67B-25 |
|
Y.-S. WONG, Biology Department, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China and L.-K. Ngai. Flavonoids are major antioxidants in food plants. Many health-promoting properties of dietary flavonoids are associated with their antioxidant activities. Over four thousand different flavonoids have been identified within the six major flavonoid classes including flavone, flavonol, flavanone, flavan, anthocyanidin and isoflavone. These flavonoids share the same basic structure consisting of two aromatic rings joined in a chromane structure by a three-carbon unit: C6-C3-C6. The objective was to determine the structure and antioxidant activity relationship of flavonoids using three different assay methods. The structure and DNA protective effects of flavonoids was also studied. Thirty three representative flavonoids were selected for the comparative study. Three antioxidant assay methods including the beta-carotene bleaching method, the DPPH radical scavenging method and the TEAC assay method were employed in this investigation. The single cell gel electrophoresis method (Comet assay) was used to evaluate the protective effects of flavonoids on hydrogen peroxide-mediated DNA damage. Our results showed that the structural requirements for the antioxidant and free radical scavenging functions of flavonoids include the following: (1) a hydroxyl group at C3, (2) a double bond between C2 and C3, (3) the conjugation of the double bond with a carbonyl group at C4, and (4) the polyhydroxylation of A and B aromatic rings. The protective effects on hydrogen peroxide-mediated DNA damage also showed similar structure and activity relationship, that is, flavonoids with structure confer to higher antioxidant activity exhibited stronger protective effect. The antioxidant activity of any flavonoid with known structure can be evaluated based on the structure and antioxidant activity relationship proposed.
Session 67B, Food Chemistry: Antioxidants and bioactive agents
|