Phytoestrogens

Plant Estrogens

Plants have naturally occurring compounds that have been found to possess estrogen-like properties. These compounds were subsequently named phytoestrogens (PEs). PEs are similar in structure to the hormone estradiol, thereby allowing these compounds to possess estrogen-like properties (Food standards agency, 2002). PEs are broken down into three main groups; isoflavonoids, flavonoids and lignans (Apers et al, 2003). However, the majority of PEs known are believed to be non-steroidal compounds, which are from the flavonoid group, not possessing estrogen-like properties. Flavonoids are a component of many plants, constituting up to 7% of the dry weight of certain plants (Food standards agency, 2002). The other main group, isoflavonoids, is broken down into two classes; isoflavones and comestans. In addition, the isoflavone class is broken down into 5 subgroups; genistein, daidzein, glycitein, biochanin A and formonoetin.

Isoflavonoids

Leguminosae

Isoflavonoids also belong to the family Leguminosae. The Leguminosae are known to be one of the largest flowering plant families, otherwise known as legumes. A species of legume that is native to Eastern Asia is soybeans. Soybeans are rich in genistein, daidzein and glycitein, and therefore, also rich in isoflavonoids (Barrett, 1996). The remaining two subgroups of isoflavones; Biochanin A and formononetin are less concentrated among soy plants. In contrast, they are mostly concentrated in clover and alfalfa sprouts. The second class of isoflavonoids are the coumestans (Cohick et al, 2004). The coumestans have a structural relation to isoflavones which is seen in the type of legumes they are found in. For example, coumestans, in comparison to biochanin A and formononetin (subgroups of isoflavone) are found in clover and alfalfa sprouts (Cohick et al, 2004). Moving into the third major group of PEs, lignans, it is seen that they are highly concentrated in foods like grains, seeds and other foods that are rich in fiber (Kurzer et al, 1997; Apers et al, 2003).

References:

Food standards agency. 2002.
http://www.foodstandards.gov.uk/multimedia/webpage/phytoreportworddocs - Accessed March 4, 2007.

Apers S., Cos P., De Bruyne., Pieter L., Vanden Berghe D., and Vlietinck AJ. 2003. Phytoestrogens: Recen developments. Planta Medica. 69:589-599.

Barrett J. 1996. Phytoestrogens: Friends or Foes? Environmental Health Perspectives. 104(5):478-482.

Cohick W., Cornwell T., and Raskin I. 2004. Dietary phytoestrogens and health. Phytochemistry. 65:996-1016.

Kurzer MS., and Xu X. 1997. Dietary Phytoestrogens. Annu Rev Nutr. 17:353-381.

Yang M, Park MS, and Lee HS. 2006. Endocrine Disrupting Chemicals: Human Exposure and Health Risks. J. Environmental Science and Health Part C. 24: 183-224.