Isoflavones from green vegetable soya beans and their antimicrobial and antioxidant activities

Green vegetable soya beans, known as Maodou in China, are supplied as vegetable-type fruits of the soybean plant. Previous study indicated that green vegetable soya beans exhibited antioxidative and anti-inflammatory activities. However, the material basis and pharmacological activities of green soybean plant were not unravelled clearly. In this study, we investigated the chemical ingredients and their pharmacological activities.

Investigation of the chemical ingredients indicated that two new isoflavones, 2'-hydroxyerythrin A (1), and daidzein-7-O-β-d-{6″-[(E)-but-2-enoyl]}glycoside (2), together with seven known ones - 7,4'-dihydroxy-6-methoxyisoflavone (3), daidzein (4), daidzin (5), genistein (6), formononetin (7), ononin (8), and isoerythrinin A (9) - were obtained. The structures of compounds 1-9 were elucidated on the basis of spectroscopic and chemical analysis. We evaluated the antimicrobial efficacies and free-radical scavenging potential of the isolated compounds (1-9). Compounds 1 and 9 exhibited the most pronounced efficacy against the tested bacterial strains with IC₅₀ values ranging from 10.6 to 22.6 μg mL^-1 . The isolated compounds showed moderate radical scavenging properties with compound 6 being the most active, followed by compounds 3, 1 and 4.

This study indicated that the isoflavones from soya beans could be considered as potential antioxidants or antimicrobials in the food, cosmetics and pharmaceutical industries. © 2017 Society of Chemical Industry.