Phenolic acids in black raspberry and in the gastrointestinal tract of pigs following ingestion of black raspberry

Black raspberries (BRB) contain high levels of polyphenols and have been demonstrated to be chemopreventive. In order to investigate the underlying mechanism and study the metabolism of anthocyanins, pigs were fed freeze-dried BRB powder or purified diet (control) and three segments of the gastrointestinal (GI) tract (small intestine, cecum, and colon; 4 h after feeding) were collected for analysis of phenolic acids. Protocatechuic acid was the major phenolic acid (8.35 mg/100 g, dry weight (DW)) in BRB, followed by p-coumaric acid (1.63 mg/100 g, DW), caffeic acid (1.34 mg/ 100 g, DW), ferulic acid (0.24 mg/100 g, DW), and 3-hydroxybenzoic acid (0.20 mg/100 g, DW). Recoveries of these five phenolic acids in the whole GI tract were 199.9 ± 54.0%, 7.0 ± 3.0%, 37.0 ± 9.7%, 56.6 ± 31.3%, and 916.8 ± 642.3% (mean ± SEM, n=5), respectively, and quantities in contents of the GI tract ranged from 0.13 ± 0.05 μmol (p-coumaric acid) to 23.47 ± 6.09 μmol (protocatechuic acid) (mean ± SEM, n = 5). Six other phenolic acids were detected primarily in the cecum and/or colon which were not in BRB, with total contents in the GI tract ranging from 0.18 ± 0.18 μmol (homovanillic acid) to 8.49 ± 4.31 μmol (homoprotocatechuic acid). Total phenolic acids in the GI tract were 49.32 ± 16.37 μmol (mean ± SEM, n = 5). Phenolic acids measured in the GI tract accounted for only 6.31% of the degraded anthocyanins.