CARCINOGENESIS: DNA adduct formation by allyl glycidyl ether

Abstract

Glycidyl ethers are reactive epoxides used as components of a variety of epoxy materials. These compounds are known to cause allergic reactions, but since they are generally also genotoxic it would be of interest to evaluate the risk for induction of such effects. Reaction products of allyl glycidyl ether with nucleic acid components were therefore studied. Adduct standards of expected major products in DNA were prepared and assigned to N-7-guanine, N-1- and N-3-adenine and N-3-cytosine. The adducts were characterized by UV spectroscopy, and the adduct to N-1-adenine also by mass spectrometry and nuclear magnetic resonance spectroscopy. In analogy with the formation of corresponding reaction products of other simple epoxides the N-1-adenine adduct rearranged in a base catalysed reaction to N⁶ and the N-3-cytosine adduct deaminated to form the corresponding N-3-uracil adduct For allyl glycidyl ether these further reactions of the N-1-adenine and N-3-cytosine adducts were, however, slower than has been observed for corresponding products of other epoxides, but faster than for methylated and ethylated products. In double-stranded salmon testis DNA treated in vitro with allyl glycidyl ether, the major product was found at N-7-guanine, followed by those at N-1-adenine, N-3-adenine and N-3-cytosine (including N-3-uracil). A minor amount of an N6-adenine adduct was also detected, but only after 48 h of reaction. In single-stranded DNA the yield of the N-1-adenine adduct was increased to about the level of the N-7-guanine adduct The level of the N-3-cytosine adduct was also considerably higher in single-stranded DNA and was the third largest adduct The reactivity of N-3-adenine was decreased in single-stranded DNA and since other adducts increased the relative yield of this adduct was very low. The N-7-guanine and N-3-adenine adducts were lost from DNA as a consequence of depurination with half-lives in double-stranded DNA at 37°C and pH 7.4 of 38 and 20 h, respectively. The rates of losses (due to depurination or rearrangement) of initially formed adducts in DNA increased in the order N-1-adenine < N-7-guanine ≈ N-3-cytosine < N-3-adenine and were faster in single- than in double-stranded DNA. Taking only the rate of formation and chemical stability into consideration, the adducts with N-1-adenine and N-7-guanine seem to be the most promising candidates for monitoring allyl glycidyl ether exposures in vivo.