Occurrence of low-molecular-weight and high-molecular-weight selenium compounds in fish

Abstract

Muscle from four species of fish, plaice ( Pleuronectes platessa), mackerel ( Scomber scombrus), cod ( Gadus morhua), and herring ( Clupea harengus), was analyzed for selenium in intact tissue and soluble and insoluble fractions obtained by centrifugation at 850 × g and 100 000 × g. In cod and herring muscle, 74–81% of the selenium was found in the 850g pellet, and the rest was mainly in the 100 000 × g supernatant (14–24%). For plaice and mackerel, larger proportions were found in the latter fraction (29–60%). Gel chromatography of the soluble fraction was performed to study the occurrence of low- and high-molecular-weight forms of selenium. The 100 000g supernatant from plaice and mackerel contained a high proportion of low-molecular-weight selenium compounds but the pattern of different peaks was not the same in the two species. The 100 000g supernatant from cod contained mainly high-molecular-weight selenium compounds. Storage of cod or herring in the cold for one week did not significantly affect the proportion of low-molecular-weight selenocompounds. The results indicated that the distribution of low- and high-molecular-weight selenocompounds varied in different species of fresh fish and of fish obtained frozen.