Activity‐guided isolation of phase II enzyme inducers from buckwheat flour methanolic extracts.

Abstract: BACKGROUND: Buckwheat is an important alternative crop and a raw material for functional food formulation. Phase II detoxification proteins/enzymes provide cytoprotective roles against oxidative stress and inflammation originating from various stressors. We aimed to identify and characterize potential phase II enzyme inducers from methanolic extracts of buckwheat flour, using an activity‐guided fractionation based on the induction of quinone reductase (QR) (EC 1.6.5.2) in Hepa 1c1c7 cells. RESULTS: We isolated the QR inducers N‐trans‐feruloyltyramine (I), syringic acid (II), quercetin (III) and myricetin (IV). The relative QR‐inducing ability, as well as the concentration required to double QR specific activity (CD values, in parentheses), decreased in the order: quercetin (3.0 µmol L–1) > N‐trans‐feruloyltyramine (24 µmol L–1) > myricetin (58 µmol L–1) > syringic acid (5.4 mmol L–1). Quercetin and N‐trans‐feruloyltyramine exhibited the greatest extent of QR induction of an approximately four‐fold maximum induction and these compounds also exhibited the greatest values for the ratio of IC50 (i.e. level to reduce viability by 50%): CD values of 11 and > 8.3, respectively, among the four QR inducers isolated. Isobologram analyses for binary combinations of compounds I–IV revealed primarily antagonistic interactions for QR induction. CONCLUSION: These findings add to our understanding of the nutraceutical potential of buckwheat as a chemoprophylactic dietary component. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]