| Abstract
| - Sorghum bran is concentrated with procyanidins (predominately polymers), which may be beneficialfor health in humans; however, the bioavailability of procyanidins is not well-understood. FemaleSprague−Dawley rats were fed an AIN93G diet containing 0, 5, 10, 20, or 40% Hi-tannin sorghumbran (n = 5−7 for each group) for 50 days. Sorghum bran contained 23.3 mg/g of procyanidins. Theurinary excretions of catechin, epicatechin, methylated catechins, and phenolic acids were analyzedusing liquid chromatography−tandem mass spectrometry. Sorghum bran dose dependently increasedthe urinary excretion of catechin (0−2.2 nmol/day) and 3‘-O-methylcatechin (0−9.5 nmol/day). Theirserum concentrations also increased with dose (range of 0−14 nM for 3‘-O-methylcatechin). Amongthe 14 phenolic acids analyzed, 3,4-dihydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, and4-hydroxyphenylacetic acid dominated in the serum (1.8−8 μmol/L). In the urine, 3-methoxy-4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and 3-hydroxyphenylpropionic acid dominatedand their excretion increased significantly with the level of sorghum bran in the diet. The summedphenolic acid excretion was 0.8 μmol/day in the control group and increased to 23 μmol/day for 40%sorghum bran group. The hippuric acid excretion ranged from 2.2 to 16.2 μmol/day and peaked inthe 10% sorghum bran group. On the basis of chromic oxide, a nonabsorbable marker, totalprocyanidins and polymers disappeared progressively, and significant degradation occurred in thececum and colon. Catechins and procyanidins in sorghum were bioavailable; however, bacteria-derived phenolic acids were the predominant metabolites of procyanidins. Procyanidins degraded inthe gastrointestinal tract. Depolymerization was not observed. Keywords: Sorghum; procyanidins; catechin; epicatechin; phenolic acids
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