The synergistic effect of ascorbic and abscisic acids on enriching AVC-dominated avenanthramides in oat germination process

Abstract

Avenanthramides are a group of antioxidants, of which avenanthramide C (AVC) shows the strongest antioxidant activity. Germination is conducive to the accumulation of total avenanthramides. However, it is unclear how to regulate the proportion of AVC in total avenanthramides by controlling the oat-germination process. To increase the proportion of AVC in total avenanthramides, single or combined treatments with abscisic (ABA) and ascorbic acid (Asc) during the steeping or germination period was performed. Compared to the control (541 μg/g dry weight), the 300 μM-ABA treatment during the steeping period significantly increased the proportion of AVC in total avenanthramides from 30.93 to 40.70%, which was accompanied by a remarkable increase in the content of total avenanthramides (1.8- fold). The content of total avenanthramides and the proportion of AVC within increased significantly (3.35-fold and by 9.28%, respectively) compared to the control when successively treated with 300 μM ABA during the steeping period and 20 mM Asc during the germination period. Moreover, ABA and Asc were synergistic in increasing the activities of hydroxycinnamoyl-CoA:hydroxyanthranilate N-hydroxycinnamoyl transferase (HHT) and tyrosine ammonia-lyase (TAL), but reduced the activity of peroxidase (POD), which resulted in the accumulation of AVC-dominated avenanthramides. These findings provide novel information on the bio-concentration of AVC by regulation of the oat-germination process.