The potent bacterial mutagen and drinking water disinfection byproduct 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was reacted with 2'-deoxyadenosine and calf thymus DNA in aqueous solutions at neutral conditions. HPLC analyses of the 2'-deoxyadenosine reaction mixtures showed that two previously unidentified products were formed. The products were isolated by preparative C18 chromatography, and their structures were characterized by UV absorbance, fluorescence emission, 1H and 13C NMR spectroscopy, and mass spectrometry. It was concluded that in both products a propeno bridge had been incorporated between N-1 and N6 of the adenine unit. In one of the products, the propeno bridge carried a formyl group [3-(2'-deoxy-beta-D-ribofuranosyl)-7H-8-formyl[2,1-i]pyrimidopurine++ + (pfA-dR)], and in the other the substituents consisted of a formyl group and a chlorine atom [3-(2'-deoxy-beta-D-ribofuranosyl)-7H-8-formyl-9-chloro[2,1-i]pyrimid opurine (Cl-pfA-dR)]. These novel adducts exhibited fluorescence in the visible region with emission maxima around 460 nm. The yields of the products in reactions performed at pH 7.4 and 37 degrees C were about 0.03 mol %. In reaction of MX with calf thymus DNA, the adduct pfA-dR was formed and its yield was about 0.6 adduct/10(5) nucleotides.

2'-Deoxyadenosine was reacted with malonaldehyde in the presence of formaldehyde or acetaldehyde. The reactions were carried out at 37 degrees C in aqueous solution at acidic conditions. The reaction mixtures were analyzed by HPLC. In both reactions, two major products were formed. The reaction products were isolated and purified by C18 chromatography, and their structures were characterized by UV absorbance, fluorescence emission, (1)H and (13)C NMR spectroscopy, and mass spectrometry. The reaction products isolated from the mixture containing formaldehyde, malonaldehyde, and deoxyadenosine were identified as 3-(2'-deoxy-beta-D-ribofuranosyl)-7H-8-formyl[2,1-i]pyrimidopurine (M(1)FA-dA) and 9-(2'-deoxy-beta-D-ribofuranosyl)-6-(3,5-diformyl-1, 4-dihydro-1-pyridyl)purine (M(2)FA-dA). In the reaction mixture consisting of acetaldehyde, malonaldehyde, and deoxyadenosine, the identities of the products were determined to be 3-(2'-deoxy-beta-D-ribofuranosyl)-7-methyl-8-formyl[2, 1-i]pyrimidopurine (M(1)AA-dA) and 9-(2'-deoxy-beta-D-ribofuranosyl)-6-(3,5-diformyl-4-methyl-1, 4-dihydro-1-pyridyl)purine (M(2)AA-dA). The yields of the compounds were 1.8 and 0.7% for M(1)FA-dA and M(2)FA-dA, respectively, and 6.8 and 10% for M(1)AA-dA and M(2)AA-dA, respectively. All compounds exhibited marked fluorescent properties. These findings show that in addition to direct reaction of a specific aldehyde with 2'-deoxyadenosine, aldehyde conjugates also may react with the base. Although three of the adducts (M(1)FA-dA, M(2)FA-dA, and M(1)AA-dA) could not be detected in reactions carried out under neutral conditions, the possibility that trace amounts of the adducts may be formed under physiological conditions cannot be ruled out. Therefore, conjugate adducts must be considered in work that aims at clarifying the mechanism of aldehyde genotoxicity.

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is a potent direct-acting bacterial mutagen and a rodent carcinogen occurring in chlorine-disinfected drinking water. In this study, we have reacted MX with guanosine, cytidine, thymidine, and calf thymus DNA in aqueous solutions. HPLC analyses of the reaction mixture of MX with guanosine showed that one main product peak was formed. In the reactions of MX with cytidine or thymidine, no product peaks representing base-modified nucleosides could be observed. The product from the MX guanosine reaction mixture was isolated by preparative chromatography on reversed phase C18 columns, and its structure was determined by UV absorbance, 1H and 13C NMR spectroscopy, and mass spectrometry. The product was identified as 3-(beta-D-ribofuranosyl)-7-formylimidazo[1,2-a]purin-9(4H)-one (epsilonfGuo), and the yield for the reaction carried out at pH 7.4 and 37 degrees C was about 0.3 mol %. The adduct could not be observed at the detection limit of five adducts per 10(7) bases in the hydrolysate of the calf thymus DNA reacted with MX. However, this failure does not rule out the possibility that lower amounts of the adduct might be involved in the observed mispairing (adenine incorporated opposite an adducted guanine base) caused by MX in the Salmonella typhimurium strain TA100.