Catechin hydrate

Acetic anhydride, bismuth nitrate, and sodium nitrite were obtained from Panreac^® (Barcelona, Spain). Diphenylboric acid-β-ethylamino ester, fast blue B salt, gallic acid, iodine, oleanolic acid, polyethylene glycol-4000, protocatechuic acid, and vanillin were obtained from Sigma-Aldrich^® (Steinheim, Germany). Ethanol was obtained from Aga^® (Prior Velho, Portugal). Glacial acetic acid and sulfuric acid were obtained from Chem-Lab^® (Zedelgem, Belgium). Acetone, Folin–Ciocalteu reagent, hydrochloric acid 37% extra pure, iron trichloride, perchloric acid, potassium iodate GR, sodium carbonate, sodium hydroxide, and TLC cellulose plates (catalog number 105552) were obtained from Merck^® (Darmstadt, Germany). Butanol-1 and methanol were obtained from Fisher Chemicals^® (Leicestershire, UK). Ferrous sulfate was obtained from May and Baker LTD^® (Dagenham, UK). The (+)-Catechin (hydrate) was obtained from Cayman Chemical Company^® (Ann Arbor, MI, USA). Aluminum chloride was obtained from Fluka^® (Buchs, Switzerland). Acetonitrile was obtained from Honeywell Riedel-de Haën™ (Seelze, Germany). Formic acid 99–100% was obtained from VWR Chemicals (Fontenay-sous-Bois, France). All used reagents were of analytical grade.

Analytical phenolic standards (caffeic acid, cinnamic acid, chlorogenic acid, daidzein, (−)-epicatechin, ferulic acid, gallic acid, genistein, hesperetin, p-coumaric acid, p-hydroxybenzoic acid, kaempferol, phloretin, procyanidin A2, procyanidin B2, protocatechuic acid, quercetin, quercetin-3-O-glucoside, quercetin 3-O-galactoside, resveratrol, rutin, syringic acid and vanillic acid) were obtained from Sigma-Aldrich (St. Louis, MO, USA). The (+)-catechin hydrate, cyanidin chloride and delphinidin chloride were purchased from Cayman Chemicals (Ann Arbor, MI, USA). Acacetin, apigenin, luteolin, LCMS-grade methanol, acetone (ACS grade), naringenin and naringenin chalcone were purchased from Fisher Scientific (Pittsburgh, PA, USA). Ultra-pure water (with a resistivity of 18 MΩ.cm and a TOC level < 5 ppb) for all the experiments was prepared from a Milli-Q purification system (Millipore, MA, USA).