Phytoestrogens biological effects

Phytoestrogens may elicit their biological effects by binding to estrogen receptors (ERs). Until recently, only a single ER isoform, ERa, had been identified however, a second receptor termed ERp has also been identified (Enmark et al, 1997, 1999 Saunders et al, 2000, 2001). It has been shown that the ERs have different intracellular and tissue distribution patterns and are responsible for different biological effects (see Table 5.1). A number of spliced variants of both ERa and ERp have also been identified (Inoue et al, 2000 Ogawa et al, 1998 Vladusic et al, 1998). 

The public health implications of dietary phytoestrogens have received a great deal of attention over the last few years. However, despite substantial data from epidemiological and experimental studies, the biological effects of phytoestrogens remain equivocal. 

Irvine, C.H., Fitzpatrick, M.G., and Alexander, S.L. 1998. Phytoestrogens in soy-based infant foods concentrations, daily intake, and possible biological effects. Proc Soc Exp Biol Med 217, 247-253. 

Isoflavones belonging to the phytoestrogens also expose marked biological activity [99], Their effect and fate of isoflavones in organisms have been extensively investigated... 

Isoflavones are flavonoids commonly called as phytoestrogens and one of the most extensively investigated polyphenols. These are present in soybeans, soybean products, and other pulses, widely consumed in Asian and Southeast Asian coim-tries. Isoflavones have attracted attention mainly due to their role in the ameliora-ti(Mi of postmenopausal symptoms such as hot flushes and osteoporosis [52,58,59]. The other beneficial and important biological properties have been established which are related to effects on cardiovascular diseases, cognitive functions, and breast and prostate cancers. These conclusions were based on wide-ranging studies and parameters which showed positive effects, for example, reduction of hot flushes, the excretion of Ixme resorption markers, increase in bone mineral density, the lower LDL and total cholesterol, reduction in colon cancer, and modulation of immune function [60, 61]. Chemical structures of some important molecules of these phytochemical classes are represented in Fig. 82.3. 

Wang, C.N., Chi, C.W., Lin, Y.L., Chen, C.F., and Shiao, Y.J. 2001. The neuroprotective effects of phytoestrogens on amyloid beta protein-induced toxicity are mediated hy abrogating the activation of caspase cascade in rat eortieal neurons. The Journal of biological chemistry, 276(1), 5287-95. 

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