Elucidation of phenolic antioxidants in barley seedlings (Hordeum vulgare L.) by UPLC-PDA-ESI/MS and screening for their contents at different harvest times

The changes in phenolic and antioxidant capacities of seedlings of various barley cultivars through four different harvest times were investigated. Ten phenolics were characterised as hydroxycinnamic acid, orientin, isoorientin, and isovitexin derivatives using UPLC-PDA-ESI/MS and NMR. In particular, lutonarin (2) and saponarin (3) were the predominant constituents (71-75%) with significant differences in cultivars and harvest times. The highest average total phenolic content was found as 2671.8 mg/100 g on 23 days after the sowing, whereas the lowest was 1400.8 mg/100 g on 56 days. The radical scavenging abilities also exhibited considerable differences in 80% of methanol extracts (40 µg/mL), depending upon the phenolic contents. Interestingly, isoorientin (5) and orientin (6) possessed potent antioxidant effects with IC50 values of 20.7 ± 1.1 and 27.5 ± 7.3 µM (DPPH) and 5.7 ± 0.3 and 8.2 ± 0.3 µM (ABTS), respectively. These results may be contributed to enhancing the value of barley as a functional food ingredient and dietary supplement.