Effect of Soy Isoflavones on DNA Metabolic Enzyme Inhibitory Activity and Anticancer Activity

Soybeans and soyfoods are the natural dietary sources of isoflavones for humans. Furthermore, clinical data suggest that a modest amount of dietary soy provides sufficient isoflavones to exert physiological effects. Soybeans contain three predominant isoflavone species, with 57% being genistein, 37% daidzein, and 6% glycitein. This chapter discusses the ability of various soy isoflavones to inhibit pol and topo activity. It also examines the effect of these compounds on DNA replication and cellular proliferation in human cancer cells. It is possible that soy isoflavones have anticancer activity. The ability of each soy isoflavone to inhibit the activity of mammalian pols was investigated using calf pol α, rat pol β, human pol γ, and human pol κ. Pols α, β, γ, and κ were used as representatives of the B, X, A, and Y families of pols, respectively. The chapter investigates the mode by which genistein inhibits DNA metabolic enzymes.