Isolation of Bilberry Anthocyanidin 3-Glycosides Bearing ortho-Dihydroxyl Groups on the B Ring by Forming an Aluminum Complex and Their Antioxidant Activity

摘要

Bilberry anthocyanin bearing an ortho-dihydroxyl group on the B ring was selectively isolated by complex formation with flavocommelin and aluminum ions (Al~(3+)). The interaction between the anthocyanins, flavocommelin, and Al~(3+) might have happened in a manner similar to rigid supramolecules, such as commelinin, protocyanin, and other complex pigments. Complex blue pigment (CP, 8.85 ± 0.26 mg) with Al~(3+) was formed from 18.6 mg (15 μmol) of bilberry pigment, 18.2 mg (30 μnol, 2.0 equiv) of flavocommelin, and 0.03 mL of 0.5 M aluminum chloride aqueous solution (15 μmol, 1.0 equiv), yielding 36.5 ± 0.7% recovery of anthocyanins in the complex after precipitation by ethanol. Consequently, anthocyanins bearing ortho-dihydroxyl groups on the B rings (delphinidin 3-glycosides, cyanidin 3-glycosides, and petunidin 3-glycosides) predominating (98.0 ± 0.2%) in the complex were selectively isolated in a dose-dependent manner by the addition of Al~(3+), increasing the antioxidative activity of the mixture of anthocyanins.