Equol metabolism

ROWLAND I R, WISEMAN H, SANDERS T A, ADLERCREUTZ H and BOWEY E A (2000) luteriudividual variation in metabolism of soy isoflavones and lignans influence of habitual diet on equol production by the gut microflora. Nutr Cancer 36, 27-32. 

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. ... 

Interindividual variation in ability to metabolize daidzein to equol (more estrogenic and a more potent antioxidant than daidzein) could thus influence the potential health protective effects of soy isoflavones. The extent of gut microflora metabolism in humans is variable, approximately 35% of a Western population can produce equol. ... 

A variable metabolic response to isoflavones has been shown for subjects following consumption of soy flour urinary excretion concentrations of genistein, daidzein, equol, and O-DMA were increased 8-, 4-, 45-, and 66-fold, respectively, compared to baseline. Considerable interindividual variation in metabolic response was reported with the peak levels of equol showing the most variation. ... 

Ueno T, Uchiyama S. Identification of the specific intestinal bacteria capable of metabolizing soy isofiavone to equol. Am. Nutr. Metab. 45, 114 (abstract), 2001. 

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]. 

According to Rowland et al [92] dietary fat decreases the capacity of gut microbioflora to synthesize equol. Additionally, the subjects may be poor or good equol excretors, confirming that extensive interindividual variation in isoflavone metabolism exists. 

Yuan JP, Wang JH, Liu X. 2007. Metabolism of dietary soy isoflavones to equol by human intestinal microflora—implications for health. Mol Nutr Food Res 51 765-781. 

Coumestans, such as coumestrol, are found in high concentrations in alfalfa and clover and have been recognized, along with formononetin, as the cause of infertility in grazing herbivores. Whereas coumestrol acts as an estrogen mimic directly, formononetin has to be metabolized to the estrogenically active compounds diadzein, equol, or >-demethylangolensein. 

Regarding the formation of these isoflavone derivatives, it is extremely interesting that some people are unable to produce equol or that they produce it in very low amounts. In fact, studies report that a third part of the general population cannot form equol. This demonstrates that the breakdown of isoflavones by the microflora in the gut determines the recovery of the compounds, and that the excretion to the urine of equol and other isoflavones derivatives, such as O-DMA, is dependent on the different composition of intestinal microflora. To confuse the issue even more, some researchers report that the production of isoflavone derivatives, such as equol, also depends on diet and gender a high fat/meat content diet increases equol production in women but not in men, which is explained by promotion of the growth or the activity of the bacterial populations responsible for equol production. On the other hand, no age-related differences for isoflavone metabolism have been reported [12, 13],... 

Hall, W.L. K. Vafeiadou J. Hallund S. Bugel M. Reimann C. Koebnick H.J.F. Zunft M. Ferrari F. Branca T. Dadd, et al. Soy-isoflavone-enriched foods and markers of lipid and glucose metabolism in postmenopausal women Interactions with genotype and equol production. Am. J. Clin. Nutr. 2006, 83, 592-600. 

Tang BY, Adams NR. Effects of equol on oestrogen receptors and on synthesis on DNA and protein in the immature rat uterus. J Endocrinol Metabol 1979 49 152-154. 

Isoflavans, such as (90), represent the most reduced structures of isoflavonoids about 51 stiuctures have been reported (Dewick, 1988 Williams and Harbome, 1989b). The animal flavonoid metabolite, equol (91), is a representative of this class of compounds. Equol is formed in animals from the metabolism of compounds such as formononetin (82). Other isoflavans are known to occur in plants for example, (- )-5 -methoxysativan is found in alfalfa foliage (Fig. 11.29) (Dewick, 1982 Miller et al., 1989). 

Naturally occurring isoflavones and coumestans have relatively weak oestrogenic activity, but this activity can be increased as a result of metabolism in the rumen. For example, the main isoflavone in subterranean clover, formononetin, is converted to equol in the rumen. Some plants, e.g. T. repens (white clover), are normally non-oestrogenic but when infected with fungi can produce high concentrations of coumestan. 

First, the deconposition by isoflavone metabolism enzymes could change isoflavones such as daidzein (6) to their metabolites such as equol (7). 

ISOFLAVONES ALSO COULD BE PRODUCED IN HUMAN Body Equol (49) of Isoflavone Metabolism Product with Estrogen Activity... 

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