Identification of α-glucosidase inhibitors from a new fermented tea obtained by tea-rolling processing of loquat (Eriobotrya japonica) and green tea leaves

Asami Toshima, Toshiro Matsui, Mai Noguchi, Ju Qiu, Kei Tamaya, Yuji Miyata, Takashi Tanaka, Kazunari Tanaka

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Background: A new fermented tea produced by tea-rolling processing of loquat (Eriobotrya japonica) leaf with green tea leaf (denoted as LG tea) showed a potent antihyperglycaemic effect in maltose-loaded rats. The aim of this study, therefore, was to identify α-glucosidase inhibitors in the antihyperglycaemic tea product. Results: LG tea had a threefold higher maltase-inhibitory activity (IC50 0.065 mgdried extractm L-1) than either the constituent loquat leaf or green tea alone. In addition, LG tea favourably inhibited maltase action rather than sucrase action. As a result of bioguided high-performance liquid chromatography separations of LG tea, theasinensin A, theasinensin B, strictinin and 1,6-digalloylglucose were newly identified asmaltase inhibitors with IC50 values of 142, 225, 398 and 337 μmol L-1 respectively, along with previously identified catechins and theaflavins. Conclusion: Judging from the magnitude of the α-glucosidase-inhibitory contribution of each isolated compound to the overall inhibition of LG tea, catechins were the main candidates responsible for α-glucosidase or maltase inhibition in LG tea, followed by theaflavins, theasinensins, strictinin and 1,6-digalloylglucose.

Original languageEnglish
Pages (from-to)1545-1550
Number of pages6
JournalJournal of the Science of Food and Agriculture
Volume90
Issue number9
DOIs
Publication statusPublished - Jul 1 2010

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Agronomy and Crop Science
  • Nutrition and Dietetics

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