Human metabolism of arsenolipids present in cod liver |
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Authors: | Ernst Schmeisser Walter Goessler Kevin A Francesconi |
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Institution: | (1) Institute of Chemistry—Analytical Chemistry, Karl Franzens University Graz, Universitaetsplatz 1, 8010 Graz, Austria |
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Abstract: | We report results from the first investigation of the human metabolism of arsenic-containing lipids (arsenolipids), significant
arsenic constituents of some seafood products. Two male volunteers ingested canned cod liver and the arsenic metabolites in
their urine were monitored by high-performance liquid chromatography inductively coupled plasma mass spectrometry over a 66-h
period. Volunteer A consumed 85 g (wet mass) of cod liver containing a total of approximately 120 μg arsenic, 77% of which
was present as arsenolipids, and volunteer B consumed 85 g (wet mass) of cod liver, 25% of which was present as arsenolipids,
together with 20 g of cod liver oil, containing a total of about 180 μg arsenic. The structures of the arsenolipids are currently
unknown, whereas the majority of the non-lipid arsenic in the cod liver was identified as arsenobetaine, which was excreted
unchanged. The arsenolipids were rapidly metabolised to water-soluble compounds and excreted in the urine; peak arsenic concentrations
were recorded between 7 and 15 h (volunteer A) and between 6.5 and 15 h (volunteer B), and by the end of the experiment about
90% of the ingested arsenic had been accounted for in the urine for both volunteers. The major arsenolipid metabolite was
dimethylarsinate (DMA), constituting 73% (volunteer A) or 41% (volunteer B) of the total urinary arsenic, and most of the
remaining arsenolipid-derived arsenic, constituting about 10% (volunteer A) and 5% (volunteer B), comprised four novel arsenic-containing
fatty acids, namely oxo-dimethylarsenopropanoic acid, thio-dimethylarsenopropanoic acid, oxo-dimethylarsenobutanoic acid,
and thio-dimethylarsenobutanoic acid. Unchanged arsenobetaine (15% for volunteer A and 51% for volunteer B) made up the remaining
urinary arsenic together with trace quantities of other, mostly unknown, arsenicals. In a second experiment (volunteer A only),
performed with pure cod liver oil, which contains only arsenolipids, DMA and the same four arsenic fatty acids were excreted
in the urine. The study shows that arsenolipids in cod liver are bioavailable, and that they are quickly biotransformed to
several water-soluble arsenicals, the structures of which suggest that the native arsenolipids contain a dimethylarsine oxide
moiety. |
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Keywords: | Arsenolipids Biotransformation Arsenic speciation Urine metabolites |
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