title: In vitro antioxidant and pancreatic α-amylase inhibitory activity of isolated fractions from water extract of Qingzhuan tea.
abstract: In the present work, Qingzhuan tea, a unique dark tea produced by post-fermentation technology, was selected to investigate its antioxidant and pancreatic α-amylase inhibiting activities. Water extract of Qingzhuan tea was successively isolated by solvent partitioning procedures to obtain chloroform, ethyl acetate, n-butanol, sediment and residual aqua fractions. Of different fractions, the ethyl acetate fraction (QEF) had the highest total polyphenols and catechins contents, demonstrated the strongest DPPH radical scavenging activity and exhibited the greatest inhibitory effect on porcine pancreatic α-amylase activity in vitro. Further separation of QEF by a Sephadex LH-20 column generated eight subfractions (QEF1-QEF8), with QEF8 being the most active subfraction based on the assays above mentioned. The major active components in QEF8 were identified as catechins EGCG and ECG by LC-MS analysis, with contents of 22.29 % and 11.11 % respectively. Inhibitory effects of catechin standards EGCG and ECG on porcine pancreatic α-amylase activity were also observed. In conclusion, Qingzhuan tea or its water extract could be potentially used as complementary therapy ingredients for diabetes treatment through lowering postprandial blood glucose, and catechins EGCG and ECG may be the most efficient components in the water extract.
authors.affiliation: College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cheng
authors.affiliation: College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
authors.forename: Shengbao
authors.initials: S
authors.lastname: Cai
authors.affiliation: College of Horticulture and Forestry Science, Huazhong Agricultural University, No.1, Shizishan Street, Hongshan District, Wuhan, Hubei Province 430070 China.
authors.forename: Dejiang
authors.initials: D
authors.lastname: Ni
authors.affiliation: College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
authors.forename: Ruojun
authors.initials: R
authors.lastname: Wang
authors.affiliation: College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.affiliation: College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
authors.forename: Baoping
authors.initials: B
authors.lastname: Ji
authors.affiliation: College of Horticulture and Forestry Science, Huazhong Agricultural University, No.1, Shizishan Street, Hongshan District, Wuhan, Hubei Province 430070 China.
authors.forename: Yuqiong
authors.initials: Y
authors.lastname: Chen
keywords: Antioxidant; Column chromatography; Polyphenol; Qingzhuan tea; Tea extract; α-amylase