Bioavailability and Metabolic Fate of (Poly)phenols from Hull-Less Purple Whole-Grain Barley in Humans

Background and Objectives: Anthocyanin-rich barley varieties have recently gained attention due to their high (poly)phenolic content and potential health benefits, yet human data on their bioavailability remain scarce. This study aimed to characterize the absorption, metabolism, and excretion of (poly)phenolic compounds from a novel hull-less purple whole-grain barley (WGB) genotype. Methods: Eleven healthy volunteers consumed 140 g of purple WGB biscuits, and plasma and urine samples were collected over 6 h and 48 h, respectively. Results: UPLC-MS/MS analysis revealed a broad range of metabolites, with 11 (poly)phenolic compounds identified in plasma and 80 in urine. The biscuits were particularly rich in flavones (217 mg/140 g, mainly chrysoeriol derivatives), followed by hydroxycinnamic acids (~54 mg, mainly 4'-hydroxy-3'-methoxycinnamic acid), anthocyanins (44.8 mg), and flavan-3-ols (16.8 mg). In plasma, glycosylated anthocyanins and flavone conjugates (e.g., peonidin-3-O-glucuronide, chrysoeriol-O-glucuronide) were detectable within 1-2 h, consistent with early absorption. In contrast, microbial-derived catabolites-including valerolactones, phenylacetic and benzoic acids-were mainly excreted in urine between 8 and 24 h, reaching concentrations above 1000 nM. Conclusions: These findings provide novel insights into the bioavailability and metabolic fate of barley (poly)phenols, supporting their potential contribution to host and gut health. As a proof-of-concept study, it complements the limited data available from pigmented cereals and underscores the need for validation in larger cohorts.