Studies of the reaction of malondialdehyde with cytosine nucleosides.

The reaction of malondialdehyde (MDA) with cytosine nucleosides was investigated, and the structures of 1:1 and 3:1 MDA-cytosine adducts were identified. Ultraviolet and NMR spectroscopy indicates the structure of the 1:1 adduct is N4-(3-oxo-1-trans-propenyl)cytosine (M1C) and the structure of the 3:1 adduct is 6-(5*,7*-diformyl-2*H-3*,6*-dihydro-2*,6*-methano-1*,3*-oxazoci n-3*yl)-2- oxopyrimidine (M3C). Both adducts are analogous to previously identified MDA-adenine adducts. The time courses of adduct formation in the reaction of MDA with deoxycytidine at different pH's and using different sources of MDA were determined. M3C-deoxyribose is the major product at acidic pH whereas M1C-deoxyribose appears to be the sole adduct formed at neutral pH. These results suggest that adducts formed between nucleic acid bases and oligomers of MDA may not play a major role in MDA mutagenesis.