Comparison of flavonoids profile in sprouts of common buckwheat cultivars and wild tartary buckwheat

Tartary buckwheat rutin: Accumulation, metabolic pathways, regulation mechanisms, and biofortification strategies

Rutin is a significant flavonoid with strong antioxidant property and various therapeutic effects. It plays a crucial role in disease prevention and human health maintenance, especially in anti-inflammatory, antidiabetic, hepatoprotective and cardiovascular effects. While many plants can synthesize and accumulate rutin, tartary buckwheat is the only food crop possessing high levels of rutin. At present, the rutin content (RC) is regarded as the key index for evaluating the nutritional quality of tartary buckwheat. Consequently, rutin has become the focus for tartary buckwheat breeders and has made considerable progress. Here, we summarize research on the rutin in tartary buckwheat in the past two decades, including its accumulation, biosynthesis and breakdown pathways, and regulatory mechanisms. Furthermore, we propose several strategies to increase the RC in tartary buckwheat seeds based on current knowledge. This review aims to provide valuable references for elevating the quality of tartary buckwheat in the future.

Fine-Scale analysis of both wild and cultivated horned galls provides insight into their quality differentiation

BACKGROUND

Galla chinensis is a traditional Chinese medicine (TCM) produced due to the interaction between the Fordinae aphids and the Rhus plant species. Horned galls with high tannin content are the most widely cultivated gall type, and Wufeng county of Hubei province in China is the center of cultivation. However, long-term artificial cultivation and domestication of horned galls to meet the increasing production demand have led to quality degradation. Understanding the reasons underlying quality degradation is urgent for horned gall production and application. The present study used a combination of metabolic, genetic, and ecological analyses to investigate the quality and genetic differentiation of the horned galls under long-term domestication as well as the potential relationships between them.

RESULTS

Analysis of gallic acid content and other three phenotypic traits (fresh weight, gall size, and wall thickness) revealed quality differentiation of horned galls collected from five locations in Wufeng, in which the cultivated samples from Wang Jiaping (WJP) showed the highest degradation. Genetic differentiation between the cultivated and wild Rhus chinensis trees in WJP, and between WJP and the other populations was detected based on SSR molecular markers, however, no significant difference in genetic structure was seen for the aphid populations. Among the various ecological factors examined, temperature was identified as the primary one affecting the quality of horned galls.

CONCLUSIONS

Both genetic and ecological factors caused quality differentiation of horned galls. The collection of diverse germplasm of host trees and aphids will help reduce the quality degradation of horned galls in Wufeng.

Changes in the Carbohydrate Profile in Common Buckwheat (Fagopyrum esculentum Moench) Seedlings Induced by Cold Stress and Dehydration

Plant species are sensitive to stresses, especially at the seedling stage, and they respond to these conditions by making metabolic changes to counteract the negative effects of this. The objectives of this study were to determine carbohydrate profile in particular organs (roots, hypocotyl, and cotyledons) of common buckwheat seedlings and to verify whether carbohydrate accumulation is similar or not in the organs in response to cold stress and dehydration. Roots, hypocotyl, and cotyledons of common buckwheat seedlings have various saccharide compositions. The highest concentrations of cyclitols, raffinose, and stachyose were found in the hypocotyl, indicating that they may be transported from cotyledons, although this needs further studies. Accumulation of raffinose and stachyose is a strong indicator of the response of all buckwheat organs to introduced cold stress. Besides, cold conditions reduced d-chiro-inositol content, but did not affect d-pinitol level. Enhanced accumulation of raffinose and stachyose were also a distinct response of all organs against dehydration at ambient temperature. The process causes also a large decrease in the content of d-pinitol in buckwheat hypocotyl, which may indicate its transformation to d-chiro-inositol whose content increased at that time. In general, the sucrose and its galactosides in hypocotyl tissues were subject to the highest changes to the applied cold and dehydration conditions compared to the cotyledons and roots. This may indicate tissue differences in the functioning of the protective system(s) against such threats.

Advances in the study of the function and mechanism of the action of flavonoids in plants under environmental stresses

MAIN CONCLUSION

This review summarizes the anti-stress effects of flavonoids in plants and highlights its role in the regulation of polar auxin transport and free radical scavenging mechanism. As secondary metabolites widely present in plants, flavonoids play a vital function in plant growth, but also in resistance to stresses. This review introduces the classification, structure and synthetic pathways of flavonoids. The effects of flavonoids in plant stress resistance were enumerated, and the mechanism of flavonoids in plant stress resistance was discussed in detail. It is clarified that plants under stress accumulate flavonoids by regulating the expression of flavonoid synthase genes. It was also determined that the synthesized flavonoids are transported in plants through three pathways: membrane transport proteins, vesicles, and bound to glutathione S-transferase (GST). At the same time, the paper explores that flavonoids regulate polar auxin transport (PAT) by acting on the auxin export carrier PIN-FORMED (PIN) in the form of ATP-binding cassette subfamily B/P-glycoprotein (ABCB/PGP) transporter, which can help plants to respond in a more dominant form to stress. We have demonstrated that the number and location of hydroxyl groups in the structure of flavonoids can determine their free radical scavenging ability and also elucidated the mechanism by which flavonoids exert free radical removal in cells. We also identified flavonoids as signaling molecules to promote rhizobial nodulation and colonization of arbuscular mycorrhizal fungi (AMF) to enhance plant-microbial symbiosis in defense to stresses. Given all this knowledge, we can foresee that the in-depth study of flavonoids will be an essential way to reveal plant tolerance and enhance plant stress resistance.

Inhibition mechanism of α-glucosidase inhibitors screened from Tartary buckwheat and synergistic effect with acarbose

Tartary buckwheat has been shown to provide a good antihyperglycemic effect. However, it is unclear which active compounds play a key role in attenuating postprandial hyperglycemia. Presently, acetone extract from the hull of Tartary buckwheat had the best effect for α-glucosidase inhibition (IC₅₀ = 0.02 mg/mL). Twelve potential α-glucosidase inhibitors from Tartary buckwheat were screened and identified by the combination of ultrafiltration and high-performance liquid chromatography coupled with mass spectrometry. Myricetin and quercetin exhibited the highest anti-α-glucosidase activity with IC₅₀ values of 0.02 and 0.06 mg/mL, respectively. These inhibitors manifested different types of inhibition manners against α-glucosidase via direct interaction with the amino acid residues. The results of structure-activity relationships indicated that an increase in the number of -OH on the B-ring greatly strengthened α-glucosidase inhibitory activity, but glucoside and rutinoside replacement on the C-ring obviously weakened this influence. Furthermore, a synergistic effect was observed between inhibitors with different inhibition manners.

Analysis of Phenolic Compounds in Buckwheat (Fagopyrum esculentum Moench) Sprouts Modified with Probiotic Yeast

Buckwheat sprouts are a source of various nutrients, e.g., antioxidant flavonoids, which have a positive effect on human health. This study analyzed the content of phenolic compounds and assessed their impact on the antioxidant and anti-inflammatory properties and dietary fiber in modified buckwheat sprouts. For this purpose, the buckwheat seeds were modified by adding Saccharomyces cerevisiae var. boulardii. The modified buckwheat sprouts showed a higher content of total phenol compounds (1526 µg/g d.w.) than the control sprouts (951 µg/g d.w.) and seeds (672 µg/g d.w.). As a consequence, a higher antioxidant activity and anti-inflammatory effect were noted. Probiotic-rich sprouts also had the highest content of total dietary fiber and its soluble fraction. A correlation between phenolic compounds and the antioxidant and anti-inflammatory effects, as well as dietary fiber, was shown. The interaction between dietary fiber and phenolic compounds affects the bioaccessibility, bioavailability, and bioactivity of phenolic compounds in food. The introduction of probiotic yeast into the sprouts had a positive effect on increasing their nutritional value, as well as their antioxidant and anti-inflammatory activity. As a consequence, the nutraceutical potential of the raw material changed, opening a new direction for the use of buckwheat sprouts, e.g., in industry.

Isolation of bioactive peptides and multiple nutraceuticals of antidiabetic and antioxidant functionalities through sprouting: Recent advances

The employment of proteases directly from enzymes or indirectly from microorganisms during fermentation for the purpose of proteolysis of food proteins has been the conventional trend for the derivation of bioactive peptides from food matrices. However, recent studies have shown that inherent protease enzymes can be activated for this activity for vegetable foods using the sprouting process. The benefits of ease of operation, and reduced processing costs are formidable advantages for the optimal consideration of this technique. On another note, the demand for functional foods with therapeutic health effects has increased in recent years. Globally, plant foods are perceived as dietetic choices bearing sufficient quantities of concomitant nutraceuticals. In this manuscript, the sprouting route for the isolation of peptides and glucosinolates, and for the enhancement of total phenolic contents, polyunsaturated fatty acid profiles, and other bioactive constituents was explored. Advances regarding the phytochemical transformations in the course of sprouting, the therapeutic functionalities, and microbiological safety concerns of vegetable sprouts are delineated. In addition, consumption of vegetable sprouts has been shown to be more efficient in supplying nutraceutical components relative to their unsprouted counterparts. Biochemical mechanisms involving the inhibition of digestive enzymes such as α-amylase, β-glucosidase, and dipeptidyl peptidase IV (DPP-IV), single electron transfer, and metal chelation, for impartation of health benefits, have been reported to occur from bioactive components isolated from vegetable sprouts. PRACTICAL APPLICATIONS: Sprouting initiates proteolysis of vegetable proteins for the release of bioactive peptides. Abiotic stresses can be used as elicitors during the sprouting process to achieve enhanced phytochemical profiles of sprouts. Sprouting is a relatively more convenient approach to the improvement of the health benefits of vegetable foods. Vegetable sprouts are potential for the management of metabolic syndrome disorders.

Phenolic compounds in common buckwheat sprouts: composition, isolation, analysis and bioactivities

Phenolic compounds in common buckwheat sprouts (CBSs) have gained research interest because of their multiple health benefits. Phenolic acids, flavanones, flavonols, flavan-3-ols, and anthocyanins are important bioactive components of CBS that exhibit biological activities, including anti-inflammatory, antioxidant, anti-proliferative, and immunomodulatory effects. The isolation and quantitative and qualitative analyses of these phenolic compounds require effective and appropriate extraction and analytical methods. The most recent analytical method developed for determining the phenolic profile is HPLC coupled with a UV-visible detector and/or MS. This review highlights the extraction, purification, analysis, and bioactive properties of phenolic compounds from CBS described in the literature.

Chemical Profile, Antimicrobial and Antioxidant Activity Assessment of the Crude Extract and Its Main Flavonoids from Tartary Buckwheat Sprouts

The purpose of this study was to investigate the major flavonoids content and bioactivities of Tartary buckwheat sprouts. The crude methanol extract (ME) of Tartary buckwheat sprouts was abundant in flavonoids, and six major flavonoids, including isoorientin, vitexin, isovitexin, rutin, quercetin, and kaemferol were successfully determined from the sprouts by the high-performance liquid chromatography (HPLC) method. Generally, the flavonoid content of buckwheat sprouts was in the order of rutin > quercetin > isovitexin > vitexin> isoorientin > kaemferol. The highest rutin content of the ME and sprout cultures was 89.81 mg/g and 31.50 mg/g, respectively. Antibacterial activity results indicated the ME displayed notable inhibitory activity against the five tested bacteria, and its minimum inhibitory concentration (MIC) values ranged from 0.8 mg/mL to 3.2 mg/mL. Among the six flavonoids, quercetin was the most active compound, which exhibited strong activity against all tested bacteria except for E. coli and S. epidermidis, with its MIC values ranging from 0.2 mg/mL to 0.4 mg/mL. For the antifungal activity assay, the ME of Tartary buckwheat sprouts and four flavonoids could significantly inhibit the spore germination of two pathogenic fungi, and their inhibitory efficiency was concentration dependent. Quercetin was the most active one, which significantly inhibited the spore germination of F. oxysporum f. sp. vasinfectum and F. oxysporum f. sp. cucumerinum, and its median effective inhibitory concentration (IC50) value was 42.36 and 32.85 µg/mL, respectively. The antioxidant activity results showed that quercetin, kaemferol, and rutin displayed excellent antioxidant activity in the DPPH radical scavenging test, and their IC50 value was calculated as 5.60, 16.23, and 27.95 µg/mL, respectively. This is the first report on the antimicrobial activity of the crude extract of Tartary buckwheat sprouts. These results indicated that the methanol extract of Tartary buckwheat sprouts could be used as a potential antimicrobial or antioxidant agent in the future.

Analysis of Flavonoid Metabolites in Buckwheat Leaves Using UPLC-ESI-MS/MS

Flavonoids from plants are particularly important in our diet. Buckwheat is a special crop that is rich in flavonoids. In this study, four important buckwheat varieties, including one tartary buckwheat and three common buckwheat varieties, were selected as experimental materials. The total flavonoid content of leaves from red-flowered common buckwheat was the highest, followed by tartary buckwheat leaves. A total of 182 flavonoid metabolites (including 53 flavone, 37 flavonol, 32 flavone C-glycosides, 24 flavanone, 18 anthocyanins, 7 isoflavone, 6 flavonolignan, and 5 proanthocyanidins) were identified based on Ultra Performance Liquid Chromatography–Electrospray Ionization–Tandem Mass Spectrometry (UPLC-ESI-MS/MS) system. Through clustering analysis, principal component analysis (PCA), and orthogonal signal correction and partial least squares-discriminant analysis (OPLS-DA), different samples were clearly separated. Considerable differences were observed in the flavonoid metabolites between tartary buckwheat leaves and common buckwheat leaves, and both displayed unique metabolites with important biological functions. This study provides new insights into the differences of flavonoid metabolites between tartary buckwheat and common buckwheat leaves and provides theoretical basis for the sufficient utilization of buckwheat.

Buckwheat and buckwheat enriched products exert an anti-inflammatory effect on the myofibroblasts of colon CCD-18Co

Buckwheat (BW) constitutes a good source of bioactive components that show anti-inflammatory effects in vitro and in vivo. The use of functional foods in the prevention and treatment of inflammatory bowel diseases (IBDs) has aroused increasing interest. This study investigates the effect of in vitro digested BW and BW-enriched products (BW-enriched wheat breads, roasted BW groats -fermented and non-fermented-, and BW sprouts) on colon myofibroblasts, the cells involved in the regulation of inflammatory response in the intestine. The cells were treated with different digested-BW products, alone or together with TNF-α (20 ng mL-1), and the effects on the cell migration, mitochondrial membrane potential and cell cycle, processes altered during intestinal inflammation, were investigated. A significant reduction in TNF-α-induced migration (25.5%, p < 0.05) and attenuation of the TNF-α-altered cell cycle (p < 0.05) was observed in myofibroblasts treated with BW-enriched white wheat bread. These results contribute to extend the beneficial effects derived from BW bioactive compounds, and suggest that BW consumption can exert beneficial effects on IBDs.

Chemical composition and health effects of Tartary buckwheat

Tartary buckwheat (Fagopyrum tataricum) contains a range of nutrients including bioactive carbohydrates and proteins, polyphenols, phytosterols, vitamins, carotenoids, and minerals. The unique composition of Tartary buckwheat contributes to their various health benefits such as anti-oxidative, anti-cancer, anti-hypertension, anti-diabetic, cholesterol-lowering, and cognition-improving. Compared with the more widely cultivated and utilised common buckwheat (F. esculentum), Tartary buckwheat tends to contain higher amounts of certain bioactive components such as rutin, therefore, showing higher efficiency in preventing/treating various disorders. This review summarises the current knowledge of the chemical composition of Tartary buckwheat, and their bio-functions as studied by both in vitro and in vivo models. Tartary buckwheat can be further developed as a sustainable crop for functional food production to improve human health.