Comprehensive Evaluation of the Effect of Ultraviolet Stress on Functional Phytochemicals of Hulless Barley (Qingke) Grass in Different Growth Times at Vegetative Stage

The present study was executed to analyze the functional phytochemicals of hulless barley grass grown under different intensities of ultraviolet stress. The wheat seedlings were imposed to 0.5, 1.0, 1.5, 2.0, and 2.5 h ultraviolet radiation and harvested in different times at vegetative stage. Specifically, the contents of total polyphenols, total flavonoids, total triterpenes, total polysaccharides, proanthocyanidins, and chlorophyll were determined and antioxidants capacity was evaluated by OH^• and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging ability. A mathematical model (Technique for Order Preference by Similarity to Ideal Solution, TOPSIS) was also employed for the comprehensive evaluation of functional components of hulless barley grass at different growth stages. The results showed that the UV stress could efficiently improve/preserve the contents of total polyphenols, total flavonoids, total triterpenes, total polysaccharides, proanthocyanidins, chlorophyll a, chlorophyll b, and total chlorophyll, as well as the OH^• and ABTS scavenging capacity. TOPSIS evaluation revealed that the highest phytochemical contents were yield on the 15th day under 1.0 h ultraviolet treatment.