Characterisation of estrone–nucleic acid adducts formed by reaction of 3,4‐estrone‐o‐quinone with 2′‐deoxynucleosides/deoxynucleotides using capillary liquid chromatography/electrospray ionization mass spectrometry

Abstract

Xenobiotic and endobiotic molecules can react with DNA leading to formation of so-called DNA adducts. This modified DNA can be repaired enzymatically, but, if not, these modifications are believed to be responsible for the initiation of carcinogenic processes. Hence, we studied the interaction of 2 0 -deoxynucleosides and 2 0 -deoxynucleotides with 3,4-estronequinone (3,4-E 1 Q), a metabolite of estrone (E 1 ) and a supposed carcinogen. These estrone-nucleic acid adducts were analysed by capillary liquid chromatography (CapLC) coupled to electrospray ionization mass spectrometry (ESI-MS). Knowledge of their behaviour from in vitro studies is a prerequisite for detecting adducts in in vivo studies. Our initial attempts to synthesise nucleos(t)ide adducts of 3,4-E 1 Q in an aprotic solvent (dimethylformamide) yielded no adducts. However, under acidic aqueous conditions, adducts were obtained. With dGuo, a dGuo adduct was found in addition to a Gua adduct. Earlier publications on adduct formation in protic solvents failed to report formation of any adduct with dAdo. A N 3 -Ade adduct was reported upon reaction of 3,4-E 1 Q with Ade base and with DNA. With dAdo, we obtained two nucleoside adducts and six Ade adducts due to loss of 2 0 -deoxyribose.Thus, contrary to general belief that only 2,3-E 1 Q can form stable adducts, we showed formation of substantial amounts of intact DNA adducts with 3,4-E 1 Q in addition to deglycosylated adducts. Adducts were also obtained with dGMP and dAMP, but no phosphate alkylation was found. Adducts of dCyd, dCMP, dThd, and dTMP were not detected. Using chromatographic-MS data a structural relationship between the 2 0 -deoxynucleoside, 2 0 -deoxynucleotide and base adducts was found in the various reaction mixtures. The adducts of dGuo and dGMP reaction mixtures were alkylated at the same N 7 -position of the nucleobase, as indicated by the occurrence of a rapid deglycosylation reaction. In dAdo and dAMP reaction mixtures, 14 adducts were detected; their relationships from the LC and MS data reduced the number of structures to six adenine base alkylated adducts with respect to alkylation between N 1 , N 3 , N 7 and/or N 6 in the adenine and C 1 , C 2 and/ or C 6 in 3,4-E 1 Q. We could infer, in addition, whether they had an A ring attachment or a C 6 attachment on the estrone moiety. Copyright # 2004 John Wiley & Sons, Ltd.The longer that women are exposed to estrogens, either through early menarche and late menopause and/or through estrogen replacement therapy (ERT) or use of oral contraceptives, the higher is the risk of developing cancer in several tissues especially the breast and endometrium. 1,2 A formulation containing up to 46-53% estrone together with other exogenous estrogens is the estrogen replacement treatment of choice and continues to be one of the most widely dispensed prescriptions in the USA. In this context we studied the in vitro reactions between an endogenous estrogen, estrone, and 2 0 -deoxynucleosides/2 0 -deoxynucleotides.Estrogens are accumulated and exert m...

Analysis of Cordyceps by multi-column liquid chromatography

“…Peaks 6–11 were positively identified as phenylalanine (6), uridine (7), hypoxanthine (8), inosine (9), guanine (10), guanosine (11) by compared with retention time, UV data and MS data with reference compounds. Peaks 5 and 12–15 were tentatively identified as AMP (5), dAMP (12), adenosine (13), adenine (14), cordycepin or isomer (15) by comparison of MS data with previous reports12, 22, 23. These results are similar to those reported in the literature 22 , with the major nucleosides including AMP, uridine, guanosine and adenosine, all found in Cordyceps.…”

“…Based on the characteristic UV absorption of components (Table 2) 12 21 22 and previous reports 10 , the detection wavelength was set at 260 nm. The MS condition was modified from Refs.…”

Efficient Synthesis, Liquid Chromatography Purification, and Tandem Mass Spectrometric Characterization of Estrogen-Modified DNA Bases

“…To facilitate future studies of the mechanism of tumor initiation by endogenous estrogens and of the prospect for developing a biomarker for breast cancer, we report a simple synthesis of these modified nucleobases for use as reference materials and a characterization of their mass spectral fragmentations. The published chemical methods for preparing catechol estrogen-modified nucleobases utilize multistep reactions – . In light of the recently reported one-step reaction to convert estrogen to CEQ by using 2-iodoxybenzoic acid (IBX) as an oxidant , we implemented a simpler method to synthesize and isolate purine bases modified by CEQs by using only one purification step to obtain the putative biomarker, 4-hydroxyestrone-1-N3Ade (4-OH-E 1 -1-N3Ade).…”