Abstract
Polyphenols from food materials were investigated to determine their physiological functions and the mechanisms responsible for them. The results obtained are summarized as follows: (1) Flavanonols present in tea from leaves of Engelhardtia chrysolepis and Ampelopsis grossedentata exhibited activity to prevent liver injury due to oxidative stress. (2) Anthocyanins such as malvin, rubrobrassicin and nasunin showed antioxidative and radical scavenging activities, along with activity to reduce the levels of both serum and liver total cholesterol and increase the level of HDL-cholesterol, suggesting that they are active in improving the levels of lipid. Some antho-cyanins were effective in suppressing oxidative stress caused by radical generation in vivo. Cyanidin glycosides, which are low-molecular-weight anthocyanins, exhibited activity to suppress in vivo oxidation during the progres-sion of diabetes. (3) Among the catechins, (−)-epigallocatechin gallate suppressed in vivo oxidation caused by radical generation in vivo most effectively, followed by (−)-epicatechin gallate, and/or (−)-epigallocatechin. (−)-Epicatechin had no effect. (4) Glycosylation of flavonol at its 3´ and/or 4´ position did not affect its activity to suppress liver injury caused by in vivo oxidation, but glycosylation of flavonol at its 7´ position caused a marked decrease in its suppressive activity on liver injury. (5) Flavones with a sugar moiety at the 7 position showed enhanced protective activity against liver injury when the sugar moiety was malonylated.
