Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: METABOLIC VARIABLES AFFECTING THE EFFICACY, SAFETY, AND FATE OF AGRICULTURAL CHEMICALS

Location: Animal Metabolism-Agricultural Chemicals Research

Title: Synthesis and characterization of radiolabeled 17ß-estradiol conjugates

Authors
item Shrestha, Suman -
item Bai, Xuelain -
item Smith, David
item Hakk, Heldur
item Casey, Francis -
item Larsen, Gerald
item Padmanabhan, G -

Submitted to: Journal of Labelled Compounds and Radiopharmaceuticals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2010
Publication Date: May 15, 2011
Citation: Shrestha, S.L., Bai, X., Smith, D.J., Hakk, H., Casey, F.X.M., Larsen, G.L., Padmanabhan, G. 2011. Synthesis and characterization of radiolabeled 17ß-estradiol conjugates. Journal of Labelled Compounds and Radiopharmaceuticals. Vol. 54(5):267-271.

Interpretive Summary: The use of radioactive versions of emerging contaminants in environmental fate and transport studies, especially those that break down in the environment quickly, offers the best way to track these compounds and/or their metabolites and to determine mass-balances. Vertebrates can add water-soluble moieties to these contaminants when ingested, called conjugates, to facilitate elimination. The contribution of conjugates in the fate and transport of endocrine-disrupting steroid hormones in soil-water systems is not known. Lack of commercially available, radiolabeled estrogen conjugates has thus far limited systematic investigations of such compounds in environmental studies. The aim of this study was to synthesize 14C-labeled glucuronide and sulfate conjugates of 17ß-estradiol (E2). The conjugates 17ß-[4-14C]estradiol-3-glucuronide (E2-3-G) and 17ß-[4-14C]estradiol-17-sulfate (E2-17-S) were synthesized utilizing a one-step enzymatic synthesis and a three-step chemical synthesis, respectively. For E2-3-G synthesis, the required enzymes were harvested from a phenobarbital induced pig, and were immobilized to a stationary support. Synthesis of E2-17-S involved introducing a blocking group at one alcohol position, sulfating the other alcohol position, and finally deblocking to yield the desired synthetic product. Successful syntheses of E2-3-G and E2-17-S were achieved as verified by numerous analytical methods. Radiochemical yields of 84 and 44% were achieved for E2-3-G and E2-17-S, respectively. Purified synthetic products will be used for further fate and transport studies in soil/water systems.

Technical Abstract: The use of radioactive tracers for environmental fate and transport studies of emerging contaminants, especially for those that are labile, offers convenience in tracking study compounds and their metabolites and in calculating mass-balances. The contribution of conjugated forms of natural steroid hormones in the fate and transport of parent hormones in soil-water systems is not well known. Lack of commercially available radiolabeled estrogen conjugates has thus far limited systematic investigations of such compounds in environmental studies. The aim of this study was to synthesize radiolabeled glucuronide and sulfate conjugates of 17ß-estradiol (E2). The conjugates 17ß-[4-14C]estradiol-3-glucuronide (E2-3-G) and 17ß-[4-14C]estradiol-17-sulfate (E2-17-S) were synthesized utilizing an immobilized enzyme synthesis and a chemical synthesis approach, respectively. For E2-3-G synthesis, microsomal uridine 5'-diphospho-glucuronosyltransferase (UGT) from the liver of a phenobarbital induced pig were harvested and used to glucuronidate [14C]17ß-E2. Synthesis of E2-17-S consisted of a three-step chemical process, which involved introducing a blocking group at the C-3 position, sulfation at C-17 position, and subsequent deblocking to yield the desired synthetic product. Successful syntheses of E2-3-G and E2-17-S were achieved as verified by HPLC, radiochemical analyses, (-)LC/MS, and 1H and 13C NMR. Radiochemical yields of 84 and 44% were achieved for E2-3-G and E2-17-S, respectively. Synthetic products were purified using HPLC and radiochemical purities of 98% or greater were obtained.

Last Modified: 7/23/2014
Footer Content Back to Top of Page