Background: In biological systems, the individual stereoisomers of chiral
substances possess significantly different biochemical properties because the specific
structure-activity relationships are required for a common site on biomolecules. In the
past decade, there has been increasing concern over the enantioselective toxicity of environmental
chiral pollutants, especially chiral pesticides. Different responses and activities
of a pair of enantiomers of chiral pesticides were often observed. Therefore, assessment
of the enantioselective toxicological properties of chiral pesticides is a prerequisite
in application of single-isomer products and particularly important for environmental
protection. The development of biomarkers that can predict enantioselective effects from
chiral pesticides has recently been gained more and more attention. The biomarkers of
oxidative stress have become a topic of significant interest for toxic assessments.
Methods: In this review, we summarized current knowledge and advances in the understanding of enantiomeric
oxidative processes in biological systems in response to chiral pesticides.
Results: The consistent results in two types of chiral insecticides (synthetic pyrethroids and organochlorine
pesticides) showed the significant difference in cytotoxicity of enantiomers, suggesting the antioxidant enzymes
are reliable biomarkers for the assessment of toxicity of chiral chemicals. Results indicate that antioxidant
enzymes are sensitive and valid biomarkers to assess the oxidative damage caused by chiral herbicides.
In addition, it can be inferred that the enantioselectivity of chiral herbicides on antioxidant enzymes
exists in other species. Compared with insecticides and herbicides, researches about the enantioselectivity
of oxidative stress caused by chiral fungicides are quite limited. Only two kinds of chiral fungicides has
been used to study the enantioselectivity of oxidative stress by now.
Conclusion: The current knowledge that enantioselective processes of oxidative damage occur in organisms
or cells extends toxicological studies of environmental contamination by chiral chemicals. These studies
indicate that oxidative biomarkers can be useful for monitoring enantioselective toxicity of chiral contaminates,
while comparing enantiomer-induced responses in different species should be approached with
caution because of differences in uptake, target sites, biotransformation and pharmacokinetics of the enantiomers.