title: Tentative Structural Assignment of a Glucuronide Metabolite of Methyltestosterone in Tilapia Bile by Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry.
abstract: Methyltestosterone (MT), a strong androgenic steroid, is not approved for use in fish aquaculture in the United States. It is used in the U.S. under an investigational new animal drug exemption (INAD) only during the early life stages of fish. There is a possibility that farmers feed fish with MT to enhance production for economic gains. Therefore, there is a need to develop methods for the detection of MT and its metabolite residues in fish tissue for monitoring purposes. Previously, our laboratory developed a liquid chromatography-quadrupole time-of-flight (LC-QTOF) method for characterization of 17-O-glucuronide metabolite (MT-glu) in bile of tilapia dosed with MT. The system used was an Agilent 6530 Q-TOF equipped with electrospray jet stream technology, operating in positive ion mode. Retrospective analysis of the data generated in that experiment by a feature-finding algorithm, combined with a search against an in-house library of possible MT-metabolites, resulted in the discovery of a major glucuronide metabolite of MT in the bile extracts. Preliminary data indicate it to be a glucuronide of a hydroxylated MT (OHMT-glu) which persists in tilapia bile for at least 2 weeks after dosing. We present the tentative structural assignment of the OHMT-glu in tilapia bile and time course of development. This glucuronide can serve as a marker to monitor illegal use of MT in tilapia culture.
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Upul
authors.initials: U
authors.lastname: Nishshanka
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Pak-Sin
authors.initials: PS
authors.lastname: Chu
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Evans
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Renate
authors.initials: R
authors.lastname: Reimschuessel
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hasbrouck
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Kande
authors.initials: K
authors.lastname: Amarasinghe
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, United States.
authors.forename: Hiranthi
authors.initials: H
authors.lastname: Jayasuriya
mesh_terms: D000728:Androgens / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001646:Bile / Q000737:chemistry* / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods*; D020719:Glucuronides / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods*; D008777:Methyltestosterone / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D017210:Tilapia / Q000378:metabolism*
chemical_list: D000728:Androgens; D020719:Glucuronides; D008777:Methyltestosterone
keywords: MS/MS; MT-glu; OHMT-glu; QTOF; bile; methyltestosterone; tilapia