Arsenic containing fatty acids were reported for the first time in cod-liver oil (in Rumpler A., Angew. Chem. Int. Ed 2008, 47, 2665). These compounds may be considered as true arsenolipids in contrast with commonly called “arsenolipids” which are only lipid-soluble arsenicals. Total arsenic analyses on fish oils from various origins gave concentrations from 4.3 to 10.5 mg As per kg (Schmeisser E et al., The Analyst 2005, 130, 948). Six arsenic-containing fatty acids have been identified (Rumpler A et al., Angew Chem Int Ed 2008, 47, 2665). Among them, a homologous series of arsenic-containing saturated fatty acids of the type (CH3)2As(O)-(CH2)nCOOH (n = 12, 14, 16, and 18) with a dimethylarsinoyl group was determined. Two further unsaturated compounds are likely analogous to oleic acid (18:1 n-9) and 7,10,13,16,19-docosapentaenoic acid (22:5 n-3) commonly found in cod-liver oil. Two of these compounds are shown bellow.
The toxicological relevance of these arsenic-containing fatty acids in cod-liver oil remains to be evaluated.
A review of occurrence and chemistry of arsenolipids in marine oils and fats have been reviewed (Sele V et al., Food Chem 2012, 133, 618).
Very recently, the synthesis of four arsenic-containing fatty acids was reported. In that work, bis(dimethylarsenic) oxide was reacted with brominated compounds (Taleshi MS et al., Organometallics 2014,33,1397). The synthesis of two new arsenic-containing fatty acids and their identification infish by liquid chromatography coupled simultaneously to mass spectrometry has been reported (Arroyo-Abad U et al., Eur J Lipid Sci Technol 2016, 118, 445).