Finger millet (Eleusine coracana L.) is a nutrient-dense cereal with high flavonoid content, yet the mechanisms regulating its secondary metabolite biosynthesis remain underexplored. Various exogenous stimuli can readily activate the enzymatic pathways and gene expression associated with flavonoid biosynthesis in plants, which are regulated by developmental cues. Research has established that methyl jasmonate (MeJA) application enhances secondary metabolite production in plant systems. This investigation examined MeJA’s influence on flavonoid accumulation and physiological responses in finger millet sprouts to elucidate the molecular mechanisms underlying MeJA-mediated flavonoid accumulation. The findings revealed that MeJA treatment significantly suppressed sprout elongation while enhancing the biosynthesis of total flavonoids and phenolic compounds. MeJA treatment triggered oxidative stress responses, with hydrogen peroxide and superoxide anion concentrations increasing 1.84-fold and 1.70-fold compared to control levels at 4 days post-germination. Furthermore, the antioxidant defense mechanisms in finger millet were upregulated following treatment, resulting in significant enhancement of catalase and peroxidase enzymatic activities and corresponding transcript abundance. MeJA application augmented the activities of key phenylpropanoid pathway enzymes—phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H)—and upregulated their respective gene expression. At 4 days post-germination, EcPAL and EcC4H transcript levels were elevated 3.67-fold and 2.61-fold, respectively, compared to untreated controls. MeJA treatment significantly induced the expression of downstream structural genes and transcriptional regulators. This study provides a deeper understanding of the mechanism of flavonoid accumulation in foxtail millet induced by MeJA, and lays a foundation for exogenous conditions to promote flavonoid biosynthesis in plants.

Germination is an effective measure to regulate the accumulation of secondary metabolites in plants. In this study, we optimized the germination conditions of finger millet by response surface methodology. Meanwhile, physiological characteristics and gene expression were measured to investigate the mechanism of flavonoid accumulation in finger millet at the germination stage. The results showed that when germination time was 5.7 d, germination temperature was 31.2 °C, and light duration was 17.5 h, the flavonoid content of millet sprouts was the highest (7.0 μg/sprout). The activities and relative gene expression of key enzymes for flavonoid synthesis (phenylalanine ammonia-lyase, 4-coumarate-coenzyme a ligase, and cinnamate 4-hydroxylase) were significantly higher in finger millet sprouts germinated at 3 and 5 d compared with that in ungerminated seeds (p < 0.05). In addition, germination enhanced the activities of four antioxidant enzymes (catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase) and up-regulated the gene expression of PAL and APX. Germination increased malondialdehyde content in sprouts, which resulted in cell damage. Subsequently, the antioxidant capacity of the sprouts was enhanced through the activation of antioxidant enzymes and the up-regulation of their gene expression, as well as the synthesis of active substances, including flavonoids, total phenolics, and anthocyanins. This process served to alleviate germination-induced cellular injury. These findings provide a research basis for the regulation of finger millet germination and the enhancement of its nutritional and functional properties.

Light treatment is an innovative method to enhance the synthesis of secondary metabolites in plants and improve the quality of plant-based food ingredients. This study investigated the effects of red light treatment on the physiological and biochemical changes during wheat germination, aiming to produce high-quality wheat sprouts with strong antioxidant capacity. Using response surface methodology, the study optimized the conditions for phenolic accumulation in wheat sprouts under red light treatment and explored the molecular mechanisms behind the enhancement of total phenolic content (TPC) and quality. The results indicated that red light treatment significantly increased the TPC in wheat sprouts. The highest TPC, reaching 186.61 μg GAE/sprout, was observed when wheat sprouts were exposed to red light at an intensity of 412 μmol/m²/s for 18.2 h/d over four days. Compared to no light, red light treatment significantly increased the content of photosynthetic pigments (chlorophyll and carotenoids). Red light treatment notably heightened the levels of both free and bound phenolic in the germinating wheat. Red light treatment markedly boosted the activities and relative gene expression levels of enzymes related to phenolic biosynthesis, including phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate-CoA ligase. Additionally, red light treatment enhanced the antioxidant capacity of wheat sprouts by improving the activity and gene expression of four key antioxidant enzymes, thereby promoting growth and germination. This research suggested that red light treatment is an effective strategy for stimulating total phenolic biosynthesis, enhancing antioxidant capacity, and producing highly nutritious wheat sprouts, thus laying the groundwork for developing total phenolic-enriched wheat sprouts as valuable food ingredients in the future.

In this research, we investigated the physiological modifications, flavonoid metabolism, and antioxidant systems of two buckwheat (Fagopyrum esculentum Moench.) cultivars, Pintian and Suqiao, during germination. The results demonstrated an initial increase followed by a subsequent decline in the flavonoid content of the buckwheat sprouts throughout germination. On the third day of germination, the highest flavonoid concentrations were observed, with the Pintian and Suqiao varieties reaching 996.75 and 833.98 μg/g fresh weight, respectively. Both the activity and relative gene expression level of the flavonoid metabolizing enzyme showed a significant rise in 3-day-old buckwheat sprouts, which was strongly correlated with the flavonoid content. The correlation analysis revealed that the buckwheat sprouts accumulated flavonoids by enhancing the activities and gene expression levels of flavonoid synthases. The antioxidant capacity and the activities and gene expression profiles of the antioxidant enzymes in both buckwheat cultivars notably increased after three days of germination. The correlation analysis indicated a significant positive link between antioxidant capacity and the activity and gene expression levels of the antioxidant enzymes, flavonoid content, and total phenol content. This research demonstrated that germination treatment can significantly boost the accumulation of flavonoids and total phenols, thereby enhancing the antioxidant properties of buckwheat sprouts, despite variations among different buckwheat varieties.

The enhancement of flavonoid content and antioxidant capacity in plants remains a significant area of focus in the investigation of plant-derived functional foods. This study systematically investigated the impact of exogenous zinc sulfate (5 mM ZnSO₄) stress on flavonoid content and antioxidant capacity in finger millet (Eleusine coracana L.) sprouts, along with its underlying molecular mechanisms. The results demonstrated that treatment with 5 mM ZnSO₄ significantly increased the flavonoid content in sprouts, reaching a maximum value of 5.59 μg/sprout on the 6th day of germination. ZnSO₄ stress significantly enhanced the activities of PAL, 4CL, and C4H, while also considerably upregulating the expression levels of flavonoid-biosynthesis-related genes. Physiological indicators revealed that ZnSO₄ stress increased the contents of malondialdehyde, hydrogen peroxide, and superoxide anion in the sprouts, while inhibiting sprout growth. As a stress response, ZnSO₄ stress enhances the antioxidant system by increasing antioxidant capacity (ABTS, DPPH, and FRAP), antioxidant enzyme activity (POD and SOD), and related gene expression (POD, CAT, and APX) in sprouts. This study provides experimental evidence for ZnSO₄ stress to improve flavonoid accumulation and antioxidant capacity in finger millet sprouts and provides important theoretical and practical guidance for the development of high-quality functional foods.

Finger millet (Eleusine coracana L.) is rich in bioactive compounds, including flavonoids. Following exogenous substance regulation, its sprouts can achieve efficient flavonoid enrichment. This study investigates the regulatory effects of exogenous salicylic acid (SA) and γ-aminobutyric acid (GABA) on the physiological metabolism, oxidative stress response, and flavonoid biosynthesis of finger millet sprouts subjected to 5 mM zinc sulfate (ZnSO₄) stress. Compared to treatment solely with ZnSO₄, the application of both 50 μM salicylic acid (SA) and 1 mM gamma-aminobutyric acid (GABA) markedly enhanced flavonoid biosynthesis, with respective yields of 8.53 μg/sprout and 8.85 μg/sprout observed by 6 days post-germination. Concurrently, SA and GABA attenuated ZnSO₄-induced oxidative damage. During days 4 and 6 post-germination, malondialdehyde and hydrogen peroxide levels in sprouts were significantly reduced, with levels at 6 days showing a particularly notable decrease. Moreover, the catalytic activities of catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase were significantly upregulated. Further analysis revealed that both treatments significantly activated the phenylpropanoid biosynthesis pathway. The activities of key rate-limiting enzymes, phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate-CoA ligase, along with the expression levels of their corresponding genes, were markedly upregulated. Concurrently, the expression of genes and transcription factors, specifically myeloblastosis and NAC transcription factors, involved in regulating reactive oxygen species homeostasis also increased. These findings suggest that exogenous SA, GABA, and ZnSO₄ cotreatment can effectively enhance the accumulation of flavonoids and the nutritional quality of finger millet sprouts by bolstering antioxidant capacity and modulating the flavonoid biosynthesis pathway. This investigation establishes a theoretical framework for the production of superior, bioactive finger millet sprout ingredients.