Page 848 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

806 SECTION | XIII Estrogenic Toxicants

VetBooks.ir CH 3 OH C H OH O CH 3 CH 3
N
2 5

C H
HO HO 2 5
17-β-Estradiol DES Tamoxifen

OH OH
HO
S

O
HO R2
ICI Compounds Raloxifene

FIGURE 59.1 Structures of 17β-estradiol, DES and the clinically used SERMs tamoxifen, ICI compounds (R 5 C 14 H 24 F 5 OS, fulvestrant),
and raloxifene.

OH O OH HO O HO O

HO O OH O OH
Genistein Equol Daidzein

HO HO CH OH OH
2
O
CH OH
2
O
OH
OH OH HO
Enterolactone Enterodiol Resveratrol

FIGURE 59.2 Structures of the phytoestrogenic flavonoids (genistein, equol, and daidzein), lignans (enterolactone and enterodiol), and resveratrol.

compounds are present in fruits, nuts and vegetables and nonylphenol, which are widely used in industry as
are particularly high in many soy products that are ethoxylates. These compounds are surfactants and are
enriched in isoflavonoids (Havsteen, 2002). Fig. 59.2 used in detergents, paints, herbicide/pesticide formula-
shows the structures of genistein, a major isoflavonoid in tion and plastics. Alkyl hydroxybenzoates (parabens)
soy; equol, a genistein metabolite; and naringenin, a fla- (Fig. 59.3) used as preservative agents and cosmetic UV
vonoid found in grapefruit. Genistein and equol can be filters such as 4-methylbenzylidene camphor that are
detected in human serum and urine along with the estro- used in homecare products also exhibit estrogenic activ-
genic lignans enterodiol and enterolactone and these com- ity (Schreurs et al., 2005). Bisphenol A (BPA) is per-
pounds are used as biomarkers of exposure to dietary haps one of the most controversial xenoestrogens since
phytoestrogenic compounds. Resveratrol is an estrogenic it is extensively used in plastic production and plastic
polyphenolic stilbene analog found in grapes and wine. liners for cans in which trace levels of BPA have lea-
The list of synthetic estrogenic compounds continues ched directly into food products. This estrogenic com-
to grow as testing of current and new synthetic indus- pound has also been identified in the environment.
trial chemicals progresses and expands through the aus- Other estrogens of concern include PCBs and hydroxy-
pices of EPA and the ToxCast program (Janesick et al., PCBs, have been identified in the environment and in
2016; Rotroff et al., 2013). A major class of xenoestro- humans, the pesticide metabolite DDE and kepone.
gens of concern are the alkylphenols such as These compounds are persistent environmental