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Fagopyrum esculentum Möench, commonly called buckwheat, is a traditional agricultural product historically grown in Asia and Central and East Europe [50]. It belongs to the family Polygonaceae, unlike most other cereals [51, 52]. However, buckwheat seeds can be classified as a cereal due to their chemical and usage properties, similar to cereal grains [53]. It is also known as a pseudocereal because of its differences from cereals [50, 53, 54]. The fundamental difference in terms of its structure is that buckwheat is dicotyledonous, as opposed to monocotyledonous species of cereal. The buckwheat seed’s embryo is found within the endosperm’s center, having two cotyledons. The embryo, endosperm, and seed coat are tightly surrounded by the hull (also known as the pericarp), which is hard and fibrous. Meanwhile, the walls of the cells that form the endosperm are quite thin [50, 55, 56].

Although numerous species of buckwheat are harvested globally, only 9 of them possess value for agricultural purposes [57–59]. There are varieties of buckwheat that can be harvested in summer, in autumn, and in the middle of the two seasons [53]. In general, two species are utilized globally: that known as common buckwheat (F. esculentum) and that known as Tartary buckwheat (F. tataricum). While the former is grown in more widely spread and diverse environments, the latter is farmed in mountainous areas [57–59]. Buckwheat seeds are triangular and have blackcolored hulls that cover the kernels, with the kernels ranging in color from white to light shades of green. Color saturation opens towards the kernel’s innermost layers. The density of the hull is lower than that of water; therefore, hulls can be removed more easily from kernels [57, 59]. Hull hardness varies among different species. F. esculentum is generally less hard than F. tataricum. F. esculentum has a harsher flavor, while F. tataricum is slightly bitter. The bitter compounds in F. tataricum seeds can be extracted by assorted techniques, such as various chemical methods and isoelectric precipitation [57, 60].

Buckwheat contains relatively high amounts of dietary fiber, protein, some types of vitamins, and some types of minerals in comparison to other types of wheat or rice [53]. Protein levels of buckwheat range from 12% to 18.9% [61, 62]. The proteins found in buckwheat possess well-balanced amino acids and generally have high biological value [47, 61]. Buckwheat flour has lower ratios of glutelin and prolamin but higher ratios of globulin and albumin [53, 63, 64]. Gluten content is either very little or nonexistent [53, 65]. Thus, buckwheat plays an important dietary role as a gluten-free option that is suitable for people afflicted with celiac disease [53]. Starch levels are in the range of 59%–70% while lipid levels range from 1.5% to 4%. More than 40% of the 80% unsaturated fatty acids in its structure are polyunsaturated fatty acids (PUFA) [47, 59]. Multiple studies have reported that buckwheat’s total polyphenol content is 6.8–20.7 mg GA/g, while free polyphenol content is 4.5–17.1 mg GA/g, insoluble dietary fiber content is 2.3%–8.6%, soluble dietary fiber content is 1.4%–3.4%, and finally, total dietary fiber content is 3.6%–10.6% [62, 66]. Buckwheat is also a valuable resource for including macroelements such as Na, K, Mg, and Ca [47, 67] and microelements as Se, Zn, Mn, and Cu into the human diet [47, 68]. It is a grain rich in vitamins B₁ and B₂ [69, 70]. The significant contents and potential antioxidant activities of rutin and other polyphenols are very important for the dietary value of buckwheat [47, 69, 71]. In its grains and hulls, 6 flavonoids have been identified, including rutin, quercetin, orientin, vitexin, isoorientin, and isovitexin. On the other hand, only rutin and isovitexin have been determined in buckwheat seeds [51, 59, 72].

The consumption of buckwheat and buckwheat products is associated with many healthy biological activities including antidiabetic, anticancer, hypocholesterolemic, anti-inflammatory, neuroprotective, and hypotensive effect. Buckwheat proteins and polyphenols are supposed to be responsible for these effects [73, 74]. It has been accepted that some of the effects mentioned can be related to these two compounds in buckwheat. However, recently identified action mechanisms may also be exerting the health-promoting benefits that have been observed in cases of buckwheat consumption [74–76].