Changes in polyphenol biosynthesis induced in Gynura bicolor DC. leaves by infrared irradiation.

摘要

Effects of IR irradiation (IRI) on polyphenols biosynthesis and antioxidative activity in Gynura bicolor leaves were determined. IR light lamps were placed 75 cm above the top of the canopy, and plants were covered with a black nylon mesh to exclude the influence of natural light. Higher activities of ascorbate peroxidase (APX), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), L-phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO; catechol oxidase) were detected in leaves when plants were subjected to IRI. Although IRI resulted in a significant decrease in anthocyanins content, HPLC analysis of phenolic components showed a higher content of chlorogenic acid that was accompanied by a higher DPPH radical-scavenging activity in IRI-treated leaves. Results suggest that IRI causes oxidative stress and stimulates the activities of enzymes that regulate non-flavonoid polyphenol biosynthesis in G. bicolor leaves.