Effect of light quality on Betalain content of red beet ( L.) cultured

Background
Red beet ( L.) is the most important edible crop that belongs to the family Amaranthaceae. It is considered as an excellent source of foliate and manganese. It contains betalains, which are considered as natural pigments consisting of two major components, the yellow betaxanthin and violet betacyanin.
Objectives
In this paper, the effect of different light qualities [white, blue, green, red, and ultraviolet (UV)] on the red beet extract content was examined. The main aim of this study was to choose the light quality which will elevate betalains.
Materials and methods
Red beet seeds were well sterilized and germinated on Murashigue and Skoog basal medium. After 4 weeks, the germinated seedlings (explants) were exposed to different wave lengths. Three replicates for each wavelength treatment were collected after 10, 20, and 30 days. Regarding UV treatment, cultures were exposed to UV rays type C for 10, 20, or 30 min, and three replicates for each time period were collected. Fresh weight of each explants was measured and stored at −20°C till further usage. Overall, 0.2 g of fresh weight was used for extraction using 2 ml extraction solvent (80 ml methanol+20-ml sterilized distilled water+100 μl phosphoric acid). The antioxidant activity, total phenols, and betalains were determined using spectrophotometer.
Results and conclusion
The highest values of both fresh weight and free radical scavenging capacity of 2,2-diphenyl-1-picrylhydrazyl percentage were recorded with exposing the cultures to the blue light for 30 days or the exposure to UV rays for 30 min (1.285 and 0.746 g and 42.27 and 43.88%, respectively). It was obviously recorded that exposing the cultures to the red light for 10 days or exposing them to the UV rays for 10 min gave the highest values of the total phenol (1.54 and 0.88 mg GAE/g FW, respectively). The highest value of betalains (Betacyanin and Betaxanthin) was recorded with exposing the cultures to the red light for 30 days (0.12 and 0.077 mg/g FW, respectively).