Isolation and identification of cytoprotective agents from nonpolar extracts of buckwheat flour

Buckwheat is a raw material used in formulating many foods, and some evidence exists that it can contribute health benefits beyond simple nutritive value. The objective of this study was to isolate and identify potential cytoprotective agents from buckwheat crude extracts using a bioassay-guided strategy. Crude extracts were obtained by successively extracting with n-hexane and ethyl acetate, followed by solvent partitioning. The active fraction(s) were then screened by a quinone reductase (QR) induction bioassay in vitro, and subjected to sequential fractionation with flash column chromatography and preparative thin-layer chromatography. Consequently, three pure compounds were isolated, identified and evaluated for bioactivity. Ferulic acid ethyl ester (1) was the most potent isolate (reported for the first time in buckwheat), doubling QR specific activity (CD value) at 2.1 μM, whereas furaneol (2) was a moderate QR inducer with a CD value of 185 μM. Protocatechuic acid (3) was least ineffective at inducing QR with a CD value of 2.0 mM. Binary mixtures of the three isolated components acted borderline additively/antagonistically in the QR bioassay.