Tannins comprise a large and diverse class of polyphenolic compounds (31, 32) . Our search for the active components in the tannin fraction of BE was made much easier after we discovered that commercially available tannic acid (TA) shows similar glucose transport stimulatory activity to BE (29) . The main components of TA are gallotannins, a subclass of the tannins usually consisting of a glucose core connected to a variable number of galloyl groups via ester bonds (Fig. 5) .