Fagopyrin and flavonoid contents in common, Tartary, and cymosum buckwheat

Fagopyrin is a phototoxic substance found in buckwheat products in varying amounts. The aim of this study was to determine the fagopyrin, rutin, and quercetin contents of plant samples taken from 3 buckwheat species, namely common (Fagopyrum esculentum), Tartary (F. tataricum), and cymosum buckwheat (F. cymosum). HPLC was optimized for fagopyrin analysis using a fluorescence detector, and for other components a UV/VIS detector, while hypericin, rutin, and quercetin were used as standards. Common buckwheat leaves contained high levels of fagopyrin (322–2300 μg g−1) while even higher levels were found in other samples such as the flowers (≤4830 μg g−1). The highest fagopyrin content (20,700 μg g−1) was found in the flowers of F. cymosum. Two cymosum samples had a high proportion of fagopyrin relative to rutin (∼200 μg fagopyrin mg−1 rutin), whereas this proportion was lower (15–90 μg fagopyrin mg−1 rutin) in other samples.