Contribution of each caffeoyl residue of the pigment molecule of gentiodelphin to blue color development

To clarify the function of each caffeoyl residue in the diacylated anthocya nin gentiodelphin, a pigment from the blue flower of Gentiana makinoi, two mono-deacyl derivatives were compared for both color development and stabil ity. In neutral solution, 3.5-di-O-beta-D-glucopyranosyl-3'-O-(6-O-caffeoyl -beta-D-glucopyranosyl)delphinidin was both bluer and more stable than 3,3' -di-0-8D-glucopyrannsyl-5-O-(6-O-caffeoyl-beta-D-glucopyranosyl)delphinidin . Conformational analysis of each derivative under acidic conditions reveal ed only the 3'-O-caffeoylglucopyranosyl derivative to demonstrate intramole cular stacking. Additionally, the acyl residue in the B-ring contributed mo re to blue color development than that in the A-ring. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.