Quercetin dehydrate

Folin-Ciocalteu’s phenol reagent, sodium carbonate (99%), catechin (98%), protocatechuic acid, p-hydroxybenzoic acid, gentisic acid, p-coumaric acid, sinapic acid, ferulic acid, sodium nitrite (97%), aluminium chloride (99.9%), and vanillin (99%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Procyanidin B2, rutin, epicatechin, kaempferol, quercetin dehydrate, daidzein and genistein were purchased from Extrasynthese (Genay, France). Sulphuric acid (95–97%) and gallic acid (98%) were purchased from Fluka (Seelze, Germany). Sodium hydroxide (98%) was purchased from Merck (Darmstadt, Germany). Absolute ethanol (99.9%) and methanol (99.9%) were purchased from Carlo Erba Reagents (Rodano, Italy). Milli-Q^® water (18.2 MΩ.cm) was obtained in a Millipore–Direct Q3 UV System equipment (Molsheim, France).

Acetonitrile HPLC quality was supplied by Labscan (Dublin, Ireland), and formic acid HPLC quality was from Acros Organic (Geel, Belgium). Protocatechuic acid, vanillic acid, syringic acid, caffeic acid, 3-coumaric acid, ethyl gallate, 3,4′,5 trihydroxystilbene-3-O-d-glucoside (trans-piceid), (+)-catechin, (−)-epicatechin, epicatechin gallate, procyanidin B₁, procyanidin B₂, quercetin-3-O-galactoside (hyperoside), quercetin-3-O-rutinoside (rutin), quercetin-3-O-glucuronide, quercetin-3-O-glucoside, and quercetin dehydrate were purchased from Extrasynthèse (Genay, France). Glucose, xylose, phenol, gallic acid, 4-hydroxybenzoic acid, trans-caftaric acid, ellagic acid, protocatechuic aldehyde, trans-resveratrol, 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), potassium persulfate, 2,2´ azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), 2,2 diphenyl-1-picrylhydrazyl (DPPH), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) were obtained from Sigma-Aldrich (Madrid, Spain). Disodium carbonate, Folin-Ciocalteau reagent, methanol, and ethanol were purchased from Panreac (Barcelona, Spain).