The influences of light-emitting diodes (LEDs) on the phenolic content and antioxidant enzymes of basil using a plant factory system

Abstract

We used two types of Ocimum basilicum plants and white light-emitting diode (LED) lights as controls (plant factory unit 1, PFU 1). We applied four composite LED light treatments, 125:125:125 white, red, blue (PFU 2), 0.0:250:125 white, red, blue (PFU 3), 125:125:57 white, red, blue (PFU 4) and 125:57:125 white, red, blue (PFU 5) to evaluate light quality effects on antioxidant capacity of O. basilicum plants. The results revealed that the composite lights of PFUs 2,3,4 and 5 were beneficial for the accumulation of flavonoids and glutathione but were not beneficial forthe proanthocyanidin content; the plants subjected to the PFUs 2,3,4 and 5 treatments had a higher laccase activity and proline content and a lower malondialdehyde (MDA) content, polyphenol oxidase activity and peroxidase activity than the control plants.Analysis via high-performance liquid chromatography revealed that protocatechuic acid, gentisic acid, chlorogenic acid, syringic acid, cinnamic acid, quercetin, apigenin, kaempferol, chrysin, p-hydroxybenzoic acid, p-coumaric acid, apigenin-7-glucoside, rutin, rosmarinic acid were the major phenolic components in the O. Basilicum extracts, and sufficient composite lighting of O. basilicum plants significantly enhanced these antioxidant concentrations. Our results indicate that the use of LEDs with different light qualities to irradiate O. basilicum significantly improved the antioxidant capacity which could be a beneficial for nutrition and health benefits.