Dietary flavonoids fail to suppress F2-isoprostane formation in vivo ☆

Abstract Dietary antioxidants, including α-tocopherol (α-TOH) and polyphenolic flavonoid compounds, have been the subject of much research interest, but few studies have investigated interactions between these two antioxidants in vivo. We have conducted a feeding study to determine if supplementation with dietary flavonoids or polyphenol-containing compounds will provide antioxidant protection in tocopherol-deficient animals or exceed the antioxidant protection provided by α-TOH alone, using the sensitive and specific measure of lipid peroxidation, F 2 -isoprostanes. Seventy-two male Sprague Dawley rats were divided into 12 treatment groups to receive either α-TOH-sufficient or -deficient AIN93-G diet supplemented with one of five compounds: 0.5% quercetin, catechin, or epicatechin; or 1% cocoa powder or lignin. The fat source was polyunsaturated oil, increased from 7 to 11.05% (w/w with diet) to maximize lipid peroxidation while staying within a physiological range. After 7 weeks of treatment, animals were sacrificed with plasma and hearts analyzed to determine differences in F 2 -isoprostane levels. None of the treatment compounds significantly decreased plasma or heart F 2 -isoprostanes compared to the control beyond the significant protection displayed by α-tocopherol. We conclude that under these experimental conditions, quercetin, catechin, and epicatechin do not suppress lipid peroxidation in vivo.