Flavonoid composition related to petal color in different lines of Clitoria ternatea.

Flavonoids in the petals of several C. ternatea lines with different petal colors were investigated with LC/MS/MS. Delphinidin 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside was newly isolated from the petals of a mauve line (wm) together with three known anthocyanins. They were identified structurally using UV, MS, and NMR spectroscopy. Although ternatins, a group of 15 (poly)acylated delphinidin glucosides, were identified in all the blue petal lines (WB, BM-1, 'Double Blue' and 'Albiflora'), WM accumulated delphinidin 3-O-(6"-O-malonyl)-beta-glucoside instead. The white petal line (WW) did not contain anthocyanins. Quantitative data showed that the total anthocyanin contents in WB and 'Double Blue' were ca. 8- and 10-fold higher than that in BM-1, a bud mutant of 'Double Blue', respectively. The total anthocyanin content in 'Albiflora' was less than 2 x 10(-3) times those in WB or 'Double Blue'. While all the lines contained the same set of 15 flavonol glycosides in similar relative ratios, the relative ratio of myricetin glycosides in ww and 'Albiflora' was ca. 30-70 times greater than those in the other lines. The change in flower color from blue to mauve was not due to a change in the structure of an anthocyanidin from delphinidin, but to the lack of (polyacylated) glucosyl group substitutions at both the 3'- and 5'-positions of ternatins. This implies that glucosylation at the 3'- and 5'-positions of anthocyanin is a critical step in producing blue petals in C. ternatea.