Biotransformation of Barley Phenolamide by Mice and the Human Gut Microbiota and Quantitative Analysis of the Major Metabolites in Mice

Abstract

This study investigates the metabolism of p-coumaroylagmatine (pCAA), one of the phenolamides in barley, in mice, and by human gut microbiota, and measures the concentrations of its main metabolites in mice. Nine major metabolites are identified from fecal and urinary samples collected from pCAA treated mice via analysis of their LC chromatograms and tandem mass spectra compared to the commercial and synthesized standards. These nine metabolites are generated through four different biotransformation pathways: double bond reduction, amide bond hydrolyzation, cleavage of guanidine, and oxidation of guanidine. Furthermore, interindividual differences in the formation of dihydro-pCAA (M3), high and low metabolizers, are observed in human in vitro intestinal microbial conversion. Moreover, significant amount of pCAA is detected in mice (29.33± 1.58µmolg-1 in feces and 2020.44± 130.07µM in urine), and the concentrations of agmatine (M1) are increased to 177.6 times and 3.2 times in mouse feces and urine, respectively. This study demonstrates that pCAA is metabolized in mice and by human gut microbiota to generate potential bioactive metabolites through four major metabolic pathways. pCAA and its metabolites have the potential to be used as the exposure biomarkers to reflect the intake of whole grain barley.