title: Effects of Oolong tea polyphenols, EGCG, and EGCG3″Me on pancreatic α-amylase activity in vitro.
abstract: In order to investigate the inhibitory effects and possible mechanisms of Oolong tea polyphenols, (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) on pancreatic α-amylase, the inhibition, enzyme kinetics, ultraviolet (UV) absorption spectrum and fluorescence spectrum of α-amylase were investigated. The results showed that Oolong tea polyphenols, EGCG, and EGCG3″Me all exhibited inhibitory effects against α-amylase, and their half inhibitory concentration (IC50) values were 0.375, 0.350, and 0.572 mg/mL, respectively. The results of Lineweaver-Burk double reciprocal plot indicated that the inhibitory types of Oolong tea polyphenols and EGCG were competitive, whereas EGCG3″Me was in a noncompetitive pattern. Oolong tea polyphenols, EGCG, and EGCG3″Me all induced red-shift of UV absorbance and quenching of fluorescence of α-amylase, suggesting possible changes in the conformation of α-amylase. The differences of inhibitory effects and inhibition types for EGCG and EGCG3″Me might be due to their structural difference (the hydroxyl group at C-3 in D ring of EGCG substituted by methoxy group, forming EGCG3″Me).
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University , Nanjing 210095, People's Republic of China.
authors.forename: Qunqin
authors.initials: Q
authors.lastname: Fei
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
authors.forename: Bing
authors.initials: B
authors.lastname: Hu
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
authors.forename: Saqib
authors.initials: S
authors.lastname: Jabbar
authors.forename: Xiaoxiong
authors.initials: X
authors.lastname: Zeng
mesh_terms: D000818:Animals; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D007700:Kinetics; D010179:Pancreas / Q000737:chemistry / Q000201:enzymology*; D010936:Plant Extracts / Q000737:chemistry*; D059808:Polyphenols / Q000737:chemistry*; D013552:Swine; D000516:alpha-Amylases / Q000037:antagonists & inhibitors* / Q000737:chemistry
chemical_list: D004791:Enzyme Inhibitors; D010936:Plant Extracts; D059808:Polyphenols; D005707:Gallic Acid; D002392:Catechin; C045651:epigallocatechin gallate; D000516:alpha-Amylases; C573278:epigallocatechin-3-O-(3''-O-methyl)-gallate
keywords: EGCG; EGCG3″Me; Oolong tea polyphenols; fluorescence spectroscopy; ultraviolet absorption spectroscopy; α-amylase