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J Agric Food Chem. 2010 Jan 13;58(1):148-54. doi: 10.1021/jf903011g.

Evaluation of different teas against starch digestibility by mammalian glycosidases.

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  • 1Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Republic of Singapore.


Current work investigated the ability of different tea (green, oolong and black teas) in inhibiting human salivary alpha-amylase (HSA) and mammalian alpha-glucosidase (AGH). The inhibitory profiles were correlated to their major polyphenol content (theaflavins and catechins). The fully fermented black tea was demonstrated to be most potent in inhibiting HSA and AGH (IC50 of 0.42 to 0.67 and 0.56 to 0.58 mg of tea leaves/mL respectively). Its capability in retarding the digestion of a real food system (rice noodle) was further elucidated with an in vitro digestion study. Results indicated that black tea was able to retard starch digestion moderately, thereby allowing a gradual reduction of sugar liberation. Polyphenolic profile analysis suggested that the oxidized catechins, theaflavins, may be responsible for its activity. We have found that refractive index (RI) measurement is a rapid, direct, and highly convenient method for quantifying the degree of enzymatic starch digestion and kinetics. The RI method has good linearity range, limit of detection (0.1596 mg/mL, maltose equivalent) and limit of quantitation (0.6312 mg/mL) and was successfully applied in our study.

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