Distribution of bound hydroxycinnamic acids and their glycosyl esters in barley (Hordeum vulgare L.) air-classified flour: comparative study between reversed phase-high performance chromatography-mass spectrometry (RP-HPLC/MS) and spectrophotometric analysis.

The level of bound hydroxycinnamic acid was determined by spectrophotometry (as total hydroxycinnamic compounds and free-radical-scavenging activity) and reversed-phase high-performance chromatography (RP-HPLC) coupled to mass spectrometry (MS) in barley flours (whole meals and air-classified fractions: coarse fraction and fine fraction). Hydroxycinnamic acids and their derivatives were the main bound phenols in barley flours. A total of 12 different hydroxycinnamic acids were identified and quantified by HPLC/diode array detector (DAD)-MS within 90 min. Ferulic acid (as a simple and glycosylated derivative) was the main phenolic acid in barley flours, representing 89-93% of total hydroxycinnamic acids. The amount of total hydroxycinnamic acid in air-classified coarse fraction was 2 and 3 times higher than those of whole meal and the air-classified fine fraction, respectively. Similarly, the coarse fraction showed higher antioxidant activity (650.03 micromol of TEAC/100 g of flour) compared to whole meal and the fine fraction (388.78 and 320.27 micromol of TEAC/100 g of flour, respectively).