Excretion of Avenanthramides, Phenolic Acids and their Major Metabolites Following Intake of Oat Bran

Abstract

ScopeWholegrain has been associated with reduced chronic disease mortality, with oat intake particularly notable for lowering blood cholesterol and glycemia. To better understand the complex nutrient profile of oats, we studied urinary excretion of phenolic acids and avenanthramides after ingestion of oat bran in humans.Methods and resultsAfter a 2‐d (poly)phenol‐low diet, seven healthy men provided urine 12 h before and 48 h after consuming 60 g oat bran (7.8 μmol avenanthramides, 139.2 μmol phenolic acids) or a phenolic‐low (traces of phenolics) control in a crossover design. Analysis by ultra‐high performance liquid chromatography (UPLC)–MS/MS showed that oat bran intake resulted in an elevation in urinary excretion of 30 phenolics relative to the control, suggesting that they are oat bran‐derived. Mean excretion levels were elevated between 0–2 and 4–8 h, following oat bran intake, and amounted to a total of 33.7 ± 7.3 μmol total excretion (mean recovery: 22.9 ± 5.0%), relative to control. The predominant metabolites included: vanillic acid, 4‐ and 3‐hydroxyhippuric acids, and sulfate‐conjugates of benzoic and ferulic acids, which accounted collectively for two thirds of total excretion.ConclusionOat bran phenolics follow a relatively rapid urinary excretion, with 30 metabolites excreted within 8 h of intake. These levels of excretion suggest that bound phenolics are, in part, rapidly released by the microbiota.

Determination of selected phenolic acid and majoritarian avenanthramides in different varieties of naked oats (Avena sativa L.) grown in Slovakia

“…The p-coumaric acid (97.87 -211.03 mg/kg) and o-coumaric acid (126.53 -575.87 mg/kg) were determined in the corn (Hung 2014). The intervention diet (60 g oat bran) contained 28.6 mg of total phenolics (24 % in the soluble fraction), with FA being the predominant PAs (16.8 mg) followed by PCA (3.3 mg) and the three AVNs totally amounting to 2.5 mg (Schär et al 2018). FA, PCA and AVN 2p accounted only for small percentages of the total excreted phenolics and AVNs 2f and 2c were not detected, suggesting that these dietary forms are subject to extensive metabolism (Schär et al 2018).…”

“…The intervention diet (60 g oat bran) contained 28.6 mg of total phenolics (24 % in the soluble fraction), with FA being the predominant PAs (16.8 mg) followed by PCA (3.3 mg) and the three AVNs totally amounting to 2.5 mg (Schär et al 2018). FA, PCA and AVN 2p accounted only for small percentages of the total excreted phenolics and AVNs 2f and 2c were not detected, suggesting that these dietary forms are subject to extensive metabolism (Schär et al 2018). AVNs content in whole oat extracts was 3.7 to 48.41 mg/kg for AVN 2c, 1.05 to 43.77 mg/kg for 2p and 3.66 to 58.63 mg/kg for 2f in the varieties of oats from Canada (Chu et al 2013).…”

“…Oats and products present data for oats from China were studied and published in several other studies (Ren et al 2011;Li et al 2017;Chen et al 2018), husked oat from Finland (Multari et al 2018). Several studies assessed AVNs content in human materials such as plasma (Chen et al 2007) and urine (Schär et al 2018). However, data on content of AVNs in oats and oats products are still rather limited.…”

The gut microbiota and cardiovascular health benefits: A focus on wholegrain oats

“…Our group reported intake of 60 g oat bran (2.5 mg avenanthramides, 28.6 mg phenolic acids) resulted in elevated urinary excretion of 30 phenolic acids metabolites, amounting to total recovery of 22.9% ± 5.0%, mainly between 0–2 and 4–8 hours (Schar et al . ). The predominant metabolites included vanillic acid, 4‐ and 3‐hydroxyhippuric acids and sulphate conjugates of benzoic and ferulic acid (accounting for two‐thirds of total phenolic excretion).…”

In vitro evaluation of digestive enzyme inhibition and antioxidant effects of naked oat phenolic acid compound (OPC)

“…Phenolic compounds can reduce postprandial blood glucose and insulin levels and its related enzymes. Significant interest in the identification of phenolic compounds constituents of oats has led to discovery of several avenanthramides, caffeic acid, quercetin‐3,4′‐O‐di‐beta‐glucopyranoside derivative, sinapic acid and p ‐coumaric acid (Schar et al , ). Ultrasound‐assisted and pressurised organic solvent extraction can break the cell wall and tissue of oat granules compared to conventional extraction, allowing more phenolic compounds to be released, while exhibiting stronger total phenolic and physiological activities (Mir et al , ).Therefore, the objective of this work was to study the interactions between semi‐purified and organic solvent extraction phases phenolic compounds from naked oat bran and carbohydrate metabolism‐related enzymes using detailed kinetics of inhibition.…”