The influence of the solvents DMSO and ethanol on the genotoxicity of α,β-unsaturated aldehydes in the SOS chromotest

α,β-Unsaturated aldehydes are ubiquitous environmental pollutants, important industrial chemicals, have mani-fold biological functions in plants and insects and are natural products in food. They are endogenously formed in animals and humans during lipid peroxidation and arachidonic acid oxidation and are genotoxic, mutagenic and carcinogenic. Crotonaldehyde and 2-hexenal in food may contribute to general carcinogenicity in humans. The high bacterial toxicity of these compounds leads to problems in genotoxicity testing in bacterial systems. Recently, we have shown that using ethanol as solvent instead of dimethylsulfoxide (DMSO) results in an increase in the induction factors and the SOS-inducing potency of α,β-unsaturated ketones in the SOS chromotest. Here, we demonstrate that utilization of ethanol as solvent also improves the testing of α,β-unsaturated aldehydes. Five aldehydes out of nine tested were clearly positive in the SOS chromotest according to the criteria of Quillardet, i.e. acrolein, crotonaldehyde, 2,4-hexadienal, 2-methylacrolein and 2-ethylacrolein, three further, 2-hexenal, 2-heptenal and 2-propylacrolein showed a dose dependent increase of the induction factors which was however lower than 1.5 times that of the background. Only 2-butylacrolein did not lead to an increase in the induction factors. With DMSO as solvent only the three aldehydes acrolein, crotonaldehyde and 2,4-hexadienal showed an increase in the induction factor, which was however lower than 1.5 that of the background. Utilization of ethanol allows to establish structure genotoxicity relationships for α,β-unsaturated aldehydes in the SOS chromotest. Genotoxicity decreases with increasing degree of substitution. The decreasing genotoxicities can be explained (a) by increasing bacterial toxicity due to increasing lipophilicities of the higher substituted aldehydes and (b) by decreasing reactivity due to steric hindrance by the alkyl substituents.