Tetra-acylated cyanidin 3-sophoroside-5-glucosides from the flowers of Iberis umbellata L. (Cruciferae)

Abstract

The structures of 11 acylated cyanidin 3-sophoroside-5-glucosides (pigments 1– 11), isolated from the flowers of Iberis umbellata cultivars (Cruciferae), were elucidated by chemical and spectroscopic methods. Pigments 1– 11 were acylated with malonic acid, p-coumaric acid, ferulic acid, sinapic acid and/or glucosylhydroxycinnamic acids. Pigments 1– 11 were classified into four groups by the substitution patterns of the linear acylated residues at the 3-position of the cyanidin. In the first group, pigments 1– 3 were determined to be cyanidin 3- O-[2- O-(2- O-(acyl)-β-glucopyranosyl)-6- O-( trans- p-coumaroyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 1, ferulic acid for pigment 2 and sinapic acid for pigment 3. In the second one, pigments 4– 6 were cyanidin 3- O-[2- O-(2- O-(acyl)-β-glucopyranosyl)-6- O-(4- O-(β-glucopyranosyl)- trans- p-coumaroyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 4, ferulic acid for pigment 5 and sinapic acid for pigment 6. In the third one, pigments 7– 9 were cyanidin 3- O-[2- O-(2- O-(acyl)-β-glucopyranosyl)-6- O-(4- O-(6- O-( trans-feruloyl)-β-glucopyranosyl)- trans- p-coumaroyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 7, ferulic acid for pigment 8, and sinapic acid for pigment 9. In the last one, pigments 10 and 11 were cyanidin 3- O-[2- O-(2- O-(acyl)-β-glucopyranosyl)-6- O-(4- O-(6- O-(4- O-(β-glucopyranosyl)- trans-feruloyl)-β-glucopyranosyl)- trans- p-coumaroyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside], in which acyl moieties were none for pigment 10 and ferulic acid for pigment 11. The distribution of these pigments was examined in the flowers of four cultivars of I. umbellata by HPLC analysis. Pigment 1 acylated with one molecule of p-coumaric acid was dominantly observed in purple-violet cultivars. On the other hand, pigments ( 9 and 11) acylated with three molecules of hydroxycinnamic acids were observed in lilac (purple-violet) cultivars as major anthocyanins. The bluing effect and stability on these anthocyanin colors were discussed in relation to the molecular number of hydroxycinnamic acids in these anthocyanin molecules.