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. 2015 Feb;52(2):928-35.
doi: 10.1007/s13197-013-1059-y. Epub 2013 Jun 18.

In vitro antioxidant and pancreatic α-amylase inhibitory activity of isolated fractions from water extract of Qingzhuan tea

Qian Cheng  1 , Shengbao Cai  1 , Dejiang Ni  2 , Ruojun Wang  1 , Feng Zhou  1 , Baoping Ji  1 , Yuqiong Chen  2
Affiliations

In vitro antioxidant and pancreatic α-amylase inhibitory activity of isolated fractions from water extract of Qingzhuan tea

Qian Cheng et al. J Food Sci Technol. 2015 Feb.

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.

Keywords: Antioxidant; Column chromatography; Polyphenol; Qingzhuan tea; Tea extract; α-amylase.

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Figures

Fig. 1
Fig. 1
Chromatogram of QEF8 from the ethyl acetate fraction by HPLC. QEF8, the eighth subfraction of ethyl acetate fraction through Sephadex LH-20 column
Fig. 2
Fig. 2
The basic structures of catechins considered in the present study
Fig. 3
Fig. 3
Inhibitory effects of EGCG and ECG on pancreatic a-amylase activity. EGCG, (-)-epigallocatechin gallate; ECG, (-)-epicatechin gallate. Values are expressed as mean ± SD (n = 3).
See this image and copyright information in PMC

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