Arsenocholine- and dimethylated arsenic- containing lipids in starspotted shark Mustelus manazo

We have investigated lipid-soluble arsenic compounds present in the tissues of a demersal shark, the starspotted shark Mustelus manazo. Arsenic compounds were extracted with chloroform–methanol from several tissues taken from each of five individuals, subjected to mild alkaline hydrolysis and fractionated into alkali-labile and alkali-stable fractions. Ordinary muscle, kidney and brain contained alkali-labile arsenic compounds; liver, stomach, heart and gall bladder contained alkali-stable compounds; and intestine, skin, dark muscle, spleen and bone contained both types of arsenic compounds. After further hydrolysis, the hydrolysates from ordinary muscle and liver were chromatographed with HPLC–ICP–MS. Arsenocholine was detected in the hydrolysates from the muscle, suggesting that arsenolecithins were present in the tissues. However, dimethyl-­arsinic acid was detected in the hydrolysates from the liver, suggesting the presence of di-­methylated arsenolipid in it.