Flavonoid Chemistry of Polygonum Sect. Echinocaulon: A Systematic Survey

Abstract

Thirteen species of Polygonum sect. Echinocaulon were examined for leaf flavonoid constituents. Thirty-six flavonoid compounds were isolated and identified, most of which were glycosylated and/or methoxylated derivatives of the flavonols kaempferol, quercetin, and myric- etin, and of the flavones apigenin and luteolin. Among them, quercetin 3-0-glycosides were major flavonoid constituents, and present in all species. Species of section Echinocaulon exhibit relatively complex patterns of leaf flavonoid constituents. Although the flavonoid data for some species are lacking, those available appear to be very useful for species delimitation and for recognizing species relationships in the section. Most species of section Echinocaulon are readily distinguished by their flavonoid profiles, and the cladogram based on nine flavonoid characters suggests four basic chem- ical lineages in the section. Section Echinocaulon of Polygonum (Polygo- naceae), first recognized by Meisner (1832), is morphologically distinct and characterized by recurved prickles on the angles of the stems, petioles, and midribs. Additional characters separating this from other sections of Polygo- num include scandent to climbing habit and el- liptic to triangular leaf shapes with sagittate to