Genistein is an isoflavone isolated from soy, the structure of which is shown in Figure 7. Recent interest in genistein has been stimulated by epidemiological studies which correlate diets high in soy with reduced incidence of cardiovascular disease (123), osteoporosis (123), and certain cancers in humans (124-126).
The direct anticarcinogenic action of genistein is documented. Animal studies demonstrate protection against bladder, breast, colon, liver, lung, prostate, and skin cancer with oral genistein (124,127), and dietary soy inhibits chemically induced skin cancer in mice (128). Growth of many in vitro cancer cell lines is inhibited by genistein (127). Genistein also arrests the growth and induces the differentiation of malignant melanoma cells in vitro (129) and inhibits pulmonary metastases of malignant melanoma cells in vivo (130,131).