Issue Date: August 11, 2008
Arsenolipids In Fish Oil
ARSENIC, a hazardous heavy metal, associates with lipids in fish, researchers have found (Chem. Commun., DOI: 10.1039/b808049f). 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.
Arsenic is a lethal poison and thus a major environmental and health hazard. Most human exposure to the metal occurs through water, and the majority of research on arsenic toxicity has focused on this. Scientists had previously believed that any arsenic found in fish would be water-soluble; they were surprised to find it in lipids. This discovery of arsenic in fish oil adds to health concerns, especially because many dietitians encourage people to increase their fish consumption.
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 analyzing the purified fractions with mass spectrometry, they identified three different arsenic-containing compounds: two dimethylarsinoyl alkanes and a dimethylarsinoyl alkene. The study provides potentially important new information about the molecular form arsenic adopts in capelin and perhaps other fish.
Francesconi says that arsenolipids had never 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 (see page 39). The researchers hypothesize that the alkene results from a biosynthetic error during which arsenic is substituted for a carbon atom in DHA.
Jörg Feldmann, professor of chemistry at the University of Aberdeen, in Scotland, comments that the newly identified arsenic-containing compounds are "not only of academic interest. It might be that we actually consume a lot of arsenic in this form." The potential toxicity of arsenolipids depends on how people metabolize them, which Francesconi and coworkers hope to investigate in the near future.
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