Enterodiol

DMA) and equol, while for lignans enterodiol and enterolactone should be used. 

Recently, some of the specific faecal bacteria involved in the metabolism of dietary isoflavonoids were isolated (Hur et al., 2000). They have been shown to selectively convert genistin and daidzin to their respective aglycones. One of the isolated bacteria, under anoxic conditions, was further shown to metabolise genistein and daidzein to their respective dihydroxy-genistein and dihydroxy-daidzein. In the case of lignans, enterodiol and enterolactone were shown to be excreted in vivo only in rats harbouring a gut microflora (Rowland et al, 1999). 

Fig. 2.86. Chemical structures of the iosflavones daidzein, genistein, O-desmethylangolensin, equol, and the lignans enterolactone and enterodiol. Reprinted with permission from Z. Kuklenyik el al. [209].

Gut microflora metabolites may also be important. As discussed above, the mammalian lignan aglycones, enterodiol and enterolactone, are estrogenic, and equol is more estrogenic than its dietary precursor, the isoflavone daidzein. ... 

Wang, L.Q., Meselhy, M.R., Li, Y., Qin, G.W., and Hattori, M., Human intestinal bacteria capable of transforming secoisolariciresinol diglucoside to mammalian lignans, enterodiol and enterolactone, Chem. Pharm. Bull, 48, 1606, 2000. 

Jacobs, E., Kulling, S.E., and Metzler, M., Novel metabolites of the mammalian lignans enterolactone and enterodiol in human urine, J. Steroid Biochem. Mol Biol, 68, 211, 1999. 

Heinonen, S., Nurmi, T., Liukkonen, K., Poutanen, K., Wahala, K., Deyama, T., Nishibe, S., and Adlercreutz, H., In vitro metabolism of plant lignans new precursors of mammalian lignans enterolactone and enterodiol, J. Agric. Food Chem., 49, 3178, 2001. 

Figure 10.5 Typical LC-MS/MS trace by negative ESI of isoflavonoids from a urine extract. Measured concentrations in bracket. F-axis units in relative intensity EL = enterolactone, ED = enterodiol, other abbreviations see figure.

Adlercreutz H, Fotsis T, Heikkinen R, Dwyer JT, Woods M, Goldin BR, Gorbach SL. 1982. Excretion of the lignans enterolactone and enterodiol and of equol in omnivorous and vegetarian postmenopausal women and in women with breast cancer. Lancet 2 1295-1299. 

The presence of the oxidized metabolites is unique and may provide additional reasons for the health benefits of lignans. Classical antioxidant mechanisms show that the addition of an ortho hydroxyl group to a monophenol enhances the antioxidant activity of the original monophenol. Thus, some of the mammalian lignan metabolites may actually have greater or different activity than the parent lignan. Kitts et al (1999) reported that enterolactone and enterodiol had greater antioxidant activity than the parent... 

In contrast, enterodiol and enterolactone were believed to be partly responsible for the growth inhibition of three human prostate cancer cell lines (Lin et al., 2001). Morton et al. (1997) reported that higher enterolactone levels in prostatic fluid were associated with populations with a low risk of prostate cancer. In a small clinical study, prostate cancer cell proliferation decreased and apoptosis increased in men fed 30 g of flaxseed per day (Demark-Wahnefried et al., 2001). A significant factor which may have influenced this study was that the subjects were on a low-fat diet. A subsequent study by the authors further supported the role of flaxseed in combination with a low-fat diet as a means to control prostate growth (Demark-Wahnefried et al., 2004). In this study, prostate-specific antigen level and cell proliferation both decreased from baseline after only 6 months on the dietary regime. 

Kitts, D.D., Yuan, Y.V., Wijewickreme, A.N., and Thompson, L.U. 1999. Antioxidant activity of the flaxseed lignan secoisolariciresinol diglycoside and its mammalian lignan metabolites enterodiol... 

Power, K.A., Saarinen, N.M., Chen, J., and Thompson, L.U. 2004. Lignans (enterolactone and enterodiol) negate the proliferative effect of sioflavone (genistein) on MCF-7 breast cancer cells in vitro and in vivo (abstract). Proc. AACR 45, 878. 

Prasad, K. 2000b. Antioxidant activity of secoisolariciresinol diglucoside-derived metabolites, secoi-solariciresinol, enterodiol, and enterolactone. Inti. J. Angiol. 9, 220-225. 

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