In vitro study on the biotransformation and cytotoxicity of three hexabromocyclododecane diastereoisomers in liver cells
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Keywords:
Hexabromocyclododecane
Biotransformation
Diastereomer
Viability assay
Hexabromocyclododecane
Diastereomer
Cis–trans isomerism
Characterization
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Hexabromocyclododecane
Brominated flame retardant
Biota
Tetrabromobisphenol A
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Diastereomer
Enantiomeric excess
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The preparation of single enantiomers (ee ~100%) is one of the most important demands both for industrial practice and research. Actually, the resolution of the racemic compounds still remains the most common method for producing pure enantiomers on a large scale. To obtain the pure enantiomers, it is necessary to find the appropriate conditions and resolving agents. During the separation of diastereomeric mixtures, similar trends can be observed as in course of the distribution of enantiomeric mixtures between phases, because just the presence of one-third chiral compound (namely the resolving agent) is the difference. This chapter presents new observations and establishments about the new opportunities to optimize the separation of chiral mixtures, especially the diastereomeric mixtures.
Diastereomer
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Diastereomer
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Hexabromocyclododecane
Diastereomer
Structural isomer
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Diastereomer
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The article is focused on environmental aspects of production and use of hexabromocyclododecane (HBCDD). The compound is used mainly as a flame retardant in polystyrene insulation products. Of particular concern is the ability of this persistent lipophilic organic pollutant to accumulate in the food chain, leading to its progressively increasing levels in human tissues and in wildlife. The extent of accumulation correlates with its ever-increasing use. Despite this alarming trend, only li¬mited toxicological information is available to assess its long-term implications for human health and the environment. HBCDD continues to be used despite the availability of alternative chemicals.
Hexabromocyclododecane
Chlorinated paraffins
Brominated flame retardant
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α-, β-, and γ-Hexabromocyclododecanes (HBCDs) were subjected to in vitro biotransformation experiments with rat and trout liver S9 fractions for different incubation times (10, 30, and 60 min) at 2 concentration levels (1 and 10 μM). The metabolic degradation of target HBCDs followed first order kinetics. Whereas β-HBCD undergoes rapid biotransformation (t0.5 = 6.4 and 38.1 min in rat and trout, respectively), α-HBCD appears the most resistant to metabolic degradation (t0.5 = 17.1 and 134.9 min). The biotransformation rate in trout was slower than in rat. Investigation of HBCD degradation profiles revealed the presence of at least 3 pentabromocyclododecene (PBCD) and 2 tetrabromocyclododecadiene (TBCD) isomers indicating reductive debromination as a metabolic pathway for HBCDs. Both mono- and di- hydroxyl metabolites were identified for parent HBCDs, while only mono hydroxyl metabolites were detected for PBCDs and TBCDs. Interestingly, δ-HBCD was detected only in trout S9 fraction assays indicating metabolic interconversion of test HBCD diastereomers during biotransformation in trout. Finally, enantioselective analysis showed significant enrichment of the (-)-α-HBCD enantiomer (EF = 0.321 and 0.419 after 60 min incubation in rat and trout, respectively). The greater enrichment of (-)-α-HBCD in rat than in trout underlines the species-specific differences in HBCD metabolism and the need for caution when extending similar results from animal studies to humans.
Biotransformation
Hexabromocyclododecane
S9 fraction
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