Synthesis and structure elucidation of estrogen quinones conjugated with cysteine, N-acetylcysteine, and glutathione.
Catechol estrogen quinones (CE-Q) have been implicated as ultimate carcinogenic metabolites in estrogen-induced carcinogenesis. CE-Q may covalently bind to DNA to initiate cancer. These quinones can also be conjugated with glutathione, a reaction that prevents damage to DNA by CE-Q. The glutathione conjugates are then catabolized through mercapturic acid biosynthesis to cysteine and N-acetylcysteine conjugates. This may be the most important detoxification pathway of CE-Q. The chemical synthesis and characterization of these conjugates are the first essential steps to better understand their function in biological systems. Eighteen conjugates were synthesized by reaction of estrone-3,4-quinone (E1-3, 4-Q), estradiol-3,4-quinone (E2-3,4-Q), estrone-2,3-quinone (E1-2, 3-Q), or estradiol-2,3-quinone (E2-2,3-Q) with various sulfur nucleophiles, RSH, in which R is the cysteine, N-acetylcysteine, or glutathione moiety. Reactions of E1-3,4-Q and E2-3,4-Q produce regiospecifically 4-OHE1-2-SR and 4-OHE2-2-SR, respectively, in almost quantitative yield. E1-2,3-Q and E2-2,3-Q react regioselectively and quantitatively to form 2-OHE1(E2)-1-SR and 2-OHE1(E 2)-4-SR, in which the 1-isomers are always the major products. The ratio between 1 and 4 isomers is 3.5 for cysteine, 2.7 for N-acetylcysteine, and 2.5 for glutathione. The synthesized conjugates will be used as standards in the identification of these compounds formed in biological systems.
Cao
K
K
Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
Stack
D E
DE
Ramanathan
R
R
Gross
M L
ML
Rogan
E G
EG
Cavalieri
E L
EL
D000111:Acetylcysteine / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D002393:Estrogens, Catechol / Q000737:chemistry*; D005978:Glutathione / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011809:Quinones / Q000737:chemistry*
D002393:Estrogens, Catechol; D011809:Quinones; D005978:Glutathione; D003545:Cysteine; D000111:Acetylcysteine