Background: Enantiomers of chiral compounds commonly undergo enantioselective
transformation in most biologically mediated processes. As chiral persistent
organic pollutants (POPs) are extensively distributed in the environment, differences between
enantiomers in biotransformation should be carefully considered to obtain exact
enrichment and specific health risks. This review provides an overview of in vivo
biotransformation of chiral POPs currently indicated in the Stockholm Convention and
their chiral metabolites.
Methods: Peer-reviewed journal articles focused on the research question were thoroughly
searched. A set of inclusion and exclusion criteria were developed to identify
relevant studies. We mainly compared the results from different animal models under
controlled laboratory conditions to show the difference between enantiomers in terms of distinct transformation
potential. Interactions with enzymes involved in enantioselective biotransformation, especially cytochrome
P450 (CYP), were discussed. Further research areas regarding this issue were proposed.
Results: Limited evidence for a few POPs has been found in 30 studies. Enantioselective biotransformation
of α-hexachlorocyclohexane (α-HCH), chlordane, dichlorodiphenyltrichloroethane (DDT), heptachlor, hexabromocyclododecane
(HBCD), polychlorinated biphenyls (PCBs), and toxaphene, has been investigated
using laboratory mammal, fish, bird, and worm models. Tissue and excreta distributions, as well as bioaccumulation
and elimination kinetics after administration of racemate and pure enantiomers, have been analyzed
in these studies. Changes in enantiomeric fractions have been considered as an indicator of enantioselective
biotransformation of chiral POPs in most studies. Results of different laboratory animal models revealed
that chiral POP biotransformation is seriously affected by chirality. Pronounced results of species-,
tissue-, gender-, and individual-dependent differences are observed in in vivo biotransformation of chiral
POPs. Enantioselective biotransformation of chiral POPs is dependent on enzyme amounts and activities.
However, the role of cytochrome P450 in enantioselective biotransformation has not yet been confirmed.
Conclusion: Currently available data on biotransformation of chiral POPs provide a preliminary understanding
of the fate of chiral compounds in organisms. Further detailed studies of species-dependent
biotransformation pathway and molecular mechanism in various animal models should be performed to
comprehensively understand chiral POP biotransformation.