Arsenic, a hazardous metalloid, is found in more than 245 minerals and more than 25 different As compounds have been identified in biological samples. This high number of compounds was identified despite the fact that scientists have focused mostly on the water-soluble fraction. An international research group now found arsenic in lipids from fish oil. The discovery of arsenic in oil from capelin (Mallotus villosus), a North Atlantic fish in the smelt family, and the prospect that it could also be present in other fatty fish, could have important implications for human health and the ocean environment.
Background:
Inorganic arsenic is classified to be a cancerogenic poison and thus a major environmental and health hazard. Most human exposure to inorganic arsenic occurs through water, and the majority of research on arsenic toxicity has focused on this. However, arsenic exposure through food, especially rice, has recently been raising concerns. The discovery of arsenic in fish oil adds to these concerns, especially because many dietitians encourage people to increase their fish consumption.
The new study:
A group led by
Kevin A. Francesconi, professor of chemistry at the University of Graz, in Austria, has now isolated arsenic-containing oil from capelin by heating and compressing whole fish and extracting the oil with hexane. The researchers then used high-performance liquid chromatography to purify arsenolipids in the oil.
By analyzing the purified fractions with mass spectrometry for arsenic speciation analysis, they identified three different arsenic-containing compounds: two dimethylarsinoyl alkanes and a dimethylarsinoyl alkene.
Fig. 1: Dimethylarsinoyl alkene
(analog to
all-cis-4,7,10,13,16,19-docosahexaenoic acid)Approximately 70% of all of the lipid-soluble arsenic in capelin is contained in these three compounds. The study provides potentially important new information about the molecular form arsenic adopts in capelin and perhaps other fish.
"Until now," Francesconi says, "arsenolipids have not been investigated" as a potential source of arsenic contamination.
The dimethylarsinoyl alkene identified by the researchers is an arsenic-containing analog of docosahexaenoic acid (DHA), a common omega-3 fatty acid. The researchers hypothesize that the alkene results from a biosynthetic error during which arsenic is substituted for a carbon atom in DHA.
The toxicity of arsenolipids is not known up to now and depends on how people metabolize them. Therefore the metabolism of arsenolipds is a new topic, which Francesconi and coworkers have started to investigate.
The original publication
Mojtaba S. Taleshi, Kenneth B. Jensen, Georg Raber, John S. Edmonds, Helga Gunnlaugsdottir,
Kevin A. Francesconi,
Arsenic-containing hydrocarbons: natural compounds in oil from the fish capelin, Mallotus villosus, Chem. Commun., 2008.
DOI: 10.1039/b808049fRelated studies Alice Rumpler, John S. Edmonds, Mariko Katsu, Kenneth B. Jensen,
Walter
Goessler, Georg Raber, Helga Gunnlaugsdottir,
Kevin A. Francesconi,
Arsenic-Containing Long-Chain Fatty Acids in Cod-Liver Oil: A Result of Biosynthetic Infidelity?, Angew. Chem., Int. Ed. Engl., 47/14 (2008) 2665-2667.
DOI: 10.1002/anie.200705405 Ernst Schmeisser,
Walter Goessler,
Kevin A. Francesconi,
Human metabolism of arsenolipids present in cod liver, Anal. Bioanal. Chem., 385/2 (2006) 367-376.
DOI: 10.1007/s00216-006-0401-x E. Schmeisser, A. Rumpler, M. Kollroser, G. Rechberger,
W. Goessler,
Kevin A. Francesconi,
Arsenic fatty acids are human urinary metabolites of arsenolipids present in cod liver, Angew. Chem., Int. Ed. Engl., 45 (2006) 150-154.
DOI: 10.1002/anie.200502706
Ernst Schmeisser,
Walter Goessler, Norbert Kienzl,
Kevin A. Francesconi,
Direct measurement of lipid-soluble arsenic species in biological samples with HPLC-ICPMS, Analyst (London), 130/6 (2005) 948-955.
DOI: 10.1039/b502445e Valery M. Dembitsky, Dmitrii O. Levitsky,
Arsenolipids, Prog. Lipid Res., 43/5 (2004) 403-448.
DOI: 10.1016/j.plipres.2004.07.001
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contamination of soils and groundwater with toxic arsenic species last time modified: June 26, 2020
