Epicatechin

The solvents, n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc), acetone, and methanol (MeOH), were purchased from Wako Pure Chemical Industries (Osaka, Japan). The standard compounds, epicatechin, gallic acid, and 4-hydroxybenzoic acid, were purchased from Wako Pure Chemical Industries (Osaka, Japan). Quercetin and luteolin were purchased from Sigma-Aldrich (St. Louis, MO, USA). Apigenin, protocatechuic acid, and kaempferol were purchased from Tokyo Chemical Industry (Tokyo, Japan).

The analytical standards of (−)-epigallocatechin-3-gallate (EGCG), (−)-epigallocatechin gallate (EGCG), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), and (−)-epicatechin (EC) were purchased from Wako (Osaka, Japan). Benzo[α]pyrene (B[α]P), α-amylase from human saliva, pepsin, from porcine gastric mucosa, bile extract from porcine, lipase from porcine pancreas, and pancreatin from porcine pancreas were obtained from Sigma Aldrich (St. Louis, MO, USA). Water, methanol, acetonitrile, and acetic acid with a grade for ultra-performance liquid chromatography (UPLC) were purchased from J.T. Baker (Phillipsburg, NJ, USA.) and Sigma Aldrich (St. Louis, MO, USA), respectively. Sodium acetate, dichloromethane (DCM), and ethyl acetate were obtained from Samchun Chemicals (Seoul, Korea).

(+)-Catechin, (−)-epicatechin, CMC sodium salt, methanol, and water were purchased from Wako Chemicals (Tokyo, Japan). (+)-Afzelechin was purchased from ChemFaces (Wuhan, China). Procyanidin B1 and procyanidin B2 were purchased from Funakoshi Co. (Tokyo, Japan). Procyanidin C1 and cinnamtannin A2 were purchased from Kanto Chemical Co. (Tokyo, Japan). CHCA, 9AA, and DAN were purchased from Tokyo Kasei Co. (Tokyo, Japan). Indium-tin-oxide (ITO)-coated glass slides (100 Ω without MAS coating) were purchased from Matsunami Glass (Osaka, Japan). Peptide calibration stndards containing bradykinin (1–7), angiotensin II, and angiotensin I were purchased from Bruker (Billerica, MA, USA). All reagents and solvents used in this study were of analytical grade.