Abstract
Estrogens that originate from humans and animals are thought of as a factor of endocrine disruptors in the environment. We investigated their halogenated derivatives, which could be produced by chlorine treatment at a sewage treatment plant. The chlorinated derivatives of estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2) were produced by the reaction with hypochlorous acid in organic solvents and also brominated derivatives when bromide ions were present. The structures of chlorinated and brominated estrogens isolated were determined by MS and NMR spectroscopy. The estrogenic activities of the halogenated derivatives were measured by yeast two-hybrid assays incorporating the human estrogen receptor α (hERα) or medaka fish (Oryzias latipes) estrogen receptor α (medERα). Although the activities of 4-chloroestrone (4-ClE1) and 10-chloro-1,4-estradiene-3,17-dione were similar to those of E1, the activities of 2-ClE1 and 2,4-dichloroestrone (2,4-diClE1) were approximately 4/5 and 1/50 that of E1, respectively, in an agonist assay for hERα. No activity was detected in 2,4,16,16-tetrachloroestrone (2,4,16,16-tetraClE1). The estrogenicities of chlorinated derivatives of E2, E3, and EE2 showed a similar tendency to that of E1. The brominated derivatives showed slightly weaker activity than the corresponding chlorinated derivatives. However, many estrogens halogenated at the 2 and 4 positions still had activity that was approximately 103-104 times stronger than that of bisphenol A.
