###### Abstract  
Phenylpropanoids are naturally occurring compounds that exert beneficial pharmacological effects on human health.henylpropanoids can act as antioxidants and are involved in resistance to ultraviolet light and cancer; these compounds possess anti-inflammatory, antiviral, and antibacterial activity, and aid in wound healing. The expression of genes involved in phenylpropanoid biosynthesis, and consequent accumulation of phenylpropanoids in wheat sprout under conditions of stress, have not been extensively studied. This is the first study to examine the effects of light-emitting diodes (LED) on the expression of genes involved in phenylpropanoid biosynthesis and accumulation of phenylpropanoids in wheat sprouts. Our results, obtained using qRT-PCR and HPLC analyses, indicate that white light (380 nm) was the optimal wavelength for epicatechin biosynthesis in wheat sprouts. Compared with the effects of white light, blue light (470 nm) enhanced the accumulation of gallic acid and quercetin, but decreased the levels of p-coumaric acid and epicatechin; red light (660 nm) increased the accumulation of ferulic acid at 8 day and p-coumaric acid at 12 day. Compared gene expression with phenylpropanoid content showed that _TaPAL3_, _TaPAL4_, and _TaDFR_ maybe important genes in phenylpropanoid biosynthesis in wheat sprout. This study provides insights into the effects of led lights on phenylpropanoid production in wheat sprouts. This knowledge will help improve secondary metabolite production in wheat sprouts. Keywords:wheat sprouts; phenylpropanoid; LED irradiation; gene expression +
Footnote †: journal: Medical  
us to assess how different narrow-band wavelengths of light impact the accumulation of secondary compounds, and seedling morphology and physiology, in controlled environments. Numerous studies have examined the influence of LEDs on plant production of secondary metabolites. LEDs have been used to examine the production of secondary metabolites in lettuce [6; 7], buckwheat [8; 9], lemon balm [10], pea seedling [11], broccoli [3], bitter melon [12], Chinese cabbage [13], rapeseed [14], and kale [2]; however, the influence of LEDs on the production of secondary metabolites in wheat sprouts has not been investigated. Phenylpropanoids are a large class of secondary metabolites, including coumarins, aurones, catechin, isoflavonoids, lignin, lignocellose, flavonoids, and stilbenes [15].henylpropanoids are present in fruits, vegetables, medicinal herbs (seeds, root, and leaves), and nuts [16; 17].henylpropanoids possess anti-inflammatory, antiviral, anti-allergenic, antibacterial, and antioxidant properties, which are beneficial to human health [18; 19; 20]. Phenylpropanol is also reported to inhibit carcinogenesis and reduce the risk of diabetes and heart disease [21; 22]. In plants, the major component of plant cell walls is lignin [23]. The antimicrobial properties of certain phenylpropanoids are also used in the defense of the plant during plant-microbe interactions [24]. Phenylalanine is involved in the phenylpropanoid biosynthetic pathway (Figure 1). In the first three steps, phenylalanine ammonia lyase (PAL), cinnamate 4-hydroxylase (C4H), and p-coumaroyl coenzyme A ligase (4 CL) catalyze the conversion of phenylalanine into p-coumaroyl CoA; this is termed the general phenylpropanoid pathway (GPP) [25]. Ferulic acid is formed from p-coumaric acid via the activity of 4-hydroxycinnamate 3-hydroxylase (CH3) and caffe acid 3-o-methyltransferasease (COMT). In the next three steps, dihydrohaempferol is formed from p-coumaroyl CoA via chalcone synthase (CHS), chalcone isomerase (CHI), and flavone 3-hydroxylase (F3H). Subsequently, flavonoid 3'-hydroxylase (F3\({}^{\prime}\)H) catalyzes the production of dihydroquercetin and splits it into two branches. Flavonol synthase (FLS) converts dihydroquercetin to quercetin. Dihydroflavonol-4 reductase (DFR) catalyzes the transformation of dihydroquercetin into leucocyanidin, and then into epicatechin.