Determination of free and bound phenolics using HPLC-DAD, antioxidant activity and in vitro digestibility of Eragrostis tef

Abstract

White and brown Eragrostis tef were assessed for total flavonoid and phenolic content, HPLC profile of the most common phenolics and antioxidant activity including both free and bound phenolics. Antioxidant activity was evaluated in correlation with free and bound phenolics and in vitro digestibility was determined. Content of flavonoids (0.52-1.02mg RE/g) and phenolics (0.90-1.42mg GAE/g) as well as antioxidant activity (1.70-4.37μmol TEAC/g using ABTS method) was higher in free phenolic fraction. Correlation showed that bound flavonoids were not significant contributors to antioxidant activity (R2=0.4513 and 0.4893, respectively). The main free phenolics in brown teff were trans-p-coumaric, protocatechuic, ferulic and gallic acids, while the major free phenolics in white teff were rutin, protocatechuic and ferulic acids. The main bound phenolics in brown teff were ferulic and gallic acids, quercetin and catechin, in white teff ferulic acid, rutin, catechin and quercetin. Cooked teff showed very high level of in vitro organic matter digestibility (80.5-85.1%), whereas brown teff was significantly more digestible than white teff (P<0.05). © 2015 Elsevier Inc.