Abstract
Prooxidant activities of fish skin were assayed for 31 marine and fresh water species. Prooxidant activity was measured by increase in absorption at 234 nm due to the conjugated diene produced during incubation with linoleic acid or eicosapentaenoic acid. Prooxidant activity for linoleic acid was present in all of the fish skin extracts tested, and ranged from 1.24 units/mg extractable protein in the John dory Zeus japonicus to 9.16 units/ mg extractable protein in the yellow tail Seliora quinqueradiata. The activities of extracts from fishes of the Order Clupeiformes tended to be high and labile to heating. Since specific lipoxygenase inhibitors, oleic acid and eicosatetraynoic acid, as well as hemoprotein inhibitors, potassium cyanide and o-phenanthroline, inhibited the prooxidant activity of some skin extracts, it is likely that the hemoprotein and lipoxygenase-like enzyme may contribute to the prooxidant activity in fish skins. Catechin mixtures prepared from tea also effectively prevented the prooxidant activity in fish skin extracts as well as catechin and epigallocatechin. The use of catechins is advantageous from a viewpoint of preventing both enzymatic and non-enzymatic lipid peroxidation in fish skins.
