Soybean isoflavone

Soybean is the most common dietary legume with high content of isoflavone in its seed. There are two main soybean isoflavones: daidzein (40,7-dihydroxyisoflavone) and genistein (40,5,7-trihydroxyisoflavone), which are similar in structure. Some studies indicated that daidzein and genistein had the similar functions in prevention of cancer.


Daidzein might suppress neuronal tumor cells growth by arrest of cell cycle progression at G2/M and induced apoptosis. Genistein also can bind to ER, and induce apoptosis; additionally, genistein is able to induce apoptosis by inducing p53 and regulation of expression of anti-apoptotic genes, which does not involve in binding to ER. It is not difficult to explain why isoflavone is considered as potential alterative therapies potential alternative therapies for a range of hormone dependent conditions, including cancer, cardiovascular disease (Davis et al., 2008).

The soybean seed is the most important staple of isoflavone, isoflavone products of which are available as commercial product in the nutrient market. During extract processing, isoflavones migrate with the protein fraction of the soybean, so there are low concentration of isoflavone in soybean oil which is consumed, as the main source of oil, by western families. There were reports that the intake of isoflavone in western population is less than 1 mg/d. Contrarily, in Asia, soybean is the most important source of protein, such as in China and in Japan. The intake of isoflavone is estimated up to 20, even 50 mg/d. The different intakes of isoflavone in quantity are also considered to be one of the reasons of area differences of cancer risks (Setchell & Cassidy, 1999).