Degradation of the potential rodent contraceptive quinestrol and elimination of its estrogenic activity in soil and water.

Quinestrol has shown potential for use in the fertility control of the plateau pika population of the Qinghai-Tibet Plateau. However, the environmental safety and fate of this compound are still obscure. Our study investigated degradation of quinestrol in a local soil and aquatic system for the first time. The results indicate that the degradation of quinestrol follows first-order kinetics in both soil and water, with a dissipation half-life of approximately 16.0 days in local soil. Microbial activity heavily influenced the degradation of quinestrol, with 41.2% removal in non-sterile soil comparing to 4.8% removal in sterile soil after incubation of 10 days. The half-lives in neutral water (pH 7.4) were 0.75 h when exposed to UV light (λ = 365 nm) whereas they became 2.63 h when exposed to visible light (λ > 400 nm). Acidic conditions facilitated quinestrol degradation in water with shorter half-lives of 1.04 and 1.47 h in pH 4.0 and pH 5.0 solutions, respectively. Moreover, both the soil and water treatment systems efficiently eliminated the estrogenic activity of quinestrol. Results presented herein clarify the complete degradation of quinestrol in a relatively short time. The ecological and environmental safety of this compound needs further investigation.

Photodegradation of quinestrol in waters and the transformation products by UV irradiation.

Quinestrol is synthetic estrogen used in contraceptive and hormone replacement therapy and occasionally for treating breast cancer and prostate cancer. It can make its way into the environment through sewage discharge and waste disposal produced by human excretions. In this study, the photodegradation kinetics of quinestrol in various conditions was investigated by UV and solar irradiation. The affecting factors were studied including concentration of hydrogen peroxide, different water types, and the initial concentrations of quinestrol. Concurrently, the transformation products and presumed pathways of quinestrol in distilled water by UV irradiation were identified and proposed. The results showed that the degradation of quinestrol in both irradiation conditions followed the pseudo-first-order kinetics. More rapid degradation was observed by UV irradiation (k=0.018 min(-1)) than solar irradiation (k=0.004 h(-1)), and the photodegradation rate of quinestrol depended on the concentration of hydrogen peroxide, the initial concentration of quinestrol and water types. The transformation products of quinestrol in distilled water were identified by gas chromatography/mass spectrometry. When exposed to UV irradiation, quinestrol in aqueous solution was rapidly degraded, giving at least ten photodegradation products. The chemical structures of ten degradation products were identified on the basis of mass spectrum interpretation and literature data.

High-pressure liquid chromatographic assay of quinestrol tablets.

A specific assay for quinestrol was developed using high-pressure liquid chromatography. The estrogen was separated from tablet excipients on a chemically bonded hydrocarbon column utilizing acetonitrile-water as the mobile phase. Linearity studies were carried out using peak height measurements, and the detector response to the concentration of the steroid was confirmed. This procedure was rapid, accurate precise, and specific for the assay of the synthetic estrogen in the presence of formulation excipients and structurally similar estrogens.

GLC determination of 17 alpha-ethynylestriol 3-cyclopentyl ether.

A rapid, sensitive, and accurate GLC method of analysis of a new estrogenic drug, 17 alpha-ethynylestriol 3-cyclopentyl ether, was developed. The drug and the internal standard, tetratriacontane, are dissolved in chloroform, and an aliquot is heated with N-trimethylsilylimidazole at 80 degrees for 30 min. The silylated sample is chromatographed using a column packed with 1% methyl vinyl silicone gum on Gas Chrom Q. Quantitation is achieved by computer calculation of the peak area ratios. The observed peak is the 16alpha,17beta-bistrimethylsilyl derivative of the new drug substance. The GLC method was applied to the quantitative determination of the estrogenic compound in a tablet formulation containing 25 mug/tablet.