Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2005
Publication Date: 10/4/2005
Citation: Prior, R.L., Wu, X. 2005. Anthocyanins: structural characteristics that result in unique metabolic patterns and biological activities [abstract]. In: roceedings of the 2nd International Conference on Polyphenols and Health, October 4-7, 2005, Davis, California. 2005 CDROM.
Interpretive Summary: Anthocyanins are the components in foods that give the dark red, blue or black colors in many foods, particularly fruits and berries. Because of the number of different sugars and other chemical structures that can be attached to the basic anthocyanin molecule, there are over 600 different compounds that have been identified. The absorption/metabolism of anthocyanins has been studied in several berries with quite different anthocyanin compositions. The stability of anthocyanins within the gastrointestinal tract has a direct bearing on the amounts of anthocyanins that are absorbed. Anthocyanins with a sugar moiety of xylose and glucose (sambubiose) or xylose, glucose and rhamnose had greater recovery within the gastrointestinal tract 4 h after a meal and had a higher recovery in the urine, indicating increased absorption. The presence of 2 sugars on an anthocyanin also prevented their metabolism and thus more of the intact anthocyanin was absorbed and excreted in the urine. Some marked differences in apparent absorption and metabolism of different individual anthocyanins were observed which may have important implications in the biological effects observed following consumption of fruits and berries containing different anthocyanins. Data clearly demonstrate that aglycone and sugar moieties can alter the apparent absorption/metabolism of anthocyanins.
Technical Abstract: Anthocyanins (ACNs) are unique among flavonoids in that they have a low apparent absorption, are absorbed intact as the glycoside and thus metabolized differently. Main metabolites of ACNs are glucuronidated and/or methylated forms of the original ACNs containing 3' and 4' hydroxyl groups on the B-ring. Delphinidin ACNs, which contain 3 hydroxyl groups on the B-ring, show no appreciable metabolism. ACNs with different sugar moieties have significant differences in their recovery within the gastrointestinal (GI) tract with sambubiose > sambubiose-rhamnose = rutinose (rutin) >> glucose (glc) and also differing elimination patterns. Recovery of ACNs within the GI tract was positively and linearly associated with urinary recovery. The main metabolites of cyanidin (Cy) ACNs, which account for over 80% of the ACNs in fruits/berries, are glucuronidated and/or methylated forms. Cy-3-glc and Cy-3-rutin have similar apparent excretion rates as a %-age of dose, while urinary excretion of pelargonidin-3-glcoside (Pg-3-glc) was 8-10-fold higher than Cy-3-glc. Most of Cy-3-glc and Pg-3-glc were excreted as of metabolites. Over 80% of the ACNs containing the rutinose or sambubiose glycoside were excreted in the urine as the intact molecule. A small amount of the methylated forms was observed. At high doses of Cy-3-glu about equal proportions of methylated vs glucuronidated conjugates were formed, but at low doses much high proportions of glucuronidated conjugates were formed relative to methylated forms. Plasma concentration/dose ratio of Cy-3-rutin was significantly higher than that of Cy-3-glc. Data clearly demonstrate that aglycone and sugar moieties can alter the apparent absorption/metabolism of ACNs.