3 4 dihydroxybenzoic

Pepsin from porcine stomach mucosa (250 U/mg), pancreatin (8 × USP) from porcine pancreas, porcine bile extract, mucin from porcine stomach-type II, albumin, resazurin, cysteine, peptone, yeast extract, pectin, xylan, gum arabic, potato starch, casein, glucose, and inulin were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Phenolic compounds standards (2,4 dihydroxybenzoic, 3,4 dihydroxybenzoic, gallic, benzoic, caffeic, ferulic, p-coumaric, salicylic, rosmarinic, and 5-caffeoylquinic acids) were purchased from Sigma-Aldrich Chemical Co. All solvents were HPLC grade from Tedia (Fairfield, OH, USA). HPLC grade water (Milli-Q system, Millipore, Bedford, MA, USA) was used throughout the experiments.

All the used reagents and solvents were of analytical or liquid chromatography purity and were obtained from Merck (Darmstadt, Germany). Formic and phosphoric acids, anhydrous sodium carbonate, aluminium chloride, sodium acetate and 96% ethanol were analytical grade, while methanol and acetonitrile were for liquid chromatography use. The Folin–Ciocalteu phenol reagent (2 N), 2,2-Diphenyl-1-picrylhydrazyl and 6-hydroxy- 2,5,7,8-tetramethyl-2-carboxylic acid (Trolox) used for the determination of total polyphenols composition and antioxidant activity were purchased from Sigma-Aldrich (St. Louis, MO, USA). All phenolic standards (caffeic, gallic, ferulic, p-coumaric, p-hydroxybenzoic, 3,4-dihydroxybenzoic, t-cinnamic and chlorogenic acids, catechin, epicatechin, quercetin, rutin, t-resveratrol, ursolic and oleanolic acids) had purities corresponding to high performance liquid chromatography (HPLC) and were purchased from Sigma-Aldrich (Steinheim, Germany). Stock and working standard solutions were prepared in methanol. Deionised water, produced by a Milli-Q Millipore system (Bedford, MA, USA), was used for the preparation of aqueous solutions and mobile phases.

Pepsin, pancreatin, Folin–Ciocâlteu phenol reagent, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′–azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS), 2,4,6-tris(2-pyridyl)-S-triazine (TPTZ), gallic acid, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), vanillic acid, chlorogenic acid, catechin, epicatechin, p-coumaric acid, ellagic acid, naringenin, hesperidin, resveratrol, ferulic acid, quercetin, 3,4-dihydroxybenzoic, taxifolin, aloin, kaempferol, ferric chloride hexahydrate, sodium acetate trihydrate, glacial acetic acid, hydrochloric acid, and sodium acetate trihydrate were purchased from Sigma-Aldrich Ltd. (St. Louis, MO, USA). All chemicals used were of analytical grade, and the water was ultra-pure Milli-Q water.