Abstract
We measured the estrogen agonist activity of four phenolic chemicals, 3-methyl-4-nitrophenol, 3-methyl-4- (methylthio) phenol, 2-isopropyl-6-methyl-4-pyrimidinol, 4- (methythio) phenol which have been formed by hydrolysis of organophosphorus compounds commercialized as insecticides in Japan by using yeast two-hybrid assay system.
It was found that both phenolic compounds substituted at 4-position with the methylthio-moiety exhibited human estrogen receptor α, hERα, agonist activity judging from the values of ECx10and that the activity was about a half or one-third compared with that of Bisphenol-A (BPA) . On the other hand, the others expressed cytotoxicity for the yeast cells rather than the activity.
In order to estimate the possibility of incorporation into the yeast cells, the common logarithm ofn-octanol/water partition coefficient, logKow, and aqueous solubility, Sw, were used as indexes. In addition, to reveal the relationships between the activity and the molecular structure of the phenolic chemicals, 17β-estradiol (E2), and BPA, the atom charge and the dipole moment (μ) were calculated by using Gaussian R 98W program package in terms of B3LYP and 6-311G basis set, and correlation analysis on the charge distribution among the chemicals was carried out.
It was found that the low estrogenic activity was explained on the basis of the low ability of the incorporation into the yeast cells in terms of logKow and Sw, and that there was significant correlation between the estrogenic activity and μ, in the range from 2 to 3 Debye, rather than the charge distribution at the aromatic ring including hydroxyl group in the present study.
