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.

Structural characterization and bioactivity of proanthocyanidins from indigenous cinnamon (Cinnamomum osmophloeum)

“…Comparatively, subfractions F2–F10 from BSF of CoTE showed better DPPH free radical scavenging activity (IC 50 < 71.2 µg mL −1 ) than the subfractions of the A. confusa bark extract. Cheng et al reported the ethyl acetate soluble fraction of Qingzhuan tea was separated into eight subfractions by Sephadex LH‐20 gel chromatography, and the DPPH free radical scavenging and α‐amylase inhibitory activities increased from subfractions F1 to F8. The IC 50 values of DPPH free radical scavenging and α‐amylase inhibitory activities of subfraction F8 were 4.6 µg mL −1 and 0.4 mg mL −1 , respectively.…”

Assessment of the Bioactive Capacity of Mixed Juice Scum Extracts from Sugarcane Mills

“…; Cheng et al . ). While ABTS is another organic free radical and is more versatile than DPPH due to its application of assessing the scavenging capacity for both polar and nonpolar samples (Basha and Priscilla ; Shang et al .…”

Changes of porcine pancreas α‐amylase in activity and secondary conformations under inhibition of tea polyphenols

“…Cheng et al . () also found that water extract from Qingzhuan tea exhibited a dose‐dependent inhibitory effect against pancreatic α‐amylase activity. As the main catechin monomers of TP, nongalloylated catechins and galloylated catechins were found to act as the natural inhibitors of human α‐amylase.…”