Flavonoid analysis of buckwheat sprouts

• A flavonoid compound from buckwheat sprout extracts was detected by HPLC analysis.
• In previous researches, the compound were not separated with rutin.
• We separated rutin and the previously unidentified compound by using a gradient elution.
• The compound was identified by NMRs as the rutin epimer quercetin-3-O-robinobioside.
• Common buckwheat sprouts contained the compound but not in tartary buckwheat sprouts.

It is known that common buckwheat sprouts contain several flavonoids, including orientin, isoorientin, vitexin, isovitexin, rutin, and quercetrin, whereas tartary buckwheat sprouts contain only rutin. In this study, we evaluated flavonoids present in buckwheat sprouts and identified a previously unreported flavonoid. Simultaneous detection by HPLC was used to separate rutin and a compound that was not separated in previous studies. We used a novel HPLC elution gradient method to successfully separate rutin and the previously unidentified compound, for which we performed structural analysis. The identification of six flavonoids by HPLC was confirmed using HPLC–ESI–MS/MS analysis. The newly identified compound, [M + H]+ = 611.17, was identified by NMR as the rutin epimer quercetin-3-O-robinobioside. Unlike common buckwheat sprout, tartary buckwheat sprout contained rutin as a main flavonoid, whereas other flavonoids appeared only in trace amounts or were not detected. Quercetin-3-O-robinobioside was not detected in tartary buckwheat sprout.