*2.2.2. Antioxidants determination*

Soybean samples approximately (1 g) were powdered and homogenized in 10 ml 80% methanol. The mixture was shaken at 300 rpm at room temperature for 3 h. Then the extract was centrifuged for 10 min at 3000 rpm and upper aqueous phase were transferred to new Eppndorf tubes. Moreover, the residues were again extracted with 5 ml 80% methanol overnight. The extraction was performed in three replicates, later on extracts combined and stored in dark at 4°C. The Folin-Ciocalteu reagent was used to determine the total phenolic compounds from the extracts using gallic acid calibration curve as standard. The total phenolics were expressed as mg/g gallic acid equivalents (GAE). An extract was aliquot (50 μl) and mixed with Folin-Ciocalteu reagent of 250 μl and 7.5% sodium carbonate of 750 μl. The volume was increased to 5 ml with water and sample was incubated for 2 h. The absorbance was measured at 765 nm against distilled water as blank. The flavonoid determination was measure by aluminum chloride method with the help of Quercetin equivalent as standard. An aliquot of extract (250 μl) was mixed with ddH2O and 5% NaNO2 (15:1, v/v). After 6 min, 150 μl of 10% AlCl3 was added to the mixture. A 500 μl of 1 M NaOH was added to the mixture at the 5th min, and volume made up to 2.5 ml with distills water and the absorbance was measured spectrophotometrically at 410 nm.

among genotypes were recorded and that might observed due to differences in genetic background and/or origin. The higher protein content in the genotypes is also reported previously which ranged from 43 to 45% [18]. These results are also in line with Zarkadas et al. [19, 20] who reported crude protein contents in soybean ranging from 33.67 to 42.11%. The minimum moisture contents were recorded in Giza 83 (3.08%) while maximum was recorded for Indo-1 (5.88%) with an average (4.90%) mean value showing non-significant difference. Ash contents ranged from 4.55 to 6.28% with an average of 5.44%. The maximum was recorded for Giza 111 (6.28%) genotype while Romal-1 genotype had the lowest (4.55%) of ash contents. The moisture and ash contents values were recorded lower than that reported by [21]. Total fat ranged from 16.92 to 22.94% with a mean value of 21.16%. The genotype Indo-black contained the lowest while the genotype 3803 recorded the highest content. Soybean is considered about 47% of its energy value in fat content [22, 23] which is compared to other legumes. Our results regarding total fat were in line with that of [24] who reported that that total fat value ranged 18 and 22 g/100 g in soybean genotypes. The minimum carbohydrate content in Clark (26.11%) while maximum in Argentinian (33.18%), with an average (29.48%) was recorded

Phytochemical Profiling of Soybean (*Glycine max* (L.) Merr.) Genotypes Using GC-MS Analysis

http://dx.doi.org/10.5772/intechopen.78035

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Flavonoid and phenolic compounds are the important phytochemicals and natural antioxidants founds in fruits, vegetable and cereals grains. It serves as multiple biological functions, i.e., defense against cardiovascular disease, cancer and aging [25]. The results regarding total phenolic and flavonoids contents for 24 soybean genotypes are presented in **Table S1**, and significant differences were recorded for all soybean genotypes. The seed extracted results indicated that the maximum phenolic contents was recorded in Romal-1 (1.7 mg/g) while minimum in Giza 111 (1.15 mg/g) with an average 1.45 GAE/g mg/g (**Table 2**). However, total flavonoid content ranged 0.68 to 2.13 mg QE/g (**Table 2**). Phenolic content is strongly linked with antioxidant capacity [26, 27] and can contribute towards antioxidants activities [28]. The use and demands of phenolic are

increasing rapidly in food industry to enhance nutritional value and quality of food [29].

N 24 24 24 24 24 24 24 Min 35.63 3.08 4.55 16.92 26.11 1.15 0.68 Max 43.13 5.88 6.28 23.61 33.18 1.77 2.13 Mean 39.02 4.90 5.44 21.16 29.48 1.45 1.24

**Total fat (g/100 g)**

2.09 0.65 0.33 1.41 1.86 0.16 0.36

5.35 13.26 6.11 6.68 6.30 11.58 29.32

**Carbohydrate (g/100 g)**

**Total phenolic content (TPC)**

**Total flavonoid content (TFC)**

among soybean genotypes.

**Crude protein (g/100 g)**

Stand. dev.

Coeff. Var.

**Moisture (g/100 g)**

**Ash (g/100 g)**

**Table 2.** Descriptive statistics of chemical composition in 24 soybean genotypes.

**3.2. Flavonoid and phenolic contents**

#### *2.2.3. Gas chromatography-mass spectroscopy*

The GC-MS analysis of fractions were performed using a TSQTM 8000 Evo Triple Quadrupole GC-MS/MS (Thermo Fisher Scientific) equipped with an Elite-5 capillary column (length 30 nm and inner diameter 0.25 mm and film thickness 0.25 μm) and mass detector was operated in electron impact (EI) mode with full scan (50–550 amu). Helium was used as the carrier gas at constant flow rate 1 mL/min and an injection volume of 1 μL. The oven injector temperature was programmed from 50°C with an increase of 8°C/min to 200°C, then 7°C/min to 290°C/min. The results were compared using the database of National Institute Standard and Technology (NIST).

## **2.3. Data analysis**

The data were subjected to descriptive statistics (mean, standard deviation, coefficient of variability, minimum and maximum values) and principal component analysis (PCA) using statistical software Past3 program [17].
