Polyethylene membranes

Standards of (−)-epicatechin and (+)-catechin (purity > 98%), gallic acid (purity > 97%), and malvidin-3-glucoside (purity > 90%); 0.45 µm pore size membranes and methylcellulose (1500 cP viscosity at 20 g/L) were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Polyethylene membranes with a pore size of 0.22 μm were purchased from EMD Millipore (Burlington, MA, USA). HPLC grade ethyl acetate, diethyl ether, hydrochloric acid, sulfuric acid, acetonitrile, acetic acid, formic acid, methanol, potassium metabisulfite, sodium hydroxide, and vanillin (990 g/L) were acquired from Merck (Darmstadt, Germany). All reagents were of analytical grade or higher. Phosphate buffer (pH 7) was purchased from Mallinckrodt Baker (Philipsburg, PA, USA). For column calibration in gel permeation chromatography (GPC) analysis, Leuconostoc dextran analytical standards were used (dextran 5000, 12000, 25000, 50000, 80000, 150000, 270000, 410000, and dextran 670000) (Sigma-Aldrich Co., St. Louis, MO, USA). Nitrogen was provided by INDURA S.A. (Santiago, Chile).

The standards of gallic, protocatechuic, caffeic, syringic, p-coumaric, ferulic, ellagic and caftaric acids, tyrosol, thyptophol, quercetin, myricetin, astilbin, (+)-catechin and (−)-epicatechin, dextrans, and pectins were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Polyethylene membranes of 0.45 μm and 0.22 μm pore size were acquired from EMD Millipore (Billerica, MA, USA). Sodium sulphate (anhydrous), potassium metabisulfite, vanillin (99%), ethyl acetate, diethyl ether, sodium hydroxide, acetic acid, formic acid, sulphuric acid, ethanol, hydrochloric acid and high-performance liquid chromatography (HPLC)-grade acetonitrile, methanol, and ammonium formate were purchased from Merck (Darmstadt, Germany). All the reagents were of analytical grade or higher.

Cyanidin-3-glucoside (C3G) and cyanidin-3-rutinoside (C3R) were purchased from Chengdu Biopurify Phytochemicals (China) and Extrasynthese (France), respectively. Merck (Santiago, Chile) supplied sodium hydroxide, sulfuric acid, high-performance liquid chromatography (HPLC)-grade acetonitrile, acetic acid, formic acid, and methanol. All reagents were of an analytical grade or higher. Polyethylene membranes of 0.22-μm pore size were acquired from EMD Millipore (Billerica, MA, USA). Gallic acid, catechin, dimethyl-amino-cinnamaldehyde (DMAC), FeSO₄heptahydrate, trifluoroacetic acid (TFA), Trolox and Folin-Ciocalteu reagent were obtained from Sigma-Aldrich (Santiago, Chile).