Extraction of free and bound phenolics from glabrous canary seed (Phalaris canariensis L.) hulls

Abstract

The aim was to extract free phenolics using a green solvent (ethanol), and bound phenolics from glabrous canary seed hulls. The efficiency of ethanol 75% was compared with that of other sol-vents used in the literature (acetone 70%; methanol 80%) in terms of phenolic yield and antioxidant ac-tivity. Bound phenolics were extracted with ethyl acetate, prior to hydrolysis with NaOH 2 M. The phenolic extracts obtained were characterized ac-cording to extraction yield, total phenols, flavo-noides, antioxidant activity, radical DPPH; and phe-nolic profile, HPLC. Methanol 80% had lower ex-traction yield, and acetone 70% had lower antioxi-dant activity; whereas ethanol 75% was the most efficient solvent to obtain free phenolics. Extraction yield of bound phenolics (6411.13 mg/100g hulls d.b.) doubled the value of free phenolics. Thus, antioxi-dant activity was four times higher (78.67% inhibi-tion of radical DPPH). On the other hand, phenolic acids predominated over flavonoids compounds in a rate 26/1. Ferulic acid was the dominant (42.48 mg/100g hulls), followed by p-coumaric (39.07 mg/100g hulls). Although the use of glabrous canary seed is new, interest in its processing at industrial level makes canary seed hulls a potential waste ma-terial that could be leveraged as a source of bioactive compounds with several applications.