroxybenzoic acid and myricetin were purchased from Acros Organics (Geel, Belgium). The cis-isomer of caftaric acid was obtained by UV illumination of a Methanol solution containing the trans-isomer for four hours [30 (link)]. Anthocyanins (monoglucoside chlorides) were purchased from Biosynth Carbosynth (Bratislava, Slovakia). Ultrapure water and all the reagents (60% HNO₃) and standards for analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) were obtained from Merck (Darmstadt, Germany).

The standards caffeic acid, caftaric acid, coutaric acid, fertaric acid, kaempferol-3-O-rutinoside, quercetin-3-rutinoside, kaempferol 3-O-galactoside, quercetin-3-glucuronide, quercetin-3-galactoside, quercetin-3-glucoside, quercetin-3-rhamnoside, kaempferol-3-O-glucoside, isorhamnetin 3-glucoside, dihydroquercetin-3,5-rhamnoside, dihydrokaempferol-3-glucoside, procyanidin trimer, procyanidin B2, procyanidin tetramer, (−)-epicatechin, (−)-epicatechin 3-gallate, petunidyn-3-O-glucoside, malvidyn-3-O-glucoside, delphinidyn-3-O-(6′-acetyl)-glucoside, petunidyn-3-O-(6″-p-coumaroyl)-glucoside and malvidyn-3-O-(6″-caffeoyl)-glucoside were purchased from Extrasynthese (Lyon Nord, France). 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid, ABTS), gallic acid, FeCl₃, Trolox and all solvents were purchased from Sigma-Aldrich (Steinheim, Germany). Pectinex^® Ultra SP-L was obtained from Novozymes (Bagsvaerd, Denmark).

Acetonitrile, formic acid, and methanol (MeOH) were of HPLC-gradient grade and were purchased from Panreac (Barcelona, Spain). The water was treated in a Milli-Q system (Millipore, Milford, MA, USA). Catechin, epiCatechin, Catechin gallate, epiCatechin gallate, procyanidins B1 and B2, myricetin-3-glucoside, myricetin-3-galactoside, querce-tin-3-glucoside, quercetin-3-glucuronide, kaempherol-3-glucoside, kaempherol-3-rutinoside, isorhamnetin-3-glucoside, and isorhamnetin-3-rutinoside were purchased by Extrasynthese (Lyon, France) and gallic, caffeic, ferulic, and coutaric acids were purchased from Aldrich (Munich, Germany).