Author
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MA, LI - University Of California |
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Yates, Scott |
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Submitted to: Journal of Pharmaceutical and Biomedical Analysis
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/31/2017 Publication Date: 8/1/2017 Citation: Ma, L., Yates, S.R. 2017. Degradation and metabolite formation of estrogen conjugates in an agricultural soil. Journal of Pharmaceutical and Biomedical Analysis. 145:634-640. doi: 10.1016/j.jpba.2017.07.058. Interpretive Summary: There is increasing concern over the presence of steroidal hormones in environment and agricultural systems. There can be many adverse effects from exposure to hormones, which include intersexuality, masculinization, and reproductive and behavioral problems. The movement of hormones from urban and agricultural systems to surface water poses potential risks to wildlife and humans. Also, hormonal chemicals moving through environment/agricultural systems may enter the food chain impacting public health. Therefore, highly accurate and reliable information is needed on soil transformation of hormones to better understand its environmental fate. Experiments were conducted to determine the degradation rate of conjugated hormones, which was found to be very rapid, with 95% of mass lost within 4 h (low initial concentration) and 24 h (high initial concentration) for some hormones. It was also found that the rate of biodegradation varied for different hormones. The major transformation pathway for the hormones studied was oxidation, which yielded several metabolites which are commonly found in environmental samples. This study provides useful information on the behavior of hormones in the environment and can be used in an effort to develop new strategies to mitigate hormone contamination. The new degradation rates and information on transformation should be of interest to researchers, regulators, commodity groups, farmers, and the public. Technical Abstract: Estrogen conjugates are precursors of free estrogens such as 17beta-estradiol (E2) and estrone (E1), which causes potent endocrine disrupting effects on aquatic organisms. In this study, microcosm laboratory experiments were conducted in an agricultural soil to investigate the aerobic degradation and metabolite formation kinetics of 17beta -estradiol-3-glucuronide (E2-3G) and 17beta -estradiol-3-sulphate (E2-3S). The aerobic degradation of E2-3G and E2-3S followed a first-order kinetic and the degradation rate was inversely related to their initial concentrations. The degradation of E2-3G and E2-3S was extraordinarily rapid with 95% of mass lost within 4 h and 24 h incubation for low and high initial concentrations, respectively. Biodegradation rate constants of E2-3G (0.227–0.668 1/h) were greater compared to E2-3S for high initial concentration (0.168 1/h) but smaller for low initial concentration (1.04 1/h). Considerable amount of E2-3G (7.68 ng/g) and E2-3S (4.84 ng/g) (for high initial concentration particularly) can be detected at the end of the 20-d experiment. The major transformation pathway of E2-3G and E2-3S was oxidation, yielding the primary metabolites 17beta-estrone-3-glucuronide and 17beta-estrone-3-sulphate, respectively. Common metabolites were E2, the second primary metabolite, and E1, the secondary metabolite. Additionally, three conjugated equine estrogens (or their sulfates) were tentatively proposed as minor metabolites. The persistence of E2-3G and E2-3S (up to 20 d) suggests that the high rate application of conjugated estrogen-containing stuff could be responsible for the frequent detection of free estrogens in surface and subsurface water. |
