Electron spin resonance (ESR) spectroscopic assessment of the contribution of quercetin and other flavonols to the antioxidant capacity of red wines

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

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 68 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(19990515)79:7<1011::aid-jsfa320>3.0.co;2-y

✦ Synopsis

Health bene®ts of red wine have been ascribed in part to the antioxidant properties of quercetin and other ¯avonols. Red wines, however, contain many other polyphenolic compounds with antioxidant potential. The present study has assessed the antioxidant capacity of seven red wines using electron spin resonance spectrometry to measure their ability to donate hydrogen atoms to a stable Fremy's radical. Antioxidant capacity of the wines was strongly related to the total phenol content (r = 0.872, P 0.01) but less so to total ¯avonol content (r = 0.651, P 0.10). The only ¯avonols detected in the wines by HPLC with post-column derivatisation were the aglycones and conjugated forms of quercetin and myricetin. These accounted for less than 2% of total phenolic content when expressed as gallic acid equivalents. Although these ¯avonols showed marked ability to quench Fremy's radical, they contributed less than 1.5% to the total antioxidant capacity of the wines. Consequently, quercetin is not a major antioxidant in red wine. The antioxidant activity of other polyphenols may be of greater importance in contributing to the reputed health bene®ts of moderate wine consumption.