Nonenzymatic <i>C</i>-Glycosylation of Flavan-3-ols by Oligo- and Polysaccharides
作者:Timo Stark、Daniela Keller、Kerstin Wenker、Hedda Hillmann、Thomas Hofmann
DOI:10.1021/jf0719508
日期:2007.11.1
Model reactions between the polysaccharide amylose and the polyphenol (-)-epicatechin followed by partial enzymatic hydrolysis of the reaction products formed led to the detection of mono- and oligo-C-glucosylated flavan-3-ols by means of LC-MS/MS experiments. To confirm the structure of these putative flavan-3-ol/oligosaccharide conjugates, (-)-epicatechin was reacted with maltose and maltotriose, respectively, giving rise to a series of previously unreported flavan-3-ol/maltose and flavan-3-ol/maltotriose conjugates, namely, (-)-epicatechin-8-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside, (-)-catechin-C- 8-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside, (-)-catechin-6-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside, (-)-catechin-8-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside, (-)-catechin-6-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside, and (-)-epicatechin-6/8-C-beta-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranosyl-(4 -> 1)-O-alpha-D-glucopyranoside. Furthermore, quantitative analysis of flavan-3-ol-C-glucosides in an enzymatic total hydrolysate using a newly developed stable isotope dilution assay (SIDA) enabled a first insight into the yield of the formation of polyphenol/polysaccharide cross-links, for example, an amount of 14.0, 9.0, and 0.15 mu mol of flavan-3-ol-6-C-beta-D-glucopyranoside, flavan-3-ol-8-C-beta-D-glucopyranoside, and flavan-3-ol-6-C,8-C- beta-D-glucopyranoside were per mmol (-)-epicatechin when reacted with amylose.