Changes in phenolic acid composition and associated enzyme activity in shoot and kernel fractions of brown rice during germination

Abstract

Phenolic acid composition and activities of two associated enzymes such as PAL (phenylalanine ammonia-lyase) and CW-PRX (cell wall peroxidase) in brown rice (BR) were examined during a germination for 4 days. Shoot and kernel fractions of the germinated brown rice were separated, and soluble extracts and insoluble residues of the fractions were analyzed. In the shoot fraction, the PAL activity and soluble phenolic acid content reached to its maximum on the second day of atmospheric germination, and decreased thereafter. In contrast, the amount of insoluble phenolic acids and CW-PRX activity continuously increased during the germination for 4 days. Comparing the shoot fractions, the kernel fraction exhibited lower activities of PAL and CW-PRX, but showed an increase in total phenolic acid content during germination. Germination raised the antioxidant activity of brown rice, especially in the shoot fraction which contained more phenolic acids than the kernel fraction.