Metabolism of isoflavones

Isoflavonoid has been used as dietary biomarkers [103,104], It has been further established that isoflavonoids influence receptor expression [105] and induce immune changes [106,107], The individual variation in metabolism of isoflavones has also been extansively studied [108,109], It has been further demonstrated that flavonoids show antiinflammatory effects on adjuvant arthritis [110], and protect mice from two types of lethal shock caused by endotoxin [111],... 

The metabolism and bioavailability of isoflavonoids is likely to be of crucial importance to their ability to help protect human health against disease. Many studies have been published on the metabolism and bioavailability of isoflavones in adults. The metabolism of isoflavones is of particular interest because the potency of isoflavone metabolites differs from that of the parent compounds. The daidzein metabolite equol is three times as potent as is daidzein in an endometrial tumor line. Equol is also a more potent antioxidant in vitro (see Sections 7.3.5 and 7.4.2) ° and the clinical significance of the ability to form equol has been considered in depth. ... 

The importance of the gut microflora in the metabolism of isoflavones has been demonstrated. Antibiotic administration blocks isoflavone metabolism and germfree animals do not excrete metabolites. Moreover, only germfree rats colonized with microflora from a good equol producer excrete equol when fed soy. ... 

Bowey E, Aldercreutz A, Rowland I. Metabolism of isoflavones and lignans by the gut microflora a study in germ-free and human flora associated rats. Food Chem. Toxicol. 41, 631-636, 2003. 

Furthermore, the metabolism of isoflavones is influenced by different components of the diet. A high fiber diet may increase the growth and/or activity of bacteria responsible for equol production in the colon [90]. This is relevant since equol has an oestrogenic potency higher than the precursor daidzein [91]. 

King R. 2002. Digestion, absorption, and metabolism of isoflavones. In Gilani G, Ed. Phytoestrogens and Health. Illinois AOCS Press, PP. 209-234. 

BARZ, W., WELLE, R., Biosynthesis and metabolism of isoflavones and pterocarpan phytoalexins in chiekpea, soybean and phytopathogenic fungi, in ... 

Roberts, D.W., D.R. Doerge, M.L Churchwell, et al. 2004. Inhibition of extrahepatic human cytochromes P450 lAl and IBl by metabolism of isoflavones found in Trifolium pratense (red clover). /. Agric. Food Chem. 52(21) 6623-6632. 

Possemiers S, Bolca S, Eeckhaut E, Depypere H, Verstraete W. Metabolism of isoflavones, lignans and prenylflavonoids by intestinal bacteria producer phenotyping and relation with intestinal community. FEMSMicrobiol Ecol 61(2), 372-383, 2007. 

Ruminal metabolism of isoflavones has been studied mainly in sheep, and it is suggested to resemble qualitatively that in cattle (Lundh, 1995). Recent studies show that bovine ruminal bacteria can convert daidzein and genistein to dihydrodaidzein and dihydrogenistein, respectively (Wang et al, 2005), and can produce X-equol (vide infra) from daidzein through dihydrodaidzein (Wang et al, 2007). 

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