Polyphenols in amaranth (A. manteggazianus) flour and protein isolate: Interaction with other components and effect of the gastrointestinal digestion

RODRÍGUEZ, MARIELA; TIRONI, VALERIA A.

FOOD RESEARCH INTERNATIONAL

ELSEVIER SCIENCE BV

Año: 2020 vol. 137

0963-9969

In this work, there were analysed the interaction between phenolics present in amaranth flour (F) and amaranthprotein isolate (I) with other components, as well as the effect of the gastrointestinal digestion on them (Fd andId). Extractions were performed under different conditions (temperature, acid, organic solvent, alkali).Methanol/water extracts (25 °C and 80 °C) from F showed the presence of isoquercetin/rutin, quercetin,kaempferol and two unidentified peaks (II and III). In the presence of acid (much more evident at 80 °C), theextraction of some components increased: catechin, 4-hydroxibenzoic acid, isoquercetin/rutin, II, III. Whenmethanol/acetone/water extraction was performed, p-coumaric acid and a new unidentified peak (IV) wereobserved. About 15% of the total phenol ?namely; p-coumaric, rutin/isoquercetin, and kaempferol? were linkedto the protein fraction. After the proteins were isolated (I), the amount of some of the compounds which wereoriginally present in a soluble form (e. g. catechin) and in the protein-bound fraction were decreased. Simulatedgastrointestinal digestion of flour released some phenolics (catechin, phenolic acids) that were ligated to proteins,and they significantly incremented the ORAC and ABTS activity of most of the extracts. Isoquercetin/rutin,quercetin and kaempferol remained after digestion. Extracts from the digested protein isolate presented differencesin the composition and lower ORAC and/or ABTS activities for some of them. The study of the effect ofthe simulated gastrointestinal digestion process on bioaccessibility and on antioxidant activity (an aspect that, toour knowledge, has not been previously studied on amaranth polyphenols) yielded promising results, whichsuggest that amaranth flour is a potential antioxidant functional ingredient.