Isoflavone content and β-glucosidase activity in soybean cultivars of different maturity groups

Soy isoflavones are phenolic compounds comprised of aglucones, β-glucosides and β-glucosides conjugated with malonyl and acetyl groups. The β-glucosidases are a heterogeneous group of enzymes which hydrolyse β-glucosidic links of oligosaccharides and other glucosides conjugates releasing glucose. Thus the objective of this study was to determine the isoflavone forms content, β-glucosidase activity and their correlation in 18 soybean cultivars of different maturity groups under the same cultivation conditions. The predominant isoflavone forms were malonyldaidzin and malonylgenistin in all cultivars, corresponding to 67.0%, while β-glucoside and aglucone forms corresponded to 31.0% and 2.0%, respectively, of the total isoflavones; the acetylated form was not detected. This proportion among different forms was similar to all soybean cultivars studied. Regression analysis between number of days of maturity and all isoflavone forms were not significant. The relationship between maturity days and β-glucosides and malonyl-glucosides showed no correlation. However, a correlation was observed between maturity days and aglucones (P<0.08). Regression analysis and correlation between β-glucosidase activity and cultivars of different number of days of maturity were not significant, and β-glucosidase activity did not correlate with isoflavone forms contents (P<0.05).