Transformation of polyphenols found in pigmented gluten-free flours during in vitro large intestinal fermentation

Food Chem. 2019 Nov 15;298:125068. doi: 10.1016/j.foodchem.2019.125068. Epub 2019 Jun 24.

Abstract

In this work, 18 gluten-free flours (prepared from cereals, pseudocereals and legumes), differing in pigmentation, were screened for their phenolic profiles, cooked and, then, subjected to digestion and large intestinal fermentation in vitro. A combined targeted/untargeted metabolomic approach was used to elucidate the microbial biotransformation processes of polyphenols following digestion. This preliminary work demonstrated an increase in 3,5-dihydroxybenzoic acid (on average from 0.67 up to 1.30 μmol/g dry matter) throughout large intestinal fermentation of pseudocereals (esp. quinoa), due to their high alkylresorcinol contents. Isoflavones were converted into equol- or O-desmethylangolensin- derivatives, whereas anthocyanins were degraded into lower-molecular-weight phenolics (i.e., protocatechuic aldehyde and 4-hydroxybenzoic acid, with the latter exhibiting the highest increase over time). A decreasing trend was observed for antioxidant activities (i.e., FRAP and ORAC values) moving from digested to faecal fermented samples. These findings highlight that gluten-free flours are able to deliver bioaccessible polyphenols to the colon.

Keywords: Food metabolomics; In vitro large intestinal fermentation; Pigmented flours; Polyphenols; UHPLC-Orbitrap; UHPLC-QTOF.

MeSH terms

  • Animals
  • Bacteria / growth & development
  • Bacteria / isolation & purification
  • Batch Cell Culture Techniques
  • Chromatography, High Pressure Liquid
  • Cooking
  • Feces / microbiology
  • Flour / analysis*
  • Intestine, Large / microbiology*
  • Polyphenols / analysis
  • Polyphenols / chemistry
  • Polyphenols / metabolism*
  • Spectrometry, Mass, Electrospray Ionization
  • Swine

Substances

  • Polyphenols