Flavonoids in Common and Tartary Buckwheat Hull Extracts and Antioxidant Activity of the Extracts against Lipids in Mayonnaise

Abstract

Buckwheat hulls, generally discarded as waste, have been known to possess various flavonoids and high antioxidant activities. However, studies on the flavonoid of common and tartary buckwheat hulls and their application are still limited. The objective of this study was to determine the effect of extracting solvents (water, ethanol (20%, 50%, 80%, and 100%), methanol, and acetone) on flavonoid composition and content and to analyze antioxidant activities of common and tartary buckwheat hull extracts. Antioxidative effect of common and tartary buckwheat hull extracts on lipids in mayonnaise was also investigated.

Vitexin, isovitexin, isoorientin, orientin, rutin, isoquercetin, and quercetin were identified in the common buckwheat hull extracts, while rutin, quercetin, isoorientin, and isoquercetin were in the tartary buckwheat hull extracts. Vitexin was more extracted from common buckwheat hulls when using methanol than the other solvents. Rutin, the major flavonoid in the tartary buckwheat hull extracts, was much more detected in the 80% ethanol and methanol extracts than in the others. Total phenolic content and antioxidant activities were higher in the aqueous ethanol extracts from both of the hulls.

Common and tartary buckwheat hull extracts using 50% ethanol were applied in mayonnaise at 0.02 and 0.08% (w/w). Peroxide value, 2-thiobarbituric acid value, p-anisidine value, and total oxidation value of the mayonnaises stored at 35 °C for 31 days were determined. Addition of the common and tartary buckwheat hull extracts retarded lipid oxidation in mayonnaise. In conclusion, common and tartary buckwheat hull extracts possess high antioxidant activity with various flavonoids and they may be used as efficient antioxidants for mayonnaise.