Oolong tea is traditionally reported to prevent obesity and improve lipid metabolism, and it is assumed that habitual ingestion is effective to enhance the metabolic rates and lipid catabolism (25). Han et al. reported that the antiobesity action of oolong tea was due to the enhancing effect of caffeine on noradrenaline-induced lipolysis in adipose tissue and to the inhibitory action of teasaponin on pancreatic lipase activity (26).Teasaponins, such as teasaponin E1 and E2, showed lipase inhibitory effects, but the concentration of teasaponin of oolong tea was only 0.6% (27).
Oolong tea contains many varieties of polyphenols involved in oligomeric flavan-3-ols. Oolong tea polyphenols have inhibi-tory activities against some enzymes, such as glycosyltransferase of mutans streptococci (28). Therefore, it is expected that oolong tea polyphenols are effective for lipase inhibition and preventing obesity.
In the present study, the inhibitory effects of dimeric flavan-3-ols on pancreatic lipase and the structure-activity relationship
were evaluated. Furthermore, the inhibitory activity of polym-erized polyphenols prepared from oolong tea was examined.