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

Abstract

Scope: 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. Methods and results: 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 ± 1.58 μmol g −1 in feces and 2020.44 ± 130.07 μM in urine), and the concentrations of agmatine (M1) are increased to 177.6 times and 3.2 times in mouse feces and urine, respectively. Conclusion: 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.

Barley Phenolamides Effectively Scavenge Harmful Methylglyoxal In Vitro and in Mice

“…Two barley phenolamides, pCAA and FAA (Figure 1a), were synthesized in-house according to our previous methods. [24] After incubating pCAA, FAA, or metformin with MGO, the percentages of remaining MGO at each time point from each reaction model were measured and shown in Figure 1b. MGO levels in three reaction systems decreased rapidly as incubation time increased.…”

“…Our previous data revealed that pCAA is well absorbed in mice. [24] pCAA can reach up to 2020.44 ± 130.07 μm in mouse urine within 24 h after oral administration of pCAA with a dose of 200 mg kg −1 . [24] In the present study, our results demonstrated that absorbed pCAA and FAA could trap endogenous MGO via the formation of imidazolonetype mono-MGO adducts in mice after oral administration.…”

“…[24] pCAA can reach up to 2020.44 ± 130.07 μm in mouse urine within 24 h after oral administration of pCAA with a dose of 200 mg kg −1 . [24] In the present study, our results demonstrated that absorbed pCAA and FAA could trap endogenous MGO via the formation of imidazolonetype mono-MGO adducts in mice after oral administration. Moreover, non-absorbed pCAA and FAA could also react with MGO in the gastrointestinal tract via the construction of the same type of imidazolone adducts.…”