Effects of exogenous additives on the nutrient composition and metabolites of buckwheat¹

Efeitos de aditivos exógenos na composição de nutrientes e metabólitos do trigo sarraceno

ABSTRACT

Germination can modify the nutritional composition of buckwheat, improving its nutritional value and health benefits. The aim of this study was to investigate the effects of exogenous additives on the nutrient composition, particularly the role of different exogenous additives in the accumulation of buckwheat flavonoids and the mechanism underlying its accumulation. In this manuscript, it was evaluated studies on the physiological functions of buckwheat after germination, the effect of adding exogenous substances to improve the nutritional properties of the sprouts, and the impact of enriching bioactive substances and bioactive functions, with emphasis on exploring the mechanism of buckwheat flavonoids accumulation. Based on the aforementioned literature review, it was found that buckwheat seeds or sprouts were treated with various exogenous substances, including salts (e.g., NaCl, NaHCO₃, CaCl₂), phytohormones (e.g., indole-3-acetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA), amino acids ((e.g. L-phenylalanine (L-phe)), vitamins (e.g. tyridoxal phosphate) and fungal extracts. A significant increase in flavonoids was found in the nutrient content of sprouted buckwheat. Moreover, this approach provides guidance for cultivating high-nutrient buckwheat and optimizing its utilization while offering a theoretical foundation for further research on grain germination.

Key words:
Fagopyrum esculentum; exogenous substances; buckwheat sprouts; nutritional composition; flavonoids

HIGHLIGHTS:

The addition of exogenous substances improves the content of secondary metabolites in plants.

The nutritional composition of buckwheat is improved when its seed germinates.

The addition of exogenous substances causes flavonoids accumulation in buckwheat sprouts.

RESUMO

A germinação pode modificar a composição nutricional do trigo-sarraceno, melhorando seu valor nutricional e benefícios à saúde. O objetivo deste artigo foi investigar os efeitos de aditivos exógenos na composição de nutrientes, particularmente o papel de diferentes aditivos exógenos na acumulação de flavonoides no trigo-sarraceno e o mecanismo subjacente à acumulação desses flavonoides. Neste artigo, foram avaliados os estudos sobre as funções fisiológicas do trigo-sarraceno após a germinação, o efeito da adição de substâncias exógenas na melhoria das propriedades nutricionais dos brotos e o impacto no enriquecimento de substâncias bioativas e funções bioativas, com foco especial na exploração do mecanismo de acumulação de flavonoides no trigo-sarraceno. Através da revisão da literatura dos estudos mencionados, descobriu-se que sementes ou brotos de trigo-sarraceno foram tratados com várias substâncias exógenas, incluindo sais (por exemplo, NaCl, NaHCO₃, CaCl₂), fitohormônios (por exemplo, ácido indol-3-acético (IAA), ácido giberélico (GA), ácido abscísico (ABA)), aminoácidos (por exemplo, L-fenilalanina (L-phe)), vitaminas (por exemplo, fosfato de piridoxal) e extratos fúngicos. As concentrações de nutrientes no trigo-sarraceno germinado é aumentado, com aumento significativo nos flavonóides. Além disso, esta abordagem fornece orientação para o cultivo de trigo-sarraceno altamente nutritivo e para a otimização de sua utilização, ao mesmo tempo que oferece uma base teórica para pesquisas adicionais sobre a germinação de grãos.

Palavras-chave:
Fagopyrum esculentum; sustâncias exógenas; brotações de trigo sarraceno; composição nutricional; flavonóides

Introduction

Buckwheat (Fagopyrum esculentum) is an annual plant belonging to the family Polygonaceae (Lu et al., 2021). It is abundant in nutrients such as flavonoids, proteins, and minerals (Lee et al., 2016; Almuhayawi et al., 2021; Wang et al., 2024), and widely used in both medicine and food (Gao et al., 2016). It is also rich in nutrients and functional components like rutin and quercetin (Zhou et al., 2016; Fan, 2016; Ebrar & Nihal, 2024). Contemporary medical studies have confirmed that flavonoids exhibit antioxidant properties, such as being free-radical scavenging (Ardestani & Yazdanparast, 2007).

Studies have shown that, compared to seeds, germinated buckwheat contains higher levels of protein, vitamins, and an optimal proportion of amino acids (Zhang et al., 2017; Peng et al., 2023). Additionally, after germination, certain trace elements can transition from an inorganic to an organic form (Zhang et al., 2005a), thereby significantly enhancing their nutritional value. During germination, the activity of the rutin-degrading enzyme (RDE) decreases, while the content of active flavonoids increases markedly (Zhang et al., 2005b; Wang et al., 2013a). Germination breaks down and significantly reduces the anti-nutritional factors in Tartary buckwheat (Wang et al., 2013b), improving its bioavailability and nutritional value. Plant hormones (Chang et al., 2017), salts (Wan et al., 2016), sugars (Gang et al., 2012), amino acids (Seo et al., 2015) as well as other inducers, precursor treatments and stress factors, play a crucial role in promoting seed germination and the accumulation of bioactive substances (Jaecheol et al., 2023).

This review aimed to investigate the effects of exogenous additives on the nutrient composition of buckwheat, with particular emphasis on how different exogenous additives contribute to the accumulation of buckwheat flavonoids and the underlying mechanism of this accumulation. Moreover, it could offer valuable insights for improving the quality of buckwheat, advancing its processing and utilization, and providing a theoretical foundation for further studies on grain germination.

Nutritional Value of Germinated Buckwheat

Germination not only improves the nutritional value of buckwheat (Peng et al., 2023; Yan et al., 2024), but also decreases the activity of trypsin inhibitors and other anti-nutritional compounds in buckwheat seeds (Wang et al., 2013a; Ebrar & Nihal, 2024), thus improving protein digestibility and significantly increasing nutrient utilization (Wang et al., 2013a).

Improvement in nutritional value: An appropriate concentration of Al³⁺ can decrease membrane permeability, minimize the extravasation of intracellular nutrients, improve amylase activity, and increase the soluble-sugar content in buckwheat seeds (Li et al., 2006). Li et al. (2004) studied different buckwheat varieties under Al³⁺ stress and observed that the levels of proline and soluble sugar increased significantly in buckwheat seedlings treated with Al³⁺ at 5000 mg L^-1, with 40-70% increase in free proline. Similarly, treating buckwheat with 3% sucrose and 7.5 mmol L^-1 CaCl₂ significantly increased the levels of vitamins C and E in sprouts without affecting germination (Sim et al., 2020). Moreover, it has been reported that treatment of F. esculentum with high concentrations of gibberellin (GA) not only increased the yield of sprouts, but also enhanced the levels of vitamin C (Li & Ren, 2009). Lu et al. (2020) demonstrated that treatment with 20 mmol L^-1 of Ca(NO₃)₂ and 10 μmol L^-1 of abscisic acid (ABA) significantly increased the accumulation of amino acids and carbohydrate metabolites in salt-sensitive buckwheat varieties under salt stress, thereby improving its nutritional value. Ma et al. (2019) revealed that microwave treatment (400 W for 10 seconds) combined with the application of L-Phe (5 mmol L^-1) significantly increased the levels of reducing sugars and total soluble sugars in Tartary buckwheat sprouts. Compared to those in the control group (CK), the levels of reducing sugars and total soluble sugars in 7-day-old sprouts reached peak, being 59.61 and 28.16% higher, respectively.

Improvements in protein digestion and utilization: In humans, the effects of different metals on protein digestibility and trypsin inhibition vary for Tartary buckwheat, with the former being negatively correlated with trypsin inhibition. Wang et al. (2013b) showed that Al³⁺, Cu²⁺, and Zn²⁺ significantly improved the protein digestibility of Tartary buckwheat sprouts and effectively reduced the activity of trypsin inhibitors. After treatment, 97.1% protein digestibility of Tartary buckwheat sprouts was achieved, representing a 7% increase compared to the control group (CK). Furthermore, Zhu & Guo (2015) reported that after exposure to metal-ion stress, the trypsin inhibitory activity in germinated Tartary buckwheat decreased rapidly, leaving the residual activity inactive, while the protein digestibility increased significantly within a short period and was strongly related to the decrease in trypsin inhibitor activity.

Enrichment of Bioactive Components

Flavonoids, including catechin and caffeic acid, as well as GABA, represent a major class of secondary metabolites in plants, often synthesized in response to harsh ecological conditions over the course of long-term ecological adaptation (Jiang et al., 2020). The metabolism and accumulation of these bioactive compounds are stimulated by external stress factors in plants.

The effects of plant growth regulators such as GA, indoleacetic acid (IAA), methyl jasmonate (MeJA), and other similar substances play an essential regulatory role in the biosynthesis of buckwheat flavonoids (Chang et al., 2017). Studies have reported that IAA and GA, within the concentration range of 0.1-1 mg L^-1, promote the synthesis and accumulation of total phenolic compounds and specific flavonoids, including rutin and catechin, in buckwheat sprouts (Chang et al., 2017). Similarly, it has been reported that GA treatment at a concentration of 10-20 mg L^-1 positively impacted the germination of Tartary buckwheat and the synthesis of flavonoids in sprouts; however, higher concentrations inhibited flavonoids synthesis (Li & Ren, 2009). Studies have shown that the total flavonoid content (TFC) of Tartary buckwheat (Fagopyrum tataricum Gaertn.) cotyledons treated with MeJA gradually increased with prolonged culture time (Luo et al., 2015), and the total phenol content (TPC) increased 1.6 fold compared to the control group (CK) (Kim et al., 2011). After treatment with 0.1 mg L^-1 GA, Chang et al. (2017) found that the concentrations of catechin, caffeic acid, and rutin in Tartary buckwheat sprouts increased by 1.26, 1.72, and 1.23 times, respectively, compared with the control. Similarly, treatment with 0.1 mg L^-1 of IAA, resulted in the total phenolic content (TPC) of Tartary buckwheat sprouts increasing to 1,580.49 ± 11.19 g g^-1 DW (dry weight). Furthermore, ABA treatment was found to promote the accumulation of organic acids and alcohol metabolites in salt-tolerant buckwheat varieties under salt stress (Lu et al., 2020), thus significantly improving its nutritional value.

Effects of salt ions: Salt ions affect the biosynthesis of buckwheat flavonoids, and the severity depends on the degree of stress. Treatment of Tartary buckwheat sprouts with low salt concentrations can significantly increase the TFC and TPC (Qin et al., 2016; Wan et al., 2016). Lim et al. (2012) found that NaCl treatment at a certain concentration, was suitable for the enrichment of phenolic compounds and carotenoids in buckwheat sprouts and confirmed that the accumulation of phenolic compounds was mainly attributable to an increase in the levels of isoorientin, orientin, rutin, and vetoritin. It has been confirmed that applying 40-120 mmol L^-1 NaCl to Tartary buckwheat increases the rutin and quercetin content in sprouts by 67 and 33%, respectively, after 7 days of germination (Wan et al., 2016). However, different concentrations of Al³⁺, Cu²⁺, and Zn²⁺ were found to significantly increase the content of TF and D-chiro-inositol (DCI) in Tartary buckwheat sprouts. Particularly, treatment with 1000 mg L^-1 Al³⁺ resulted in the optimal enrichment of TF and DCI, with their levels increasing to 1,315.52 mg 100 g^-1 DW and 63 mg g^-1 DW, respectively (Wang et al., 2013b). Studies have shown that using a certain concentration of Mn²⁺ stress to treat germinated Tartary buckwheat seeds could increase the TFC in sprouts by 14%, merely 12 days after germination compared with the control (Li & Li, 2010). Exogenous calcium (Ca(NO₃)₂) treatment could significantly promote the accumulation of organic acids and alcohol metabolites in salt-tolerant buckwheat (Lu et al., 2020).

Effects of sugars: Sugars are the carbon source facilitating the synthesis of secondary metabolites in plants. Jeong et al. (2018) found that sucrose treatment enhanced the activity of tyrosinase and phenylalanine ammonia-lyase (PAL), leading to an increase in the content of four flavonoid glycosides and rutin in buckwheat. Similarly, sucrose treatment could effectively improve the GABA content in buckwheat sprouts (Zhu & Guo, 2015). Sim et al. (2020) reported that treating buckwheat sprouts with 3% sucrose combined with 7.5 mmol L^-1 CaCl₂, significantly increased the accumulation of TP and TF to 490.07 ± 6.92 gallic acid mg 100 g^-1 FW and 182.88 ± 3.08 rutin mg 100 g^-1 FW, respectively. Exogenous yeast polysaccharides (Gang et al., 2012) and lentinan (Zhang et al., 2014) could also promote the germination of Tartary buckwheat seeds and the synthesis and accumulation of active flavonoids. Exogenous polysaccharide inducers had a stimulatory effect on the growth of sprouts and the accumulation of functional metabolites, which primarily depended on the type of polysaccharide and the treatment dose. Zhao et al. (2015) showed that the application of 150-200 mg L^-1 of surface polysaccharides, water-soluble mycelia polysaccharides, and alkali-extracted mycelia polysaccharides extracted from buckwheat endophytes increased the rutin and quercetin content in buckwheat sprouts by 1.57-1.66 times compared with the control. Similarly, Jiang et al. (2020) found that treatment with 200 g mL^-1 of sodium alginate facilitated the growth of Tartary buckwheat sprouts and the synthesis of flavonoids. Moreover, the TFC in the sprouts reached 54.69 mg g^-1, equivalent to 1.12 times that of the control. Similarly, the rutin and quercetin contents were 1.11- and 1.62-fold higher compared with the control, respectively.

L-Phe is a precursor in flavonoid synthesis. Seo et al. (2015) found that treatment with 5 mmol L^-1 of exogenous L-Phe could significantly promote the synthesis of phenolic monomers and TPC in Tartary buckwheat sprouts, with the rutin content increasing to 60.42 mg g^-1 DW, equivalent to 1.5 times that of the control. Ma et al. (2019) pointed out that appropriate microwave treatment combined with the application of L-Phe could significantly increase the content of bioactive substances in Tartary buckwheat sprouts. They reported that the TP and TF on day 7 of germination were 23.33 mg g^-1 and 5.10 g 100 g^-1 DW, respectively, representing 38.37 and 35.28% increase, respectively, compared with the control.

Effects of fungi and bacterial treatment: Fungi and bacteria affect the accumulation of bioactive substances in buckwheat. Epigenic and endophytic fungi from buckwheat are effective biological factors inducing the synthesis of buckwheat flavonoids. Li et al. (2009a) showed that inducing seeds with the epiphytic fungi, K11 and K18, from bitter buckwheat seeds could promote the synthesis of bitter buckwheat flavonoids. After treatment with K11 and K18 at concentrations of 200 and 50 mg L^-1, respectively, the TFC in Tartary buckwheat sprouts (6 d) reached its peak, increasing by 24.5 and 6.6%, respectively, compared with the control. Previous studies have reported that water-extracted, sodium hydroxide-extracted, and hydrochloric acid-extracted mycelial polysaccharides, as well as the exo-polysaccharide obtained from the endophytic Fusarium oxysporum Fat9, can promote the growth of buckwheat sprouts to different degrees. The cumulative amounts of the flavonoids, including rutin and quercetin, increased by 1.11 to 1.40 times compared with the control (Zhong et al., 2016). Studies have indicated that 400 mg L^-1 of yeast polysaccharides can effectively increase rutin and quercetin content on day 6 of buckwheat germination, with their levels reaching 42.8 mg g^-1 DW, approximately 1.4 times higher compared with the control (Zhao et al., 2012a).

Improvement of Biological Activity Function

Buckwheat is an important source of rutin, which is known for its antioxidant and hypoglycemic effects (Chia-Ling et al., 2008). Several enzymes are activated during germination and many physiological and biochemical reactions occur in seeds, resulting in an increase in the content of functionally active compounds, such as flavonoids and phenolic substances (Lü et al., 2014), which enhance the nutritional value of sprouts and seedlings. The addition of exogenous substances accumulates and affects the nutrient composition of buckwheat sprouts. Table 1 shows the effects of exogenous additives on the nutrient composition of buckwheat reported in previous studies.

Table 1
Effects of exogenous additives on the nutrient composition of buckwheat reported in studies

Material	Type of additives	Methods of treatment	Nutrient composition categories	Changes in nutrient content	References
Tartary buckwheat	Pyridoxal phosphate (PLP)	Seeds were soaked in 2.5 mM PLP at 30 ℃ for 24 hours	γ-aminobutyric acid	Reaching 3.82 g kg-1 and was 8.67-fold that of the control	Yan et al. (2024)
Buckwheat	Sucrose + CaCl2	The sprouts were sprayed for 5 min every 6 hours with 3% Sucrose + 7.5 mM CaCl2	Total polyphenol	Reaching 490.07 mg 100 g-1 FW, while 298.96 mg 100 g-1 FW of control	Sim et al. (2020)
			Total flavonoid	Reaching 182.88 mg 100 g-1 FW, while 115.69 mg 100 g-1 FW of control
			Rutin	Reaching 38.70 mg 100 g-1 FW, while 28.89 mg 100 g-1 FW of control
Tartary buckwheat	NaCl+abscisic acid (ABA)	The sprouts were treated with 100 mmol L-1 NaCl+40 μmol L-1 ABA	Protocatechuic acid	Reaching about 2 mg g-1 DW	Lu et al. (2020)
Tartary buckwheat	Sodium alginate	Seeds were soaked in 200 μg L-1 sodium alginate for 12 hours	Flavonoids	Reaching 54.69 mg g-1 DW and was 1.12 times higher than the control	Jiang et al. (2020)
Tartary buckwheat	Microwave + L-phenylalanine (L-phe)	Seeds were treated with microwave condition of 400W 10s, and the sprouts received 5 mmol L-1 L-Phe.	Total phenolic compound	Reaching 23.33 mg g-1 DW and was 38.37% higher than the control	Ma et al. (2019)
			Flavonoids	Reaching 5.10 g 100g-1 DW and was 35.28% higher than the control
Buckwheat	Indole-3-acetic acid (IAA)	The growth patterns of buckwheat sprouts supplemented with 0.5 mg L-1 of IAA.	Caffeic acid	Reaching 26.34 μg g-1 DW and was 1.63 times higher than the control	Chang et al. (2017)
	Gibberellic acid (GA)	The same method with 0.1 mg L-1 of GA.	Rutin	Reaching 866.13 μg g-1 DW and was 1.23 times higher than the control
Tartary buckwheat	NaHCO3	The sprouts were sprayed with 0.05% NaHCO3	Flavonoids	Reaching 26.69 mg g-1 DW	Qin et al. (2016)
			Total phenolic compound	Reaching 29.31 mg g-1 DW
Tartary buckwheat	NaCl	The sprouts were sprayed with 80 mmol L-1 NaCl.	Flavonoids	Reaching 47.32 mg g-1 DW and was 73.2% higher than the control	Wan et al. (2016)
Tartary buckwheat	Water-extracted mycelia polysaccharide (WPS) obtained from the endophytic fungus Bionectra pityrodes Fat6	The sprouts were administered 200 mg L-1 WPS	Total rutin and quercetin	Reaching 52.27 mg (100 sprouts)-1 and was 1.66 fold of control	Zhao et al. (2015)
Buckwheat	MnSO4	Seeds were soaked in 0.05% MnSO4 for 24 hours	Flavonoids	Reaching 420.8 mg g-1 and was 14% higher than the control	Li & Li (2010)

Germination can significantly improve the antioxidant properties of Tartary buckwheat compared to seeds (Wang et al., 2013a; Zhou et al., 2015), and significantly enhance the free radical scavenging activity of the edible components (Kim et al., 2007). Lim et al. (2012) found that NaCl treatment could improve the antioxidant activity of the ethanolic extracts of buckwheat sprouts. Lin et al. (2008) showed that buckwheat sprouts possess strong free radical scavenging abilities, which effectively reduced the liver/body weight ratio and serum triglyceride levels in Syrian hamsters. Zhou et al. (2009) found that under weakly acidic conditions, germinated Tartary buckwheat significantly scavenged ·O₂ ^-, ·OH, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical, and nitrite. They also reported that its antioxidant effect was better than that of vitamin C and dibutylhydroxytoluene. Sim et al. (2020) pointed out that sucrose and CaCl₂ induction not only significantly enhanced the antioxidant activity of buckwheat sprouts in HepG2 cells, but also had a protective effect against the oxidative damage induced in fibroblasts. Treatment with CaCl₂ effectively maintained the levels of bioactive compounds in buckwheat sprouts, and enhanced the antioxidant effect induced by sucrose. The alleviation of oxidative damage by the active components of buckwheat sprouts in HepG2 cells was mainly achieved by regulating the production of ROS, malondialdehyde, and the activity of antioxidant enzymes (Jeong et al., 2018).It has been shown that the antioxidant activity of buckwheat sprouts was significantly improved by exogenous MeJA treatment (Kim et al., 2011).

Hypoglycemia: In its free form, DCI is an insulin-like bioactive compound that lowers blood sugar levels in obese rhesus monkeys with spontaneous insulin resistance. DCI is a natural α-glycosidase inhibitor used in the management of diabetes. As a messenger in insulin signal transmission, it directly facilitates the binding of insulin to its receptor, enhancing insulin activity and reducing blood glucose levels (Bode et al., 2000). It has previously been reported that buckwheat DCI mostly exists in the form of buckwheat phenol and can be transformed into free DCI during germination (Hu et al., 2015). Wang et al. (2013b) found that an appropriate concentration of metal ions (Al³⁺, Cu²⁺, and Zn²⁺) could improve the activity of α-glycosidase in Tartary buckwheat sprouts, triggering hydrolysis, producing sugar alcohol, and releasing more free DCI. A significant positive correlation has been highlighted between lactase activity and DCI content. It has also been reported that treatment of Tartary buckwheat with low concentrations of NaHCO₃ (0.05%) increased the DCI content in sprouts by up to ninefold compared to seeds (Qin et al., 2016). In conclusion, after treatment with exogenous substances, buckwheat germination yielded an increase in DCI levels, which could enhance α-glycosidase inhibition resulting in a glucose-lowering effect.

Mechanisms of Flavonoid Enrichment

Flavonoid biosynthesis occurs through the phenylpropane pathway (Justyna et al., 2014). Chalcones are formed from the starting substrates, 4-coumaroyl-CoA and malonyl-CoA, in the presence of chalcone synthase (CHS), catalyzed by chalcone isomerase (CHI) to yield 4,5,7-trihydroxyflavanone as the primary metabolite, and subsequently participates in other biochemical reactions to yield different flavanones (Ferreyra et al., 2012). In flavonoids biosynthesis, phenylalanine ammonia-lyase (PAL) and CHI are the key rate-limiting enzymes and their activities are closely related to TFC in plants (Besseau et al., 2007). Among them, PAL connects the primary metabolism to that of phenylpropane and catalyzes the first step of the phenylpropanoid metabolism. It is also the most-studied enzyme in the phenylpropane metabolic pathway (Liu et al., 2006c). In plants, CHI is a crucial enzyme upstream of the flavonoid metabolic pathway that regulates flavonol synthesis (Md-Mustafa et al., 2014).

Under adverse stress conditions, plants stimulate the activity of key enzymes and respond by producing hormones, such as jasmonic acid (JA) and increased levels of MeJA. These hormones induce the expression of a series of stress-resistant-related genes, including protease inhibitors, sulfur-containing proteins, and phenylalanine aminotransferase. Enzymes involved in the phenylalanine pathway (such as PAL, etc.) are induced by JA and its derivative MeJA, to enhance plant resistance and promote the accumulation of phenolic compounds (Kim et al., 2011). Through the accumulation of endogenous JA (Pedranzani et al., 2007) and the activation of PAL (Liu et al., 2006b), plants under salt solution stress can also induce the phenylpropyl pathway. Moreover, various external factors such as light exposure and mechanical damage, can induce PAL and CHI activity during seed germination (Anterola & Lewis, 2002).

Studies have shown that under Al³⁺ stress, buckwheat secretes flavonoids and oxalates from its roots to alleviate Al³⁺ toxicity by chelating Al³⁺ ions (Ma & Furukawa, 2003). Ma & Furukawa (2003) found that when seeds are soaked in low concentrations of Al³⁺, the activities of PAL and CHI rapidly increase, as well as the phenylpropanoid metabolism and TFC. However, when a certain concentration of Al³⁺ is exceeded, the enzymatic activities of PAL and CHI could decline probably due to Al³⁺ poisoning. This could simultaneously lead to the production of flavonoids that chelate Al³⁺, resulting in a rapid decrease in TFC. Moreover, Cu²⁺ and Zn²⁺, as components of the active centers of PAL and CHI, can directly affect their activities, thereby altering the TFC (Wang et al., 2013b).

In plants, endogenous phenylpropanoid compounds serve as substrates for flavonoids synthesized through a series of anabolic pathways catalyzed by specific enzymes (Yang et al., 2007). L-Phe acts as a substrate in the phenylpropanoid metabolic pathway and serves as a precursor for flavonoids synthesis. Studies (Shin et al., 2023; Fabiola et al., 2024; Wang et al., 2024) have shown that L-Phe promotes flavonoids synthesis and accumulation in plant sprouts by regulating PAL activity, thereby increasing the production of intermediate chalcones and subsequent flavonoid synthesis (Ferreyra et al., 2012). Spraying ethylene on Tartary buckwheat during germination has been shown to improve PAL activity and increase TFC, indicating a linear correlation between PAL activity and TFC changes (Liu et al., 2006a). The effect of GA on flavonoids is because GA activates phenylalanine aminotransferase activity and promotes the phenylpropanoid metabolic pathway, thereby increasing the TFC (Li & Ren, 2009). Studies have reported that polysaccharide treatment also stimulates the phenylpropanoid pathway, promoting flavonoid accumulation in the buds of Tartary buckwheat (Zhao et al., 2015). Jeong et al. (2018) reported that sucrose treatment could increase the activities of tyrosinase and phenylalanine ammonia-lyase (PAL), thereby causing increased TFC in Tartary buckwheat sprouts.

Inducing the expression of key enzyme genes is critical for regulating flavonoid synthesis in plants. The type, concentration, and treatment duration of plant hormones directly affect the accumulation of buckwheat flavonoids, by regulating the genes of key enzymes involved in flavonoid synthesis. The expression level of key enzymes in the phenylpropanoid metabolic pathway directly affects flavonoid biosynthesis in plants. Salicylic acid (SA) treatment can increase the expression of FtCHS, FtFLS-like, FtF3H, and Ft4CL in buckwheat, thereby improving its rutin content (Sun et al., 2012). Li et al. (2013) found that FtFLS isomers (FtFLS1 and FtFLS2) are present in buckwheat and play different physiological roles in response to environmental stress. ABA and SA, as endogenous hormones, can inhibit the expression of FtFLS1, whereas the FtFLS2 gene is induced and upregulated by SA. Fungi inducers are specific chemical signals from fungi, and can rapidly trigger the defensive response of plants when interacting with fungi. This, in turn, induces the expression of specific genes in plants and promotes the accumulation of secondary metabolites such as flavonoids (Li et al., 2009b).

The MYB (MYB proto-oncogene, transcription factor) transcription factor plays an important regulatory role in the biosynthesis of buckwheat flavonoids. It is involved in multiple branches of flavone synthesis and metabolism and can regulate flavonoid biosynthesis in coordination with multiple genes (Schijlen et al., 2004). Studies have shown that MYB regulates the transcription of target genes either by binding directly to the promoter region of the target gene or by interacting directly with other proteins (such as WD40 and bHLH), thereby regulating flavonoid biosynthesis (Gonzalez et al., 2008). Zhou et al. (2017) confirmed that FtSAD2 (sensitive to ABA and drought) and FtJAZ1 (a JA signal transduction inhibitor) can interact synergistically with MYB, thus affecting the accumulation of flavonoids in Tartary buckwheat. The MYB transcription factors FtMYB13, FtMYB14, and FtMYB15 in buckwheat are induced by JA at the protein level and can directly inhibit the expression of FtPAL, thereby reducing flavonoids accumulation. Furthermore, FtSAD2 and FtJAZ1, which interact with FtMYB11, FtMYB13, FtMYB14, and FtMYB15, can significantly increase the inhibitory activity (protein-protein interaction) of FtMYBs, thereby affecting flavonoid biosynthesis (Zhou et al., 2017; Zhang et al., 2018).

Luo et al. (2015) studied the key enzyme genes in flavonoid synthesis and found that TFC was significantly positively correlated with FtMYB2 (r = 0.864) and FtJAZ1 (r = 0.863), negatively correlated with FtMYB3 (r = -0.70), and positively correlated with all key enzyme genes involved in flavonoid synthesis. The total flavonoid accumulation in cotyledons was positively correlated with FtMYB3 expression and negatively correlated with FtMYB2 expression (Zhao et al., 2012b). However, a relatively complex relationship was found between PAL, CHI, and flavonol synthase (FLS) of key enzyme genes and FtMYB1, FtMYB2, and FtMYB3, while the transcription of key enzyme genes and transcription factors was relatively weak. Therefore, it was proposed that certain key enzyme genes in flavonol synthesis may be regulated only by specific transcription factors, precisely activating one or more branches of flavonol synthesis. However, the change in TFC alone lacks the ability to reflect this characteristic.

Conclusions

1. Germination improves the nutritional value of buckwheat, and the addition of exogenous substances such as salts, phytohormones, Gibberellic acid, abscisic acid, amino acids, vitamins and fungal extracts increase the nutrient content in sprouted buckwheat, especially flavonoids. At the same time, the inhibitory effect of buckwheat on human trypsin diminishes or is completely reversed.

2. Researchers worldwide are paying great attention to studies on the accumulation mechanism of flavonoids in buckwheat sprouts. Flavonoid-enriched biosynthesis occurs via the phenylpropane pathway, with chalcone synthase (CHS), chalcone isomerase (CHI), phenylalanine ammonia-lyase (PAL) and flavonol synthase (FLS) as the key enzymes, with PAL and CHI serving as rate-limiting enzymes. When PAL and CHI activities increase, benzene propane metabolism is accelerated, leading to an increase in flavonoids. Furthermore, the key enzymes were positively correlated with the transcription factors FTMYB, FtCHS, FtFLSe, FtF3H and Ft4CL.

Acknowledgments

The authors are grateful for the support of the Anhui Provincial Department of Education.

Literature Cited

• Almuhayawi, M. S.; Hassan, A. H. A.; Abdel-Mawgoud, M.; Khamis, G.; Selim, S.; Al Jaouni, S. K.; AbdElgawad, H. Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation. Journal of Photochemistry and Photobiology B: Biology, v.66, p.30-36, 2021. https://doi.org/10.1016/S1011-1344(01)00272-X
  » https://doi.org/10.1016/S1011-1344(01)00272-X
• Anterola, A. M.; Lewis, N. G. Trends in lignin modification: a comprehensive analysis of the effects of genetic manipulations/mutations on lignification and vascular integrity. Phytochemistry, v.61, p.221-294, 2002. https://doi.org/10.1016/S0031-9422(02)00211-X
  » https://doi.org/10.1016/S0031-9422(02)00211-X
• Ardestani, A.; Yazdanparast, R. Antioxidant and free radical scavenging potential of Achillea santolina extracts. Food Chemistry, v.104, p.21-29, 2007. https://doi.org/10.1016/j.foodchem.2006.10.066
  » https://doi.org/10.1016/j.foodchem.2006.10.066
• Besseau, S.; Hoffmann, L.; Geoffroy, P.; Lapierre, C.; Pollet, B.; Legrand, M. Flavonoid accumulation in Arabidopsis repressed in lignin synthesis affects auxin transport and plant growth. The Plant Cell, v.19, p.148-162, 2007. https://doi.org/10.1105/tpc.106.044495
  » https://doi.org/10.1105/tpc.106.044495
• Bode, M.; Eder, S.; Schürmann, G. Antihyperglycemic effects of 3-O-methyl-D-chiro-inositol and D-chiro-inositol associated with manganese in streptozotocin diabetic rats. Hormone and Metabolic Research, v.32, p.129-132, 2000. https://doi.org/10.1055/s-2007-978606
  » https://doi.org/10.1055/s-2007-978606
• Chang, P.; Hyeon, Y.; Yun, P.; Abubaker, M.; Mariadhas, V. A.; Naif, A.-D.; Sang, P. Influence of indole-3-acetic acid and gibberellic acid on phenylpropanoid accumulation in common buckwheat (Fagopyrum esculentum Moench) sprouts. Molecules, v.22, e22030374, 2017. https://doi.org/10.3390/molecules22030374
  » https://doi.org/10.3390/molecules22030374
• Chia-Ling, L.; Yih-Shyuan, C.; Joan-Hwa, Y.; Been-Huang, C. Antioxidant activity of tartary (Fagopyrum tataricum (L.) Gaertn.) and common (Fagopyrum esculentum moench) buckwheat sprouts. Journal of Agricultural and Food Chemistry, v.56, p.173-178, 2008. https://doi.org/10.1021/jf072347s
  » https://doi.org/10.1021/jf072347s
• Ebrar, A.; Nihal, G. Impact of germination pre-treatments on buckwheat and Quinoa: Mitigation of anti-nutrient content and enhancement of antioxidant properties. Food Chemistry, v.21, e101182, 2024. https://doi.org/10.1016/j.fochx.2024.101182
  » https://doi.org/10.1016/j.fochx.2024.101182
• Fabiola, A. G.; Ciro, B. M.; Cristina, M. V. Time maters: Exploring the dynamics of bioactive compounds content, bioaccessibility and antioxidant activity during Lupinus angustifolius germination. Food Research International, v.187, e114426, 2024. https://doi.org/10.1016/j.foodres.2024.114426
  » https://doi.org/10.1016/j.foodres.2024.114426
• Fan, Z. Chemical composition and health effects of Tartary buckwheat. Food Chemistry , v.203, p.231-245, 2016. https://doi.org/10.1016/j.foodchem.2016.02.050
  » https://doi.org/10.1016/j.foodchem.2016.02.050
• Ferreyra, M. L. F.; Rius, S. P.; Casati, P. Flavonoids: biosynthesis, biological functions and biotechnological applications. Frontiers in Plant Science, v.3, e00222, 2012. https://doi.org/10.3389/fpls.2012.00222
  » https://doi.org/10.3389/fpls.2012.00222
• Gang, Z.; Zhao, J. L.; Peng, L. X.; Zou, L.; Wang, J. B.; Zhong, L. Y.; Bing, X. D. Effects of yeast polysaccharide on growth and flavonoid accumulation in Fagopyrum tataricum sprout cultures. Molecules, v.17, p.11335-11345, 2012. https://doi.org/DOI10.3390/molecules171011335
  » https://doi.org/DOI10.3390/molecules171011335
• Gao, J. F.; Kreft, I.; Chao, G. M.; Wang, Y.; Liu, X. J.; Wang, L.; Wang, P. K.; Gao, X. L.; Feng, B. L. Tartary buckwheat (Fagopyrum tataricum Gaertn.) starch, a side product in functional food production, as a potential source of retrograded starch. Food Chemistry , v.190, p.552-558, 2016. https://doi.org/10.1016/j.foodchem.2015.05.122
  » https://doi.org/10.1016/j.foodchem.2015.05.122
• Gonzalez, A.; Zhao, M.; Leavitt, J. M.; Lloyd, A. M. Regulation of the anthocyanin biosynthetic pathway by the TTG1/bHLH/Myb transcriptional complex in Arabidopsis seedlings. Plant Journal, v.53, p.814-827, 2008. https://doi.org/10.1111/j.1365-313X.2007.03373.x
  » https://doi.org/10.1111/j.1365-313X.2007.03373.x
• Hu, W. H.; Chang, Z. Y.; Gao, H. L.; Jia, C. F. Acid alpha-galactosidase is involved in D-chiro-inositol accumulation during tartary buckwheat germination. Acta Societatis Botanicorum Poloniae, v.84, p.53-58, 2015. https://doi.org/10.5586/asbp.2015.002
  » https://doi.org/10.5586/asbp.2015.002
• Jeong, H.; Sung, J.; Yang, J.; Kim, Y.; Jeong, H. S.; Lee, J. Effect of sucrose on the functional composition and antioxidant capacity of buckwheat (Fagopyrum esculentum M.) sprouts. Journal of Functional Foods, v.43, p.70-76, 2018. https://doi.org/10.1016/j.jff.2018.01.019
  » https://doi.org/10.1016/j.jff.2018.01.019
• Jaecheol, K.; Ryun, H. K.; Keum, T. H. Flavonoids in different parts of common buckwheat (Fagopyrum esculentum) and Tartary buckwheat (F. tataricum) during growth. Journal of Food Composition and Analysis, v.120, e105362, 2023. https://doi.org/10.1016/j.jfca.2023.105362
  » https://doi.org/10.1016/j.jfca.2023.105362
• Jiang, L.; Zhao, J. L.; He, X. H.; Wu, Z. W.; Zhou, M.; Lin, Y. C.; Zhao, G. Effects of sodium alginate on the sprout growth and the flavonoids enrichment of Tartary buckwheat. Food Research and Development, v.41, p.40-44, 2020. https://doi.org/10.12161/j.issn.1005-6521.2020.20.007
  » https://doi.org/10.12161/j.issn.1005-6521.2020.20.007
• Justyna, M.; Kamil, K.; Anna, K. Flavonoids as important molecules of plant interactions with the environment. Molecules, v.19, p.16240-16265, 2014. https://doi.org/10.3390/molecules191016240
  » https://doi.org/10.3390/molecules191016240
• Kim, H. J.; Park, K. J.; Lim, J. H. Metabolomicanalysis of phenolic compounds in buckwheat (Fagopyrum esculentum M.) sprouts treated with methyl jasmonate. Journal of Agricultural and Food Chemistry, v.59, p.5707-5713, 2011. https://doi.org/10.1021/jf200396k
  » https://doi.org/10.1021/jf200396k
• Kim, S. J.; Zaidul, I.; Maeda, T.; Suzuki, T.; Hashimoto, N.; Takigawa, S.; Noda, T.; Matsuura-Endo, C.; Yamauchi, H. A time-course study of flavonoids in the sprouts of tartary (Fagopyrum tataricum Gaertn) buckwheats. Scientia Horticulturae, v.115, p.13-18, 2007. https://doi.org/10.1016/j.scienta.2007.07.018
  » https://doi.org/10.1016/j.scienta.2007.07.018
• Lü, J. L.; Wang, G. Z.; You, X. Y. Research progress of germinated grain. Cereals and Oils, v.27, p.5-7, 2014.
• Lee, L. S.; Choi, E. J.; Kim, C. H.; Sung, J. M.; Kim, Y. B.; Seo, D. H.; Choi, H. W.; Choi, Y. S.; Kum, J. S.; Park, J. D. Contribution of flavonoids to the antioxidant properties of common and Tartary buckwheat. Journal of Cereal Science, v.68, p.181-186, 2016. https://doi.org/10.1016/J.JCS.2015.07.005
  » https://doi.org/10.1016/J.JCS.2015.07.005
• Li, C. S.; Liu, P.; Xu, G. D.; Zhang, W. J.; Chen, W. W.; Wang, B. Y. Effect of seed soaking with aluminum on seed germination and seedling physiology of buckwheat. Acta Ecologica Sinica, v.6, e203864651, 2006.
• Li, C. S.; Peng, L.; Xu, G. D.; He, W. B.; Jia, Z. Effect of acid-Al on the germination of soaked buckwheat seeds. Seed, v.23, p.9-11, 2004. https://doi.org/10.1300/J064v24n01_09
  » https://doi.org/10.1300/J064v24n01_09
• Li, H. P.; Li, L. Z. Effect of MnSO₄ soaking on the vigor of buckwheat seeds and yield and quality of buckwheat sprouts. Acta Agriculturae Boreali-Occidentalis Sinica, v.19, p.75-77, 2010.
• Li, H. P.; Ren, C. W. Effect of GA seed soaking on germination physiological characteristics in buckwheat seeds. Journal of Shanxi Agricultural Sciences, v.37, p.19-21, 2009a.
• Li, X. H.; Kim, Y. B.; Kim, Y. J.; Zhao, S. C.; Kim, H. H.; Chung, E.; Lee, J.; Park, S. Differential stress-response expression of two flavonol synthase genes and accumulation of flavonols in tartary buckwheat. Journal of Plant Physiology, v.170, p.1630-1636, 2013. https://doi.org/10.1016/j.jplph.2013.06.010
  » https://doi.org/10.1016/j.jplph.2013.06.010
• Li, X. Y.; Zhen, R. Y.; Zhang, R. Q.; Sheng, L. M. Effects of fungal elicitors on synthesis of flavonoids in germinating Tartary buckwheat. Journal of Tianjin Agricultural University, v.16, p.34-37, 2009b.
• Lim, J. H.; Park, K. J.; Kim, B. K.; Jeong, J. W.; Kim, H. J. Effect of salinity stress on phenolic compounds and carotenoids in buckwheat (Fagopyrum esculentum M.) sprout. Food Chemistry , v.135, p.1065-1070, 2012. https://doi.org/10.1016/j.foodchem.2012.05.068
  » https://doi.org/10.1016/j.foodchem.2012.05.068
• Lin, L. Y.; Peng, C. C.; Yang, Y. L.; Peng, R. Y. Optimization of bioactive compounds in buckwheat sprouts and their effect on blood cholesterol in hamsters. Journal of Agricultural and Food Chemistry, v.56, p.1216-1223, 2008. https://doi.org/10.1021/jf072886x
  » https://doi.org/10.1021/jf072886x
• Liu, J. F.; Li, X. Y.; Meng, R. A preliminary study on the factors promoting flavonoid synthesis in Tartary buckwheat during germination. Science and Technology of Food Industry, p.106-108, 2006a.
• Liu, L. P.; Zang, X. Y.; Yuan, Q. Y.; Cai, Q. S. Mitigating effect of exogenous sucrose on root growth of buckwheat (Fagopyrum esculentum Moench) seedlings under salt stress. Plant Physiology Communications, v.42, p.847-850, 2006b.
• Liu, R. R.; Xu, S. H.; Li, J. L.; Hu, Y. L.; Lin, Z. P. Expression profile of a PAL gene from Astragalus membranaceus var. Mongholicus and its crucial role in flux into flavonoid biosynthesis. Plant Cell Reports, v.25, p.705-710, 2006c. https://doi.org/10.1007/s00299-005-0072-7
  » https://doi.org/10.1007/s00299-005-0072-7
• Lu, Q. H.; Wang, Y. Q.; Xu, J. P.; Cai, X. Y.; Yang, H. B. Effect of ABA on physiological characteristics and expression of salt tolerance-related genes in Tartary buckwheat. Acta Physiologiae Plantarum, v.43, p.1-11, 2021. https://doi.org/10.1007/s11738-021-03238-w
  » https://doi.org/10.1007/s11738-021-03238-w
• Lu, Q. H.; Wang, Y. Q.; Yang, H. B. Effects of exogenous calcium and abscisic acid treatments on contents of metabolites in Tartary buckwheat under salt stress. Journal of Qingdao Agricultural University (Natural Science), v.37, p.95-101, 2020.
• Luo, X. P.; Zhu, D. Y.; Huang, Y. J.; Li, M. F.; Yao, P. F.; Fei, G.; Li, C. L.; Zhao, H. X. Effects of methyl jasmonate accumulation of flavonoids and related gene expression of buckwheat sprouts. Genomics and Applied Biology, v.34, p.1040-1046, 2015.
• Ma, H.; Bian, Z. X.; Chen, X. Y.; Chu, Y.; Wang, S. M. Effects of microwave assisted L-phe treatment on main nutrients of Tartary buckwheat during germination. Journal of Anhui Polytechnic University, v.34, p.1-7, 2019.
• Ma, J. F.; Furukawa, J. Recent progress in the research of external Al detoxification in higher plants: a minireview. Journal of Inorganic Biochemistry, v.97, p.46-51, 2003. https://doi.org/10.1016/s0162-0134(03)00245-9
  » https://doi.org/10.1016/s0162-0134(03)00245-9
• Md-Mustafa, N. D.; Khalid, N.; Gao, H.; Peng, Z.; Alimin, M. F.; Bujang, N.; Ming, W. S.; Mohd-Yusuf, Y.; Harikrishna, J. A.; Othman, R. Y. Transcriptome profiling shows gene regulation patterns in a flavonoid pathway in response to exogenous phenylalanine in Boesenbergia rotunda cell culture. BMC Genomics, v.15, e984, 2014. https://doi.org/10.1186/1471-2164-15-984
  » https://doi.org/10.1186/1471-2164-15-984
• Peng, W. P.; Dong, Y. L.; Wang, J. Z.; Wang, S. M.; Wang, N. Effects of exogenous solution treatment on germination, antioxidation and flavonoid biosynthesis of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) Food Bioscience, v.56, e103367, 2023. https://doi.org/10.1016/j.fbio.2023.103367
  » https://doi.org/10.1016/j.fbio.2023.103367
• Pedranzani, H.; Sierradegrado, R.; Vigliocco, A.; Miersch, O.; Abdala, G. Cold and water stresses produce changes in endogenous jasmonates in two populations of Pinus pinaster Ait. Plant Growth Regulation, v.52, p.111-116, 2007. https://doi.org/10.1007/s10725-007-9166-2
  » https://doi.org/10.1007/s10725-007-9166-2
• Qin, P. Y.; Wei, A. C.; Zhao, D. G.; Yao, Y.; Yang, X. S.; Dun, B. Q.; Ren, G. X. Low concentration of sodium bicarbonate improves the bioactive compound levels and antioxidant and α-glucosidase inhibitory activities of Tartary buckwheat sprouts. Food Chemistry , v.224, p.124-130, 2016. https://doi.org/10.1016/j.foodchem.2016.12.059
  » https://doi.org/10.1016/j.foodchem.2016.12.059
• Shin, J. Y.; Yang, J. H.; Yang, J. H. Germination of tartary buckwheat at various light strengths to enhance flavonoid content and scale-up of the process using smart-farm systems, Journal of Cereal Science , v.112, e103727, 2023. https://doi.org/10.1016/j.jcs.2023.103727
  » https://doi.org/10.1016/j.jcs.2023.103727
• Schijlen, E. G. W. M.; Vos, C. H. R. D.; Tunen, A. J. V.; Bovy, A. G. Modification of flavonoid biosynthesis in crop plants. Phytochemistry, v.65, p.2631-2648, 2004. https://doi.org/10.1016/j.phytochem.2004.07.028
  » https://doi.org/10.1016/j.phytochem.2004.07.028
• Seo, J. M.; Arasu, M. V.; Kim, Y. B.; Park, S. U.; Kim, S. J. Phenylalanine and LED lights enhance phenolic compound production in Tartary buckwheat sprouts. Food Chemistry , v.177, p.204-213, 2015. https://doi.org/10.1016/j.foodchem.2014.12.094
  » https://doi.org/10.1016/j.foodchem.2014.12.094
• Sim, U.; Sung, J.; Lee, H.; Heo, H.; Jeong, H. S.; Lee, J. Effect of calcium chloride and sucrose on the composition of bioactive compounds and antioxidant activities in buckwheat sprouts. Food Chemistry , v.312, e126075, 2020. https://doi.org/10.1016/j.foodchem.2019.126075
  » https://doi.org/10.1016/j.foodchem.2019.126075
• Sun, Z. X.; Hou, S. Y.; Yang, W. D.; Han, Y. H. Exogenous application of salicylic acid enhanced the rutin accumulation and influenced the expression patterns of rutin biosynthesis related genes in Fagopyrum tartaricum Gaertn leaves. Plant Growth Regulation , v.68, p.9-15, 2012. https://doi.org/10.1007/s10725-012-9688-0
  » https://doi.org/10.1007/s10725-012-9688-0
• Wan, Y.; Xiang, D. B.; Zeng, X. L.; Wang, X.; Yuan, Z. H.; Tan, M. L.; Zou, L.; Zhao, G. Salt stress influence on yield of Tartary buckwheat sprouts and flavonoids content. Science and Technology of Food Industry , v.37, p.328-332, 2016. https://doi.org/10.13386/j.issn1002-0306.2016.07.054
  » https://doi.org/10.13386/j.issn1002-0306.2016.07.054
• Wang, X. Y.; Wang, A. Q.; Zhuang, M.; Ke, S.; Ning, M.; Zhou, Z. K. Impact of metabolites derived from Bacillus velezensis on the germination of tigernut seeds and the underlying molecular regulatory mechanism. Food Bioscience, v.62, e105169, 2024. https://doi.org/10.1016/j.fbio.2024.105169
  » https://doi.org/10.1016/j.fbio.2024.105169
• Wang, J. B.; Zhang, J. L.; Peng, L. X.; Zou, L.; Zhao, G. Development on flavonoids and antioxidant activity of tartary buckwheat sprout. Modern Food Science and Technology, v.29, p.965-968, 2013a.
• Wang, L.; Zhao, J. L.; Mao, Y. B.; Liu, L. L.; Li, C. L.; Wu, H. L.; Zhao, H. X.; Wu, Q. Tartary buckwheat rutin: Accumulation, metabolic pathways, regulation mechanisms, and biofortification strategies. Plant Physiology and Biochemistryrotations, v.208, e108503, 2024. https://doi.org/10.1016/j.plaphy.2024.108503
  » https://doi.org/10.1016/j.plaphy.2024.108503
• Wang, L.; Li, X. D.; Niu, M.; Wang, R.; Chen, Z. X. Effect of additives on flavonoids, d-chiro-Inositol and trypsin inhibitor during the germination of tartary buckwheat seeds. Journal of Cereal Science , v.58, p.348-354, 2013b. https://doi.org/10.1016/j.jcs.2013.07.004
  » https://doi.org/10.1016/j.jcs.2013.07.004
• Yang, Y.; He, F.; Ji, J. X.; Lei, J.; Chen, X. H.; Yu, L. J. The effect of precursor feeding on flavonoids biosynthesis in cell suspension cultures of glycyrrhiza inflata bat. Plant Science Journal, v.25, p.484-489, 2007.
• Zhang, C.; Huang, W. N.; Lu, Y. Research progress in nutrition and mass production of buckwheat sprout. Journal of Cereals and Oils, v.5, p.9-11, 2005a.
• Zhang, C. Q.; Zhao, J. L.; Gang, Z.; Wang, X. P.; Liu, X. Q.; Liang, Z. Effects of lentinan on germination and flavonoid biosynthesis in Fagopyrum tataricum sprout cultures. Food Industry, v.35, p.123-126, 2014.
• Zhang, K. X.; Logacheva, M. D.; Meng, Y.; Hu, J. P.; Wan, D. P.; Li, L.; Janovska, D.; Wang, Z. Y.; Georgiev, M. I.; Yu, Z. Jasmonate-responsive MYB factors spatially repress rutin biosynthesis in Fagopyrum tataricum Journal of Experimental Botany, v.69, p.1955-1966, 2018. https://doi.org/10.1093/jxb/ery032
  » https://doi.org/10.1093/jxb/ery032
• Zhang, M. L.; Wu, J. H.; Zhao, L.; Hu, X. S. Nutrition estimation of fatty acids of buckwheat grains after germination. Journal of the Chinese Cereals and Oils Association, v.20, p.44-47, 2005b. https://doi.org/10.1007/s11769-005-0030-x
  » https://doi.org/10.1007/s11769-005-0030-x
• Zhang, Y. W.; Jing, M. L.; Li, X. P.; Wei, S. F.; Hu, X. Z.; Ma, Z.; Liu, L. Principal component analysis and comprehensive evaluation of protein and amino acid in different varieties of buckwheat and buckwheat sprout. Food and Fermentation Industries, v.43, p.214-221, 2017.
• Zhao, G.; Zhao, J. L.; Peng, L. X.; Zou, L.; Wang, J. B.; Zhong, L. Y.; Xiang, D. B. Effects of yeast polysaccharide on growth and flavonoid accumulation in Fagopyrum tataricum sprout cultures. Molecules, v.17, p.11335-11345, 2012b. https://doi.org/10.3390/molecules171011335
  » https://doi.org/10.3390/molecules171011335
• Zhao, H. X.; Wu, X. F.; Bai, Y. C.; Li, C. L.; Chen, H.; Shao, J. R.; Wu, Q. Gene expression analysis of key enzymes and MYB transcription factors in flavonoid biosynthesis pathway during germination of Fagopyrum tataricum Journal of Agricultural Biotechnology, v.20, p.121-128, 2012a. https://doi.org/10.1007/s00438-015-1013-y
  » https://doi.org/10.1007/s00438-015-1013-y
• Zhao, J. L.; Zou, L.; Zhong, L.; Peng, L. X.; Ying, P. L.; Tan, M. L.; Zhao, G. Effects of polysaccharide elicitors from endophytic Bionectria pityrodes Fat6 on the growth and flavonoid production in tartary buckwheat sprout cultures. Cereal Research Communications, v.43, p.661-671, 2015. https://doi.org/10.1556/0806.43.2015.013
  » https://doi.org/10.1556/0806.43.2015.013
• Zhong, L. Y.; Niu, B.; Tang, L.; Chen, F.; Zhao, G.; Zhao, J. L. Effects of polysaccharide elicitors from endophytic fusarium oxysporum Fat9 on the growth, flavonoid accumulation and antioxidant property of Fagopyrum tataricum sprout cultures. Molecules, v.21, e1590, 2016. https://doi.org/10.3390/molecules21121590
  » https://doi.org/10.3390/molecules21121590
• Zhou, J.; Li, C. L.; Gao, F.; Luo, X. P.; Li, Q. Q.; Zhao, H. X.; Yao, H. P.; Chen, H.; Wang, A. H.; Wu, Q. Characterization of three glucosyltransferase genes in Tartary buckwheat and their expression after cold stress. Journal of Agricultural and Food Chemistry, v.64, p.6930-6938, 2016. https://doi.org/10.1021/acs.jafc.6b02064
  » https://doi.org/10.1021/acs.jafc.6b02064
• Zhou, M. L.; Sun, Z. M.; Ding, M. Q.; Logacheva, M. D.; Kreft, I.; Wang, D.; Yan, M. L.; Shao, J. R.; Tang, Y. X.; Wu, Y. M. FtSAD2 and FtJAZ1 regulate activity of the FtMYB11 transcription repressor of the phenylpropanoid pathway in Fagopyrum tataricum New Phytologist, v.216, p.814-828, 2017. https://doi.org/10.1111/nph.14692
  » https://doi.org/10.1111/nph.14692
• Zhou, X. L.; Song, X. L.; Zhou, Y. M.; Wen, T. Study on antioxidative activities in the sprouts of Tartary (Fagopyrum Tataricum Gaertn.) buckwheat. Food Industry, v.30, p.9-11, 2009.
• Zhou, Y. M.; Wang, H.; Cui, L. L.; Zhou, X. L.; Tang, W.; Song, X. L. Evolution of nutrient ingredients in tartary buckwheat seeds during germination. Food Chemistry , v.186, p.244-248, 2015. https://doi.org/10.1016/j.foodchem.2015.03.115
  » https://doi.org/10.1016/j.foodchem.2015.03.115
• Zhu, Y. H.; Guo, Y. X. Optimization of culture conditions for accumulating γ-aminobutyric acid (GABA) in germinated Tartary buckwheat under salt stress by response surface methodology. Food Science, v.36, p.96-100, 2015. https://doi.org/10.7506/spkx1002-6630-201519017
  » https://doi.org/10.7506/spkx1002-6630-201519017
• Yan, H.; Chen, H. X.; Liu, J.; Yao, T.; Xia, M. Y.; Liao, Q. X.; Huang, L. D.; Li, W. J.; Song, Y.; Peng, L. X.; Zhao, J. L.; Zou, L.; Zhao, G. Pyridoxal phosphate promotes the γ-aminobutyric acid accumulation, antioxidant and anti-hypertensive activity of germinated tartary buckwheat. Journal of Cereal Science , v.120, e104024, 2024. https://doi.org/10.1016/j.jcs.2024.104024
  » https://doi.org/10.1016/j.jcs.2024.104024

• ¹ Research developed at Bozhou University, College of Biological and Food Engineering, Bozhou, Anhui, China

Supplementary documents

• The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Financing statement

• This publication was supported by grants from the Excellent Top Talents Cultivation Funding Project of Anhui Universities (grant number gxyqZD2022086), the Provincial Quality Engineering Program for Higher Education Institutions in Anhui Province (grant number 2022xsxx132), the Provincial Quality Engineering Program for Higher Education Institutions in Anhui Province (grant number 2023zygzts103), and the Natural Science Research Project of Anhui Universities (grant number 2022AH052410).

Edited by

• Editors: Ítalo Herbet Lucena Cavalcante & Walter Esfrain Pereira

Data availability

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Publication Dates

• Publication in this collection
  10 Mar 2025
• Date of issue
  July 2025

History

• Received
  11 Apr 2024
• Accepted
  18 Jan 2025
• Published
  30 Jan 2025