Phenolic Acid Composition of Sprouted Wheats by Ultra-Performance Liquid Chromatography (UPLC) and Their Antioxidant Activities

Food Chem. 2011 Jun 15;126(4):1896-901. doi: 10.1016/j.foodchem.2010.12.015. Epub 2010 Dec 10.

Abstract

The phenolic acid profiles of flours from two Canadian wheat classes, Canadian Western Red Spring (CWRS) and Canadian Western Amber Durum (CWAD), were investigated using two different extraction mediums and analysed on an ultra-performance liquid chromatography (UPLC) system at different degrees of sprout damage. A sound (non-sprouted) control sample as well as two different sprouted sub-samples, derived from different germination protocols of the control, were prepared for both the CWAD and CWRS. Free phenolic acids were extracted from the ground whole wheat meal using three repetitive 80% ethanol extractions. Bound phenolic compounds were subsequently released from the residue by alkaline hydrolysis followed by triplicate extraction with diethyl ether:ethyl acetate (1:1, v/v). Twelve phenolic acid standards were clearly resolved and quantified using a short 5min elution gradient. Seven phenolic acids (4-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric, ferulic and sinapic) were detected in the CWRS and CWAD alcoholic and alkaline extracts. Syringic acid was the main compound in the free phenolic alcoholic extracts of the wheat meal representing 77.0% and 75.3% of the total amount of detected free phenolic compounds for CWRS and CWAD, respectively. However, the major released phenolic compound detected in the alkaline hydrolysed extracts was ferulic acid accounting for 72.3% and 71.0% for CWRS and CWAD respectively total bound phenolics. During germination, syringic acid levels rose as the length of germination time increased, resulting in the increase in total phenolic compound and antioxidant activity of the sprouted wheat flours. There was an increase in total phenolic compounds and the antioxidant activity of the alcoholic extracts from the CWRS and CWAD wheat flours as the germination time was extended. As a result, the sprouted wheats exhibits better nutritional properties than un-germinated wheat and could be used to improve the nutrition value in food products.

Keywords: Antioxidant; Germination; Phenolic compound; Sprouted wheat.