This, together with the inhibition of the enzymes needed for cell proliferation, such as tyrosine kinase and ornithine decarboxylase, leads to a longer cell cycle and a lower cellular turnover, since fewer damaged cells need to be replaced. The implications for anti-aging and cancer prevention are profound. You may wonder why flavonoids have such a wide range of physiological effects, resembling those of hormones. Apparently this stems from the fact that flavonoids have chemical and structural similarities to steroid hormones, thyroid hormones, prostaglandins, retinoids, and fatty acids. Thus it should not be altogether surprising that flavonoids can even affect gene expression-both the expression of our own genes, and the genes of the various bacteria and viruses that may invade us.
Flavonoids can also attach themselves to proteins, modulating the action of enzymes.
They inhibit certain digestive enzymes and also the kinase enzymes necessary for cell proliferation. This partly explains how flavonoids can serve as a valuable adjunct cancer therapy for many kinds of cancer. In fully developed cancer, however, tumor cells cannot survive in the resting state. On the other hand, very high levels of flavonoids are undesirable for women seeking to become pregnant, since these compounds are also known to decrease fertility, possibly by modulating hormone levels and even by interfering with the critical early stages of pregnancy. Soy and red clover phytoestrogens are a particular culprit here, acting as endocrine disruptors because of their high ability to bind to estrogen receptors.