Changes in enzyme activities and amino acids and their relations with phenolic compounds contents in okra treated by LED lights of different colors

Abstract

Light-emitting diodes (LEDs) of different wavelengths or colors (i.e., white, red, blue, and green) were used to treat postharvest okra, which is a rich source of phenolic compounds. Relationships between changes in the activities of key enzymes involving in the formation of phenolics (i.e., 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, chorismate mutase, anthranilate synthase, and phenylalanine ammonia lyase) and their contents upon different LED light treatments were for the first time investigated and are fully discussed. The contents of three intermediate amino acids (i.e., phenylalanine, tyrosine, and tryptophan) that formed during light treatments were also measured to confirm the enzyme activities data. White and blue light treatments increased the content of phenolics in the treated okra, while red and green lights increased the formation of other compounds. These results could be well explained by the changing levels of the measured enzyme activities and amino acids contents.