Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2006
Publication Date: 3/27/2006
Citation: Gu, L., House, S., Prior, R.L. 2006. Sorghum bran in the diet dose dependently increased excretion of catechins and microbial derived phenolic acids in rats [abstract]. The FASEB Journal. 20(4):A573. Interpretive Summary: Sorghum bran is a rich source of procyanidins, which are very large compounds found in many fruits and some vegetables and that have been shown to be beneficial for health in humans. Because of the large size of these compounds, the amount that is actually absorbed into the body is thought to be low. These compounds can be degraded by bacteria in the gastrointestinal tract. This study represents the first study to demonstrate the absorption and excretion of some of these bacterial metabolites using the rat as an animal model. Some key metabolites were identified that were excreted in the urine in direct proportion to the amount of procyanidins included in the diet. Disappearance of procyanidins in the gastrointestinal tract of the rat was also evaluated. They were found to disappear progressively throughout the gastrointestinal tract; however, bacterial-derived breakdown products were the predominant components that were absorbed. Sorghum is used as an infant cereal in many developing countries, and means of using sorghum in foods in this country are being studied. Studies of the way in which these components are absorbed is critical to understanding mechanisms of potential health effects.
Technical Abstract: Sorghum bran is a rich source of procyanidins (predominately polymers), which are shown to be beneficial for health in humans. Bioavailability of procyanidin polymers is thought to be low. Female Sprague-Dawley rats were fed AIN93G diet containing 0, 5, 10, 20 or 40% sorghum bran (n=5 for each group) for 50 days. Sorghum bran contained 23.3 mg/g of procyanidins. Urinary excretion of catechin, epicatechin, methylated catechin, and phenolic acids were analyzed on LC/MS/MS. Sorghum bran dose dependently increased urinary excretion of catechin (0 to 2.2 nmole/day) and 3'-O-methyl catechin (0 to 9.5 nmole/day). Epicatechin was not detected. Among the fourteen phenolic acids analyzed, vanillic acid, 3-hydroxyphenylacetic acid, homovanillic acid, 3-hydroxyphenylpropionic acid, p-coumaric acid, caffeic acid, and ferulic acid increased significantly with dose. Summed phenolic acid excretion was 0.8 umole/day in the control group and increased to 23 umole/day for 40% sorghum bran group. Hippuric acid excretion ranged from 2.2 to 16.2 umole/day and peaked at 10% sorghum bran group. Disappearance of procyanidins in the gastrointestinal tract was evaluated using chromic oxide as a non-absorbable marker. Total procyanidins and polymers disappeared progressively, and significant degradation occurred in the cecum and colon. Procyanidins in sorghum are bioavailable as catechins; however, bacterial-derived phenolic acids were the predominant metabolites.