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Structures of the DNA adducts formed in mouse liver after administration of the proximate hepatocarcinogen 1'-hydroxyestragole

Research output: Contribution to journalArticle

D H Phillips, J A Miller, E C Miller, B Adams

Original languageEnglish
Pages (from-to)176-186
Number of pages11
JournalCancer Research
Volume41
Issue number1
Publication statusPublished - Jan 1981

King's Authors

Abstract

1′-Hydroxyestragole is a proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen estragole (1-allyl-4-methoxybenzene). Two major (I and II) and 2 minor (III and IV) nucleoside adducts were found by high-performance liquid chromatography (HPLC) of enzymatic hydrolysates of hepatic DNA isolated from adult female CD-1 or preweanling C57BL/6 × C3H/He F1 mice that had been given i.p. injections of 1′-[2′,3′-3H]hydroxyestragole. Reaction of 1′-acetoxyestragole, a model electrophilic and mutagenic ester, with [14C]deoxyguanosine ([14C]dGuo) yielded products that coeluted on HPLC with Adducts I, II, and III, while Adduct IV coeluted with a product of the reaction of 1′-acetoxyestragole with [14C]deoxyadenosine. The in vivo adducts did not comigrate with any major reaction products of either 1′-hydroxyestragole-2′,3′-oxide or 1′-oxoestragole with [14C]dGuo or [14C]deoxyadenosine. The pH partition coefficient patterns of the in vivo- and in vitro-derived dGuo Adducts I, II, and III together with the 3H:14C ratios of the three adducts from the reaction of 1′-acetoxyestragole with [8-14C,8-3H]dGuo indicated that each of these adducts contains a N2-substituted dGuo residue. Synthetic samples of Adducts II and IV were characterized from their nuclear magnetic resonance spectra and assigned the structures N2-(trans-isoestragol-3′-yl)deoxyguanosine and N2-(trans-isoestragol-3′-yl)deoxyadenosine, respectively. Hydrolysis at 100° with 0.1 N HCl for 30 min of the in vivo Adducts I and II yielded in each case radioactivity which coeluted on HPLC with 3′-hydroxyisoestragole. If Adduct I was first reduced with H2:platinum and then hydrolyzed, radioactivity eluted with 1′-hydroxy-2′,3′-dihydroestragole. Adduct I is therefore assigned the structure N2-(estragol-1′-yl)deoxyguanosine. Adduct III was converted in part to Adduct II on chromatography on HPLC and is thus tentatively regarded as N2-(cis-isoestragol-3′-yl)deoxyguanosine. All four adducts in the mouse liver can be accounted for by the reaction of a metabolically derived ester of 1′-hydroxyestragole with purine bases in DNA by SN1, SN2, or SN2′ mechanisms.

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