White LED Light Radiation Promotes Growth and Phytochemical Accumulation in Moringa Seedlings as Promising Functional Microgreen

This study investigated the effects of white light-emitting diode (LED) radiation on the growth and phytochemical accumulation of moringa seedlings. Specifically, we identified the optimal light radiation conditions (intensity and photoperiod) for growth, fresh weight accumulation, and physiological performance of moringa seedlings. We further elucidated the changes in the functional properties of and mechanisms underlying phytochemical accumulation in moringa seedlings under light radiation. The results showed that under the optimal light radiation conditions (5 μmol/m2·s and 8 h/d), the fresh weight, hypocotyl length, and respiratory intensity of moringa seedlings increased significantly, while electrolyte leakage decreased significantly. Light radiation markedly enhanced the contents of total phenolics, total flavonoids, and specific phytochemicals (quercetin 3-O-(6-O-malonyl-β-D-glucoside), phloretin, 1-O-vanilloyl-β-D-glucose, 4-coumaric acid, and 3-coumaric acid); enhanced bioactivity-related functional properties, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, superoxide radical absorbance capacity (SORAC); and enhanced the inhibitory activities of α-glucosidase, pancreatic lipase, and angiotensin-converting enzyme during the growth of moringa seedlings. The expression of genes (Mo4CL, MoF3H, MoLAR) and the activities of enzymes (PAL, C4H, 4CL) involved in the phenylpropanoid pathway were also markedly upregulated. Overall, white LED light radiation (5 μmol/m2·s and 8 h/d) can be used as an effective approach to promote the growth of and phytochemical accumulation in moringa seedlings, supporting their potential as a functional microgreen.