Extended glucuronidation is another major path of cyanidin 3-O-β-D-glucopyranoside metabolism in rats

We previously determined that five rather. hydrophobic metabolites appeared in blood plasma after oral administration of cyaniclin 3-O-beta-D-glucopyranoside, but a group of hydrophilic metabolites still remained unidentified. In the present study, 12 hydrophilic metabolites found were collected from urine and plasma samples by high-performance liquid chromatography (HPLC) and then analyzed by tandem MS spectrometry. From the MS spectra, four metabolites out of 12 were assigned as glucuronicles of cyaniclin 3-O-beta-D-glucopyranoside and six out of 12 were glucuronides of the primary metabolites of cyaniclin 3-O-beta-D-glucopyranoside (O-methyl cyaniclin 3-O-beta-D-glucopyranoside). Extended glucuronicles of cyanidin 3-O-beta-D-glucopyranoside and O-methyl cyanidin 3-O-beta-D-glucopyranoside showed their maximum plasma concentrations at 15 and 60 min (or 30 min) after oral administration, respectively. Their maximum plasma concentrations ranged from 15 to 70 nM. From the profile of urinary-excreted anthocyanins after intravenous administration, it was deduced that extended glucuronicles of cyaniclin 3-O-beta-D-glucopyranoside and O-methyl cyaniclin 3-O-beta-D-glucopyranoside were mainly produced in the liver rather than by intestinal flora. The area under the plasma concentration curve was 0.25 mu mol min/L for extended glucuronicles of cyaniclin 3-O-beta-Dglucopyranoside and 0.14 mu mol min/L for amethyl cyaniclin 3-O-beta-D-glucopyranoside, respectively, when evaluated as cyanidin 3-O-beta-D-glucopyranoside equivalent, indicating that extended glucuronidation is a critical pathway in cyaniclin 3-O-beta-D-glucopyranosicle metabolism in rats.