Electron spin resonance spectroscopic assessment of the antioxidant potential of teas in aqueous and organic media

✍ Scribed by Gardner, Peter T; McPhail, Donald B; Duthie, Garry G

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 204 KB
• Volume: 76
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199802)76:2<257::aid-jsfa944>3.0.co;2-b

✦ Synopsis

Electron spin resonance methodology has been used to assess the hydrogen-donating (antioxidant) ability of catechins and extracts of green and black tea to FremyÏs radical and galvinoxyl radical in aqueous and organic solutions, respectively. Catechin Ñavanols accounted for 77È82% of the total antioxidant activity of green tea but only 47È58% of that of black tea. The radical quenching ability of the green tea was 21È24% more e †ective than that of the black tea in both aqueous and lipophilic systems. Epigallocatechin gallate was the most e †ective at reducing the two radical species, whereas epigallocatechin was least e †ective in the galvinoxyl/ethanol system, and catechin least e †ective in the FremyÏs radical/water system. In a model system comprising a mixture of the Ñavanols in ethanolic or aqueous solution, in the same concentrations as they were present in the tea extracts, the antioxidant potential was a simple summation of the activity of the individual components indicating no synergistic or antagonistic side reactions. Results demonstrate that Ñavanol components of teas exhibit potent antioxidant activity in both aqueous and organic media. This will be of physiological relevance if such compounds partition into both the aqueous and lipid compartment of cells.

1998 SCI.