Background : Light-Emitting Diodes (LEDs) have been reported to alter the composition of the secondary metabolites present in many plants. For example, light exposure has been reported to significantly affect secondary metabolite biosynthesis in plants, and irradiance levels have been reported to affect the concentration and production of both phenylpropanoids and carotenoids. Therefore, the objective of the present study was to determine the most effective LED light source in enhancing growth and secondary metabolites (polyphenols and carotenoids) and investigate the effect of LED illumination on production the of primary and secondary metabolites (polyphenols and carotenoids) in Vigna unguiculata L. Walp. sprouts
Methods and Results : In order to determine the effect of light-emitting diodes (LEDs) on plant metabolism, the present study examined the primary and secondary metabolite profiles of Vigna unguiculata L. Walp. sprouts that were exposed to red, blue, white, or a combination of red and blue LEDs using high-performance liquid chromatography (HPLC), electrospray ionization-mass spectrometry (ESI-MS), gas chromatography-mass spectrometry (GC-MS), and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). A total of 39 hydrophilic compounds were identified and quantitated using GC-TOF-MS, and six phenylpropanoids and six carotenoids were quantified using HPLC. The plants grown under blue LED light contained the highest level of total carotenoids (253.72 ± 17.27 ㎍/g) and phenylpropanoids (2,600.51 ± 4.90 ㎍/g). Thus, the current study provides a new approach for enhancing the carotenoid and phenylpropanoid production of V. unguiculata.
Conclusion : This study suggests that blue LED light source is the most appropriate for the sprout growth and production of phenolic compounds and carotenoids in cowpea sprouts. Furthermore, these findings confirm that HPLC, GC-MS, and GC-TOF-MS are suitable for investigating metabolic relationships and offer a tenable strategy for enhancing secondary metabolite production using LED light sources.