Abstract
The impact of beta-glucan-rich oat bran on the bioavailability of orange juice (OJ) flavanones was investigated. Volunteers consumed 500 mL of OJ with and without 22 g of oat bran containing 6 g of beta-glucan (OB-6). Urine collected 12 h prior to and over a 0-24 h period post-supplementation was analysed by UHPLC-HRMS. Sixteen flavanone metabolites and thirty-nine colon-derived phenolic catabolites were identified and quantified. The major compounds were hesperetin-3 '-glucuronide, along with hippuric acids and the C6-C3 phenolic acids 3-(3 '- hydroxy-4 '-methoxyphenyl)hydracrylic acid and 3-(4 '-hydroxy-3 '-methoxyphenyl)propanoic acid. A marked reduction in the 0-24 h excretion of flavanone metabolites from 29.7 mu mol (9.3% recovery) to 9.3 mu mol (2.9% recovery), occurred following consumption of OB-6 compared to OJ. This appeared not to be an effect of fiber on the rate of transport in the upper gut. After consumption of OJ there was a 163 +/- 15 mu mol excretion of colon -derived phenolic catabolites, equivalent to 43% of (poly)phenol intake and following OB-6 intake there was a further significant 30% increase. The beta-oat bran in OB-6 contained 5.8 mu mol of free and 52 mu mol of bound phenolic derivatives compared to 371 mu mol of OJ (poly)phenols. The elevated excretion of phenolics after OB-6 consumption appears not to be due to bound phenolics in the bran, rather it is consequence, principally, of a bran-mediated increase in the quantities of flavanones passing from the upper to the lower bowel where they were subjected to microbiota-mediated catabolism.Clinical trial registration number: This trial was registered at clinicaltrials.gov as NCT04867655.