Genistein, a soy isoflavone, is a potent α‐glucosidase inhibitor

Genistein is an isoflavone that is known to be contained in soybean. It was proved that genistein plays a pivotal role in homeostasis in the human body. In the course of screening for useful α‐glucosidase inhibitors, we isolated and identified genistein as a candidate for α‐glucosidase inhibitor from fermentation broths of a Streptomyces sp. Genistein was shown to be a reversible, slow‐binding, non‐competitive inhibitor of yeast α‐glucosidase with a K i value of 5.7×10 −8 M when the enzyme mixture was pretreated with genistein. These results show a possibility that genistein could be a useful tool for metabolic disorders.