Phytochemicals and biofunctional properties of buckwheat: A review

Abstract

A growing trend for nutraceutical and gluten-free cereal-based products highlights the need for development of new products. Buckwheat is one of the potential candidates for such products and the present paper reviews the functional and nutraceutical compounds present in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). The vital functional substances in buckwheat are flavonoids, phytosterols, fagopyrins, fagopyritols, phenolic compounds, resistant starch, dietary fibre, lignans, vitamins, minerals and antioxidants, which make it a highly active biological pseudocereal. Cholesterol-lowering effects that lessen the problems of constipation and obesity are important health benefits that can be achieved through the functional substances of buckwheat.

Full text

CROPS AND SOILS REVIEW
Phytochemicals and biofunctional properties of buckwheat:
a review
A. AHMED
1
,N.KHALID
2
*, A. AHMAD
1
,N.A.ABBASI
3
,M.S.Z.LATIF
4
AND M. A. RANDHAWA
5
1
Department of Food Technology, Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi 46300, Pakistan
2
Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1,
Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
3
Department of Horticulture, Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi 46300, Pakistan
4
Department of Biochemistry, Khawaja Muhammad Safdar Medical College, Sialkot, Pakistan
5
National Institute of Food Science and Technology, University of Agriculture, Faisalabad-38040, Pakistan
(Received 27 June 2012; revised 18 February 2013; accepted 1 March 2013)
SUMMARY
A growing trend for nutraceutical and gluten-free cereal-based products highlights the need for development of
new products. Buckwheat is one of the potential candidates for such products and the present paper reviews the
functional and nutraceutical compounds present in common buckwheat (Fagopyrum esculentum) and tartary
buckwheat (Fagopyrum tataricum). The vital functional substances in buckwheat are flavonoids, phytosterols,
fagopyrins, fagopyritols, phenolic compounds, resistant starch, dietary fibre, lignans, vitamins, minerals and
antioxidants, which make it a highly active biological pseudocereal. Cholesterol-lowering effects that lessen the
problems of constipation and obesity are important health benefits that can be achieved through the functional
substances of buckwheat.
INTRODUCTION
Buckwheat (Fagopryum esculentum Monch) is derived
from the Anglo-Saxon boc (beech) and whoet (wheat)
because it resembles the beech nut (Edwardson 1995).
It is classified as a pseudocereal because of the
similarity to conventional cereals in its use and
chemical composition (Campbell 1997). Historically,
it was a very popular food during the 17th–19th
centuries, although it was later neglected during
the 20th century in Western countries because of
competition from wheat (Cawoy et al. 2008). Yet it
is well recognized as a potential functional food
source in some countries, such as China, Japan and
Taiwan.
Buckwheat has a powerful ecological adaptability
that allows the plant to grow in almost all kinds
of extreme environments (Li & Zhang 2001). Major
cultivation areas are located in Asia and particularly in
southeast Asia, where crops are grown on marginal
and fairly unproductive land. In these areas, it is often
cultivated as a subsistence crop with barley, often
at higher altitudes. Tartary and common buckwheat
exhibit different growth behaviours: tartary buckwheat
is a frost-tolerant crop and is generally grown at higher
altitudes, whereas common buckwheat is grown at
lower altitudes. In many areas, the trend is for the
replacement of common buckwheat, which has a
lower yielding ability and lacks frost tolerance, with
finger millet or other crops (Campbell 1997).
Buckwheat is a dicotyledon and belongs to the
family Polygonaceae. Its seeds are brown in colour,
irregularly shaped and have four triangular surfaces.
Buckwheat seeds are smaller than soybean seeds by
about a factor of ten (thousand grain weight of 20 and
200 g, respectively). The seeds germinate and emerge
rapidly when planted in warm soil, typically in 3–4
days. Plants grow rapidly, producing small heart-
shaped leaves with slender, hollow stems. Flowering
begins c. 3 weeks after planting and is prolific for a
few weeks, before gradually tapering off as the plant
matures. At the peak of flowering, a buckwheat field
is a striking sea of white petals. After a flower is
pollinated, a full-sized seed will form within 10 days,
* To whom all correspondence should be addressed. Email:
nauman_khalid120@yahoo.com
Journal of Agricultural Science, Page 1 of 21. ©Cambridge University Press 2013
doi:10.1017/S0021859613000166

although that seed will need another 1–2 weeks to
reach maturity. Seeds appear and mature earlier on the
lower stem, with seed development continuing up the
stem as the plant matures. Plant height and speed of
maturity depend on planting date. If planted early in
the summer and given good fertility, plants will usually
be at least 1 m tall, and may take 11–12 weeks to
mature. If planted in the latter part of July, buckwheat
will mature in c.9–10 weeks and will be shorter,
c. 0·76 m on good soils and 0·61 m tall, or less, on poor
soils. A hot, dry period during plant development will
limit the vigour and size of the crop. Buckwheat grows
best on soils that are neither too compacted, nor too
coarse or sandy. It can tolerate wet soils to a slight
degree, but will generally fair better on soils where
drainage is adequate. Buckwheat does not require
highly fertile soils, but it benefits from having modest
levels of nitrogen (N) fertility (Ye & Guo 1992; Ohnishi
& Matsuoka 1996; Campbell 1997). The cultivation of
buckwheat has numerous advantages, such as being
easy to cultivate, having a short growing period
(70–90 days) and a longer storage time without
alteration due to its phenolic and antioxidant proper-
ties. The major disadvantages of buckwheat cultiva-
tion include lower grain yield, as its seeds ripen more
asynchronously, and as a result there are many more
technical harvesting problems compared with cereals.
Similarly, buckwheat sets seed quickly and may, if
allowed to go to seed, become a weed problem in
subsequent crops.
Many species of buckwheat are grown around
the world; however, only nine have agricultural and
nutritional value (Krkoskova & Mrazova 2005). Out
of these, only two species are used as food around
the world; common buckwheat (F. esculentum) and
tartary buckwheat (F. tataricum). Detailed classifi-
cation is presented in Fig. 1. China, the Russian
Federation, Ukraine and Kazakhstan are the leading
producers of common buckwheat (Li & Zhang 2001;
Bonafaccia et al. 2003b) with production also in
Slovenia, Poland, Hungary and Brazil (Kreft et al.
1999).The current leading producers of buckwheat,
together with yield and area harvested are presented in
Table 1 (FAOSTAT 2013).
There is interest in buckwheat for the production of
nutraceutical preparations (He et al. 1995) with the
potential for functional food development that may
provide health benefits beyond basic nutrition (Li &
Zhang 2001; Bonafaccia et al. 2003a,b). The present
review collates and synthesizes the available infor-
mation on important aspects related to the functional
potential of buckwheat that is being produced in
most parts of Asia. The emphasis is on exploiting the
importance of buckwheat as a potential functional
food and for utilization in the prevention and treatment
of human diseases.
Vernacular names in major languages
Buckwheat has been named by many people during
the history of its development. According to some
researchers, the ancient Yi people of the Yunnan
province called buckwheat er, common buckwheat er
chi, and tartary buckwheat er ka (Li & Zhang 2001).
Buckwheat names are important in order to trace its
migration through Europe and Asia. Today, common
buckwheat is called ogal in India, mite phapar in
Nepal, soba (traditional noodles) in Japan, jawas in
Pakistan, tian qiao mai in Mandarin, jare in Bhutan,
grecicha kul’furnaja in Russia and tatarka gryka or
poganka in Poland. In French, it is called sarrasin,
ble noir, renouee or bouquette, in Italy fagopiro,
grano saraceno, Sarasin or faggina and in Germany
Fig. 1. Classification of buckwheat.
Table 1. World’s largest producers of buckwheat
(production year 2011) (FAOSTAT 2013)
Countries
Production
(tonnes)
Yield
(t/ha) Area (ha)
Russian
Federation
800380 0·949 843200
China 720000* 0·962 7 48000*
Poland 92985 1·227 75768
France 91000 2·935 31000
USA 79554†1·029 77 244†
Brazil 57000* 1·239 46000*
Belarus 44456 1·091 40734
Kazakhstan 37400 1·274 66780
Japan 32000 0·567 56400
Lithuania 26 000 0·955 27 200
World total 2294 178‡0·885 2 327409‡
* FAO estimates.
†Data based on imputation methodology.
‡Aggregate data (official, semi-official and estimated).
2 A. Ahmed et al.

Buchweizen or Heidekorn (Hammer 1986; Campbell
1997).
Tartary buckwheat is called phapar in India, tite
phapar in Nepal, bjo in Bhutan and brow in Pakistan.
It is of interest to note that in both China and Nepal,
common buckwheat is referred to as sweet buckwheat,
while tartary buckwheat is called bitter buckwheat
(Ohnishi 1993).
CHEMISTRY OF BUCKWHEAT
Chemical composition of buckwheat
Buckwheat contains a variety of nutrients in its grains.
The main compounds are proteins, rutin, polysacchar-
ides, dietary fibre, lipids, polyphenols and micro
nutrients (minerals and vitamins) (Kim et al. 2004;
Qin et al. 2010). The total content of these components
depends on different factors, such as the species and
the environment (Barta et al. 2004;Qinet al. 2010).
Whole buckwheat groats (the hulled seeds) contain
550 mg/g starch, 120 mg/g protein, 70 mg/g total
dietary fibre (TDF), 40 mg/g lipid, 20 mg/g soluble
carbohydrates and 180 mg/g other components such
as organic acids, phenolic compounds, tannins, phos-
phorylated sugars, nucleotides and nucleic acids
(Im et al. 2003; Bonafaccia et al. 2003b). Detailed
composition of buckwheat flour in comparison with
wheat flour is presented in Table 2.
Buckwheat flour is mostly derived from the endo-
sperm consisting of 700–750 mg/g starch, 60–100 mg/g
proteins, 20–240 mg/g TDF, 10–30 mg/g lipids and
130 mg/g other components, while bran with little
central endosperm consists of 360 mg/g proteins,
180 mg/g starch, 150 mg/g TDF, 110 mg/g lipids,
60 mg/g soluble carbohydrates and 70 mg/g other
components (Bonafaccia et al. 2003a; Skrabanja
et al. 2004; Alvarez-Jubete et al. 2009; Lin et al.
2009;Qinet al. 2010). Buckwheat bran is a rich source
of dietary fibre, and in particular bran with hull
fragments contains 400 mg/g TDF, of which 250 mg/g
is soluble dietary fibre (SDF), while bran without hull
fragments contains 160 mg/g TDF, of which 750 mg/g
is soluble. Bran fractions also contain the highest
concentration of protein among all milling fractions
(Steadman et al. 2001b; Krkoskova & Mrazova 2005).
The proximate composition of buckwheat is well in
line with other cereals and pseudocereals consumed
all over the world (Table 3). It is important to note
that buckwheat fibre is free of phytic acid, a major
anti-nutritional factor in common wheat (Steadman
et al. 2001a). Soluble dietary fibre concentration
Table 2. Proximate composition (mg/g DW) of buckwheat flour, wheat flour and quinoa flour (Ogungbenle
2003; Lin et al. 2009; Qin et al. 2010)
Proximate
Husked
buckwheat
flour
Unhusked
buckwheat
flour
Tartary
buckwheat
flour
Common
buck wheat
flour
Wheat
flour
Quinoa
flour
Carbohydrates 616 770 702 737 835 583
Crude ash 17 16 22 22 12 12
Crude fat 22 22 28 28 26 63
Crude fibre 238 103 26 23 20 95
Crude protein 107 90 105 103 106 135
Table 3. Comparison of buckwheat flour composition (m/g DW) with other commonly used cereals and
pseudo-cereals (Bonafaccia & Fabjan 2003; Czerwin
´ski et al. 2004; Vega-Gálvez et al. 2010)
Crop Protein Ash Lipid Soluble fibre Insoluble fibre Total fibre
Wheat 115 17 10 10 15 24
Common buckwheat 110 26 34 12 53 65
Tartary buckwheat 103 18 25 5 58 63
Oats 126 18 71 33 49 82
Rye 117 15 18 36 100 136
Quinoa 165 38 61 43 96 139
Amaranth 139 21 73 63 82 145
Nutritional profile of buckwheat 3

(77–92 mg/g) in buckwheat bran is higher when
compared with wheat bran (43 mg/g), or even oat
bran (72 mg/g). In uncooked buckwheat groats, starch
resistant to digestion comprises 303–380 g/100 g of
total starch, but after cooking RS is 70–100 mg/g
(Skrabanja & Kreft 1998; Steadman et al. 2001b). It was
observed that soluble carbohydrates are concentrated
in the embryo, with a low concentration in the
endosperm but higher in the bran. Since starch is
concentrated in the central endosperm, light-coloured
flour, grits and whole groats are mostly composed of
starch (Steadman et al. 2001b).
Fatty acid composition in buckwheat
The lipids in whole buckwheat, buckwheat flour,
steamed and stored buckwheat have been reviewed by
several researchers (Pomeranz & Lorenz 1983). Seeds
of common buckwheat contain 15–37 mg/g total lipids
(Campbell 1997). The highest concentration is in
the embryo at 70–140 mg/g and the lowest is in the
hull at 4–9 mg/g. Groats or dehulled seeds of Mancan,
Tokyo and Manor buckwheat contain 21–26 mg/g
total lipids, of which 810–850 mg/g are neutral lipids,
80–110 mg/g are phospholipids and 30–550 mg/g are
glycolipids (Campbell 1997). The major fatty acids
of common buckwheat are palmitic, oleic, linoleic,
stearic, linolenic, arachidic, behenic and lignoceric
(Table 4). The long-chain acids arachidic, behenic and
lignoceric, which represent c. 80 mg/g of the total
acids in buckwheat, are only minor components or
are not present in cereals. Buckwheat contains about
the same amount of total lipids as wheat rye (Becker
2008). In buckwheat, the neutral lipids constitute
810–850 mg/g of the total lipids, compared with
c. 350 mg/g in wheat and rye. The major classes of
fatty acids of all cultivars and lipid classes were
palmitic (16: 0), oleic (18: 1) and linoleic (18: 2).
In buckwheat, lipids are also concentrated in the
embryo, making the bran the most lipid-rich fraction
during milling. Triacylglycerides are the main com-
ponent of the lipid fraction; linoleic, oleic and palmitic
account for 880 mg/g of total fatty acids (Horbowicz &
Obendorf 1992). Buckwheat is nutritionally superior in
fatty acid composition to cereal grains with 800 mg/g
unsaturated fatty acids, out of which 40 mg/g of fatty
acids are polyunsaturated (Steadman et al. 2001a).
In another study by Kim et al. (2001) total saturated
fatty acid was 200 mg/g, while unsaturated fatty acid
was 790 mg/g, with a major fraction of 460 mg/g
linoleic acid.
Proteins and amino acids in buckwheat
In buckwheat seeds, the protein content ranges from
85·1 to 188·7mg/g depending on the variety (Aubrecht
& Biacs 2001; Li & Zhang 2001; Krkoskova & Mrazova
2005). The buckwheat proteins include albumin,
globulin, prolamin and glutelin (Ikeda et al. 1999;
Ikeda & Asami 2000), but the relative content of
these individual protein fractions show considerable
variation and are dependent on variety. Buckwheat
protein consists of 180 mg/g albumin, 430 mg/g
globulin, 8 mg/g prolamin, 230 mg/g glutelin and
50 mg/g other nitrogen residues (Javornik & Kreft
1984; Ikeda et al. 1991; Ikeda & Asami 2000). It is
generally recognized that albumin and globulin are
the major storage proteins in buckwheat seeds, and
prolamin and glutelin content are very low (Guo & Yao
2006). The major storage proteins from common
buckwheat seeds, including 8S and 13S globulins,
and 2S albumins, have been characterized (Radovic
et al. 1996,1999; Fujino et al. 2001; Milisavljevic et al.
2004). Salt-soluble 13S globulin has a hexameric
structure with disulphide-bonded subunits composed
of acidic and basic polypeptides with molecular
masses between 43 and 68, 57 and 58 and 26 and
36 kDa (Radovic et al. 1996); 2S albumins are com-
posed of polypeptides of molecular mass from 8
to 16 kDa (Radovic et al. 1999). Buckwheat protein
isolate (BPI) is composed mainly of globulin and
albumin fractions. Tang & Wang (2010) studied the
conformational properties of globulin and albumin
fractions from common buckwheat seeds and com-
pared them with those of BPI; they concluded that
albumin from buckwheat seed had a higher content
Table 4. Fatty acid profile (mg/g) of tartary and
common buckwheat (Mazza 1988; Tsuzuki et al.
1991; Becker 2008; Gulpinar et al. 2011)
Fatty
acids
Tartary
buckwheat
Common
buckwheat
C16:0 171 186
C18:0 21 19
C18:1 367 359
C18:2 369 344
C18:3 16 22
C20:0 11 14
C20:1 21 30
C22:0 11 14
C22:1 5 2
C24:0 6 9
4 A. Ahmed et al.

of uncharged polar amino acids, but lower acidic
amino acids than globulin. Due to the well-balanced
amino acid composition, buckwheat proteins have a
high biological value, and the main disadvantage
of buckwheat is its low protein digestibility (79·9%)
(Ikeda & Kishida 1993). Similarly, proteins of the
albumin family with disulphide bonds appear to be
responsible for the allergic response that is induced by
buckwheat products (Satoh et al. 2008).
The protein content in buckwheat is significantly
higher than in rice, wheat, sorghum, millet and maize.
Similarly, its protein content is the second highest after
oat flour. Buckwheat has a well-balanced amino acid
profile with a good quality of lysine which is generally
recognized as the first limiting amino acid in wheat
and barley and arginine (Table 5). The quality of
protein can be judged by the fact that buckwheat flour
has an amino acid score of 100, which is one of the
highest amino acid scores among plant sources (Ikeda
2002). No or low gluten types have been identified in
buckwheat, thus contributing as an ingredient in the
gluten-free diet for people suffering from coeliac
disease.
The major problem with buckwheat protein is low
digestibility in both humans and animals (Farrell 1978;
Javornik et al. 1981). The low digestibility is because of
anti-nutritional factors present in common buckwheat,
including protease inhibitors (such as trypsin inhibi-
tors) and tannins (Ikeda et al. 1986,1991). Trypsin
inhibitors in buckwheat seeds are resistant to thermal
processing, especially at elevated temperatures and
due to acidic conditions (Ikeda et al. 1986,1991).
Germination of buckwheat seeds considerably re-
duces the activity of protease inhibitors; therefore
seedlings and buckwheat plants are a source of food
with improved utilization of proteins (Kreft 1983;
Ookubo 1992).
‘Resistant proteins’such as those in buckwheat are
also effective in lowering blood cholesterol (Kayashita
et al. 1996; Iwami 1998; Tomotake et al. 2000). Huff &
Carroll (1980) reported that ratios of lysine/arginine
(Lys/Arg) and methionine/glycine (Met/Gly) are the
key factors in determining the cholesterol lowering
properties of proteins. The ratios of Lys/Arg and
Met/Gly in buckwheat are significantly lower than in
the other plant proteins. Similarly, nutritional studies
have shown that buckwheat proteins have the highest
cholesterol-lowering properties among the plant
proteins known to science so far (Huff & Carroll
1980). The amino acids in buckwheat regulate the
hepatic low-density lipoprotein (LDL) receptors, and
thus lower the serum cholesterol, resulting indirectly
in the prevention of arteriosclerosis. Moreover,
Kayashita et al. (1995) identified that the BPI was
more efficient in cholesterol lowering than soybean
protein isolates and other plant isolates. They also
showed that weight gain of BPI-fed rats was not
negatively affected when compared with casein-fed
rats, suggesting that buckwheat proteins were suffi-
ciently digested and absorbed to provide adequate
Table 5. Essential amino acid composition (mg/g protein) of buckwheat, cereals, pseudo-cereals and egg
(Radovic et al. 1999; Mendonça et al. 2009; Tang & Wang 2010; Vega-Gálvez et al. 2010)
Amino acid Buckwheat Barley Wheat Maize Quinoa Amaranth Egg*
Lysine 51 37 25 28 61 62 60
Methionine 19 18 18 24 48 20 38
Cystine 22 23 18 22 48 20 24
Threonine 35 36 28 39 38 33 43
Valine 47 53 45 50 45 44 72
Isoleucine 35 37 34 38 44 37 59
Leucine 61 71 68 105 66 61 84
Phenylalanine 42 49 44 45 73 46 61
Histidine 22 22 23 24 32 26 22
Tryptophan 16 11 10 6 12 33 15
TD (%) 79·9 84·3 92·4 93·2 –– 99·0
BV (%) 93·1 76·3 62·5 64·3 –– 100·0
NPU (%) 74·4 64·3 57·8 59·9 –– 94·0
UP (%) 9·1 7·3 7·3 6·0 –– 12·2
TD, true protein digestibility; BV, biological value (based on amino acid composition); NPU, net protein utilization; UP,
utilizable protein (protein × NPU/100).
* For whole egg.
Nutritional profile of buckwheat 5

amount of amino acids for growth. The BPI was shown
to be more effective in lowering ‘bad cholesterol’,
LDL and very low-density lipoproteins (VLDL), when
compared with other plant and animal proteins (Saeki
et al. 1990).
Buckwheat protein isolates can also be used as a
functional food ingredient to treat hypertension,
obesity and constipation. These proteins lower the
activity of angiotensin converting enzyme (ACE) and
directly control hypertension (Kato et al. 2001;
Tomotake et al. 2001,2002). Rat feeding experiments
showed that high-fat diets and overeating did not affect
the body weight of the animals when buckwheat
protein hydrolysate was included in the diet. This
protective effect was much weaker for soybean protein
hydrolysates (Tomotake et al. 2001).
Mitsunaga et al. (1986) reported the presence of
thiamine-binding protein (TBP) in buckwheat seeds.
After ingestion, this complex is digested by proteases
and thiamine is released and absorbed. The protein
moiety in the TBP complex improves the stability of
thiamine during storage and processing and enhances
its bioavailability (Mitsunaga et al. 1986).
Buckwheat protein, together with dietary fibre, can
ameliorate constipation (Kayashita et al. 1995). Several
epidemiological studies have shown that buckwheat
proteins, like dietary fibre, can suppress the develop-
ment of colon cancer (Cassidy et al. 1994; Lipkin et al.
1999). Hard to digest proteins interact with RS and are
the main source of short chain fatty acids (SCFA),
known to positively affect the tissues and physiology of
the colon (Scheppach et al. 1992; Morishita et al.
1998). Liu et al. (2001) utilized buckwheat protein
extract containing c. 730 mg/g buckwheat protein to
assess its effect on induced colon tumours in rats.
It was shown that dietary buckwheat protein reduced
the incidence of colonic adenocarcinomas by 47%.
Buckwheat protein also reduced carcinoma cell
proliferation and expression in colonic epithelium.
The results clearly suggest that buckwheat proteins
have a protective effect against colon carcinogenesis.
Minerals in buckwheat
The nutritional functions of essential minerals in
buckwheat and foods prepared from it have been
studied by many scientists (Ikeda & Yamashita 1994;
Ikeda et al. 2001,2002,2003,2004,2005). All of
these studies concluded that buckwheat seeds are a
good source of many essential minerals (Table 6). In
comparison with other cereals such as rice, wheat flour
or maize, buckwheat contains higher levels of zinc
(Zn), copper (Cu) and manganese (Mn) (Ikeda et al.
1999; Steadman et al. 2001b)(Table 7).
The bioavailability of Zn, Cu and potassium (K) from
buckwheat is especially high. It has been determined
that 100 g of buckwheat flour can provide c.13–89%
of the recommended dietary allowance (RDA) for Zn,
Cu, magnesium (Mg) and Mn. A major quantity of
these minerals exists in bran portions, followed by
endosperm. Buckwheat flour contains relatively high
levels of Zn, Cu, Mn and Mg, with a slightly lower
content of calcium (Ca) in comparison with other
flours, especially wheat (Bonafaccia et al. 2003b).
Recently, Ikeda et al. (2006) compared the compo-
sition of eight essential minerals, i.e. Fe, Zn, Cu, Mn,
Ca, Mg, K and phosphorus (P), of buckwheat flour to
those of cereal flours by using an in vitro enzymatic
digestion technique. The results showed a higher
content of essential minerals in buckwheat flour in
comparison with other cereal flours. Further enzymatic
digestion proved that a larger portion of the Zn, Cu and
K were released in soluble form from the buckwheat
flour, relative to that in cereal flours.
Vitamins in buckwheat
Vitamins are a group of organic compounds that are
essential in very small amounts for the normal
functioning of the human body. They vary widely in
their chemical and physiological functions and are
broadly distributed in natural food sources (Wijngaard
& Arendt 2006). Vitamin content of common buck-
wheat groats are presented in Table 8. Buckwheat
grains contain higher levels of vitamin B
1
(thiamine),
B
2
(riboflavin), E (tocopherol) and B
3
(niacin and
niacinamide) compared with most cereals. Generally,
Table 6. Mineral concentrations (mg/g) in
buckwheat and milling fractions (Steadman et al.
2001b; Ikeda et al. 2006)
Minerals Whole groats Flour Bran
Potassium 5·6500 5·0030 14·1630
Phosphorus 4·9000 4·1670 13·5330
Magnesium 2·6760 2·5300 5·9910
Calcium 0·1970 0·3000 0·3330
Iron 0·0303 0·0340 0·0604
Zinc 0·0292 0·0283 0·0726
Manganese 0·0164 0·0180 0·0462
Boron 0·0067 0·0066 0·0241
Copper 0·0071 0·0070 0·0104
6 A. Ahmed et al.

tartary buckwheat has more vitamin B
1
,B
2
and B
3
, but
less vitamin E than common buckwheat (Bonafaccia
et al. 2003b; Ikeda et al. 2006).
Thiamine (vitamin B
1
) is known to adhere strongly
to TBPs in buckwheat seeds (Mitsunaga et al. 1986;
Rapala-Kozik et al. 1999). In general, tartary buckwheat
has higher levels of vitamin B than common buck-
wheat (Pomeranz & Lorenz 1983; Bonafaccia &
Fabjan 2003). Thiamine-binding proteins can improve
the stability of thiamine during storage and improve the
bioavailability of thiamine (Li & Zhang 2001). Levels of
vitamin C and the sum of vitamin B
1
and B
6
can be
increased by germinating buckwheat. The level of
vitamin C can be increased by up to 0·25 mg/g in
buckwheat sprouts (Lintschinger et al. 1997; Kim et al.
2004). Wheat, barley, oat, rye and buckwheat groats
exhibit the same maximum level of tocopherols, with
γ-tocopherol being the main one (Zielinski et al. 2001;
Kim et al. 2002), while Przybylski et al. (1998) reported
α-tocopherol as the major tocopherol in buckwheat.
Differences in tocopherol forms have been attributed
to different cultivars of common buckwheat (Przybylski
et al. 1998; Zielinski et al. 2001; Kim et al. 2002).
Tartary buckwheat contains higher levels of tocopherols
than common buckwheat (Kim et al. 2002).
Iminosugars in buckwheat
Polyhydroxylated piperidines (azasugars or imino-
sugars) have gained increasing synthetic interest
due to their high biological activity as glycosidase
inhibitors (Zechel & Withers 2000). Koyama &
Sakamura (1974) isolated 1 and 2-dideoxy-azasugars
such as D-fagomine and its stereoisomers from the
seeds of Japanese buckwheat Fagopyrum esculentum
australe Moench. If used as a dietary supplement or
functional food component, D-fagomine may reduce
the risks of developing insulin resistance, becoming
overweight and suffering from an excess of potentially
pathogenic bacteria (Amézqueta et al. 2012). These
azasugars are potential therapeutic agents for the
treatment of a wide range of diseases, including dia-
betes, cancer, AIDS, viral infections and many more
(Butters et al. 2000). Fagomine itself has strong
inhibitory activity towards mammalian α-glucosidase,
β-galactosidase (Kato et al. 1997) and has also been
found to have a potent anti-hyperglycaemic effect in
streptozocin-induced diabetic mice and a potentiation
of glucose-induced insulin secretion (Nojima et al.
1998).
Amézqueta et al. (2012) determined D-fagomine and
its diastereomer, 3,4-di-epi-fagomine in buckwheat
groats, bran and leaves, and also in buckwheat flour.
The highest content of D-fagomine and 3·4-di-epi-
fagomine was present in groats (44 and 43 mg/kg,
respectively). Fagopyrum tataricum seeds contained
less D-fagomine than F. esculentum (Amézqueta et al.
2012).
NEUTRACEUTICAL AND FUNCTIONAL
COMPONENTS OF BUCKWHEAT
Buckwheat grains and hulls consist of some com-
ponents that have biological activity, i.e. flavonoids
Table 7. Comparison of mineral composition (mg/g) of buckwheat flour with maize meal, semolina, wheat
flour, soybean flour, quinoa flour and raw amaranth (Ranhotra et al. 1993; Edwardson 1995)
Products Ca Fe Mg K Na Zn Cu Mn
Buckwheat flour 410 40 2510 3370 0 31 0·9 0·9
Maize meal 60 34 1270 2410 350 18 1·9 4·9
Semolina 170 12 470 1360 10 11 1·9 6·1
Wheat flour 150 12 220 1080 20 7 1·4 6·8
Soybean flour 2060 64 4290 4940 130 39 29·2 22·7
Quinoa flour 700–860 26–63 1610–2320 7140–8550 27–930 32–38 7–76 35·0
Raw amaranth 1590 76 2480 5080 40 28 5·3 33·3
Ca, calcium; Fe, iron; Mg, magnesium; K, potassium; Na, sodium; Zn, zinc; Cu, copper; Mn, manganese.
Table 8. Vitamin composition of common
buckwheat (Wijngaard & Arendt 2006)
Vitamins Level (mg/g)
A(β-carotene) 2·1
B
1
(thiamine) 4·6
B
2
(riboflavin) 1·4
B
3
(niacin) 18·0
B
5
(pantothenic acid) 10·5
B
6
(pyridoxine) 7·3
C (ascorbic acid) 50·0
E (tocopherols) 54·6
Nutritional profile of buckwheat 7

and flavones, phenolic acids, condensed tannins,
phytosterols, fagopyrins, RS, dietary fibre, lignans,
plant sterols, vitamins and minerals.
Dietary fibre
Dietary fibre is a nutrient used for the proper digestion
of foods, proper functioning of the digestive tract at
large and for adding bulk to food. It also gives a feeling
of satiety and helps in losing weight. A low intake
of fibre can lead to constipation, haemorrhoids and
elevated levels of cholesterol and sugar in the blood.
Conversely, an excess of fibre can sometimes lead
to bowel obstruction, diarrhoea or even dehydration
(Anderson et al. 2009).
The amount of TDF in buckwheat varies with
differences in genetic and environmental factors. The
major components of TDF are cellulose, non-starch
polysaccharides and lignin. These are concentrated in
the cell walls of starchy endosperm, aleurone, seed
coats and hulls (Joshi & Rana 1995; Zheng et al. 1998;
Steadman et al. 2001b; Izydorczyk et al. 2002).
A considerable portion of buckwheat dietary fibre
is soluble. Soluble non-starch polysaccharides of
buckwheat contain xylose, mannose, galactose and
glucuronic acid (Asano et al. 1970). Bran fractions
obtained by the milling of buckwheat are especially
rich in dietary fibre (130–160 mg/g), but buckwheat
flours contain considerably lower amounts of fibre
(17–85 mg/g) (Steadman et al. 2001a).
For nutritional purposes, TDF is classified into SDF
and insoluble dietary fibre (IDF). Insoluble dietary fibre
(IDF) decreases transit time in the stomach, small
intestine and colon and increases faecal mass. It is
commonly used as a bulking agent to prevent or treat
constipation. Soluble dietary fibre, due to its high
viscosity, slows gastric emptying, reduces the adsorp-
tion of certain nutrients and increases transit time in the
small intestine by slowing down glucose absorption.
Soluble dietary fibre and to a lesser extent IDF are
fermented by microflora in the digestive system
to produce SCFA, implicated in serum cholesterol
and colon cancer reduction (Elleuch et al. 2011).
A considerable portion of buckwheat dietary fibre
is soluble (Joshi & Rana 1995; Zheng et al. 1998;
Steadman et al. 2001b; Izydorczyk et al. 2002).
However, relatively little is known about the compo-
sition and properties of SDF in buckwheat. Asano et al.
(1970) isolated water soluble non-starch polysacchar-
ides from buckwheat and reported that they consisted
of xylose, mannose, galactose and glucuronic acid.
It was postulated that the main chain of these
polysaccharides consisted of glucuronic acid, man-
nose and galactose. More recently, arabinose and
glucose residues have also been identified in water-
extractable buckwheat polysaccharides (Izydorczyk
et al. 2002). One of the most important characteristics
of buckwheat water soluble non-starch polysac-
charides is their very high molecular weight; as a
consequence they can form very viscous solutions
when dissolved in water.
Buckwheat bran containing hulls has c. 400 mg/g
fibre, including 250 mg/g soluble fibre, while ‘pure’
bran without hulls contains c. 160 mg/g fibre, in-
cluding 750 mg/g soluble fibre (Górecka et al. 2010;
Dziedzic et al. 2012). Depending on the type of
technological processes applied in the production of
buckwheat groats, the level and fraction composition
of dietary fibre affects the functional properties
(Górecka et al. 2009,2010; Dziedzic et al. 2012). In
buckwheat grains, dietary fibre constitutes 50–110 mg/g,
and the soluble fibre content is 30–70 mg/g, while
the amount of the insoluble fibre is 20–40 mg/g
(Krkoskova & Mrazova 2005). Soluble fibre reduces
blood cholesterol levels, the risk of incidence of
ischaemic heart disease and postprandial glycaemia
(Brown et al. 1999). Functional properties of dietary
fibre, such as water holding capacity and cation
binding, play a significant role in the prevention of
diet-dependent diseases, e.g. obesity, atherosclerosis
and colon cancer (Esposito et al. 2005; Górecka et al.
2005; Mehta 2005).
Dziedzic et al. (2012) examined the influence of the
technological process of buckwheat groat production
on dietary fibre content and its fraction with the
absorption of selected bile acids by buckwheat groats
and products such as buckwheat grains, buckwheat
grains after roasting, buckwheat hull, buckwheat bran,
whole buckwheat groats, broken buckwheat groats
and buckwheat waste. They recorded the highest
content of TDF in hulls, while the lowest was in whole
and broken buckwheat groats. Buckwheat hulls
contain higher lignin and cellulose fractions, while
the hemicellulose fraction predominated in broken
groats. Similarly, roasting of buckwheat grains resulted
in an increase in the content of dietary fibre and the all
fractions dietary fibre (Dziedzic et al. 2012).
Resistant starch
The term ‘resistant starch’(RS) was first coined by
Englyst et al.(1982) to describe a small fraction of
8 A. Ahmed et al.

starch that was resistant to hydrolysis by exhaustive
amylase and pullulanase treatment in vitro. Resistant
starch is the starch that is not hydrolysed after 120min
of incubation at 37 °C (Englyst et al. 1992). However,
starch reaching the large intestine may be more or less
fermented by the gut microflora.
Starch is the major component of buckwheat
(Skrabanja & Kreft 1998). Buckwheat flour contains
700–910 mg/g of starch depending on the flour types,
and the starch consists of c. 250 mg/g amylose and
750 mg/g amylopectin (Qin et al. 2010; Takahama &
Hirota 2010). Scanning electron microscope (SEM)
studies showed granules of buckwheat starch (Fig. 2)to
be polygonal and of irregular shape (Christa et al.
2009). Buckwheat starch particles range from 2 to
9μm in diameter (Lorenz & Dilsaver 1982; Soral-
Smietana et al. 1984; Acquistucci & Fornal 1997). The
buckwheat starch has small granules as particles of
grain cotyledons and they are smaller than those of
maize starch (12·2 μm), tapioca starch (18 μm) and
potato starch (30·5 μm) (Mishra & Rai 2006).
It has been found that the consumption of boiled
buckwheat groats or bread baked using 0·50
buckwheat flour induced significantly lowered post-
prandial blood glucose and insulin responses com-
pared with white wheat bread (Skrabanja et al. 2001).
Buckwheat products may provide an important source
of retrograded starch and RS (Christa & Soral-Smietana
2008). The in vitro rate of starch hydrolysis and RS
formation in boiled and baked buckwheat indicated
the highest concentration of RS in boiled buckwheat
groats (60 mg/g total starch basis), while the RS level
in bread products based on different proportions of
buckwheat flour and groats varies from 90 to 40 mg/g.
The rate of in vitro amylolysis was significantly lower
(P<0·05) in all buckwheat products in comparison
with white flour bread (Skrabanja et al. 2001).
The inclusion of 30 g buckwheat in the daily diet has
been sufficient to produce clinically relevant reduc-
tions in serum total and LDL-cholesterol, triglycerides
and increases in HDL-cholesterol, thus reducing
the risk of cardiovascular diseases (CVD) (He et al.
1995). Their results support the view that buckwheat
proteins and RS could have beneficial effects on
various diseases, including hyperlipidemia. Similarly,
He et al.(1995) demonstrated that the inclusion
Fig. 2. Buckwheat starch micrographs from different origins adopted from Qian & Kuhn (1999).
Nutritional profile of buckwheat 9

of buckwheat in the diet of non-independent insulin
diabetes mellitus (NIDDM) led to a significant
reduction in their fasting and post-prandial blood
glucose levels since it is rich in D-chiro-inositol, which
contributes to the improvement of insulin resistance by
enhancing the action of insulin.
Antioxidant activity
Antioxidant activity is the fundamental prophylactic
property which is important for humans. A variety of
biological functions such as antimutagenic, anti-
carcinogenic and antiaging originated from an anti-
oxidant property (Holasova et al. 2002). Condensed
catechins and phenolic acids, including hydrobenzoic
acids, synigric, p-hydroxy-benzoic, vanillic and
p-coumaric acids that have antioxidant properties are
present in the bran-aleurone layer of buckwheat grains
(Przybylski et al. 1998). The primary antioxidants in
buckwheat are rutin, quercetin and hyperin (Morishita
et al. 2007). Buckwheat bran and hulls have 2–7 times
higher antioxidant activity than barley, triticale and
oats (Holasova et al. 2002; Zdunczyk et al. 2006).
Zielinski & Kozlowska (2000) established the follow-
ing hierarchy of antioxidant activity for 80% metha-
nolic extracts which originated from different whole
grains: buckwheat> barley> oat> wheat >rye.
The antioxidant activities of buckwheat are
comparable to butylated hydroxyanisole (BHA),
butylated hydroxytoluene (BHT) and tertiary butylhy-
droquinone (TBHQ), as determined by 1,1-diphenyl-
2-picrylhydrazyl (DPPH) assay and the Rancimat
method (Sun & Ho 2005). Fabjan et al. (2003)
extracted tartary buckwheat seeds (F. tataricum
Gaertn.) with methanol and found that tartary buck-
wheat seeds contained more rutin (8–17 mg/g dry
weight (DW)) than common buckwheat seeds (0·1 mg/g
DW). For buckwheat, 80% methanol was found
to extract 64 times more phenolic compounds
and four times the antioxidant activity than water
(Zielinski & Kozlowska 2000). Important components
include rutin, rutin aglycone, quercetin, epicatechin,
catechin 7-O-β-D-glucopyranoside, epicatechin, 3-O-
p-hydroxybezoate and epicatechin 3-O(3,4-di-O-
methyl)-gallate that were extracted with ethanol
from buckwheat groats (F. esculentum Moench) by
Watanabe (1998), while the presence of proanthocya-
nidins in flour (1·59 mg/g DW) was confirmed by
Quettier-Deleu et al. (2000).
Inglett et al. (2010,2011) studied the antioxidant
activity in buckwheat with water, 0·50 aqueous
ethanol, or total ethanol using microwave irradiation
or a water bath for 15 min at various temperatures
(23–150 °C). They found the highest antioxidant
activity of 5·61–5·73 μmol Trolox equivalents/g in
total ethanol extract at 100 and 150 °C, independent of
the heat source. Lin et al. (2009) proved antioxidant
activity by reducing power and DPPH radical scaven-
ging ability in buckwheat enhanced wheat bread.
Similarly, Sedej et al. (2011) proved that buckwheat
flours exhibited significantly higher (P<0·05) anti-
radical activity on hydroxyl (.OH), superoxide anion
(O
2
.) and DPPH radicals, antioxidant activity and
reducing power in comparison with wheat fractions.
Flavonoids in buckwheat
Flavonoids are polyphenolic compounds that are
ubiquitous in plants and are a group of more than
4000 polyphenolic compounds that occur naturally in
foods of plant origin. They have been shown to possess
a variety of biological activities at non-toxic concen-
trations in organisms. These compounds possess a
common phenylbenzopyrone structure (C6-C3-C6)
and they are categorized according to the saturation
level and opening of the central pyran ring, mainly into
flavones, flavanols, isoflavones, flavonols, flavanones
and flavanonols (Ren et al. 2003). Phenolic com-
pounds in buckwheat also possess antioxidant activity
(Holasova et al. 2002; Sun & Ho 2005; Sensoy et al.
2006). Four flavonol glycosides including rutin,
quercetin, kaemferol-3-rutinoside and a trace amount
of a flavonol triglycoside were found in the methanol
extract of buckwheat (Tian et al. 2002). Tartary
buckwheat has been shown to contain a higher
content of flavonoids (19·02 mg/g) in comparison
with common buckwheat (0·28 mg/g) (Jiang et al.
2007).
Buckwheat contains more rutin compared with
other grain crops. This is a quercetin-3-rutinoside
with antioxidant, anti-inflammatory and anticarcino-
genic properties, and it can also reduce the fragility of
blood vessels related to haemorrhagic disease and
hypertension in humans (Oomah & Mazza 1996;
Baumgertel et al. 2003). It has been found that whole
buckwheat contains 2–5 times more phenolic com-
pounds than oats or barley, while buckwheat bran and
hulls have 2–7 times higher antioxidant activity than
barley, triticale and oats (Holasova et al. 2002;
Zdunczyk et al. 2006). Buckwheat contains a majority
of phenolic compounds present in the free form and
distributed throughout the entire grain (Hung & Morita
10 A. Ahmed et al.

2008). Recently, 2-hydroxy-3-O-β-D-glucopyranosil-
benzoicacid,1-O-caffeoyl-6-O-alpha-rhamnopyranosyl-
β-glycopyranoside and epicatechin-3-(3′′-O-methyl)
gallate were identified in buckwheat by reverse
phase high performance liquid chromatography–
electrospray ionisation-mass spectrometry (Tian et al.
2002), and then again with reverse phase high
performance liquid chromatography–electrospray
ionization-time of flight-mass spectrometry (Verardo
et al. 2011).
The flavonoid content and composition in seeds
vary between different buckwheat species and devel-
opment phases. Flavonoid content in F. tataricum
is generally higher than that in F. esculentum.In
F. tataricum seeds, the flavonoid content is c.40mg/g,
while that of F. esculentum seeds is c. 10 mg/g (Li &
Zhang 2001). In F. tataricum flowers, leaves and
stems, the flavonoid content can exceed 100 mg/g.
Buckwheat tissues can serve as very useful resources
for high-quality flavonoids, though flavonoid con-
tent varies with development and is significantly
influenced by the contents of phenylalanine and
tyrosine and the activity of kinetin in the issues
along with different existing forms of nitrogen in the
soil (Li & Zhang 2001).
Six flavonoids (Fig. 3) have been isolated and
identified in buckwheat grain. All six flavonoids
(rutin, quercetin, orientin, vitexin, isovitexin and
isoorientin) have been found in buckwheat hulls
(Dietrych-Szostak & Oleszek 1999; Kreft et al. 1999;
Tian et al. 2002). Epidemiological studies have
suggested a protective role of dietary flavonoids
against coronary heart diseases and possibly cancer
(Chao et al. 2002). In recent years, flavonoids have
attracted increasing interest because they have various
beneficial health effects such as anti-allergic, antiviral,
anticancer and anti-oxidation properties (Fotsis et al.
1997; Chao et al. 2002). The flavonoid content in
tartary buckwheat (c. 40 mg/g) is higher than that in
common buckwheat (10 mg/g) (Li & Zhang 2001).
Flavonoids are known for their effectiveness in
reducing cholesterol levels in the blood, keeping
Fig. 3. Important phenolic compounds in buckwheat: A, isorientin; B, orientin; C, rutin; D, vitexin (Verardo et al. 2011).
Nutritional profile of buckwheat 11

capillaries and arteries strong and flexible, reducing
high blood pressure and reducing the risk of arterio-
sclerosis (Li & Zhang 2001; Fabjan et al. 2003).
Verardo et al. (2011) quantified 32 free and 24 bound
phenolic compounds in buckwheat flour and buck-
wheat spaghetti, with two new compounds, i.e.
protochatechuic-4-O-glucoside acid and procyanidin
proving the further phenolic potential of buckwheat.
Kim et al. (2011) reported the effect of methyl
jasmonate on phytochemical production in buck-
wheat sprouts cultivated in dark conditions, and
their findings proved that isoorientin, orientin, rutin
and vitexin were the main flavonoids in buckwheat
sprouts. Similarly, buckwheat flour (476·3 and
618·9 mg GAE/g extract) contain polyphenolic con-
tents four times higher than wheat flour (37·1 and
137·2 mg GAE/g extract) (Sedej et al. 2010).
Rutin content
Rutin (quercetin-3-beta-D-rutinoside) is an important
therapeutic substance that favourably influences the
increase of blood vessel elasticity (Mukasa et al. 2009),
the treatment of circulatory disorders and athero-
sclerosis, the reduction of blood pressure, and
stimulates the utilization of vitamin C (Yildizog
˘lu-Ari
et al. 1991). Rutin is widely present in plants, but is
relatively rare in their edible parts. It was first detected
in Ruta graveolens, which gave the common name to
this pharmaceutically important substance (Chen et al.
2001). No rutin has been found in cereals or
pseudocereals except buckwheat, which can be used
as a good source of dietary rutin (Ohsawa & Tsutsumi
1995; Watanabe 1998; Kreft et al. 1999; Park et al.
2000; Jiang et al. 2007). The content of rutin is
dependent on the buckwheat genotype, growing
conditions, developmental phase, plant part and year
of harvest (Table 9) (Lachmann & Adachi 1990).
Different cultivars of buckwheat may have different
contents of rutin (Ohsawa & Tsutsumi 1995) with
potential variation also in different plant parts. Most
rutin is accumulated in the inflorescence (up to
0·12 mg/g DW), in stalks (0·004–0·01 mg/g DW),
upper leaves (0·08–0·10 mg/g DW) (Hagels 1999)
and 0·12–0·36 mg/g DW in grains depending on the
variety and growth conditions (Kitabayashi et al. 1995;
Brunori et al. 2010; Park et al. 2011). The highest
quantity of rutin is found in leaves immediately before
flowering (Michalova et al. 1998) therefore providing
the opportunity for utilizing buckwheat tops for the
natural fortification of food with rutin. Among fruits,
vegetables and grain crops, grapes and buckwheat are
the most important rutin-containing foods. Ecological
factors such as ultra-violet (UV) irradiation may also
have a great influence on rutin content (Kreft et al.
2002).
In a research report by Park et al. (2004), rutin
content in 50 seeds and plants of different tartary
buckwheat strains from all over the world was
compared. These 50 strains were collected from
China (27 strains), India (5 strains), Nepal (9 strains),
Bhutan (3 strains), Pakistan (1 strain), Slovenia
(3 strains) and Japan (2 strains). They found the rutin
content in seed and plant parts of tartary buckwheat to
be higher than that of F. esculentum and F. cymosum
(Park et al. 2004). Similar results were obtained by
Jiang et al. (2007) and Brunori et al. (2010). The rutin
content of tartary buckwheat was c. 3·2 times higher in
the flower, c. 3·1 times in the stem and c. 65 times
higher in the seed compared with F. esculentum
Table 9. Rutin content (mg/g DW) in different parts
of buckwheat (Park et al. 2004; Paulícková et al.
2004)
Plant part Rutin
Hulled grains 126
Unhulled grains 178
Hulled germinated grains 366
Root 436
Germ 1692
Stalk 5634
Flower 12726
Young plants 17 920
Tops 23374
Leaves 40011
Table 10. Comparison of rutin content in leaves,
stems and seeds of tartary buckwheat of different
origins (Park et al. 2004)
Rutin content (mg/g)
Region Leaves Stems Seeds
Bhutan 53 200 8646 21397
China 41 000 5347 15115
India 42 596 5518 11994
Japan 36074 4091 12 749
Nepal 39000 6828 13 360
Pakistan 23 315 2522 14672
Slovenia 30537 2064 19 382
Total 38 537 5519 15893
12 A. Ahmed et al.

(Park et al. 2004). Similarly, rutin content in buck-
wheat varied with cultivation region (Table 10). Rutin
content in the leaf, stem and seed of the strains
collected from the Bhutan area were higher than in the
strains collected from Slovenia and Pakistan (Park et al.
2004).
Rutin has desirable physiological and biological
properties, such as anti-oxidation, anti-inflammation,
anti-hypertension, vasoconstrictive, spasmolitic and a
positive inotropic effect (Kuntic
´et al. 2011; Landberg
et al. 2011). Rutin also provides protection against
gastric lesions, improves sight and hearing, protects
against UV light, lowers plasma cholesterol, protects
from oxidative stress (Gong et al. 2010), causes muscle
hypertrophy (Gaberscik et al. 2002) and also sup-
presses gallstone formation and cholesterol levels
(Kuntic
´et al. 2011). Guo et al. (2007) concluded that
adding rutin to the digestion mixture in the flour
caused a significant increase in pepsin digestibility.
Fagopyrins and fagopyritols
Fagopyrin is a photo-sensitive substance found in
buckwheat plants, belonging to the naphthodian-
thrones and structurally related to hypericin (Kreft &
Germ 2008). The fagopyrins found in buckwheat
grains are unique, but the concentration is very low
and isolation is difficult. In buckwheat, some anthra-
noides have also been found in concentrations which
could cause very small laxative effects (Hagels 2007).
The fagopyrins found in buckwheat can be utilized in
the treatment of type II diabetes (Krkoskova & Mrazova
2005).
Buckwheat seeds accumulate the soluble carbo-
hydrates sucrose and fagopyritols in the embryo and
aleurone tissues. Fagopyritols are carbohydrate com-
pounds which were first identified in buckwheat and
are ex-galactosyl derivatives (mono, di and trigalacto-
syl derivatives) of D-chiro-inositol (Horbowicz et al.
1998).
Six fagopyritols (Figs 4 and 5), representing two
distinct series differing in bonding positions, have been
found in buckwheat seeds (Horbowicz et al. 1998;
Szczecinski et al. 1998; Obendorf et al. 2000;
Steadman et al. 2000,2001c). These are fagopyritol
A1 (α-D-galactopyranosyl-(1?3)-1D-chiro-inositol),
fagopyritol A2 (α-D-galactopyranosyl-(1?6)-α-D-ga-
lactopyranosyl-(1?3)-1D-chiro-inositol), fagopyritol
A3(α-D-galactopyranosyl-(1?6)-α-D-galactopyranosyl-
(1?6)-α-D-galactopyranosyl-(1?3)-1D–chiro-inositol),
fagopyritol B1(α-D-galactopyranosyl-(1?2)-1D-chiro-
inositol), fagopyritol B2(α-D-galactopyranosyl-(1 ?6)-
α-D-galactopyranosyl-(1?2)-1D-chiro-inositol) and
fagopyritol B3 (α-D-galactopyranosyl-(1?6)-α-D-ga-
lactopyranosyl-(1?6)-α-D-galactopyranosyl (1?2)-
1D-chiro-inositol) (Obendorf 1997; Ueda et al. 2005).
Fagopyritol B1 and A1 (Obendorf et al. 2000,2008)
are the major fagopyritols accumulated in buckwheat
Fig. 4. Fagopyritol A series present in buckwheat (Horbowicz et al. 1998).
Nutritional profile of buckwheat 13

seeds (Horbowicz et al. 1998), and these constitute
0·50 of the total soluble carbohydrates of buckwheat
embryos (Cid et al. 2004). Fagopyritols accumulate
in the dicotyledonous embryo of buckwheat seeds,
mostly in the cotyledons (Horbowicz et al. 1998).
Recently, Obendorf et al. (2008) determined the
molecular structure of fagopyritol A1 as O-α-D-
galactopyranosyl-(1-3)-D-chiro-inositol by
1
H and
13
C
NMR and concluded that fagopyritol A1 is a positional
isomer of fagopyritol B1 (O-α-D-galactopyranosyl-
(1-2)-D-chiro-inositol, which has a positive effect on
blood glucose levels and insulin activity (Fonteles et al.
2000).
Buckwheat is the richest source of these carbo-
hydrates. The bran milling fractions may contain
26 mg of fagopyritols per g DW, whereas dark and
light buckwheat flours contain 7 and 3 mg/g DW,
respectively (Fonteles et al. 2000).
Buckwheat is being studied for use in treating type II
diabetes (Kawa et al. 2003) and can also help to
control the development of polycystic ovaries (Nestler
et al. 1999): it contains D-chiro-inositol, a component
of the secondary messenger pathway for insulin signal
transduction found to be deficient in type II diabetes
and polycystic ovary syndrome (PCOS). Research
on D-chiro-inositol and PCOS has shown promising
results (Nestler et al. 1999). A buckwheat protein has
been found to bind cholesterol tightly, thus reducing
plasma cholesterol in people with hyperlipidemia
(Tomotake et al. 2001). D-chiro-inositol is a com-
ponent of galactosamine D-chiro-inositol, a putative
insulin mediator (Larner et al. 1988) believed to be
deficient in subjects with NIDDM (Asplin et al. 1993)
because of an abnormal D-chiro-inositol metabolism.
Adding D-chiro-inositol as a dietary supplement
appeared to be effective in reducing the symptoms of
NIDDM and PCOS (Ortmeyer et al. 1995; Fonteles
et al. 2000). Several research groups are developing
sources for natural and synthetic supplies of D-chiro-
inositol (Kennington et al. 1990). One natural source of
D-chiro-inositol (in free form and as galactosides,
predominantly fagopyritol A1 and fagopyritol B1) is
in buckwheat seed. During dry milling, fragments of
the outer cotyledon adhere to the bran (Steadman et al.
2001c). Therefore, the bran milling fraction from
buckwheat seed (Steadman et al. 2000,2001c) can
Fig. 5. Fagopyritol B series present in buckwheat (Horbowicz et al. 1998).
14 A. Ahmed et al.

be used for the isolation and preparation of fagopyr-
itols and can free D-chiro-inositol for the production of
nutraceuticals and pharmaceuticals (Obendorf et al.
2000,2008; Steadman et al. 2000; Kawa et al. 2003).
ALLERGIES TO BUCKWHEAT
Allergy to buckwheat was first reported in the literature
in 1909 (Smith 1909), and it is mostly an immediate
IgE-mediated reaction that can cause a severe allergic
reaction similar to that caused by peanut allergy (Asero
et al. 2009). Several buckwheat allergens have been
identified, of which the 24 kDa (Fag e 1), 26 kDa and
67–70 kDa proteins have been suggested to be of
importance (Tohgi et al. 2011). Fag e 1, which is
homologous to 11S or 12S globulin, has reacted with
the serum IgE of all buckwheat allergy patients. The
16 kDa protein (Fag e 2), which is resistant to digestion,
has been identified as a major buckwheat allergen in
Japanese and Korean patients with buckwheat allergy
(Park et al. 2000).
CONCLUSION
Buckwheat is an important food, as it contains proteins
with high biological value and balanced amino acid
composition, relatively high fibre content, high con-
tents of available Zn, Cu and Mn and dietary Se. The
nutraceutical potential of buckwheat and its use in
food products emphasizes the need to further exploit
the use of bioactive compounds and precious func-
tional ingredients which are well researched and
established by various studies in the related area.
This will not only help in the prevention and treatment
of various human diseases, it will also be helpful in
improving various traditional and local buckwheat
foods and better use of the by-products of buckwheat.
Proper utilization of buckwheat will also promote food
industries in the development of new functional foods.
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