First comparative reaction mechanisms of β-estradiol and selected environmental hormones in a redox environment

This work describes the first comparative electrochemical behavior of β-estradiol and selected important environmental hormones, specifically alkylphenols (APs). Most of the concerns about environmental hormones in humans center on their interference with estrogens, an ovarian steroid. APs are believed to have high affinity for biological receptors by generating conformational changes that can be detected by other macromolecules. However, no mechanistic or molecular evidence has been established for these studies. Here we show, an electrochemical mechanism of estradiol and selected APs including bisphenol-A (BPA), nonylphenol (NP), and diethylstilbestrol (DES) using cyclic voltammetry (CV), rotating disk electrode (RDE) and controlled potential coulometry (CPC). We observed a striking similarity in the electrochemistry of these synthetic xenobiotics and estradiol, a natural estrogen. The complete reaction mechanisms for the oxidation of NP, DES and estradiol were found to follow EC-EC scheme. Unlike most aromatic hydroxy phenols, our results showed that using bulk electrolysis with CPC, both estradiol and DES generated a ketone and quinone intermediate products, respectively. These products were isolated and confirmed using mass spectrometry. This study may provide insights into the origin of the in vivo molecular recognition since there is little steric or electronic hindrance expected at reactor sites between the APs and estradiol.