The antioxidant activity and contents of various polyphenol classes in the seeds of seven soybean varieties of different seed color and one yellow seed cultivar, representing a reference genotype, were evaluated. Total polyphenols and tannins were determined after extraction of plant material with 70% aqueous acetone, and total flavonoids were extracted with methanol and acetic acid, whereas anthocyanins were extracted with 20% aqueous ethanol. In addition, isoflavone content and composition were determined using high-performance liquid chromatography analysis. Antioxidant activity of seed extracts was evaluated by the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity assay. A positive linear correlation between antioxidant activity and contents of total polyphenols and anthocyanins was established. The highest antioxidant activity was observed in the extracts of black and brown varieties, which also showed high levels of all polyphenol classes examined. Yellow seed had the highest total isoflavone content (3.62 mg/g of dry material). The highest concentration of total daidzein was determined in black seeds (>2.0 mg/g of dry material), and the highest total glycitein and genistein contents occurred in the yellow cultivar (0.53 and 1.49 mg/g of dry material, respectively). According to our results, varieties of black and brown seeds could be of special interest not only for their large content of total polyphenols, ranging from 4.94 to 6.22 mg of gallic acid equivalents/g of dry material, but also for their high content of natural antioxidants such as anthocyanins.

The influence of soybean seed coat color and genotype on antioxidant capacity, phenolic content and isoflavone profile was investigated. Isoflavone content and composition of 21 seed samples-yellow, green, brown, black and rarely mentioned ocher and reddish, were determined by high-performance liquid chromatographic analysis. Antioxidant capacity and total phenolic content (TPC) were evaluated spectrophotometrically. Significant correlation between total isoflavone content and total genisteins was established in all colored groups. Total isoflavone content was in the range from 2.11 mg/g in a green wrinkled sample to 5.24 mg/g in yellow seed. It was found that black genotypes had the highest TPC and antioxidant capacity, which were significantly different (p<0.05) from other colored soybeans. The obtained interconnections among analyzed isoflavones can be used as a model for estimation of their specific content.

Twenty soybean cultivars, originating from the United States, Russia, Serbia, and China, were analyzed for their isoflavone composition, total polyphenolic content, and antioxidant activity. Isoflavones were extracted by aqueous methanol (80%) and analyzed by high-performance liquid chromatography=diode array detection. Precision and linearity of the applied method were within the standard limits of validation. The highest and the lowest total isoflavone contents were 4.59 and 1.45 mg=g of dried soybean weight, respectively. A significant difference (P < .05) was found in isoflavone concentration among the different cultivars, but it was observed that origin is not a significant factor that could influence isoflavone content in soybeans. Total polyphenolic content varied between 2.13 and 3.45 mg of gallic acid equivalents=g of dried soybean weight. The free radical scavenging activity of soybean extracts assayed by 2,2-diphenyl-1-picrylhydrazyl in terms of 50% inhibitory concentration (IC 50 ) ranged from 1.40 to 3.35 mg=mL. Negative correlation between total polyphenolic content and IC 50 was observed, but there was no correlation between total isoflavone content and IC 50 . On the basis of this study, soybean cultivars with larger potency for biological activity could be recognized.KEY WORDS: 2,2-diphenyl-1-picrylhydrazyl assay high-performance liquid chromatography analysis soybean phytoestrogens

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Isoflavones are a group of phytoestrogens, naturally-occurring substances important for their role in human health. Legumes, particularly soybeans ( Glycine max (L.) Merr.), are the richest source of isoflavones in human diet. Since there is not much current data on genetics of isoflavones in soybean, particularly in the aglycone form, elucidation of the mode of inheritance is necessary in order to design an efficient breeding strategy for the development of high-isoflavone soybean genotypes. Based on the isoflavone content in 23 samples of soybeans from four different maturity groups (00, 0, I and II), three crosses were made in order to determine the inheritance pattern and increase the content of total isoflavones and their aglycone form. Genotype with the lowest total isoflavone content (NS-L-146) was crossed with the low- (NS Zenit), medium (NS Maximus), and high- (NS Virtus) isoflavone genotypes. There were no significant differences in the total isoflavone content (TIF) between F 2 populations, and there was no transgression among genotypes within the populations. Each genotype within all three populations had a higher TIF value than the lower parent (NS-L-146), while genotypes with a higher TIF value than the better parent were found only in the NS-L-146 × NS Zenit cross. However, significant differences in the aglycone ratio (ratio of aglycone to glycone form of isoflavones) were found between the populations. The highest aglycone ratio was found in the NS-L-146 × NS Maximus cross. The results indicate that the genetic improvement for the trait is possible.

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The growing clinical interest and use of soybean-based food products and extracts to increase dietary phytoestrogen intake have led to medical interest in the precise determination of the phytoestrogen composition of soybean products. We have analyzed the composition of these compounds in 20 domestic and introduced varieties of genetically non-modified soybean genotypes grown under the same agroecological conditions. The isoflavone content of soybeans cultivated in this region of Serbia has not been previously reported. The assays were performed, after extraction with methanol-water (8:2, v/v), by C 18 reversed phase high-performance liquid chromatography coupled with photodiode array detection. The total phytoestrogen concentration was found to be between 2.24 and 3.79 mg g-1 dry bean weight. The total concentration of daidzein and its derivatives ranged from 0.96 to 1.82 mg g-1 , total glyciteines from 0.34-0.53 mg g-1 , and all genistein derivatives from 0.86-1.67 mg g-1 dry bean weight. Given the high biological potency of phytoestrogens and their metabolic conversion products, our data suggest that phytoestrogen content screening could be a useful tool in the selection of soybean genotypes with improved health promoting characteristics.