Inhibition of Rat Small Intestinal Sucrase and α-Glucosidase Activities by Tea Polyphenols.

(-)-Epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg) were prepared from crude catechins (containing 90% cateehin in total) as described in our previous paper,i) Crude theaflavins, theafiavin (TFI), theaflavin monogallate A (TF2A), theafiavin monogallate B (TF2B), and theaflavin digallate (TF3) were prepared from black tea by our method.S) Crude thearubigin (a group of unidentified catechin complexes oxidatively produced during black tea production) was separated by the method of Takeo and Osawa.9) The structural formulae of catechins and theafiavins are shown in Fig. 1, A crude enzyrne solution was prepared by a slight medification of the precedure of Dahlqvist, iO) The small intestinal brush border was removed