Anaerobic transformation of compounds of technical toxaphene. 2. Fate of compounds lacking geminal chlorine atoms

Abstract

The major toxaphene metabolites in sediment and soils (2-exo,3-endo,6-exo,8,9,10-hexachlorobornane [B6-923] and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane [B7-1001]) were incubated with the isolated gram-negative bacterium Dehalospirillum multivorans. Within 14 d, biotransformation of B7-1001 was nearly quantitative, resulting in two penta- and six hexachlorobornanes, as well as one unsaturated hexachloro compound of technical toxaphene. The major transformation product (approximately 50% of all metabolites) was identified as 2-exo,3-endo,5-exo,8,9,10-hexachlorobornane (B6-903). Abiotic dehydrochlorination of B7-1001 with methanolic KOH resulted in the formation and subsequent identification of the lone unsaturated compound as 2,5-endo,6-exo,8,9,10-hexachloroborn-2-ene. Thus, dehydrochlorination was found to be a minor process of the anaerobic transformation of toxaphene. Biotransformation of 70% of amended B6-923 within 14 d demonstrated that reductive dechlorination was not exclusively associated with geminal Cl atoms, as previously suggested. Three pentachlorobornanes were identified as transformation products, one of which was identical with a transformation product of B7-1001. This commonality unequivocally proves this metabolite to be 2-exo,3-endo,8,9,10-pentachlorobornane. Fifteen previously unknown metabolites of B6-923, B7-1001, and other toxaphene compounds identified in this study were detected in sediment from Lake Ontario (Canada), underscoring the importance of microbial toxaphene transformation in natural, aquatic environments.

Capabilities of Direct Sample Introduction−Comprehensive Two-Dimensional Gas Chromatography−Time-of-Flight Mass Spectrometry to Analyze Organic Chemicals of Interest in Fish Oils

“…Based on GC×GC retention times and mass spectra, we confirmed that the toxaphene congeners found in the samples matched those from the toxaphene technical product. By comparing our data with the relative retention times and characteristic mass spectra in the literature (15,16), we were able to verify that they were the most abundant toxaphene congeners found in the environment (B8-1413, B8-1414/B8-1945, B8-2229, B9-1679, and B9-1025). R-Chlordene and 1-chloro-2,2-bis(chlorophenyl)ethene (p,p'-DDMU) which is the dechlorinated form of 1,1-dichloro-2,2-bis(chlorophenyl)ethane (p,p'-DDE) were also identified using the library database.…”

“…Several halogenated natural products (HNPs) were detected in the extracts: halogenated 1′-methyl-1,2′-bipyrroles (MBPs), DMBPs, meth- 41)). d Identified by the correct retention time range on the DB-5 column type, the correct number of chlorines, characteristic features in the mass spectra, and their known abundance in cod liver oil (15,16). e Structure tentatively assigned based on the presence of these toxaphenes in cod liver oil and the known elution order on the DB-5 column type (15,16) f Tentative structural identification: 2,2′,3,3′-tetrabromo-4,4′5,5′-tetrahydroxy diphenyl methane.…”

Development of a reference dose for the persistent congeners of weathered toxaphene based on in vivo and in vitro effects related to tumor promotion

“…Toxaphene weathers in different ways in different environmental settings to produce different congener mixtures (Ruppe et al, 2003(Ruppe et al, , 2004. In addition, different animals metabolize various toxaphene congeners to varying degrees (Angerhofer et al, 1999) and different species of animals end up with different toxaphene congener profiles comprising their respective body burdens.…”

“…The persistence of the various congeners is determined by their thermodynamic stabilities and molecular structural energies (Heimstad et al, 2001). Microbial degradation of toxaphene shows specificity for the removal of chlorines in particular positions on the molecule (Ruppe et al, 2003(Ruppe et al, , 2004. In addition, biotic and abiotic transformation of toxaphene results in different mixtures of congeners (Angerhofer et al, 1999).…”

Anaerobic transformation of four abundant organochlorine pesticide residues (B8-1413, B9-1679, oxychlordane,p,p‵-DDE) in extracts of Antarctic skua eggs by the isolated bacteriumSulfurospirillum multivorans

“…For instance, the anaerobic gram negative bacterium Sulfurospirillum multivorans [5] (previously known as Dehalospirillum multivorans [6]) showed a high potential for the anaerobic transformation of tetrachloroethene (PCE) and related C 2 -compounds [7,8]. Our lab studies demonstrated that S. multivorans was also an excellent transformer of the chloropesticide toxaphene [9,10]. Toxaphene is formed by the exhaustive chlorination of camphene which yields a complex mixture of about 1000 penta-to decachlorinated compounds of technical toxaphene (CTTs) [11,13].…”