Quantitative Flavonoid Variation Accompanied by Change of Flower Colors in Edgeworthia chrysantha, Pittosporum tobira and Wisteria floribunda

The flavonoids in the flowers of Edgeworthia chrysantha, Pittosporum tobira and Wisteria floribunda were isolated and identified. Quercetin and kaempferol 3-O-glucosides and 3-O-rutinosides were found in E. chrysantha, and quercetin 3-O-rutinoside, 3-O-glucoside and 3-O-pentosylrhamnosylglucoside, kaempferol 3-O-robinobioside, 3-O-rutinoside, 3-O-glucoside and 3-O-pentosylrhamnosylglucoside, and isorhamnetin 3-O-rutinoside were isolated from P. tobira. Ten flavonoids, quercetin 3-O-sophoroside, 3-O-rutinoside, 3-O-glucoside, kaempferol 3-O-sophoroside and 3-O-glucoside, luteolin 5-O-glucoside, 7-O-glucoside and 7-O-hexoside, and apigenin 7-O-glucoside and 4′-O-hexoside were isolated from W. floribunda. The major pigments of E. chrysantha were carotenoids. Their content decreased with the change in flower color to white from yellow via cream, and total flavonoid content also slightly decreased by ca. 0.8 in cream and ca. 0.9 fold in white flowers. In contrast with E. chrysantha, white flowers of P. tobira turn to cream and then yellow in which the major pigments are also carotenoids. In this species, both carotenoid and flavonoid contents are gradually increased from white to yellow flowers. Though the petal color of Wisteria floribunda is mauve, due to anthocyanin pigments, the yellow areas are due to carotenoids; these turn to white in the late flowering stage. However, their flavonoid contents were essentially the same among the yellow, cream and white spots of flags. Thus, it was shown by HPLC analysis of the flower flavonoids of E. chrysantha, P. tobira and W. floribunda, although the visible pigments such as carotenoids and anthocyanins are quantitatively varied, the quantitative variation in UV-absorbing substances, such as flavones and flavonols, differs with plant species.