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It is important to identify the growth stage at which the plant has the maximum antioxidant properties for the production of bioactive compounds from crops or agricultural by-products or for forage as a possible source of antioxidants in livestock. Therefore, we investigated the phenolic composition and antioxidant capacity of the aerial part of soybean at seven stages classified as vegetative stages (V5 and V6) and reproductive stages (R1, R2, R3, R4, and R5). Aqueous-methanol extracts were evaluated for their total phenolic content (TPC), ferric-reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC), antioxidant activity as determined by photochemiluminescence assay (PCL-ACL), Fe 2+ chelating ability, and antiradical activity against DPPH •. The extracts with the highest TPC content were obtained at stages V6 and R5. The phenolic compounds profile, as determined by DAD-HPLC, was characterized by 19 compounds, that differed significantly by growth stage (p < 0.05). Antioxidant tests showed significant differences among stages (p < 0.05). The lowest TEAC value was found for the R2 stage and the highest values for the R3 and R1 stages. FRAP values ranged from 623 to 780 µmol Fe 2+ /g extract. PCL-ACL values ranged from 516 to 560 µmol Trolox eq./g extract; Fe 2+ chelation ability ranged from 36.5 to 51.7%. The highest antiradical activity against DPPH • was found in the extract from the V5 stage, which had the lowest EC 50 value. The extracts of soybean plant can be used in pharmacy for the production of nutraceuticals by virtue of their good antioxidant activity and content of flavonols and other bioactive constituents.
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agronomy
Article
Phenolic Composition and Antioxidant Activities of
Soybean (Glycine max (L.) Merr.) Plant during
Growth Cycle
Pier Giorgio Peiretti 1, Magdalena Karama´c 2, Michał Janiak 2, Erica Longato 3,
Giorgia Meineri 3, Ryszard Amarowicz 2,* and Francesco Gai 1
1Institute of Sciences of Food Production, National Research Council, 10095 Grugliasco, Italy;
piergiorgio.peiretti@ispa.cnr.it (P.G.P.); francesco.gai@ispa.cnr.it (F.G.)
2Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Tuwima Street 10,
10-748 Olsztyn, Poland; m.karamac@pan.olsztyn.pl (M.K.); m.janiak@pan.olsztyn.pl (M.J.)
3
Department of Veterinary Sciences, University of Turin, 10095 Grugliasco, Italy; erica.longato@unito.it (E.L.);
giorgia.meineri@unito.it (G.M.)
*Correspondence: r.amarowicz@pan.olsztyn.pl; Tel.: +49-895-234-627
Received: 5 March 2019; Accepted: 21 March 2019; Published: 23 March 2019


Abstract:
It is important to identify the growth stage at which the plant has the maximum antioxidant
properties for the production of bioactive compounds from crops or agricultural by-products or for
forage as a possible source of antioxidants in livestock. Therefore, we investigated the phenolic
composition and antioxidant capacity of the aerial part of soybean at seven stages classified as
vegetative stages (V5 and V6) and reproductive stages (R1, R2, R3, R4, and R5). Aqueous-methanol
extracts were evaluated for their total phenolic content (TPC), ferric-reducing antioxidant power
(FRAP), Trolox equivalent antioxidant capacity (TEAC), antioxidant activity as determined by
photochemiluminescence assay (PCL-ACL), Fe
2+
chelating ability, and antiradical activity against
DPPH
. The extracts with the highest TPC content were obtained at stages V6 and R5. The phenolic
compounds profile, as determined by DAD-HPLC, was characterized by 19 compounds, that differed
significantly by growth stage (p< 0.05). Antioxidant tests showed significant differences among
stages (p< 0.05). The lowest TEAC value was found for the R2 stage and the highest values for
the R3 and R1 stages. FRAP values ranged from 623 to 780
µ
mol Fe
2+
/g extract. PCL-ACL values
ranged from 516 to 560
µ
mol Trolox eq./g extract; Fe
2+
chelation ability ranged from 36.5 to 51.7%.
The highest antiradical activity against DPPH
was found in the extract from the V5 stage, which had
the lowest EC
50
value. The extracts of soybean plant can be used in pharmacy for the production
of nutraceuticals by virtue of their good antioxidant activity and content of flavonols and other
bioactive constituents.
Keywords: Glycine max; morphological stage; antioxidant activity; phenolics
1. Introduction
Soybean (Glycine max (L.) Merr.) is one of the most important plant proteins sources consumed
by humans and animals. It is attracting growing interest as a source of high-protein forage in
Europe [
1
], North America [
2
], South Asia [
3
], and Japan [
4
]. The few studies that have examined
the antioxidant activities and phenolic profiles of soybean seed found that soybean varieties differ in
their antioxidant properties, total phenolic contents, anthocyanin and flavonoid levels [
5
11
]. It has
also been demonstrated that health benefits can be derived from the antioxidant activities of some
varieties of soybean, especially in their seed coat [
12
14
] or hulls, as alternative source of bioactive
compounds [15].
Agronomy 2019,9, 153; doi:10.3390/agronomy9030153 www.mdpi.com/journal/agronomy
Agronomy 2019,9, 153 2 of 15
There is abundant research on the phenolic composition and antioxidant activities of soybean
seed and its by-products (e.g., soy milk, tofu, and fermented products) for the prevention of certain
cancers, osteoporosis, chronic renal disease, coronary heart disease, and for their anti-atherosclerotic
activity [
6
,
12
,
16
]. It has been reported that isoflavones (e.g., genistein and daidzein) in soybean
seeds may have either weak antiestrogenic or proestrogenic effects [
17
]. Isoflavones (daidzein
and genistein) are believed responsible for these observed health benefits. The isoflavone content
has been determined in a variety of soy-based foods and especially in non-fermented soy foods,
where isoflavones are present mainly as
β
-glycoside conjugates (genistin and daidzin) [
18
]. Previous
research found that the flavonoids in soy leaves are mainly kaempferol glycosides with only trace
amounts of malonyl-genistin and genistin, whereas those in soybean are mainly isoflavone glycosides
and derivatives with malonyl-genistin, which is the most abundant, followed by malonyl-glycitin,
genistin, daidzin, daidzein, genistein, and glycitin in decreasing order [
19
]. Soybean seed is rich in
glycosides (genistin, daidzin, glycitin) and malonyl-glycosides (malonyl-glycitin and malonyl-genistin).
These glycosides possess similar antioxidant activities, as determined by FRAP and DPPH assays,
and have weaker antioxidant activities, as determined by low-density lipoprotein oxidation assay,
than their corresponding aglycones (genistein and daidzein) [
6
]. Bennett et al. [
20
] reported that
genistein, daidzein, and glycitein are the main isoflavones of soybean seeds, can be synthesized
by the phenylpropanoid pathway, and then stored in vacuoles as conjugates. This is influenced by
environmental conditions during seed fill and it is cultivar-dependent [21,22].
The impact of elevated thermal stress on isoflavone and tocopherol accumulation in soybean
seeds has been studied at specific growth stages (none, pre-emergence, vegetative, early reproductive
(R1–R4), late-reproductive (R5–R8)) [
23
]. It was demonstrated that high thermal stress reduces total
isoflavone concentration compared to control seeds. Isoflavone response to thermal stress occurred at
all growth stages and was greatest when stress occurred during stages R5–R8. The contribution of
glycitein and daidzein to total isoflavone content was increased in comparison with the concentrations
found in the control soybean seeds when plants were subjected to stress at all growth stages and also at
stages R5–R8. Tsukamoto et al. [
24
] found that the isoflavone content of soybean varieties significantly
decreased in the seeds harvested after growing at high temperatures, whereas at cool temperatures it
was increased during the onset and duration of seed fill.
The content of tocopherol, isoflavone, TPC, total antioxidative capacity, and free radical
scavenging activity have been determined in immature soybean seeds harvested at three reproductive
stages (R5, R6 and R7) [
25
]. There was a reduction in TPC, total antioxidant capacity, and free
radical-scavenging activity and an increase in content of isoflavone isomers and tocopherol in
late-harvested seeds. The major form of isoflavone at all reproductive stages was genistein, which
increased from 84 to 808
µ
g/g DM at R4 stage and at complete maturity, respectively. At the same
reproductive stages, DPPH
scavenging activity, FRAP, and TPC decreased from 59 to 44%, from 55 to
21 mmol/kg DM, and from 3.1 to 1.3 mg of GAE/g, respectively. Kumar et al. [
26
] assessed isoflavones,
vitamin C, TPC, FRAP, DPPH radical-scavenging activity in soybean genotypes with varying seed
coat color (yellow, green, and black). The authors concluded that soybean with green or yellow seed
coat had lower free radical-scavenging activity than black soybean, while black and green soybean
exhibited comparatively higher FRAP values than yellow soybean.
Malenˇci´c et al. [
27
] evaluated the TPC and antioxidant ability of the seeds of 20 soybean hybrids
and found a positive linear correlation between antioxidant activity and contents of total tannins,
proanthocyanidins, and TPC. They observed higher levels of all polyphenol classes in the extracts
of soybean hybrids with the highest antioxidant activity. Moreover, they reported that because the
majority of the single-cross hybrids were poor in tannins, they could be recommended as a good
source for ensiled livestock feed. Whent et al. [
28
] studied the antioxidant properties and chemical
composition of eight soybean cultivars grown in different locations and showed that an antioxidant
property may respond to individual environmental factors differently. No difference in TPC (range,
1.2–2.1 mg of GAE/g of whole soybean) was observed in any soybean cultivars grown under three
Agronomy 2019,9, 153 3 of 15
different environmental conditions. Total isoflavones in the soybean samples ranged from 0.37 to
0.90
µ
mol/g of soybean among all genotypes grown in the different environments. The concentration
of daidzein, genistein, and glycitein in all soybean samples ranged from 29.3 to 107.7
µ
g/g, from 15.3
to 83.0 µg/g, and from 25.8 to 95.8 µg/g, respectively.
Because the polyphenolic contents and antioxidant capacities of crops, including perilla [
29
],
quinoa [
30
] and safflower [
31
] may also vary in the whole plant during growth, it is important to
identify the growth stage at which the plant has the maximum antioxidant properties for the production
of bioactive compounds from crops or agricultural by-products or for forage as a possible source
of antioxidants in livestock. The feeding value of soybean forage and the effects of plant ageing on
chemical composition, gross energy,
in vitro
true digestibility, neutral detergent fiber digestibility,
and fatty acid profile have been documented in the literature [
1
]. The innovative aspect of the present
study was to characterize the antioxidant activities and phenolic composition of the soybean plant
during its growth cycle, because, to the best of our knowledge, no research has been reported in
literature about the change of these parameters during plant ageing.
2. Materials and Methods
2.1. Chemicals
Ferrous chloride, sodium persulfate, the Folin-Ciocalteau’s phenol reagent, catechin, caffeic acid,
rutin, quercetin, 2,2
0
-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-
picrylhydrazyl (DPPH), 2,4,6-tri(2-pyridyl)-s-triazine, and 6-hydroxy-2,5,7,8-tetramethyl-
chroman-2-carboxylic acid (Trolox) were obtained from Sigma-Aldrich (St. Louis, MO, USA).
Daidzin, daidzein, genistein, and kaempferol were obtained from Extrasynthese (Genay, France).
Methanol, acetonitrile, and all other chemicals were acquired from Avantor Performance Materials
(Gliwice, Poland).
2.2. Plant Material and Growth Conditions
Soybean seeds of the cultivar Eiko, with a high content of crude protein (436 g/kg),
were purchased
from Sipcam Italia S.p.A. (Pero, Milan, Italy). The study was carried out at the
Department of Agriculture, Forestry, and Food Sciences of the University of Turin. Field trials were
carried out in Grugliasco, Piedmont, Italy (45
03
0
57.9” N 7
35
0
36.9” E, 293 m a.s.l.) in sandy soil, low in
organic matter with moderately alkaline pH, and taxonomically classified as entisol according to the
United States Department of Agriculture soil classification system [
32
]. The climate of the study site is
temperate sub-continental, characterized by two main rainy periods in spring and autumn. During the
growing season, the total precipitation varies from 76.2 mm/month (May) to 139.0 mm/month (July),
and the mean relative humidity and mean temperature is 68.6% and 20.3
C, respectively. The soybean
stands were seeded in the spring in an experimental field (4 m wide and 14 m long). Sampling was
performed without any borders, in order to obtain representative samples not affected by border
effects. No fertilizers or irrigation were applied after sowing. The herbage samples were collected with
edging shears (0.1 m cutting width) at seven progressive stages of development classified as vegetative
stages (V5 and V6) and reproductive stages (R1, R2, R3, R4, and R5), respectively [
33
]. Two sample
replicates for each stage were cut to a 1–2 cm stubble height from two subplots measuring 4 m
2
each.
Sampling was done in the morning after dew had evaporated and was never carried out on rainy days.
2.3. Extraction
After milling, the lyophilized plants were mixed with 80% (v/v) methanol at a ratio of 1:10 (w/v).
Extractions were performed in tightly closed glass vessels placed in a shaking water bath (SW22,
Julabo, Seelbach, Germany) at 65
C for 15 min and then filtered. Extraction was repeated from the
precipitates twice more. The supernatants were then combined for each sample, and methanol was
evaporated under vacuum using a rotary evaporator at 50
C (Rotavapor R-200, Büchi Labortechnik,
Agronomy 2019,9, 153 4 of 15
Flawil, Switzerland). The remaining water was removed by lyophilization (Lyph Lock 6, Labconco,
Kansas City, MO, USA). Mass balance was carried out to calculate yield (%) of extraction.
2.4. Determination of Total Phenolic Content
Colorimetric reaction with Folin-Ciocalteu’s reagent (FCR) was performed to determine the
content of phenolic compounds in soybean samples [
34
]. The reaction mixtures consisted of 0.25 mL of
samples dissolved in methanol (1.25 mg/mL), 0.25 mL of FCR, 0.5 mL of saturated solution of Na
2
CO
3
,
and 4 mL of water and were left to stand in the dark for 25 min. After centrifugation (MPW-350R,
MPW Med. Instruments, Warsaw, Poland) for 5 min at 5000
×
g, absorbance of the supernatants was
recorded at
λ
= 725 nm (DU-7500 spectrophotometer, Beckman Instruments, Fullerton, CA, USA).
TPC results were calculated on the basis of the calibration curve for catechin and were expressed as
equivalents of standard per g of extract or per g of plant fresh matter.
2.5. HPLC Analysis
Phenolic compounds of soybean extracts were separated using a high-performance liquid
chromatography (HPLC) Shimadzu system (Shimadzu, Kyoto, Japan), which consisted of a CBM-20A
controller, a DGU-20A5R degassing unit, two LC-30AD pumps, a SIL-30AC autosampler, an SPD-M30A
diode array detector, and a CTO-20AC column oven [
35
]. Portions of 10
µ
L of extract solutions in
80% (v/v) methanol were injected into a Luna C8(2) column (4.6
×
150 mm, particle size 3
µ
m,
Phenomenex, Torrance, CA, USA). The compounds were eluted in linear gradient system of solvent A
(acetonitrile-water-trifluoroacetic acid, 5:95:0.1, v/v/v) and B (acetonitrile-trifluoroacetic acid, 100:0.1,
v/v): 0–18 min, 0–60% B. The flow rate was 1 mL/min and the oven temperature 25
C. Detection was
carried out by scanning over a wavelength range from 200 to 600 nm. The contents of individual
phenolic compounds were expressed on the basis of the calibration curves of the corresponding
standards or structurally related substances.
2.6. Trolox Equivalent Antioxidant Capacity
The TEAC of soybean samples was determined according to a previously described method [
36
].
Trolox was used as standard; the results were expressed as
µ
mol Trolox equivalents per g of extract or
per g of fresh matter of plant.
2.7. Ferric-Reducing Antioxidant Power
The FRAP reagent was prepared using a previously described method [
37
]. FRAP results were
expressed as
µ
mol Fe
2+
equivalents per g of extract or per g of fresh matter using the calibration curve
for FeSO4.
2.8. Photochemiluminescence Assay
The scavenging activity of soybean samples was evaluated by a photochemiluminescence
(PCL-ACL) method [
38
] in which superoxide radical anions (O
2•−
) are generated from luminol.
Soybean extracts were dissolved in methanol (0.25 mg/mL). The reactions were carried out using
kits for the determination of antioxidant capacity of lipid-soluble substances (Analytik Jena, Jena,
Germany) mixing 2.3 mL of methanol (reagent 1), 200
µ
L of buffer solution (reagent 2), 25
µ
L of
luminol (reagent 3), and 10
µ
L of sample. Measurement was performed on a Photochem device with
PCLsoft software (Analytik Jena). Trolox was used to prepare the calibration curve. The results are
expressed as µmol of Trolox equivalents per g of extract or per g of fresh matter of plant.
2.9. Fe2+ Chelation Ability
Ferrous ion chelating ability of soybean extracts was determined by a method with ferrozine [
39
],
that was modified for reaction on multi-well plates [
40
]. Briefly, 200
µ
L of aqueous solution of extract
Agronomy 2019,9, 153 5 of 15
(0.25 mg/mL) and 20
µ
L of 0.4 mM FeCl
2×
4H
2
O were pipetted into each well. Added to this were
40
µ
L of 5 mM ferrozine; after 10 min absorbance was read at
λ
= 562 nm using an Infinite M1000
microplate reader (Tecan, Männedorf, Switzerland). Chelating ability is expressed as percentage of
Fe2+ bound.
2.10. Scavenging of the DPPH Radical
The ability of soybean extracts to scavenge DPPH
was evaluated according to a previously
described method [
41
]. Methanolic solutions of extracts (range, 2–10 mg/mL) were prepared. Portions
of 100
µ
L of these solutions were mixed with 0.25 mL of 1 mM DPPH and 2 mL of methanol.
Absorbance of mixtures was read at
λ
= 517 nm after left standing for 20 min. The results were
plotted as absorbance values vs. sample concentration (mg/assay). Additionally, EC
50
values were
defined as concentration of extract (mg/mL reaction mixture) needed to scavenge 50% of initial DPPH
and were estimated.
2.11. Statistical Analysis
The HPLC separation was conducted in duplicate. Antioxidant assays were performed in at least
three repetitions. Results are presented as means
±
standard deviation (SD). One-way ANOVA and
Fisher’s least significant difference test at a level of p< 0.05 were used to determine the significance
of differences between mean values. To determine the relation between results of total phenolics
ant antioxidant assays the Pearson correlation was used. Statistical analysis was performed with
GraphPad Prism version 6.04 for Windows (GraphPad Software, San Diego, CA, USA).
3. Results
Table 1reports the extraction yield and TPC of the soybean plant at different growth stages
expressed on the extract and the fresh matter. The highest extraction yield was obtained at the V6
stage (p< 0.05). The TPC ranged from 42.2 to 50.4 mg catechin eq./g extract, with the highest values
observed for stages V6, R4, and R5. The results reported for the plants were also the highest TPC for
these three growth stages plus V5 (p< 0.05). The TPC was lowest for extracts obtained from the R1–R3
stages; the lowest TPC values expressed on plant were observed for stages R2 and R3.
Table 1.
Yield of extraction (%) and total phenolic content (TPC) of the soybean plant extract and fresh
matter (FM) at different growth stages.
Growth Stage Days after Seeding Extraction Yield
TPC
(mg Catechin eq./g Extract) (mg Catechin eq./g FM)
V5 34 19.2 ±0.3 bc 1 47.7 ±2.6 ab 1.75 ±0.09 ab
V6 41 21.0 ±1.5 ab 50.4 ±1.1 a1.95 ±0.002 a
R1 55 18.7 ±1.4 bc 44.3 ±0.8 bc 1.63 ±0.002 bc
R2 62 19.2 ±0.5 bc 42.2 ±2.3 c1.49 ±0.09 cd
R3 69 17.6 ±1.4 c43.8 ±1.1 bc 1.40 ±0.04 d
R4 74 17.6 ±1.1 c49.6 ±3.7 a1.78 ±0.10 ab
R5 78 18.1 ±0.1 c50.4 ±2.2 a1.82 ±0.18 ab
1Means with the different letters in the same column are significantly different (p< 0.05).
The phenolic compound profile, as determined by DAD-HPLC, was characterized by
19 compounds
(Figure 1): seven hydroxycinnamic acid derivatives (compounds from 1 to 7),
five flavonol derivatives (compounds 8, 10, 11, 13, 14), three isoflavone derivatives (compounds
from 15 to 17), rutin (compound 12), daidzin (compound 9), daidzein (compound 18), and genistein
(compound 19). The content of several phenolic compounds differed significantly by growth stage
(p< 0.05) when the results were expressed on the plant extract (compounds 5, 7, 8, 9, 11, 12, 14, 18)
(Table 2) and when they were expressed on the fresh matter of soybean (compounds 5, 7, 9, 12, 14, 18)
(Table 3). HPLC revealed that the predominant compounds in all samples were 12 (rutin), 10 (flavonol,
Agronomy 2019,9, 153 6 of 15
expressed as kaempferol equivalents), and 8 (flavonol, expressed as quercetin equivalents). The sum
of flavonols differed by growth stage, with the lowest value recorded for stage V6 and highest for
stage V5 (p< 0.05), while the sum of phenolic compounds, sum of hydroxycinnamic acids, and sum of
isoflavones did not differ significantly (p0.05) across the growth cycle.
Agronomy 2019, 9, x FOR PEER REVIEW 6 of 14
(Table 2) and when they were expressed on the fresh matter of soybean (compounds 5, 7, 9, 12, 14,
18) (Table 3). HPLC revealed that the predominant compounds in all samples were 12 (rutin), 10
(flavonol, expressed as kaempferol equivalents), and 8 (flavonol, expressed as quercetin
equivalents). The sum of flavonols differed by growth stage, with the lowest value recorded for
stage V6 and highest for stage V5 (p < 0.05), while the sum of phenolic compounds, sum of
hydroxycinnamic acids, and sum of isoflavones did not differ significantly (p 0.05) across the
growth cycle.
Figure 1. HPLC chromatogram of the phenolic compounds present in the soybean plant extract.
Table 3 presents the antioxidant activity of each growth stage determined as TEAC, FRAP,
PCL-ACL, and Fe2+ chelating ability. All antioxidant tests showed significant differences between
growth stages (p < 0.05). TEAC was lowest for stage R2, when expressed on the extract and on the
fresh matter, and highest for stages R3 and R1 when the results were expressed on the extract and on
the fresh matter, respectively. FRAP values ranged from 623 to 780 μmol Fe2+/g extract and from 21.4
to 28.5 μmol Fe2+/g FM; PCL-ACL values ranged from 516 to 560 μmol Trolox eq./g extract and from
17.6 to 21.8 μmol Trolox eq./g FM. Finally, Fe2+ chelating ability ranged from 36.5% for stage R5 to
51.7% for stage R3. Figure 2 shows the antiradical activity against DPPH radical expressed as the
EC50 value, which differed significantly at different growth stages (p < 0.05). The highest antiradical
activity was obtained for extract from stage V5 with the lowest EC50 value (0.126 mg/mL); the highest
EC50 value (0.218 mg/mL) was found for stage R2.
The content of total phenolic in the extracts was not correlated with their antioxidant activity
determined with ABTS, FRAP, DPPH, PCL-ACL and Fe2+ chelation.
Figure 1. HPLC chromatogram of the phenolic compounds present in the soybean plant extract.
Table 3presents the antioxidant activity of each growth stage determined as TEAC, FRAP,
PCL-ACL, and Fe
2+
chelating ability. All antioxidant tests showed significant differences between
growth stages (p< 0.05). TEAC was lowest for stage R2, when expressed on the extract and on the
fresh matter, and highest for stages R3 and R1 when the results were expressed on the extract and on
the fresh matter, respectively. FRAP values ranged from 623 to 780
µ
mol Fe
2+
/g extract and from 21.4
to 28.5
µ
mol Fe
2+
/g FM; PCL-ACL values ranged from 516 to 560
µ
mol Trolox eq./g extract and from
17.6 to 21.8
µ
mol Trolox eq./g FM. Finally, Fe
2+
chelating ability ranged from 36.5% for stage R5 to
51.7% for stage R3. Figure 2shows the antiradical activity against DPPH radical expressed as the EC
50
value, which differed significantly at different growth stages (p< 0.05). The highest antiradical activity
was obtained for extract from stage V5 with the lowest EC
50
value (0.126 mg/mL); the highest EC
50
value (0.218 mg/mL) was found for stage R2.
Agronomy 2019,9, 153 7 of 15
Agronomy 2019, 9, x FOR PEER REVIEW 7 of 14
Figure 2. Antiradical activity of the soybean plant extracts against the DPPH at different growth
stages. Means of EC50 with different letters are significantly different (p < 0.05).
Figure 2.
Antiradical activity of the soybean plant extracts against the DPPH
at different growth
stages. Means of EC50 with different letters are significantly different (p< 0.05).
The content of total phenolic in the extracts was not correlated with their antioxidant activity
determined with ABTS, FRAP, DPPH, PCL-ACL and Fe2+ chelation.
Agronomy 2019,9, 153 8 of 15
Table 2. Phenolic compound content in soybean plant extract (mg/g) at different growth stages.
No. tR(min) λMax (nm) Compound Content
V5 V6 R1 R2 R3 R4 R5
1 4.46 328 Hydroxycinnamic acid 10.34 ±0.21 a0.47 ±0.33 a0.39 ±0.04 a0.50 ±0.12 a0.45 ±0.02 a0.44 ±0.03 a0.45 ±0.12 a
2 4.73 328 Hydroxycinnamic acid 11.23 ±0.20 a1.37 ±0.45 a1.08 ±0.26 a1.38 ±0.08 a1.27 ±0.07 a0.98 ±0.08 a1.21 ±0.20 a
3 4.86 328 Hydroxycinnamic acid 11.54 ±0.23 a1.43 ±1.08 a1.41 ±0.01 a1.72 ±0.41 a1.54 ±0.09 a1.64 ±0.02 a1.52 ±0.43 a
4 5.95 315 Hydroxycinnamic acid 10.53 ±0.08 a0.53 ±0.36 a0.54 ±0.01 a0.67 ±0.10 a0.57 ±0.06 a0.57 ±0.02 a0.57 ±0.08 a
5 6.22 321 Hydroxycinnamic acid 10.71 ±0.09 bc 1.21 ±0.12 a0.76 ±0.03 bc 0.94 ±0.22 ab 0.73 ±0.06 bc 0.63 ±0.10 c0.70 ±0.07 bc
6 6.33 325 Hydroxycinnamic acid 10.52 ±0.06 a0.52 ±0.19 a0.47 ±0.04 a0.56 ±0.10 a0.54 ±0.06 a0.53 ±0.03 a0.53 ±0.08 a
7 6.54 327 Hydroxycinnamic acid 10.82 ±0.14 ab 0.96 ±0.13 a0.69 ±0.08 b0.81 ±0.03 ab 0.76 ±0.10 ab 0.67 ±0.07 b0.79 ±0.10 ab
8 7.42 256,353 Flavonol 26.80 ±0.33 ab 3.80 ±2.97 b5.62 ±0.04 ab 6.97 ±0.52 a6.02 ±0.88 ab 7.00 ±0.89 a6.32 ±1.02 ab
9 7.71 251,295 Daidzin 0.67 ±0.17 ab 0.91 ±0.49 ab 1.50 ±0.89 a1.11 ±0.02 ab 0.75 ±0.10 ab 0.59 ±0.01 ab 0.54 ±0.12 b
10 7.87 265,346 Flavonol 34.19 ±0.33 a3.27 ±0.70 a3.97 ±0.45 a4.32 ±0.10 a3.97 ±0.70 a4.37 ±0.29 a3.89 ±0.57 a
11 8.05 255,353 Flavonol 22.50 ±0.12 a1.34 ±1.08 b2.14 ±0.01 ab 2.46 ±0.10 a2.28 ±0.28 ab 2.51 ±0.20 a2.19 ±0.32 ab
12 8.37 257,355 Rutin 32.89 ±1.10 a23.12 ±5.08 b24.45 ±0.72 b
28.09
±
1.91
ab 23.23 ±2.69 b
29.18
±
4.32
ab
25.55
±
4.43
ab
13 8.87 265,348 Flavonol 33.40 ±0.15 a2.23 ±1.12 a3.07 ±0.54 a3.13 ±0.14 a2.70 ±0.23 a3.09 ±0.26 a2.78 ±0.40 a
14 9.08 263,349 Flavonol 35.02 ±0.17 a2.61 ±1.81 b3.91 ±0.30 ab 4.24 ±0.20 ab 3.78 ±0.46 ab 4.06 ±0.39 ab 3.70 ±0.40 ab
15 9.23 259 Isoflavone 41.49 ±0.2 a1.37 ±1.11 a2.48 ±1.06 a2.16 ±0.02 a1.53 ±0.07 a1.24 ±0.07 a1.11 ±0.16 a
16 9.41 268 Isoflavone 40.57 ±0.01 a0.62 ±0.23 a0.56 ±0.13 a0.56 ±0.01 a0.46 ±0.06 a0.52 ±0.04 a0.48 ±0.06 a
17 10.56 260 Isoflavone 40.68 ±0.19 a0.67 ±0.57 a1.44 ±0.61 a1.30 ±0.10 a0.96 ±0.04 a0.90 ±0.16 a0.85 ±0.13 a
18 11.99 259 Daidzein 0.10 ±0.05 c0.25 ±0.23 bc 0.71 ±0.33 a0.67 ±0.03 a0.52 ±0.01 ab 0.62 ±0.05 ab 0.53 ±0.08 ab
19 14.10 260 Genistein 0.05 ±0.01 a0.06 ±0.05 a0.11 ±0.10 a0.11 ±0.01 a0.11 ±0.01 a0.08 ±0.01 a0.05 ±0.01 a
Sum of compounds 64.05 ±3.80 a
46.75
±
17.13
a55.30 ±5.46 a61.71 ±3.91 a52.17 ±5.56 a59.61 ±7.02 a53.76 ±8.75 a
Sum of hydroxycinnamic acids 5.69 ±1.00 a6.49 ±2.15 a5.33 ±0.39 a6.59 ±1.05 a5.86 ±0.46 a5.46 ±0.36 a5.76 ±1.07 a
Sum of flavonols 54.8 ±2.19 a36.4 ±12.76 b43.2 ±1.96 ab 49.2 ±2.98 ab 42.0 ±5.24 ab 50.2 ±6.34 ab 44.4 ±7.14 ab
Sum of isoflavones 3.56 ±0.62 a3.88 ±2.22 a6.80 ±3.12 a5.90 ±0.12 a4.33 ±0.14 a3.95 ±0.32 a3.56 ±0.54 a
1
Expressed as caffeic acid equivalents;
2
expressed as quercetin equivalents;
3
expressed as kaempferol equivalents;
4
expressed as genistein equivalents. Means with different letters in the
same row are significantly different (p< 0.05). Number of compounds correspond to peak number in Figure 1.
Agronomy 2019,9, 153 9 of 15
Table 3. Phenolic compounds content in soybean plant fresh matter (µm/g) at different growth stages.
No. tR(min) λMax (nm) Compound Content
V5 V6 R1 R2 R3 R4 R5
1 4.46 328 Hydroxycinnamic acid 112.5 ±7.7 a18.1 ±12.3 a14.3 ±1.1 a17.7 ±4.2 a14.3 ±0.7 a16.0 ±0.9 a16.5 ±5.1 a
2 4.73 328 Hydroxycinnamic acid 145.2 ±7.1 a53.1 ±16.2 a39.7 ±8.8 a48.8 ±2.9 a40.5 ±2.3 a35.2 ±2.2 a43.8 ±9.7 a
3 4.86 328 Hydroxycinnamic acid 156.2 ±8.5 a55.0 ±40.4 a52.1 ±1.5 a60.8 ±14.7 a49.4 ±3.0 a59.0 ±0.3 a55.4 ±18.5 a
4 5.95 315 Hydroxycinnamic acid 119.4 ±2.9 a20.5 ±13.6 a19.8 ±0.0 a23.5 ±3.7 a18.4 ±2.0 a20.5 ±0.4 a20.6 ±4.2 a
5 6.22 321 Hydroxycinnamic acid 126.0 ±3.1 c47.0 ±5.8 a27.9 ±1.5 bc 33.3 ±7.9 b23.2 ±2.2 bc 22.6 ±3.2 c25.2 ±3.8 bc
6 6.33 325 Hydroxycinnamic acid 118.9 ±2.0 a19.9 ±7.0 a17.3 ±1.0 a19.9 ±3.7 a17.2 ±2.0 a18.9 ±0.9 a19.2 ±3.8 a
7 6.54 327 Hydroxycinnamic acid 130.1 ±4.9 ab 37.3 ±6.1 a25.5 ±2.5 b28.6 ±1.0 ab 24.4 ±3.4 b24.3 ±2.1 b28.5 ±5.0 ab
8 7.42 256,353 Flavonol 2249 ±12 a146 ±112 a207 ±6a246 ±20 a193 ±29 a252 ±27 a229 ±50 a
9 7.71 251,295 Daidzin 24.5 ±6.3 ab 35.2 ±18.1 ab 54.8 ±31.8 a39.0 ±0.9 ab 24.1 ±3.0 ab 21.2 ±0.7 b19.7 ±5.3 b
10 7.87 265,346 Flavonol 3153 ±12 a127 ±24 a146 ±14 a153 ±4a127 ±23 a157 ±8a141 ±28 a
11 8.05 255,353 Flavonol 291.5 ±4.2 a51.6 ±40.5 a78.8 ±1.9 a86.9 ±4.0 a72.9 ±9.4 a90.5 ±5.4 a79.4 ±15.9 a
12 8.37 257,355 Rutin 1203 ±39 a895 ±176 bc 902 ±8bc 991 ±72 abc 743 ±90 c1050 ±136 ab 928 ±211 abc
13 8.87 265,348 Flavonol 3124 ±5a86 ±42 a113 ±17 a110 ±6a87 ±8a111 ±7a101 ±20 a
14 9.08 263,349 Flavonol 3184 ±6a101 ±68 b144 ±8ab 150 ±8ab 121 ±15 ab 146 ±11 ab 134 ±22 ab
15 9.23 259 Isoflavone 454.5 ±7.5 a52.5 ±41.7 a91.1 ±37.2 a76.2 ±0.3 a48.9 ±2.0 a44.5 ±1.7 a40.4 ±8.1 a
16 9.41 268 Isoflavone 421.0 ±0.4 a24.3 ±9.4 a20.6 ±4.2 a19.6 ±0.3 a14.8 ±2.0 a18.5 ±1.2 a17.4 ±3.2 a
17 10.56 260 Isoflavone 424.9 ±7.0 a25.8 ±21.5 a52.9 ±21.5 a45.7 ±3.3 a30.5 ±1.1 a32.4 ±5.3 a30.9 ±6.4 a
18 11.99 259 Daidzein 3.7 ±1.6 c9.7 ±8.9 bc 26.0 ±11.6 a23.6 ±0.9 a16.7 ±0.1 abc 22.4 ±1.3 ab 19.1 ±3.8 ab
19 14.10 260 Genistein 1.7 ±0.4 a2.1 ±2.0 a4.2 ±3.5 a4.0 ±0.1 a3.5 ±0.3 a3.0 ±0.2 a1.8 ±0.1 a
Sum of compounds 2343 ±136 a1806 ±622 a2038 ±160 a2177 ±148 a1669 ±187 a2145 ±213 a1951 ±424 a
Sum of hydroxycinnamic acids 208 ±30 a251 ±78 a197 ±10 a233 ±38 a187 ±16 a197 ±9a209 ±50 a
Sum of flavonols 2005 ±77 a1406 ±462 b1592 ±40 ab 1736 ±113 ab 1343 ±175 b1806 ±195 ab 1612 ±347 ab
Sum of isoflavones 130 ±22 a150 ±83 a250 ±110 a208 ±3a139 ±4a142 ±9a129 ±27 a
1
Expressed as caffeic acid equivalents;
2
expressed as quercetin equivalents;
3
expressed as kaempferol equivalents;
4
expressed as genistein equivalents. Means with different letters in the
same row are significantly different (p< 0.05). Number of compounds correspond to peak number in Figure 1.
Agronomy 2019,9, 153 10 of 15
4. Discussion
As far as TPC content of soybean is concerned, Riedl et al. [
42
] reported a significant variation
in TPC of soybean by environmental factors (e.g., precipitation/irrigation and temperature), while
Slavin et al.
[
43
] found that TPC did not differ in five experimental lines of lipid-altered soybeans and
ranged from 2.1 to 2.6 mg GAE/g of seeds. Chung et al. [
44
] reported that TPC was significantly
different between nine soybean varieties and ranged from 2.9 to 3.9 mg of GAE/g of seeds.
These values are not comparable with our data due to the different method used and different plant
material investigated.
The phenolic profile of four cultivars of soybean herbages were investigated by Šibul et al. [
45
].
These authors analyzed this plant material (including stem, leaves and hull without seeds), comparable
with the R4 reproductive stage, and found for DPPH radical assay EC
50
values under 0.12 mg/mL in
all investigated cultivars that resulted lower than those found in our study at similar stage. Moreover,
the most abundant detected compounds found by Šibul et al. [
45
] were quinic acid, isoflavones
(genistein and daidzein), and flavonoid glycosides and aglycones, while we found high amount of
rutin and low content of genistein and daidzein. The huge amount of rutin in comparison with other
phenolic compounds found in aerial part of soybean at different growth stages was in contrast with
literature data on soybean seed [
46
]. These authors determined the number of total flavonoids in the
seed extracts of different genotypes, only reached up to 0.61 g rutin/kg dry plant material; moreover,
they reported that antioxidant activity increased proportionally to the phenolic content. In our study
lowest values of TEAC, FRAP and PCL-ACL were found in R2 growth stage characterized by the
lowest TPC content.
The influence of the growth period on the content of phenolic compounds and antioxidant capacity
of soybean was reported by several authors. According to Song et al. [
47
], kaempferol glycosides were
increasingly synthesized from the vegetative to beginning seed stage but decreased rapidly at stages
of full seed and beginning maturity. The extensively synthesized daidzein and genistein were shown
during seed growth at the beginning and full pod.
The results of Lee et al. [
48
], showed that the total contents of daidzein, glycitein, and genistein in
soybean leaves have positively correlated with the growth period. In our study, the highest content
of isoflavones was observed at vegetative stages (Table 3). In the study of Seao et al. [
49
] the highest
contents of individual isoflavones (daidzein, glycitein, genistein, and genistein) in seeds at the growth
period of beginning maturity were higher than those at the growth period of beginning full seed and
full maturity. At the beginning of maturity, the soybean seeds showed the stronger antioxidant potential
than at the growth period of beginning full seed and full maturity [
49
]. In the cited work, the DPPH
and ABTS assays were performed. In our research reproductive stage R4 was also characterized by
high results of ABTS and FRAP assays (Table 4).
According to literature data, the changes of phenolic compounds in soybean can be related
to expression of glycosyltransferases during germination [
50
], growth of cell wall [
51
], pollen
development [
52
], and early flowering from plants [
53
]. Legume species have a unique
enzymatic mechanism causing production of the isoflavones [
54
]. These key enzymes that redirect
phenylpropanoid pathway intermediates from flavonoids to isoflavonoids are the cytochrome P450
monooxygenase and isoflavone synthase (IFS). Strong correlations were shown with the activation of
isoflavonoid biosynthesis because the soybean grows to fill the pod cavity and nodulation occurs at
R5–R6 growth stages [52].
In our previous study, the highest values of the TEAC were obtained for the aerial part of perilla
(Perilla frutescens L.) in the two last stages of growth. The lowest value of FRAP was observed at the
medium vegetative stage [
29
]. Quinoa (Chenopodium quinoa Willd.) exhibited the lowest FRAP results
at the late vegetative stage and the highest TEAC results at the early vegetative stage [
30
]. The highest
values of FRAP were noted in the two last stages of development (full branching ang early flowering)
of safflower (Carthamus tinctorius L.) [31].
Agronomy 2019,9, 153 11 of 15
Table 4. Antioxidant activity of soybean plant extract and fresh matter (FM) at different growth stages.
Growth Stage
TEAC 1FRAP 2PCL-ACL 3Fe2+ Chelating Ability
(µmol Trolox
eq./g Extract)
(µmol Trolox
eq./g FM)
(µmol Fe2+/g
Extract) (µmol Fe2+/g FM) (µmol Trolox
eq./g Extract)
(µmol Trolox
eq./g FM) (%)
V5 190 ±20 c6.93 ±0.71 ab 780 ±19 a28.5 ±0.7 a552 ±1a20.2 ±0.1 ab 49.1 ±5.2 ab
V6 201 ±5bc 7.82 ±0.03 ab 694 ±10 ab 26.9 ±1.0 a560 ±38 a21.8 ±2.0 a41.6 ±6.4 bcd
R1 229 ±39 bc 8.43 ±1.28 a651 ±61 bc 24.0 ±1.8 ab 517 ±5a19.1 ±0.2 ab 39.9 ±4.7 cd
R2 177 ±11 c6.26 ±0.41 b623 ±3bc 22.0 ±0.2 b516 ±36 a18.2 ±1.4 ab 46.4 ±1.3 bc
R3 245 ±21 ab 7.82 ±0.62 ab 670 ±77 ab 21.4 ±2.6 b552 ±2a17.6 ±0.2 b51.7 ±2.7 a
R4 220 ±12 bc 7.93 ±0.29 ab 712 ±77 ab 25.6 ±2.3 ab 534 ±30 a19.2 ±0.7 ab 39.2 ±2.2 cd
R5 219 ±26 bc 7.90 ±0.95 ab 666 ±56 ab 24.1 ±3.3 ab 531 ±61 a19.3 ±3.3 ab 36.5 ±0.8 d
1
Trolox equivalent antioxidant capacity;
2
Ferric-reducing antioxidant power;
3
Photochemiluminescence-antioxidant capacity of lipid-soluble substances; Means with different letters in
the same column are significantly different (p< 0.05).
Agronomy 2019,9, 153 12 of 15
5. Conclusions
Taken together, our results show that the phenolic composition of the aerial part of soybean differs
significantly across the growth cycle. The sum of flavonols was highest in stage V5 and lowest in stage
V6. All antioxidant tests showed significant differences between extracts of different growth stages.
Generally, the most active extracts were obtained from the V5 and R3 stages. The extracts of soybean
plant can be used in pharmacy for the production of nutraceuticals by virtue of their good antioxidant
activity and content of flavonols and other bioactive constituents. A future area of focus would be
to investigate the specific antioxidative activity of the biomolecules present in the soybean plant at
different growth stages.
Author Contributions:
Conceptualization, P.G.P. and G.M.; methodology, R.A., M.K., and M.J.; validation, R.A.
and M.K.; formal analysis, E.L., M.K., and M.J.; investigation, P.G.P., F.G., and M.K.; resources, R.A. and M.K.;
data curation, E.L., M.J., and M.K.; writing—original draft preparation, P.P.G. and M.K.; writing—review and
editing, P.G.P., F.G., and M.K.; supervision, R.A.; funding acquisition, R.A. and G.M.
Funding: This research received no external funding.
Acknowledgments:
Authors would like to express their thanks to the Italian National Research Council for a
visiting grant to R.A. in the framework of a free exchange program between the Polish Academy of Sciences and
the Italian National Research Council.
Conflicts of Interest: The authors declare no conflict of interest.
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(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
... Historical data link its origin to North and Central China (4,000 to 5,000 years ago), while it first appeared in Europe in 1712 (Liu, 1997). This is an important plant, whose grains are widely used in human and animal diet, because they contain considerable amount of proteins (Peiretti et al., 2019), and some other phytonutrients including different phenolics, phytosterols, etc. (Prabakaran et al., 2018). Moreover, some components with potentially negative impact on human health such as saponins are present in the soybean grains (Kim et al., 2013). ...
... The main part of the proteins and oils is located in the cotyledons, while in the hull these components are actually represented as minority (Liu, 1997). In this sense, the non-hulled soybean grains can be a good source of different secondary plant metabolites, i.e. phenolic acids or flavonoids, which are mostly responsible for the antioxidant potential of the plant material (Kim et al., 2016;Peiretti et al., 2019). ...
... Due to lower availability of N during organic growing process, plants synthetize higher quantities of secondary metabolites such as phenolics (Rembialkowska, 2007). In addition, genetics (Hou et al., 2009 a; and plant 52 life cycle (Peiretti et al., 2019) can also have significant influence on the content of different phytochemicals. ...
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The aim of the current study was to determine the content of several primary metabolites: total soluble sugars, starch and lipids, soluble sugars, fatty acids and triacylglycerols profile, and secondary metabolites: total phenolics and flavonoids, in the grains of soybean (Glycine max (L.) Merr.) cultivar ‘Kaća’. Additionally, grain antioxidant properties were assessed using ABTS•+ scavenging capacity and ferric reducing power (FRP) assays. Soybean was developed and grown in Serbia under two cultivation systems (conventional and organic) during two growing seasons (2016 and 2017). In both growing seasons and cultivation systems, soybean grains were characterised by reduced lipid content (8.16–14.34%) and as an excellent source of polyunsaturated fatty acids. Triacylglycerols (TAGs) with 44 equivalent carbon numbers (ECN44) represented the main fraction (30.95–32.79%) followed by ECN46 TAGs (23.27–26.36%). Low total soluble sugars (2.36–11.51%) content was determined. High-performance liquid chromatography (HPLC) analysis revealed a significant prevalence of non-reducing disaccharides (1.41–6.57%) among the individual sugars. Soybean grains were proved as a good source of phenolic (2493.9–4419.5 mg kg-1) and flavonoid (292.7–500.9 mg kg-1) compounds with the dominance of free (extractable) fractions. Strong positive correlations were observed between both cultivation systems and growing seasons indicating no clear differences for the majority of analysed parameters. All examined extracts possessed a significant ability (27.6–38.2%) to neutralize ABTS•+ radicals, while in the case of FRP assay a significant ability for iron ions (Fe3+) reduction was recorded for the samples from the second growing season.
... The total phenolic content of SCE found in this study (46.8 mg GAE / gram extract = 275 ± 13.3 µM GA/g extract) was similar to the amount (42.2-50.4 mg catechin/gram extract of whole soybean plant) found in Peiretti et al. (2019) [36]. ...
... The total phenolic content of SCE found in this study (46.8 mg GAE / gram extract = 275 ± 13.3 µM GA/g extract) was similar to the amount (42.2-50.4 mg catechin/gram extract of whole soybean plant) found in Peiretti et al. (2019) [36]. ...
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Background Hyperpigmentation, which causes excessive melanin synthesis and accumulation, is an important issue in the cosmetic industry. Since compounds developed against hyperpigmentation often come with side effects such as skin irritation and contact dermatitis, new studies focus on the use of natural agents that have no side effects. Methods and Results In this study, it was found that the effects of soybean cell culture extract (SCE) on alpha-melanocyte-stimulating hormone (α-MSH) induced melanogenesis in B16-F10 murine melanoma cells. The cells were incubated with SCE for 48 h after treatment with α‑MSH for 24 h to analysis the melanin content, cellular tyrosinase activity, and gene and protein expression. SCE at 1 mg/mL decreased melanin content and tyrosinase activity by 34% and 24%, respectively, compared to the α-MSH-treated group, which did not decrease cell viability. In addition, SCE (1 mg/mL) downregulated the expression of tyrosinase (TYR), tyrosinase-related protein (TRP)-1, tyrosinase-related protein (TRP)-2, and microphthalmia-associated transcription factor (MITF) genes 1.5-, 1.5-, 2-, and 2-fold, respectively. Furthermore, SCE inhibited the expression of TYR, TRP1, and TRP2 by decreasing the expression of MITF, as shown in a western blot assay. Conclusions This study suggests that SCE reveals dose-dependent inhibition of melanin synthesis through the suppression of tyrosinase activity as well as molecular levels of TYR, TRP1, TRP2, and MITF in B16-F10 murine melanoma cells. Therefore, SCE has the potential to be an effective and natural skin-whitening agent for application in the cosmetic industry.
... Green soybean (Glycine max L.) is a legume that has been shown to exhibit strong antioxidant activity. Peiretti et al. [9] stated that black and green soybean exhibited comparatively higher FRAP values than yellow soybean. Hence, many researchers try to use green soybean as an alternative supplement source of bioactive compounds in food products such as butter cake [10] and cookies [11]. ...
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Green soybean (Glycine max L.) pods (GSP) are agro-industrial waste from the production of frozen green soybean and milk. These pods contain natural antioxidants and various bioactive compounds that are still underutilized. Polyphenols and flavonoids in GSP were extracted by ultrasound technique and used in the antioxidant fortification of green soybean milk. The ultrasound extraction that yielded the highest total polyphenol content and antioxidant activities was 50% amplitude for 10 min. Response surface methodology was applied to analyze an optimum ultrasonic-assisted extraction (UAE) condition of these variables. The highest desirability was found to be 50% amplitude with an extraction time of 10.5 min. Under these conditions, the experimental total phenolic content, total flavonoid content, and antioxidant activity were well matched with the predicted values (R2 > 0.70). Fortification of the GSP extracts (1–3% v/v) in green soybean milk resulted in higher levels of bioactive compounds and antioxidant activity in a dose-dependent manner. Procyanidins were found to be the main polyphenols in dried GSP crude extracts, which were present at a concentration of 0.72 ± 0.01 mg/100 g. The addition of GSP extracts obtained by using an ultrasound technique to green soybean milk increased its bioactive compound content, especially procyanidins, as well as its antioxidant activity.
... Therefore, a comparative study must be conducted with firmly controlled cultivation conditions. Furthermore, agricultural products exhibit wide variation (20%-40% RSD) in phenolic composition, even if the conditions are well controlled [30]. Despite the difficulties of a study that handles field-grown plants, secondary metabolites are indisputable markers originating from inherent genetic traits [31]. ...
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Soybean (Glycine max; SB) leaf (SL) is an abundant non-conventional edible resource that possesses value-adding bioactive compounds. We predicted the attributes of SB based on the metabolomes of an SL using targeted metabolomics. The SB was planted in two cities, and SLs were regularly obtained from the SB plant. Nine flavonol glycosides were purified from SLs, and a validated simultaneous quantification method was used to establish rapid separation by ultrahigh-performance liquid chromatography-mass detection. Changes in 31 targeted compounds were monitored, and the compounds were discriminated by various supervised machine learning (ML) models. Isoflavones, quercetin derivatives, and flavonol derivatives were discriminators for cultivation days, varieties, and cultivation sites, respectively, using the combined criteria of supervised ML models. The neural model exhibited higher prediction power of the factors with high fitness and low misclassification rates while other models showed lower. We propose that a set of phytochemicals of SL is a useful predictor for discriminating characteristics of edible plants.
... Soybean Glycine max (L.) Merr. (Fabaceae) flavonoids have been broadly studied for their importance in plant metabolism, the establishment of symbiotic relationships, response to abiotic and biotic stresses and human health-promoting effects [1][2][3][4][5][6][7]. Soybean is attacked by a number of insect pests, and some of them can cause severe economic damage. ...
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Flavonoids detected in soybean Glycine max (L.) Merr. (Fabaceae) cause various alterations in the metabolism, behavior, and development of insect herbivores. The pea aphid Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) poses potential threat to soybeans, but the effect of individual flavonoids on its feeding-associated behavior is relatively unknown. We monitored probing behavior (stylet penetration activities) of A. pisum on its preferred host plant, Pisum sativum L. untreated (control) and treated with 0.1% ethanolic solutions of flavonoids apigenin, daidzein, genistein, and kaempferol. We applied the electrical penetration graph (electropenetrography, EPG) technique, which visualizes the movements of aphid stylets within plant tissues. None of the applied flavonoids affected the propensity to probe the plants by A. pisum. However, apigenin enhanced the duration of probes in non-phloem tissues, which caused an increase in the frequency and duration of stylet mechanics derailment and xylem sap ingestion but limited the ingestion of phloem sap. Daidzein caused a delay in reaching phloem vessels and limited sap ingestion. Kaempferol caused a reduction in the frequency and duration of the phloem phase. Genistein did not affect aphid probing behavior. Our findings provide information for selective breeding programs of resistant plant cultivars to A. pisum.
... This high correlation suggests that the antioxidant power found in the studied extracts could possibly be due to their phenolic content (r 2 polyphenols/FRAP = 0.86; r 2 polyphenols/DPPH = 0.87). The present data were supported by several earlier reports that highlight on the most important relationship between antioxidant activities and phenolic content [37][38][39]. ...
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Background Lkhzama ( Lavandula officinalis ), Mard-doch ( Origanum majorana ), and Lahbak ( Ocimum basilicum ) are aromatic and medicinal plants widely used in Moroccan folk medicine as a treatment for numerous diseases including liver diseases, rheumatism, and diabetes. This study was undertaken to examine the antioxidant and antihemolytic activities of the aqueous extracts of these plants. The antioxidant activity was evaluated using three in vitro tests: DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) radical scavenging activity, FRAP (ferric reducing antioxidant power assay), and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay. The antihemolytic activity of plant extracts was evaluated against AAPH (2,2′-azobis(2-amidino-propane) dihydrochloride)-induced erythrocyte hemolysis. Results Our findings showed that all plant extracts displayed significant antioxidant and antihemolytic effects. In fact, among the studied plant extracts, the highest antioxidant power was recorded in Origanum majorana , based on DPPH (IC 50 = 12.29 μg/mL), ABTS (226.13 μmol TE/g DW), and FRAP (477.82 μmol TE/g DW) assays. Moreover, the same plant also showed the best membrane protective effect (269.55%). Whereas, Ocimum basilicum exhibited the lowest antioxidant activity using DPPH (IC 50 = 42.85 μg/mL), ABTS (IC 50 = 226.13 μmol TE/g DW), and FRAP (IC 50 = 172.84 μmol TE/g DW) and, thus, the lowest membrane protective effect (182.70%). Conclusion This result supports the use of these plants in folk medicine for preventing and treating many diseases, especially those related to oxidative stress.
... The analysis showed the presence of 4 isoflavones, genistein being the most important in quantity, followed by daidzein, genistin and much lower amount of glycitein, according to that described by other authors. 27 So, we think that cardioprotection depends on synergic effects among isoflavones and the appearance of more active metabolites, such as S-equol, after intestinal/hepatic metabolism during repeated administration. 5 On this way, Huang et al. showed that soy isoflavones control the oxidative stress caused in animals, through improving intestinal morphology, as well as antioxidant and immunologic capacities. ...
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Background and aim Phytoestrogens are traditionally used for cardiovascular risks but direct effects on the ischemic heart remain unclear. Plants with phytoestrogens are used for reducing menopausic symptoms and they could also be cardioprotectives. Here we investigated whether maca (Lepidium meyenii) contains isoflavones and prevents cardiac stunning, in comparison to soy isoflavones. Experimental procedure Both products were orally and daily administered to rats during 1 week before exposing isolated hearts to ischemia/reperfusion (I/R). Young male (YM), female (YF) and aged female (AgF) rats treated with maca (MACA, 1 g/kg/day) or soy isoflavones (ISOF, 100 mg/kg/day) were compared to acute daidzein (DAZ, 5 mg/kg i.p.) and non-treated rat groups. Isolated ventricles were perfused inside a calorimeter to simultaneously measure contractile and calorimetrical signals before and during I/R. Results and Conclusion s: maca has genistein and daidzein. MACA and ISOF improved the post-ischemic contractile recovery (PICR) and muscle economy (P/Ht) in YM and YF hearts, but not in AgF hearts. DAZ improved PICR and P/Ht more in YM than in YF. The mKATP channels blockade reduced both PICR and P/Ht in DAZ-treated YM hearts, without affecting them in ISOF or MACA-treated YM hearts. In MACA treated YF hearts, the simultaneous blockade of NOS and mKATP channels, or the mNCX blockade reduced cardioprotection. Results show that subacute oral treatment with maca or with soy isoflavones was strongly preventive of cardiac ischemic dysfunction, more than the acute administration of a pure isoflavone (daidzein, genistein). Maca induced synergistic and complex mechanisms which prevented mitochondrial calcium overload.
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This is the first study to investigate antioxidant capacities of isoflavones prepared using microwave-assisted hydrolysis method from different parts (seeds, leaves, leafstalks, pods, stems and roots) of soybean at growth stages. In addition, the fluctuations in the isoflavone, protein, fatty acid, and oil contents in R6-R8 (R6: beginning; R7: beginning maturity; R8: full maturity) seeds were confirmed. The R7 seeds exhibited the most predominant contents of isoflavones (1218.1±7.3 μg/g) in the following order: daidzein (48%)>genistein (35%)>glycitein (17%). The second highest isoflavone content was found in the leaves (1052.1±10.4 μg/g), followed by R8 seeds>roots>R6 seeds>leafstalks> pods; the stems exhibited the lowest isoflavone content (57.2±1.7 μg/g). Interestingly, daidzein showed the highest individual isoflavone content with remarkable variations (57.2-766.8 μg/g), representing 46-100% of the total isoflavone content. R8 exhibited higher protein, fatty acid, and oil contents than R6 or R7. Moreover, the antioxidant capacities against two radicals in different parts of soybean plant showed considerable differences depending upon the isoflavone content. Our results suggested that soybean leaves and seeds might be useful materials for functional foods.