Flavonoid chemistry of Fallopia section Fallopia (Polygonaceae)

Five controversial species of Fallopia sect. Fallopia sensu Holub were examined for leaf flavonoid constituents. Twenty-one flavonoid compounds were isolated and identified; they were glycosylated derivatives of the flavonols kaempferol, quercetin, and myricetin, and of the flavones apigenin and luteolin. Among them, quercetin 3-O-galactoside and quercetin 3-O-glucoside were major flavonoid constituents and present in all species. Although the flavonoid data for some species are lacking, those available appear to be useful for species delimitation and for recognizing species relationships in the section. The flavonoid data, in conjunction with morphological evidence, strongly suggest that F. scandens, F. dentatoalata, F. dumetorum, and F. convolvulus are closely allied but distinct species. In addition, the flavonoid data for F. cilinodis lend additional support to the segregation of sect. Parogonum from sect. Fallopia.