Correlations between leaf flavonoids, taxonomy and plant geography in the genus Disporum

In a flavonoid survey of 10 Disporum species using hydrolysed leaf extracts, the flavonols quercetin and kaempferol were found to be the main constituents of five North American species while in the five Asian taxa the flavone luteolin was the main component with some apigenin and chrysoeriol. This clear chemical difference supports the geographical division of Disporum into two sections and possibly into two genera with the re-erection of the genus Prosartes for the North American species. This was further supported by a more detailed analysis of the flavonoid glycosides in four taxa, which showed 16 chemical differences between North American and Asian plants. A number of unusual flavone glycosides were identified including luteolin 4′-mono- and 4′-diglucosides, apigenin 4′-diglucoside, a luteolin 4′-rhamnosylglucoside and luteolin and apigenin 7,4′-diglucosides. Within the Asian taxa most species have distinct flavonoid profiles. However, there is good evidence of chemical polymorphism in the D. cantoniense-D. sessile group. Thus, at least three distinct flavonoid patterns occur amongst the different accessions of D. cantoniense from China and the Himalayas. But more surprisingly, the Japanese species D. sessile is chemically indistinguishable from some specimens of D. cantoniense even though the two species are morphologically distinct, suggesting there might have been a common ancestor for the two species before the division of the present land masses.