Stereochemistry and glycosidic linkages of C3-glycosylations affected the reactivity of cyanidin derivatives

摘要

The impact of glycosylation on anthocyanin stability has largely been associated with sugar type, site, and size, with glycosyl stereochemistry being under-explored. Seven cyanidin-3-glycosides were isolated by HPLC, diluted in pH 1-9, mixed with bisulfite or ascorbic acid at pH 3, and stored for 8 weeks ( 25 degrees C, dark). Spectral changes, half-lives, and bleaching rates were determined. Cyanidin-3-galactoside was more reactive ( susceptible to hydration and bleaching) than cyanidin-3-glucoside. The 1 - 2 disaccharides exhibited greater lambda(vis-max) (= 16 nm), resistance to hydration, and bleaching compared to 1 - 6 disaccharides. The 1 - 6 disaccharides had similar lambda(vis-max) (similar to 2 nm) to the monosaccharides but slightly improved resistance to hydration and bleaching. The tri-gly-cosylated anthocyanin had the greatest stability and its spectral and bleaching characteristics was intermediate to 1 - 2 and 1 - 6 disaccharides. The 1 - 2 disaccharides generally exhibited lower half-lives compared to monosaccharides; whereas, 1 - 6 disaccharides exhibited higher stability. These findings highlight the role of glycosyl assembly on anthocyanin reactivity and stability.