Antifreeze Polysaccharides from Wheat Bran: The Structural Characterization and Antifreeze Mechanism.

Exploring a novel natural cryoprotectant and understanding its antifreeze mechanism allows the rational design of future sustainable antifreeze analogues. In this study, various antifreeze polysaccharides were isolated from wheat bran, and the antifreeze activity was comparatively studied in relation to the molecular structure. The antifreeze mechanism was further revealed based on the interactions of polysaccharides and water molecules through dynamic simulation analysis. The antifreeze polysaccharides showed distinct ice recrystallization inhibition activity, and structural analysis suggested that the polysaccharides were arabinoxylan, featuring a xylan backbone with a majority of Araf and minor fractions of Manp, Galp, and Glcp involved in the side chain. The antifreeze arabinoxylan, characterized by lower molecular weight, less branching, and more flexible conformation, could weaken the hydrogen bonding of the surrounding water molecules more evidently, thus retarding the transformation of water molecules into the ordered ice structure.

Spermidine alleviates oxidative damage and enhances phenolic compounds accumulation in barley seedlings under UV-B stress.

BACKGROUND: Ultraviolet B (UV-B) radiation can enhance the accumulation of phenolic compounds (PCs) in barley seedling, although this may result in severe oxidative damage. In the present study, the role of spermidine in alleviating oxidative damage and regulating synthesis of PCs in barley seedlings under UV-B stress was investigated. RESULTS: Exogenous spermidine increased the length and fresh weight as well as PCs contents of barley seedlings under UV-B stress. Application of dicyclohexylamine, an inhibitor of endogenous spermidine synthesis, significantly inhibited the growth and PC accumulation of barley seedlings under UV-B stress, although this inhibitory effect can be alleviated by exogenous spermidine. Exogenous spermidine increased the contents of vanillic acid, syringic acid, protocatechuic acid and p-coumaric acid in barley seedlings under UV-B stress by 20-200% through enhancing the activities of enzymes related to synthesis of these acids. In addition, exogenous spermidine enhanced activities and gene expression of antioxidant enzymes in barley seedlings under UV-B stress, including peroxidase, glutathione reductase and glutathione S-transferase. CONCLUSION: Spermidine can alleviate oxidative damage of barley seedlings under UV-B stress and enhance the accumulation of PCs. © 2022 Society of Chemical Industry.

The mechanism of freeze-thawing induced accumulation of γ-aminobutyric acid in germinated soybean.

BACKGROUND: γ-Aminobutyric acid (GABA) is a non-protein amino acid with several functions in the human body. Although freeze-thawing could effectively accumulate GABA in soybean sprouts, the mechanism has not been revealed. The mechanism by which freeze-thawing enhances GABA accumulation in germinated soybean was revealed by evaluating GABA content, the activity of related synthesis enzymes, and the microstructure of the tissues and cells of sprouts. The germinated soybeans were treated at different temperatures (from -196 °C to 25 °C) for 12 h and then thawed at 25 °C for 6 h. RESULTS: The results showed that GABA content in frozen soybean sprouts did not change significantly before thawing. After thawing, the GABA content of sprouts increased by 83.9% and 82.9% when treated by liquid nitrogen flash freeze at - 80 °C for 12 h compared with the control (4 °C treatment for 12 h). The results indicated that GABA formation mainly occurred during thawing. However, glutamate decarboxylase (GAD), diamine oxidase (DAO), and aminoaldehyde dehydrogenase (AMADH) activity decreased during thawing. Based on the malonaldehyde (MDA) content and microstructure of sprouts, it was suggested that freezing at lower temperatures (< -20 °C) maintained the integrity of the cell structure, while the tissues and cell membranes were broken during thawing. CONCLUSION: These results could provide evidence for the hypothesis that GABA formation resulted from full contact between enzymes and substrates during thawing, rather than the contribution of higher enzyme activity. © 2019 Society of Chemical Industry.

NaCl stress on physio-biochemical metabolism and antioxidant capacity in germinated hulless barley (Hordeum vulgare L.).

BACKGROUND: Hulless barley generally grows in barren fields, where soil salinization is serious. However, only a few studies have been carried out investigating germinated hulless barley under salt stress. In the present study, the effect of NaCl stress on the physio-biochemical metabolism and antioxidant capacity of germinated hulless barley was investigated. RESULTS: NaCl stress inhibited seedling growth and caused oxidative damage, although it enhanced the accumulation of phenolic compounds and antioxidant capacity. The highest contents of total phenolic and main phenolic acids (vanillic acid, p-coumaric acid, ferulic acid and sinapic acid) were found with 60 mmol L-1 NaCl treatment, whereas 120 mmol L-1 NaCl inhibited the synthesis of phenolic components. Gene expression of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL), p-coumaric acid 3-hdroxylase (C3H) and caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT), which participated in the synthesis of phenolic compounds, was up-regulated by NaCl stress, as were the enzyme activities of PAL, C4H and 4CL. NaCl treatment also enhanced the antioxidant enzyme activities of germinated hulless barley. CONCLUSION: NaCl stress inhibited seedlings growth and caused oxidative damage. Simultaneously, the antioxidant system of germinated hulless barley was enhanced. The results of the present study provide a theoretical basis with respect to the growth of hulless barley under salt stress. © 2018 Society of Chemical Industry.

Role of Ca2+ in phenolic compound metabolism of barley (Hordeum vulgare L.) sprouts under NaCl stress.

BACKGROUND: The literature on the role of calcium ion (Ca2+ ) in relation to phenolic compounds metabolism and related enzymes activities remains controversial. It is still unclear whether Ca2+ affects phenolic compounds content of barley sprouts. This study investigated the role and function of Ca2+ in phenolic compound metabolism of barley (Hordeum vulgare L.) sprouts under sodium chloride (NaCl) stress. RESULTS: Calcium chloride (CaCl2 ) significantly improved total calcium and calmodulin (CaM) contents as well as Ca2+ concentration, and enhanced phenolic compound accumulation by regulating the gene, protein expression and the activities of enzymes related to phenolics biosynthesis. Specifically, CaCl2 significantly increased the activities of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL) and ferulic acid 5-hydroxylase (F5H) by up-regulating the corresponding protein expression. The activity of p-coumaric acid 3-hydroxylase (C3H) decreased during germination while caffeic acid O-methyltransferase (COMT) increased initially and then decreased, which was consistent with the changes in gene and protein expression under CaCl2 treatment. Conversely, lanthanum(III) chloride (LaCl3 ), ethylene glycol tetraacetic acid (EGTA) and 2-aminoethoxydiphenyl borate (2-APB) induced opposite effects. Decreased calcium and CaM contents and Ca2+ concentration were observed, and fluctuation change of relevant gene and protein expressions and PAL, C4H, 4CL, C3H, COMT and F5H activitives were also detected. CONCLUSION: Calcium ion played an important role for mediating NaCl stress-induced phenolics accumulation in barley sprouts. It required both Ca2+ influx and release from apoplast and intracellular stores, respectively. © 2019 Society of Chemical Industry.

Ca2+ influxes and transmembrane transport are essential for phytic acid degradation in mung bean sprouts.

BACKGROUND: Phytic acid is considered as an antinutrient. Ca2+ addition during germination has been proved to be an effective method for reducing phytic acid content in seeds. In this study, mung bean sprouts were treated with LaCl3 (La), verapamil (VP), ruthenium red (RR), and CaCl2 to explore the effect of Ca2+ influxes on phytic acid degradation. RESULTS: CaCl2 (6 mmol L-1 ) significantly improved extracellular and intracellular calcium precipitates and calcium content, elevated phytase and acid phosphatase activity, and further enhanced phytic acid degradation. Conversely, La, VP, or RR induced the opposite results. Among them, RR exhibited the most significant inhibitory effect. Decreased PA, PAP, MIPP, and ALP gene expression after VP or RR treatment was also observed. Enhanced or weakened extracellular Ca2+ influx or intracellular Ca2+ efflux was detected with increased or decreased calcium precipitates distributed in different compartments. However, CaCl2 addition differentially reversed the inhibitory effects of all channel blockers. CONCLUSION: CaCl2 enhanced Ca2+ influxes and accumulation in cells, which contributed to the regulation of phytic acid degradation. This study demonstrates that calcium channels play an essential role in mediating phytic acid degradation in mung bean sprouts, and both extracellular and intracellular Ca2+ -regulation were involved in phytic acid degradation. © 2017 Society of Chemical Industry.

Polyamines regulating phytic acid degradation in mung bean sprouts.

BACKGROUND: Polyamines are essentially involved in cell division and differentiation. Transport of polyamines is adenosine triphosphate (ATP)-dependent, while phytic acid is the major reserve of phosphate essential to the energy-producing machinery of cells. Thus polyamines might enhance phytic acid degradation during mung bean germination. In this study, different polyamines (putrescine (Put), spermidine (Spd) and spermine (Spm)) and dicyclohexylamine (DCHA, an inhibitor of Spd synthesis) were applied to investigate the function of polyamines on phytic acid degradation. RESULTS: Spd exhibited the best effect at the same concentration. Simultaneously, exogenous Spd improved sprout growth and enhanced the accumulation of gibberellin acid 3 (GA3 ), indole-3-acetic acid (IAA), abscisic acid (ABA) and cytokinin (CTK). This must be due to the increased endogenous polyamine contents. Apart from dramatically reducing phytic acid content, Spd resulted in the up-regulation of PA, PAP, MIPP and ALP transcript levels and the enhancement of phytase and acid phosphatase activities. However, DCHA application caused the opposite results, because it decreased endogenous polyamine contents. Furthermore, Spd alleviated the DCHA-induced inhibitory effect to some extent. CONCLUSION: Overall, polyamines, especially Spd, could accelerate phytic acid degradation in mung bean sprouts by inducing the synthesis of endogenous polyamines and phytohormones and enhancing the growth of sprouts. © 2017 Society of Chemical Industry.

Gibberellic acid promoting phytic acid degradation in germinating soybean under calcium lactate treatment.

BACKGROUND: Phytic acid as a phosphorus storage vault provides phosphorus for plant development. It is an anti-nutritional factor for humans and some animals. However, its degradation products lower inositol phosphates have positive effects on human health. In this study, the effect of gibberellic acid (GA) on phytic acid degradation under calcium lactate (Ca) existence was investigated. RESULTS: The results showed that Ca + GA treatment promoted the growth status, hormone metabolism and phytic acid degradation in germinating soybean. At the same time, the availability of phosphorus, the activity of phytic acid degradation-associated enzyme and phosphoinositide-specific phospholipase C (PI-PLC) increased. However, the relative genes expression of phytic acid degradation-associated enzymes did not vary in accordance with their enzymes activity. CONCLUSION: The results revealed that GA could mediate the transport and function of calcium and a series of physiological and biochemical changes to regulate phytic acid degradation of soybean sprouts. © 2017 Society of Chemical Industry.

Cyclic ADP-ribose and IP3 mediate abscisic acid-induced isoflavone accumulation in soybean sprouts.

In this study, the roles of ABA-cADPR-Ca2+ and ABA-IP3-Ca2+ signaling pathways in UV-B-induced isoflavone accumulation in soybean sprouts were investigated. Results showed that abscisic acid (ABA) up regulated cyclic ADP-ribose (cADPR) and inositol 1,4,5-trisphosphate (IP3) levels in soybean sprouts under UV-B radiation. Furthermore, cADPR and IP3, as second messengers of UV-B-triggered ABA, induced isoflavone accumulation by up-regulating proteins and genes expression and activity of isoflavone biosynthetic-enzymes (chalcone synthase, CHS; isoflavone synthase, IFS). After Ca2+ was chelated by EGTA, isoflavone content decreased. Overall, ABA-induced cADPR and IP3 up regulated isoflavone accumulation which was mediated by Ca2+ signaling via enhancing the expression of proteins and genes participating in isoflavone biosynthesis in soybean sprouts under UV-B radiation.

Effects of ABA and CaCl2 on GABA accumulation in fava bean germinating under hypoxia-NaCl stress.

Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.

Cloning of genes related to aliphatic glucosinolate metabolism and the mechanism of sulforaphane accumulation in broccoli sprouts under jasmonic acid treatment.

BACKGROUND: Cytochrome P450 79F1 (CYP79F1), cytochrome P450 83A1 (CYP83A1), UDP-glucosyltransferase 74B1 (UGT74B1), sulfotransferase 18 (ST5b) and flavin-containing monooxygenase GS-OX1 (FMOGS - OX1 ) are important enzymes in aliphatic glucosinolate biosynthesis. In this study, their full-length cDNA in broccoli was firstly cloned, then the mechanism of sulforaphane accumulation under jasmonic acid (JA) treatment was investigated. RESULTS: The full-length cDNA of CYP79F1, CYP83A1, UGT74B1, ST5b and FMOGS - OX1 comprised 1980, 1652, 1592, 1378 and 1623 bp respectively. The increase in aliphatic glucosinolate accumulation in broccoli sprouts treated with JA was associated with elevated expression of genes in the aliphatic glucosinolate biosynthetic pathway. Application of 100 µmol L(-1) JA increased myrosinase (MYR) activity but did not affect epithiospecifier protein (ESP) activity in broccoli sprouts, which was supported by the expression of MYR and ESP. Sulforaphane formation in 7-day-old sprouts treated with 100 µmol L(-1) JA was 3.36 and 1.30 times that in the control and 300 µmol L(-1) JA treatment respectively. CONCLUSION: JA enhanced the accumulation of aliphatic glucosinolates in broccoli sprouts via up-regulation of related gene expression. Broccoli sprouts treated with 100 µmol L(-1) JA showed higher sulforphane formation than those treated with 300 µmol L(-1) JA owing to the higher glucoraphanin content and myrosinase activity under 100 µmol L(-1) JA treatment. © 2016 Society of Chemical Industry.

Accumulation of γ-aminobutyric acid in soybean by hypoxia germination and freeze-thawing incubation.

BACKGROUND: γ-Aminobutyric acid (GABA) can be synthesised by the GABA shunt and polyamine degradation pathway in plants under hypoxia stress and lower temperature. The hypoxia germination freeze-thawing incubation was used as a new technique for accumulating more GABA in soybean. RESULTS: Results showed that glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content increased during germination within 24 h under hypoxia. However, the contents of dry matters and protein decreased. When the hypoxia-treated sprouts were frozen at -18 °C for 12 h and thawed at 25 °C for 6 h, GABA content increased drastically to 7.21-fold of the non-frozen sprouts. Subsequently, the freeze-thawing sprouts were ground into homogenates and incubated. GABA content was 14.20-fold of the only-soaked seeds when homogenates was incubated at 45 °C for 80 min within 400 µmol L(-1) pyridoxine (VB6) (pH 6.5). CONCLUSION: The hypoxia germination freeze-thawing incubation was an effective method for accumulating GABA in soybean. During incubation, DAO was more important for GABA formation in homogenate of germinated soybean compared with GAD.

Release of feruloylated oligosaccharides from wheat bran through submerged fermentation by edible mushrooms.

Wheat bran, a by-product of the flour industry, is believed to be a raw material for the production of feruloylated oligosaccharides (FOs) because of its high content of conjiont ferulic acid (FA). Studies were carried out to identify edible mushrooms that are able to release FOs from wheat bran. All the six tested mushrooms (Pleurotus ostreatus, Hericium erinaceum, Auricularia auricula, Cordyceps militaris, Agrocybe chaxingu, and Ganoderma lucium) were found to release FOs, and Agrocybe chaxingu had the highest yield, reaching 35.4 µM in wheat bran broth. Enzymes detection showed that these species secreted extracellular enzymes during fermentation, including cellulase and xylanase. Agrocybe chaxingu secreted the significant amount of xylanase (180 mU ml(-1) ), which was responsible for the release of FOs from wheat bran, while Hericium erinaceum secreted FA esterase which could disassemble FOs.

Major nutrient compositions and functional properties of sorghum flour at 0-3 days of grain germination.

Germination is of importance to improving nutritional attributes of cereal grains for human consumption. The effect of germination time on major nutrient compositions and functional properties of sorghum flour was investigated in this study. Grains of Butanua, a new Sudanese sorghum cultivar, were germinated for 0, 1, 2, and 3 days to analyze their chemical and functional properties. The contents of starch, protein, oil, foaming stability, bulk density, and least gelation concentration of sorghum flour decreased, whereas oil absorption capacity, foaming capacity, and emulsion capacity and stability enhanced with an increase in germination time. Improved functional properties of sorghum flour by germination of the grains not only make it useful and suitable for various food processing formulations, but also improve the food product quality. This new finding will beneficially help develop innovative technologies, design new types of functional foods, and promote both sorghum production and relevant food processing industry in the future.

Effect of NaCl stress on health-promoting compounds and antioxidant activity in the sprouts of three broccoli cultivars.

Health-promoting compounds, antioxidant and myrosinase activity in the sprouts of three broccoli cultivars under 40 mM, 80 mM and 160 mM NaCl were investigated. LangYan (LY) sprouts had the richest health-promoting compounds among the evaluated cultivars. Treatment of 40 mM and 80 mM NaCl significantly decreased the content of ascorbic acid and total phenolic as well as antioxidant activity, but did not affect glucoraphanin, sulforaphane and myrosinase activity compared to the control. However, 160 mM NaCl treatment significantly enhanced the level of total phenolic, glucoraphanin, sulforaphane, antioxidant and myrosinase activity, while significantly decreased ascorbic acid content. The results suggest that 160 mM NaCl treatment would enhance antioxidant activity and sulforaphane yield in broccoli sprouts. The health-promoting value of broccoli sprouts depends on plant genotype and could be affected by NaCl stress.

Sequence analysis of diamine oxidase gene from fava bean and its expression related to γ-aminobutyric acid accumulation in seeds germinating under hypoxia-NaCl stress.

BACKGROUND: γ-Aminobutyric acid (GABA) is synthesized via the polyamine degradation pathway in plants, with diamine oxidase (DAO) being the key enzyme. In this study the cDNA of DAO in fava bean was cloned and its expression in seeds germinating under hypoxia-NaCl stress was investigated. RESULTS: Fava bean DAO cDNA is 2199 bp long and contains 2025 bp of open reading frame that encodes 675 amino acid peptides with a calculated molecular weight of 76.31 kDa and a pI of 5.41. Hypoxia and hypoxia-NaCl stress enhanced DAO activity and resulted in GABA accumulation in germinating fava bean. However, DAO gene expression was down-regulated under hypoxia compared with non-stress condition, while its expression in the cotyledon and shoot was up-regulated under hypoxia-NaCl. In addition, DAO expression could be promoted to enhance GABA accumulation after increasing the stress intensity using NaCl. DAO gene expression was significantly inhibited by aminoguanidine treatment under hypoxia but increased under hypoxia-NaCl. CONCLUSION: Under hypoxia, GABA accumulation due to NaCl was mainly concentrated in the cotyledon. The GABA content increase under hypoxia did not result from DAO gene expression, but DAO existing in seeds was activated under hypoxia. DAO gene expression was up-regulated to enhance GABA accumulation after increasing the stress intensity.

Direct production of feruloyl oligosaccharides and hemicellulase inducement and distribution in a newly isolated Aureobasidium pullulans strain.

Studies were carried out to screen and identify strains that are able to directly produce ferulic oligosaccharides (FOs) from wheat bran (WB). The inducement and distribution of hemicellulases from strain 2012, which was identified as a non-melanin secreting strain of Aureobasidium pullulans (A. pullulans), were also determined. In a 60 g/L WB solution, A. pullulans could produce 545 nmol/L FOs, 64.12 IU/mL xylanase and 0.14 IU/mL ferulic acid esterase (FAE). A. pullulans was cultivated in media with WB, glucose, xylose, sucrose, lactose or xylan as the carbon source, and hemicellulases were mainly induced by xylan and WB and inhibited by glucose and sucrose. Xylanase and FAE were mainly present in the culture filtrate, xylosidase in the hyphal filaments and arabinofuranosidase was a membrane-bound enzyme. The yield of FOs was positively correlated to the hemicellulases activity, and significantly positively (P < 0.05) correlated to the xylanase activity (r = 0.992).

Enhancing the technofunctionality of γ-aminobutyric acid enriched germinated wheat by modification of arabinoxylan, gluten proteins and liquid lamella of dough.

To enhance the technofunctionality of germinated wheat enriched with γ-aminobutyric acid, xylanase (Xyn) and glucose oxidase (Gox) were incorporated with emphasis on modifying the key components. Combination of Xyn and Gox enhanced steamed bread quality with optimum loaf volume and textural property. Continuous and dense gluten network was facilitated and improved viscoelasticity of dough. Water solubility of arabinoxylan (AX) enhanced with Xyn and the molecular weight was more homogeneous distributed throughout bread making process with Xyn and Gox. Polymerization behavior of α-/γ-gliadin and glutenin was suppressed in steamed bread, while incorporation of AX to insoluble proteins was enhanced by enzymes. In addition, the promoted formation of high molecular weight glycoprotein in the liquid lamella of dough enhanced the thermal stability of foams and contribute to superior quality of steamed bread. Results demonstrated that germinated wheat could be exploited as a functional ingredient with desirable technofunctionality by modification of the components.

Purification of diamine oxidase and its properties in germinated fava bean (Vicia faba L.).

BACKGROUND: γ-Aminobutyric acid (GABA) is a non-protein amino acid with bioactive functions for human health. Diamine oxidase (DAO, EC 1.4.3.6) is one of the key enzymes for GABA formation. In the present study, this enzyme was purified from 5 day germinated fava bean and its properties were investigated in vitro. RESULTS: The molecular mass of the enzyme estimated by Sephadex G-100 gel filtration was 121 kDa. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) displayed a single band at a molecular mass of 52 kDa. The enzyme had optimal activity at 40 °C and retained its activity after being incubated at 30 °C for 30 min. It showed higher activity at pH 6.5 than at other pH values. The enzyme was significantly inhibited by Mg(2+), Cu(2+), Fe(3+), aminoguanidine, ethylene glycol tetraacetic acid (EGTA), ethylene diamine tetraacetic acid disodium salt (EDTA-Na(2)), L-cysteine and ß-mercaptoethanol. The K(m) value of DAO was 0.23 mmol L(-1) for putrescine and 0.96 mmol L(-1) for spermidine. However, the enzyme did not degrade spermine. CONCLUSION: DAO from germinated fava bean was purified. The optimal reaction temperature and pH of the enzyme were mild. The enzyme had higher affinity to putrescine than to spermidine and spermine.

UV-B- triggered H2O2 production mediates isoflavones synthesis in germinated soybean.

In this study, the functions of Hydrogen peroxide (H2O2) on the synthesis of isoflavones in germinated soybean under UV-B radiation were investigated. Results showed that the activity, gene, and protein expression of NADPH oxidase were up-regulated by 1.46, 6.92, and 1.34 times with UV-B radiation, while endogenous H2O2 content was also significantly increased. UV-B radiation and exogenous H2O2 treatment significantly increased the activities, gene and protein expression of phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), and isoflavone synthase (IFS) involved in isoflavones synthesis, and there was a synergistic effect with combining treatment. However, these up-regulation effects were suppressed by the supplementary diphenylene iodonium (DPI), which is the inhibitor of NADPH oxidase. Interestingly, the inhibition effect was largely reversed by exogenous H2O2, indicating that H2O2 was indispensable in regulating the isoflavones synthesis in germinated soybeans under UV-B radiation. Overall, H2O2 is an essential signaling molecule, mediating UV-B-induced isoflavone accumulation.