Vol. 12(15), pp.

1802-1810, 10 April, 2013

DOI: 10.5897/AJB12.2971
ISSN 1684–5315© 2013 Academic Journals African Journal of Biotechnology
http://www.academicjournals.org/AJB

Full Length Research Paper

Assessment of the protein quality of twenty nine grain

amaranth (Amaranthus spp. L.) accessions using amino
acid analysis and one-dimensional electrophoresis
Akin-Idowu, Pamela Eloho1,2*, Odunola, Oyeronke Adunni2, Gbadegesin, Michael Adedapo2,
Oke, Abiola3 and Orkpeh, Uterdzua3
1
Biotechnology Unit, National Horticultural Research Institute, P.M.B. 5432 Idi-Ishin, Ibadan, Oyo State, Nigeria.
2
Cancer Research and Molecular Biology Laboratories, Department of Biochemistry,
University of Ibadan, Oyo State, Nigeria.
3
Vegetable Program, National Horticultural Research Institute, P.M.B. 5432 Idi-Ishin, Ibadan, Oyo State, Nigeria.
Accepted 7 March, 2013

Protein deficiency in diets adversely affects growth and development. Novel source of high quality
protein and its utilization is essential in improving the nutritive status of the vulnerable groups. Total
protein content and protein fractions of 29 amaranth accessions and a soybean cultivar used as
reference were determined. The amino acid composition of ten representative accessions of amaranth
was also determined. Total protein content ranged from 11.77 to 19.01 g/100 g. One-dimensional gel
electrophoretic separations revealed albumin, globulin and glutelin as the major protein fractions;
prolamin was not detected. All accessions had similar seed protein electrophoretic profile, ranging from
6.5 to 66 kDa. The glutelin fraction of all amaranth accessions shared similar electrophoretic bands with
the soybean cultivar at the 4 to 14, 24 to 36 and 65 to 66 kDa regions. All amaranth accessions
contained a good balance of the nine essential amino acids. The sum of essential amino acids ranged
from 31.22 to 44.88 g/100 g and 60.87 g/100 g total protein in amaranth and soybean, respectively;
limited only in tryptophan and leucine for amaranth, and methionine for soybean. Amaranth is a good
source of high quality protein and may serve as a nutritive substitute for some cereals in functional
foods.

Key words: Amaranthus, amino acid, gel electrophoresis, protein quality, protein fractions.

INTRODUCTION

Proteins constitute an important group of Academy of Science (NAS) (1984). Natural vegetable
biomacromolecules that are involved in physiological proteins are useful materials owing to their safeness, high
functions (Wright, 1987). Protein malnutrition is still a biocompatibility, nutritional value and low cost. Finding
major challenge in developing countries (UNICEF, 2009; new vegetable proteins rich in essential amino acids is
Black et al., 2008). Therefore, it is essential to broaden important for the food and pharmaceutical industries
the food base by utilization of underutilized crops with (Paredes-Lopez et al., 1988). Most cereals are deficient
promising nutritive potential as recognized by National in some amino acids, for instance, corn is deficient in

*Corresponding author. E-mail: elohoidowu@hotmail.com.

 Akin-Idowu et al. 1803

lysine and tryptophan, rice in lysine and threonine compared with the soybean cultivar used as reference.
(Deshpande et al., 1955; Bressani and Garcia-Vela, Findings from this study would assist plant breeders
1990) and wheat in lysine (Howe et al., 1965). Amaranth and nutritionists in their selection of high protein quality
(Amaranthus) belongs to a nutritious class of pseudo- amaranth accessions.
cereals and it has been identified as a very promising
food crop because of its exceptional nutritive value as MATERIALS AND METHODS
judged by its protein and lipid content, as well as for its
essential amino acid composition that has relatively high Twenty nine accessions of Amaranthus belonging to five species:
lysine content (Teutonico and Knorr, 1985). There are A. caudatus, A. cruentus, Amaranthus hybrid, A. hypochondriacus
three main species of amaranth with desirable agronomic and Amaranthus hybridus were used in this study (Table 1). Twenty
seven of the accessions were obtained from the USDA-ARS North
traits namely, Amaranthus caudatus, Amaranthus Central Regional Plant Introduction Station (NCRPIS) in Ames,
cruentus and Amaranthus hypochondriacus. The protein USA; and two were obtained from the National Horticultural
content of A. cruentus, A. caudatus and A. Research Institute (NIHORT) germplasm, Ibadan, Nigeria. The
hypochondriacus are 13.2 to 18.2 g/100 g, 17.6 to 18.4 twenty nine accessions were planted in the experimental field of
g/100 g and 17.9 g/100 g, respectively (Gorinstein et al., NIHORT in 2010 in three replicates in a randomized complete block
design and harvested at maturity.
1998).
The lysine contents of amaranth species are high
ranging from 3.2 to 6.4 g/100 g when compared with Sample preparation
those found in most cereals, 2.2 to 4.5 g/100 g. The
Whole mature seeds of each accession planted in 3 replicates were
sulphur containing amino acids (2.6 to 5.5 g/100 g) is pooled together and ground in a mill. The resulting flour was
higher than that of the most important legumes (1.4 g/100 defatted with n-hexane at a flour/hexane ratio of 1:10 (w/v) prior to
g) such as pea, beans and soybeans (Gorinstein et al., protein extraction and fractionation (Barba de la Rosa et al., 1992).
1998; Juan et al., 2007). In addition, amaranths are also
good sources of minerals and vitamins and they contain
Protein extraction
larger amounts of these nutrients than most of the
common cereals and legumes (Muyonga et al., 2008). Proteins were extracted stepwise according to solubility in different
The major storage proteins in most cereal grains such solvents following the method of Landry and Moureaux (1980).
as wheat, barley, rye, maize and sorghum are the Fractionation sequences were performed first in distilled water
alcohol-water soluble prolamins (Gorinstein et al., 1991a; (albumin), followed by 0.5 M NaCl (globulin), 55% 2-propanol
(prolamin-like), 55% 2-propanol with 0.6% 2-mercaptoethanol
Kreis et al., 1985). Oats and rice have globulins and (prolamin), sodium borate buffer (pH 10) with 0.6% 2-
glutelins, respectively, as major proteins but small mercaptoethanol and 0.5 M NaCl (glutelin-like), borate buffer (pH
amounts of prolamins (Yamagata et al., 1982). In 10) with 0.6% 2-mercaptoethanol and 0.5% sodium dodecyl sulfate
amaranth, the major storage proteins are the globulins (glutelin).
and glutelins, while the amount of alcohol-soluble
prolamins is low as in oats and rice (Gorinstein et al., Protein determination
1991a).
Protein content and amino acid composition depend on Nitrogen content was determined by the micro-Kjeldahl method
genotype and growing conditions (Gorinstein et al., (Hach, 1990) and the protein content was calculated using the
2002). Also, the storage protein composition of soybean nitrogen/protein conversion factor of 6.25.
has been reported to be influenced by plant nutrient
availability (Krishnan et al., 2005). Most investigations on One dimensional electrophoresis (1-DE)
amaranth species have focused on storage protein
fractions. However, assessment of the protein quality of Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-
PAGE) was performed according to the procedure of Laemmli
Amaranthus species based on total protein content, (1970). Protein extracts were combined and diluted in a sample
protein fractions and amino acid composition, with buffer that contained 60 mM Tris-HCl (pH 6.8), 2% w/v SDS, 3.33%
reference to soybean an excellent source of high-quality v/v β-mercaptoethanol, 10% glycerol and 0.05% of bromophenol
protein (Zarkadas et al., 2007b) and amino acid blue. The samples were heated at 98°C for 5 min before loading
requirement for human according to the FAO/WHO onto a vertical slab gel (Mini-PROTEAN II Electrophoresis Cell)
(1991) and the USFDA (1993) compositional data is using a 12% gradient separating (acrylamide/bis acrylamide) gel
and a 4% (w/v) stacking gel containing 0.1% SDS. Low range
scarce. molecular weight marker (6.5 to 66 kDa) obtained from Sigma
Thus, this study was carried out to determine the levels Chemical Co was used for the estimation of the protein subunits.
of total protein and individual amino acids in 29 grain Molecular weights standard are: bovine serum albumin (66 kDa),
amaranth accessions grown under field conditions at the ovalbumin (45 kDa), phosphate dehydrogenase (36 kDa),
National Horticultural Research Institute (NIHORT), trypsinogen (24 kDa), trypsin inhibitor (20 kDa) and aprotinin (6.5
kDa). Electrophoresis was done at 125 V for about 2 h. At the end
Ibadan, Nigeria. Amaranth accessions were also of the run, the gels were stained with Coomasie Brilliant Blue R250
screened for differences in genetic variability in storage in methanol/water/acetic acid (4:5:1 v/v/v) and destained with
protein subunits by 1-DE gel electrophoresis and were methanol/water/acetic acid (4:5:1 v/v/v) over night.
1804 Afr. J. Biotechnol.

Table 1. Species and accessions of 29 grain amaranth used in this study, their pedigree and total protein contents (g/100 g).

Accession Accession Total protein

Species Origin Plant name
Numbera code content (g/100 g)
1 P1 490458 Bolivia LSK 38 14.12±0.26
2 PI 511679 Argentina RRC 551 17.30±1.12
Amaranthus caudatus United States,
3 PI 553073 LOVE-LIES-BLESSING 11.77±0.26
New Jersey
4 P1 642741 Bolivia Oscar Blanco 13.83±0.15

5 PI 477913 Mexico RRC 1011 16.10±0.20

6 PI 511719 Guatemala Niqua, alegria, chang 15.04±0.59
United states,
7 PI 515959 Montana-3 15.39±0.11
Montana
United states,
8 PI 538319 K266 16.03±0.09
Amaranthus cruentus Pennsylvania
9 PI 590992 China TIBET 18.42±0.17
United states,
10 P1 604666 RRC 1027 14.45±0.13
Pennsylvania
11 PI 641047 Nigeria, Oyo CEN/IB/97/AMA008 15.71±0.06
12 PI 641045 Nigeria, Oyo CEN/IB/97/AMA005 15.36±0.08

United states,
13 PI 538325 K593 16.57±0.08
Pennsylvania
United States,
14 PI 538326 D70-1 13.63±0.09
Pennsylvania
United States,
Amaranthus hybrid 15 PI 538327 DI36-1 17.75±0.09
Pennsylvania
16 Ames 1974 Nigeria RRC 18C 16.46±0.08
17 Ames 2256 Nigeria SP 12C 17.96±0.62
18 Ames 5644 Nigeria RRC 1044 12.81±0.30
19 Ames 5647 Nigeria RRC 1047 15.27±0.82

20 PI 337611 Uganda P 373 13.04±0.20

21 PI 511731 Mexico RRC 646 12.76±0.28
United States,
22 PI 558499 PLAINSMAN 12.82±0.04
Nebraska
23 PI 590991 China, Shanxi ZHEN PING 14.01±0.35
Amaranthus
hypochondriacus India, Himachal
24 PI 615696 Amapurna 15.16±0.12
Pradesh
United States,
25 P1 619250 K 116 14.51±0.51
Pennsylvania
26 PI 633596 Nepal Jumla 12.72±0.56
27 Ames 1972 Nigeria RRC 18A 15.53±0.43

28 NH 84/444-4 Nigeria NH Purple 19.01±0.21

Amaranthus hybridus
29 NAC 3 Nigeria NH Green 16.77±0.73

Amino acid analysis also included in this study and used for comparison as a known
high quality protein.
Only 10 out of the 29 amaranth accessions were used for this Amino acid analysis was carried out at AltaBioscience
analysis; and they included two accessions from each of the five Laboratory, University of Birmingham, Edgbaston, UK, according to
amaranth species. A soybean cultivar (TGX 1448-2E) obtained from the methods of Spackman et al. (1958) and Barrett (1985). Amino
International Institute of Tropical Agriculture (IITA) germplasm, was acid score (AAS) is the concentration of the limiting amino acid in
 Akin-Idowu et al. 1805

the food protein, which is expressed according to the method of while non-essential amino acids were higher in soybean
Young and Steinke (1992) and Zarkadas et al. (2007b) as the than in amaranth. The lysine contents: 7.89 g/100 g
proportion or percentage of the concentration of the same amino
acid in a standard or reference pattern such as for the diet of a 2-5-
protein of A. hypochondriacus (accession 27), 7.88 g/100
year-old child. g protein of A. hybridus (accession 28) and 7.77 g/100 g
protein of A. caudatus (accession 2) are higher than the
AA content (mg/g of protein) of food protein lysine contents (7.0 g/100 g protein) obtained in hen’s
AAS = whole egg (FAO/WHO, 1991); 3.2 to 6.4 g/100 g protein
AA content of FAO/WHO (1991) pattern for a 2-5-year old child
obtained in amaranth (Gorinstein et al., 1991b) and 2.2 to
4.5 g/100 g protein found among the most common
Statistical analysis cereals (Gorinstein et al., 1998). The sulphur containing
amino acids (methionine + cysteine) contents of
Analysis of variance was done on the protein and amino acid data amaranth accessions in this study ranged from 1.77 to
using Statistical Analysis System (SAS) (2003). Duncan multiple 2.74 g/100 g protein with some accessions having higher
range test was used to determine significant differences among the
amaranth accessions. P values less than 0.05 were considered
values than 2.15 g/100 g protein obtained for the
statistically significant. soybean cultivar (TGX 1448-2E). The methionine +
cysteine contents of the amaranth accessions evaluated
were also higher than 1.4 g/100 g protein obtained for
RESULTS AND DISCUSSION important legumes such as pea and beans (Gorinstein et
al., 1998). All amaranth accessions evaluated had higher
The total protein content of the twenty nine amaranth histidine, lysine and threonine contents than values
accessions evaluated ranged from 11.77 to 19.01 g/100 g obtained for hen’s whole egg (FAO/WHO, 1991).
and differed significantly (p<0.05) among the accessions The essential amino acid EAA profiles and protein
(Table 1). A. hybridus (accession 28) had the highest ratings of the 10 accessions of amaranth evaluated are
protein content (19.01 g/100 g), followed by A. cruentus compared with reference amino acid patterns for humans
(accession 9) having 18.42 g/100 g and A. hybrid (requirement for a 2-5-year old preschool child) as
(accession 17) having 17.96 g/100 g. The total protein recommended by FAO/WHO (1991) and USFDA (1993)
content of most of the amaranth accessions evaluated in (Table 3). All amaranth accessions evaluated contained
this study were higher than values obtained for wheat all the nine essential amino acids (EAA9) with values
(13.5 to 14.5 g/100 g), maize (10.6 to 13.8 g/100 g), higher than the EAA requirement for a 2-5-year old
barley (10 to 14.9 g/100 g) and oats (12.4 to 12.9 g/100 preschool child. Amaranth accessions were limited only
g) by Gorinstein et al. (2002); but lower than 32 to 38 in tryptophan, which ranged from 0.72 to 0.91 g/100 g per
g/100 g obtained for soybean by Zarkadas et al. (2007a, protein and is comparable to 1.1 g/100 g per protein
b). Total protein contents (11.77 to 19.01 g/100 g) of the recommended for a 2-5-year old preschool child
29 amaranth accessions are similar to 13 to 18 g/100 g (FAO/WHO, 1991).
obtained for some amaranth species by Dagmar et al. The sum of essential amino acids of amaranth in this
(2012). Bressani and Garcia-Vela (1990) also reported study ranged from 31.22 to 44.88 g/100 g per protein and
the total protein content of A. caudatus, A. is lower than 60.87 g/100 g per protein obtained for the
hypochondriacus and A. cruentus to be 14.5 to 14.6, 14.7 soybean cultivar (TGX 1448-2E) used for comparison.
to 15.9 and 15.3 to 16.1 g/100 g, respectively. Similar Results of this study are similar to earlier results obtained
results were obtained for the total protein content of A. in grain amaranth (47.6 g/100 g) and soybean (60.3
caudatus (16.6 g/100 g) by Gorinstein et al. (1998, 1999), g/100 g) by Gorinstein et al. (2002). Amaranth and
A. caudatus (11.0 g/100 g) by Repo-Carrasco-Valencia et soybean have higher amounts of total essential amino
al. (2010) and A. hypochondriacus (14.2 to 15 g/100 g) acids than 33.9 g/100 g reference protein pattern value of
by Czerwinski et al. (2004). FAO/WHO (1991) for the diet of a 2- to 5-year-old child,
Significant variation (p<0.05) in the amino acid and close to 51.2 g/100 g given for hen’s whole egg.
composition was observed among the ten selected These results indicate that grain amaranth provide a
amaranth accessions evaluated (Table 2). The amaranth good balance of total essential amino acids.
accessions evaluated were high in glutamic acid, aspartic From the calculated amino acid score, the limiting
acid, arginine, glycine and lysine. Similar trend was amino acid in amaranth is tryptophan and leucine while in
observed in the amino acid composition of the soybean soybean, it is methionine and tryptophan (Table 4).
cultivar (TGX 1448-2E) used for comparison in this study. Result of this study is not in agreement with result of
Zarkadas et al. (2007a, b) reported high levels of Bressani et al. (1987) in which threonine is the limiting
glutamic acid, aspartic acid, arginine, lysine, leucine and amino acid in amaranth protein. Earlier assessment of
glycine in some soybean cultivars evaluated. Most of the protein quality of soybean reported methionine as the
amaranth accessions evaluated in this study were limiting amino acid (Zarkadas et al., 2007a), this is similar
observed to have higher glycine, methionine and cysteine to result of the soybean cultivar (TGX 1448-2E) used as
contents than the soybean cultivar used as reference, reference in this study.
1806 Afr. J. Biotechnol.

Table 2. Comparison of the amino acid (AA) composition and total protein content (g/100 g of total protein; mean ± SD) of ten selected grain amaranth accessions with a soybean cultivar
(TGX 1448-2E).

Soybean Mean
AA 2 3 9 10 17 18 21 23 27 28 LSD CV
(TGX 1448-2E) AA
Aspartic acid 11.20 ± 0.20 8.60 ± 0.60 10.60 ± 0.52 10.80 ± 0.60 10.80 ± 0.36 9.47 ± 0.10 8.87 ± 0.10 11.40 ± 0.20 11.50 ± 0.40 11.00 ± 0.50 20.57 ± 0.45 13.22 0.69 3.09
Threonine 4.82 ± 0.02 3.50 ± 0.44 4.53 ± 0.03 4.58 ± 0.03 4.50 ± 0.30 4.22 ± 0.04 3.86 ± 0.06 4.78 ± 0.03 5.11 ± 0.03 4.79 ± 0.03 6.70 ± 0.30 5.28 0.31 3.52
Serine 7.37 ± 0.02 5.79 ± 0.02 7.11 ± 0.02 7.39 ± 0.10 7.22 ± 0.20 6.20 ± 0.20 5.70 ± 0.60 7.61 ± 0.01 8.14 ± 0.04 7.48 ± 0.06 8.40 ± 0.26 7.89 0.37 2.77
Glutamic acid 22.90 ± 0.40 14.10 ± 0.17 19.90 ± 0.90 22.40 ± 0.20 21.70 ± 0.30 18.40 ± 0.40 16.00 ± 0.57 23.20 ± 0.10 23.70 ± 0.20 21.50 ± 0.50 29.10 ± 0.26 23.82 0.72 1.78
Proline 4.95 ± 0.03 3.42 ± 0.02 4.64 ± 0.04 5.02 ± 0.03 5.05 ± 0.02 4.14 ± 0.03 3.39 ± 0.02 5.22 ± 0.11 5.23 ± 0.10 4.87 ± 0.07 7.60 ± 0.20 5.56 0.14 1.46
Glycine 8.82 ± 0.02 6.96 ± 0.17 8.03 ± 0.03 8.81 ± 0.01 8.67 ± 0.07 7.44 ± 0.04 6.97 ± 0.02 9.11 ± 0.10 9.04 ± 0.03 8.24 ± 0.02 6.10 ± 0.00 8.58 0.11 0.79
Alanine 4.68 ± 0.08 3.30 ± 0.30 4.30 ± 0.20 4.34 ± 0.01 4.37 ± 0.04 4.06 ± 0.03 3.59 ± 0.20 4.71 ± 0.01 4.70 ± 0.03 4.54 ± 0.04 6.45 ± 0.30 5.04 0.27 3.11
Cysteine 2.00 ± 0.20 1.13 ± 0.03 1.57 ± 0.02 1.88 ± 0.08 1.57 ± 0.03 1.32 ± 0.02 0.98 ± 0.01 1.54 ± 0.04 1.55 ± 0.03 1.47 ± 0.03 1.50 ± 0.07 1.64 0.12 4.41
Valine 5.15 ± 0.04 3.64 ± 0.03 4.69 ± 0.06 4.86 ± 0.05 4.98 ± 0.03 4.61 ± 0.01 4.19 ± 0.01 5.35 ± 0.05 5.38 ± 0.05 5.16 ± 0.02 7.30 ± 0.60 5.69 0.31 3.24
Methionine 2.74 ± 0.04 1.80 ± 0.20 2.35 ± 0.04 2.44 ± 0.04 2.32 ± 0.02 2.49 ± 0.02 1.77 ± 0.10 2.56 ± 0.10 2.45 ± 0.04 2.45 ± 0.02 2.15 ± 0.20 2.52 0.17 3.93
Isoleucine 4.75 ± 0.05 3.31 ± 0.02 4.37 ± 0.02 4.48 ± 0.02 4.65 ± 0.04 4.19 ± 0.02 3.94 ± 0.02 4.89 ± 0.02 4.98 ± 0.03 4.75 ± 0.10 7.25 ± 0.50 5.35 0.26 2.92
Leucine 7.53 ± 0.03 5.33 ± 0.03 6.94 ± 0.04 7.10 ± 0.01 7.22 ± 0.20 6.55 ± 0.15 6.00 ± 0.87 7.65 ± 0.02 7.74 ± 0.03 7.38 ± 0.03 12.25 ± 0.40 8.54 0.5 3.49
Tyrosine 3.12 ± 0.10 2.12 ± 0.01 2.82 ± 0.02 3.26 ± 0.05 2.88 ± 0.02 2.44 ± 0.03 2.27 ± 0.02 2.92 ± 0.02 3.06 ± 0.06 3.05 ± 0.05 4.95 ± 0.40 3.44 0.22 3.73
Phenylalanine 5.71 ± 0.02 4.04 ± 0.04 5.01 ± 0.01 5.39 ± 0.05 5.31 ± 0.00 4.77 ± 0.10 4.43 ± 0.02 5.66 ± 0.06 5.74 ± 0.04 5.44 ± 0.04 8.20 ± 0.20 6.17 0.13 1.21
Histidine 4.49 ± 0.10 3.07 ± 0.02 4.22 ± 0.10 4.48 ± 0.03 4.45 ± 0.03 3.53 ± 0.03 3.36 ± 0.06 4.53 ± 0.03 4.70 ± 0.20 4.30 ± 0.30 5.29 ± 0.11 4.70 0.21 2.65
Lysine 7.77 ± 0.02 5.65 ± 0.08 7.01 ± 0.01 7.42 ± 0.03 7.30 ± 0.30 6.84 ± 0.03 6.06 ± 0.06 7.88 ± 0.08 7.89 ± 0.07 7.55 ± 0.05 10.45 ± 0.70 8.39 0.40 2.80
Arginine 11.5 ± 0.50 6.70 ± 0.50 9.94 ± 0.03 11.30 ± 0.00 11.20 ± 0.40 9.13 ± 0.02 8.09 ± 0.05 11.40 ± 0.20 11.80 ± 0.70 11.40 ± 0.05 12.15 ± 0.20 11.52 0.57 2.91
Tryptophan 0.91 ± 0.02 0.88 ± 0.04 0.84 ± 0.04 0.91 ± 0.07 0.79 ± 0.04 0.72 ± 0.08 0.78 ± 0.08 0.91 ± 0.03 0.89 ± 0.04 0.81 ± 0.08 1.28 ± 0.26 0.88 0.16 1.09
Total protein (g/100 17.30 11.77 18.42 14.45 17.96 12.81 12.76 14.01 15.53 19.01 32.63 15.40 0.73 2.65
g dry matter)
Mean values and standard deviation (±) for three replicates.

Both amaranth and soybean could supply globulin are the major fractions of amaranth seed observed in the 20 and 24 kDa regions (Figure 1).
preschool child and adult requirements of proteins. Prolamin was not detected in all the 29 Electrophoretic pattern of albumin fractions of all
histidine, isoleucine, leucine, lysine, methionine, grain amaranth accessions evaluated, this is not the 29 accessions was similar; all subunits
cysteine, phenylalanine, tyrosine, threonine and in agreement with results of Gorinstein et al. migrated between 6.5 and 66 kDa and had
valine. (1998) who reported the presence of prolamin, characteristic bands at 20 and 24 kDa, this was
The sodium dodecyl sulfate polyacrylamide gel though in very low amount which may be due to similar to the soybean cultivar used for
electrophoretic separation (Figures 1 to 3) the fact that it is probably derived from the comparison. Accessions 5, 6, 7 (A. cruentus) and
revealed that albumin, globulin and glutelin are perisperm of the amaranth seeds. Konishi et al. 14 and 15 (A. hybrid) differed from others mainly
the major storage proteins in amaranth. Albumins, (1985) and Gorinstein et al. (1991) reported that in the region of 22 kDa. Globulin fractions had
globulins and glutelins showed similar patterns for the amount of alcohol soluble proteins in distinct bands at 14 to 36 kDa and just above the
homologous protein fractions isolated from amaranth was as low as in oats and rice. 45 kDa and shared similar bands with soybean
different species. Earlier reports of Silva-Sanchez Albumins are a protein fraction with polypeptides cultivar used for reference in the regions of 20 to
et al. (2008), Czerwinski et al. (2004) and of very heterogenous sizes, with low molecular 36 kDa and just above the 45 kDa (Figure 2).
Gorinstein et al. (1998) showed that albumin and weight components being the most abundant as Result of this study is similar to result of
 Akin-Idowu et al. 1807

Table 3. Comparison of the essential amino acid (EAA) scores of ten selected grain amaranth accessions and one soybean cultivar with hen’s whole egg, and the FAO/WHO EAA
Requirements of a 2-5-year-old child. The values are in mg of amino acid/g of total protein.

EAAa requirements Soybean

EAA for a preschool 2b 3 9 10 17 18 21 23 27 28 Egga
child (2-5 year old) (TGX 1448-2E)
Histidine 19 44.9 30.7 42.2 44.8 44.5 35.3 33.6 45.3 47.0 43.0 52.9 22
Isoleucine 28 47.5 33.1 43.7 44.8 46.5 41.9 39.4 48.9 49.8 47.5 72.5 54
Leucine 66 75.3 53.3 69.4 71.0 72.2 65.5 60.0 76.5 77.4 73.8 122.5 86
Lysine 58 77.7 56.5 70.1 74.2 73.0 68.4 60.6 78.8 78.9 75.5 104.5 70
Methionine + cysteine 25 47.4 29.3 39.2 43.2 38.9 38.1 18.68 41.0 40.0 39.2 36.5 57
Phenylalanine + tyrosine 63 88.3 61.6 78.3 86.5 81.9 72.1 67.0 85.8 88.0 84.9 131.5 93
Threonine 34 48.2 35.0 45.3 45.8 45.0 42.2 38.6 47.8 51.1 47.9 67.0 47
Tryptophan 11 9.1 8.8 8.4 9.07 7.9 7.2 7.8 9.1 8.9 8.07 12.8 17
Valine 35 51.5 36.4 46.9 48.6 49.8 46.1 41.9 53.5 53.8 51.6 73.0 66
mg/g Total protein EAA9 339 438.7 312.2 399.6 416.6 415.2 379.2 343.9 442.1 448.8 426.3 608.7 512
Total protein (%) EAA9 33.9 43.9 31.2 40.0 41.7 41.5 37.9 34.4 44.2 44.9 42.6 60.9 51.2
Percent amino acid scorec 73 73 73 73 73 73 73 73 73 73 91 97
a b
Data from FAO/WHO (1991). Calculation of protein ratings of the ten amaranth accessions and a soybean cultivar (TGX 1448-2E) was carried out by comparison of the amino acid
c
composition of hen’s whole egg with that of the reference pattern established by FAO/WHO (1991) for a preschool child (2-5- year-old). True protein digestibility values were taken from the
USFDA (Federal Register, Appendix B (1993) and FAO (1973) scoring pattern.

Table 4. Amino acid scores of ten selected accessions of grain amaranth, one soybean cultivar (TGX 1448-2E) and their limiting amino acid.

EAA 30
EAA 2 3 9 10 17 18 21 23 27 28
Requirement (Soybean)
Histidine 19 2.36 1.61 2.22 2.36 2.34 1.86 1.77 2.38 2.47 2.26 2.78
Isoleucine 28 1.70 1.18 1.56 1.60 1.66 1.50 1.41 1.75 1.79 1.70 2.59
Leucine 66 1.14 0.81 1.05 1.08 1.09 0.99 0.91 1.16 1.17 1.12 1.85
Lysine 58 1.34 0.97 1.21 1.28 1.25 1.18 1.04 1.36 1.36 1.30 1.80
Methionine + cysteine 25 1.89 1.17 1.57 1.73 1.56 1.52 0.75 1.64 1.60 1.57 1.46
Phenylalanine + tyrosine 63 1.40 0.98 1.24 1.37 1.30 1.14 1.06 1.36 1.40 1.35 2.09
Threonine 34 1.42 1.03 1.33 1.35 1.32 1.24 1.13 1.41 1.5 1.41 1.97
Tryptophan 11 0.83 0.80 0.77 0.82 0.72 0.65 0.71 0.83 0.81 0.73 1.16
Valine 35 1.47 1.04 1.34 1.39 1.42 1.32 1.20 1.53 1.54 1.47 2.08
Limiting amino acid Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Leu, Tryp Met, Tryp
Leu, Leucine; Try, tryptophan; Met, methionine.
1808 Afr. J. Biotechnol.

Figure 1. SDS-PAGE of albumin fractions of 29 accessions of Amaranth seeds. Lanes 1 - 4 A. caudatus; 5 - 12 A. cruentus; M-
marker; 13 - 19 A. hybrid; 20 - 27 A hypochondriacus; 28 - 29, A. hybridus; 30, soybean (TGX 1448-2E).

Figure 2. SDS-PAGE of globulin fractions of 29 accessions of Amaranth seeds. Lanes 1 - 4 A. caudatus; 5 - 12 A. cruentus; M-
marker; 13 - 19 A. hybrid; 20 - 27 A hypochondriacus; 28 and 29, A. hybridus; 30 soybean (TGX 1448-2E).

Gorinstein et al. (1991b) who reported a major globulin band at 38 kDa. The amaranth glutelin fractions had
band at 14 to 18 kDa of some amaranth species, but this three main non-separated subunits in the region of 4 to
is not in agreement with the result of Barba de la Rosa et 14 kDa, 24 to 34 kDa and 65 to 66 kDa (Figure 3). These
al. (1992) who reported that all globulins showed a major protein subunits were similar in all the 29 grain amaranth
 Akin-Idowu et al. 1809

Figure 3. SDS-PAGE of glutelin fractions from 29 accessions of Amaranth seeds. Lanes 1 - 4 A. caudatus; 5 - 12 A. cruentus;
13 - 19 A. hybrid; M-marker; 20 - 27 A. hypochondriacus; 28 - 29, A. hybridus; 30 Soybean (TGX 1448-2E).

accessions. There were outstanding similarities between be a nutritive substitute for cereals and improve value in
the electrophoretic patterns of all amaranth accessions different diets in developing countries where protein
evaluated and the soybean cultivar used for comparison. malnutrition is still a major challenge.
The abundant components in the glutelin fraction
between 4 and 14 kDa, 30 kDa and 65 and 66 kDa of all
29 amaranth accessions evaluated in this study are ACKNOWLEDGEMENT
similar to the results of Gorinstein et al. (2002) for A.
caudatus, maize and rice. It will therefore be possible to The authors are grateful to the USDA-ARS North Central
use Amaranthus species in blends with other cereals for Regional Plant Introduction Station (NCRPIS) in Ames,
food nutrients. USA for providing the amaranth seeds, as well as Lava
Kumar of the Virology Unit, IITA, Ibadan, Nigeria for
providing the facilities to carry out this investigation.
Conclusion

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