Treasure from garden: Bioactive compounds of buckwheat

Bioactive compounds, health benefits, and industrial applications of Tartary buckwheat (Fagopyrum tataricum)

Tartary buckwheat belongs to the family Polygonaceae, which is a traditionally edible and medicinal plant. Due to its various bioactive compounds, the consumption of Tartary buckwheat is correlated to a wide range of health benefits, and increasing attention has been paid to its potential as a functional food. This review summarizes the main bioactive compounds and important bioactivities and health benefits of Tartary buckwheat, emphasizing its protective effects on metabolic diseases and relevant molecular mechanisms. Tartary buckwheat contains a wide range of bioactive compounds, such as flavonoids, phenolic acids, triterpenoids, phenylpropanoid glycosides, bioactive polysaccharides, and bioactive proteins and peptides, as well as D-chiro-inositol and its derivatives. Consumption of Tartary buckwheat and Tartary buckwheat-enriched products is linked to multiple health benefits, e.g., antioxidant, anti-inflammatory, antihyperlipidemic, anticancer, antidiabetic, antiobesity, antihypertensive, and hepatoprotective activities. Especially, clinical studies indicate that Tartary buckwheat exhibits remarkable antidiabetic activities. Various tartary buckwheat -based foods presenting major health benefits as fat and blood glucose-lowering agents have been commercialized. Additionally, to address the safety concerns, i.e., allergic reactions, heavy metal and mycotoxin contaminations, the quality control standards for Tartary buckwheat and its products should be drafted and completed in the future.

BIOACTIVATED BUCKWHEAT IN TERMS OF ITS NUTRITIONAL VALUEBIOACTIVATED BUCKWHEAT IN TERMS OF ITS NUTRITIONAL VALUE

Buckwheat is a gluten-free pseudocereal crop consumed as functional food in some regions. Traditionally, buckwheat grain is used to make buckwheat groats and flour. Bioactivation improves the nutritional value of buckwheat grain by activating hydrolytic enzymes that make nutrients available for the plant’s growth and for the human body. The article contains research on the content of nutrients in bioactivated buckwheat grain of the Kupava variety grown in Belarus. The study examined hulled buckwheat kernels (not steamed) of the botanical variety Kupava, cream-coloured with a greenish hue, with the humidity 12.0%, and with the proportion of sound kernels 99.4%. At the first stage of germination, bioactivated buckwheat grain was obtained in 48 hours. It had the following characteristics: humidity (39.2±1.0)%, sprout size (2.0±0.5) mm. According to the organoleptic parameters, the grain had a pleasant sweetish taste and a subtle nutty aftertaste. The components of bioactivated buckwheat grain that provide a person with the largest amounts of macronutrients are starch (31.84±0.6)%, sugars (5.1±0.3)%, and protein (5.67±0.02)%. Bioactivated buckwheat grain contains all essential amino acids (30.5% of the total quantity of amino acids). The limiting amino acid is threonine (amino acid score 31.7%). Of nonessential amino acids, there is a high content of glutamic acid (1.0972 g per 100 g). The difference ratio of the amino acid score is 54.75%, the potential biological value of the protein is 45.25%. 100 g of sprouted buckwheat grain contains 48.5% of the daily requirement of manganese, 24.0% of copper, 18.9% and 34.0% of iron (for women and for men respectively), about 23.0% of the daily requirement of vitamin B1, and 12.7% of the daily requirement of vitamin E. Besides, bioactivated buckwheat grain contains fibre (6.5% of the daily requirement on average). Bioactivated buckwheat grain can be consumed as a meal in its own right, as a side dish, as an additive to salads and fermented dairy products, or as a dessert when mixed with fruit purée, honey, or dried fruit.

Milling fractions composition of common (Fagopyrum esculentum Moench) and Tartary (Fagopyrum tataricum (L.) Gaertn.) buckwheat

Buckwheat is a pseudocereal with important nutritional qualities and great potential for broad consumption. The study aimed to determine the biochemical composition, antioxidant properties and multi-mineral composition of the whole grains, hulls, bran, and the light flour of common (Fagopyrum esculentum Moench) and Tartary (Fagopyrum tataricum (L.) Gaertn.) buckwheat harvested in two consecutive years. Significant differences between fractions of both species were observed. On the other hand, the differences between the production years were not so significant. Biochemical and multi-mineral compositions of common and Tartary buckwheat were comparable, while significant differences between species were observed in antioxidant properties. The antioxidant potential (AOP), total phenolic content (TPC), and total flavonoid content (TFC) were higher in all fractions of Tartary buckwheat compared to individual fractions of common buckwheat. Fourteen minerals were quantified in fractions. Contents of all major minerals and most of the trace minerals were the highest in bran fraction.

Breeding Buckwheat for Nutritional Quality in the Czech Republic

Buckwheat is a nutritionally valuable crop, an alternative to common cereals also usable in gluten-free diets. The selection of buckwheat genotypes suitable for further breeding requires the characterization and evaluation of genetic resources. The main objective of this work was to evaluate selected phenotypic and morphological traits using international buckwheat descriptors, including total phenolic content and antioxidant activity, on a unique set of 136 common buckwheat accessions grown in 2019-2020 under Czech Republic conditions. In addition, UHPLC-ESI- MS/MS was used to analyze a wide spectrum of 20 phenolic compounds in buckwheat seeds, including four flavanols, three phenolic acids, seven flavonols, four flavones, and two flavanones. Significant differences among years and genotypes were observed for morphological traits (plant height and 1000-seed weight) and antioxidant activity, as well as levels of observed chemical compounds. Antioxidant activity, crude protein content, plant height and rutin content were characterized by higher mean values in 2020 than in 2019 and vice versa for total polyphenol content and 1000-seed weight. Crude protein content was the most stable across years, while total polyphenol content and rutin content varied greatly from year to year. The most abundant phenolic compounds were rutin, hyperoside, epicatechin, catechin, vitexin, isovitexin, orientin and isoorientin. Protein content was negatively correlated with plant height, catechin and epicatechin content. On the other hand, AA and TPC were positively correlated with rutin, hyperoside and chlorogenic acid. Five accessions showed high stability of the evaluated traits under changing conditions within both years of observation. These materials can be used in breeding programmes aimed at improving buckwheat genotypes with emphasis on quality traits.

Statistical Approach to Potentially Enhance the Postbiotication of Gluten-Free Sourdough

Fermented products are permanently under the attention of scientists and consumers, both due to nutritional importance and health promoting effects. The fermented functional foods contribute to a more balanced diet and increase the immune responses (among many other health effects) with positive implications for quality of life. In this sense, improving the sourdough’s fermentation to boost the biotic (postbiotic and paraprobiotic) properties of the sourdough-based products has positive impacts on the nutritional and functional properties of the final baked products. These enhanced sourdoughs can be obtained in controlled fermentation conditions and used as sourdough bread improvers or novel bioingredients. In this context, our work aimed to optimize, using statistical tools, a gluten-free sourdough based on chickpea, quinoa, and buckwheat fermentation with selected lactic acid bacteria (LAB) to enhance its postbiotic properties. The most important biotechnological parameters were selected by Plackett–Burman Design (PBD) and then Response Surface Methodology (RSM) was applied to evaluate the interactions between the selected factors to maximize the gluten-free sourdough’s properties. As a result, the optimized fermented sourdough had antimicrobial activity with inhibition ratios between 71 and 100% against the Aspergillus niger, Aspergillus flavus, Penicillium spp. molds and against the Bacillus spp endospore-forming Gram-positive rods. The optimized variant showed a total titratable acidity (TTA) of 40.2 mL NaOH 0.1N. Finally, the high-performance liquid chromatography (HPLC) analysis highlighted a heterofermentative profile for the organic acids from the optimized sourdough. Among flavonoids and polyphenols, the level of caffeic and vanillic acids increased after lactic acid fermentation. The comparison between the optimized sourdough and the control evidenced significant differences in the metabolite profiles, thus highlighting its potential postbiotication effect.

Changes in Agricultural Performance of Common Buckwheat Induced by Seed Treatment with Cold Plasma and Electromagnetic Field

The aim of this study was to determine the effects of pre-sowing seed treatment with cold plasma (CP) and an electromagnetic field (EMF) on the agricultural performance of two cultivars of common buckwheat (Fagopyrum esculentum Moench)—‘VB Vokiai’ and ‘VB Nojai’. For this, the effects of CP and EMF on seed germination, plant growth in the field, photosynthetic efficiency, biomass production, seed yield, and the amount of secondary metabolites and minerals in the harvested seeds were estimated. Although the percentage of seedlings that emerged under field conditions decreased by 11–20%, seed treatments strongly improved buckwheat growth and yield. Irrespective of differences in the dynamics of changes in the growth and photosynthetic activity between the two cultivars, the weight of seeds collected per plant for both cultivars was significantly higher (up to 70–97%) compared to the control. The biochemical composition of the harvested seeds (Fe, Zn, quercetin content) was also altered by seed treatments. Thus, pre-sowing treatment of buckwheat seeds with CP and EMF substantially stimulated plant growth in the field, increased biomass production, seed yield and nutritional quality. The results obtained strongly support the idea that plant seed treatment with physical stressors has great potential for use in agriculture.

Tartary Buckwheat in Human Nutrition

Tartary buckwheat (Fagopyrum tataricum Gaertn.) originates in mountain areas of western China, and it is mainly cultivated in China, Bhutan, northern India, Nepal, and central Europe. Tartary buckwheat shows greater cold resistance than common buckwheat, and has traits for drought tolerance. Buckwheat can provide health benefits due to its contents of resistant starch, mineral elements, proteins, and in particular, phenolic substances, which prevent the effects of several chronic human diseases, including hypertension, obesity, cardiovascular diseases, and gallstone formation. The contents of the flavonoids rutin and quercetin are very variable among Tartary buckwheat samples from different origins and parts of the plants. Quercetin is formed after the degradation of rutin by the Tartary buckwheat enzyme rutinosidase, which mainly occurs after grain milling during mixing of the flour with water. High temperature treatments of wet Tartary buckwheat material prevent the conversion of rutin to quercetin.

Implications of Fagopyrin Formation In Vitro by UV Spectroscopic Analysis

The present work aims at studying the possible biosynthesis of fagopyrin in buckwheat plants with an attempt to address the existing gaps. The developed method of differential spectrophotometry can be used for identification of naphthodianthrones fagopyrins. It was found that in the vegetative mass of buckwheat plants, fagopyrin precursor-2-(piperidine-2-yl)-emodindianthron could be present. As fagopyrin can be produced by light effect, the temperature factor may influence the formation of protofagopyrin in vitro. An optimum temperature range was estimated for protofagopyrin formation. A possible fagopyrin biosynthesis under in vitro conditions was suggested.

Metabolite profiling, antioxidant and α-glucosidase inhibitory activities of buckwheat processed by solid-state fermentation with Eurotium cristatum YL-1

Buckwheat was processed by solid-state fermentation (SSF) with the probiotic fungal strain Eurotium cristatum YL-1. The effects of SSF on the phytochemical content, as well as the antioxidant and α-glucosidase inhibitory activities, on buckwheat were revealed. Metabolite differences between non-fermented buckwheat (BW) and E. cristatum fermented buckwheat (FBW) were investigated by LC-MS/MS-based untargeted metabolomics. Results showed that 103 and 68 metabolites remarkably differed between BW and FBW in positive and negative ionization modes, respectively. Most phenolic compounds and alkaloids were significantly up-regulated during SSF. Hydrolytic enzymes (i.e., β-glucosidase, α-amylase, protease, and cellulase) were produced by the filamentous fungus E. cristatum during SSF. In vitro spectrophotometric assays demonstrated that the total phenolics content, ferric reducing antioxidant power, reducing power, scavenging activities of DPPH radical and ABTS⁺, and α-glucosidase inhibitory activity of buckwheat were considerably enhanced after processing by SSF with E. cristatum. Additionally, solvents with different polarities significantly influenced the antioxidant and α-glucosidase inhibitory activities of buckwheat extracts. Our study indicated that processing by SSF with E. cristatum can greatly improve the phytochemical components of buckwheat and consequently contribute to its antioxidant and α-glucosidase inhibitory activities. SSF with E. cristatum is an innovative method for enhancing the health-promoting components and bioactivities of buckwheat.

Comparison of Plant Morphology, Yield and Nutritional Quality of Fagopyrum esculentum and Fagopyrum tataricum Grown under Field Conditions in Belgium

Buckwheat is a pseudocereal with high nutritional and nutraceutical properties. Although common buckwheat (Fagopyrum esculentum) is the main cultivated species, Tartary buckwheat (Fagopyrum tataricum) is gaining interest. In this paper, we compared plant growth, yield-related parameters and seed nutritional qualities of two varieties of F. esculentum and F. tataricum under field conditions in Belgium. Fagopyrum esculentum flowered earlier, produced less nodes, less branches, less inflorescences, but more flowers per inflorescence than F. tataricum. The yield was higher in F. tataricum, while the thousand-grain weight was higher in F. esculentum. Yield ranged between 2037 kg/ha and 3667 kg/ha depending on the species and year. Regarding nutritional qualities, seeds of F. esculentum contained more proteins (15.4% vs. 12.8%) than seeds of F. tataricum although their amino acid profile was similar. Seeds of F. esculentum contained also more Mg (1.36 vs. 1.15 mg/g dry weight (DW)) and less Fe (22.9 vs. 32.6 µg/g DW) and Zn (19.6 vs. 24.5 µg/g DW) than F. tataricum. The main difference between seed nutritional quality was the concentration of flavonoids that was 60 times higher in F. tataricum than in F. esculentum. Both species grow well under Belgian conditions and showed good seed quality.

Breeding Buckwheat for Increased Levels of Rutin, Quercetin and Other Bioactive Compounds with Potential Antiviral Effects

Common buckwheat (Fagopyrum esculentum Moench) and Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) are sources of many bioactive compounds, such as rutin, quercetin, emodin, fagopyrin and other (poly)phenolics. In damaged or milled grain under wet conditions, most of the rutin in common and Tartary buckwheat is degraded to quercetin by rutin-degrading enzymes (e.g., rutinosidase). From Tartary buckwheat varieties with low rutinosidase activity it is possible to prepare foods with high levels of rutin, with the preserved initial levels in the grain. The quercetin from rutin degradation in Tartary buckwheat grain is responsible in part for inhibition of α-glucosidase in the intestine, which helps to maintain normal glucose levels in the blood. Rutin and emodin have the potential for antiviral effects. Grain embryos are rich in rutin, so breeding buckwheat with the aim of producing larger embryos may be a promising strategy to increase the levels of rutin in common and Tartary buckwheat grain, and hence to improve its nutritional value.