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Arsenolipids in fish oil found by arsenic speciation analysis

(08.08.2008)


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 specxiation 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/b808049f


Related 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


Related News

EVISA News, July 18, 2008: Experts detail how rice absorbs arsenic from the soil
EVISA News, March 15, 2008: Arsenic in rice milk exceeds EU and US drinking water standards
EVISA News, February 15, 2008: Arsenic speciation in rice: a question of the rice plant species
EVISA News, January 31, 2008: New arsenic species detected in carrot samples
EVISA News, March 7, 2007: Elevated Arsenic Levels Found In Rice Grown In South Central States of the USA
EVISA News, September 7, 2006: Toxic inorganic arsenic species found in Japanese seaweed food
EVISA News, October 6, 2005: Two new Thio-Arsenosugars found in Scallops
EVISA News, August 3, 2005: Surprisingly high concentrations of toxic arsenic species found in U.S. rice
 EVISA News, May 15, 2005: Use of organoarsenicals as pesticides may lead to contamination of soils and groundwater with toxic arsenic species

last time modified: March 25, 2009



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