STUDIES ON LIPID OXIDATION IN FISH PHOSPHOLIPID LIPOSOMES

Fish phospholipid liposomes were prepared and used as an artificial me mbrane system to study factors influencing lipid oxidation. The extent of lipid oxidation was indexed by measuring the amount of thiobarbitu ric acid reactive substances (TBARS) produced. Fe2+, Fe3+, and Cu2+ we re potent prooxidants in catalysing lipid oxidation. These metal ions induced lipid oxidation in a dose dependent manner. However, Zn2+, Ni2 +, and Mn2+ did not significantly (p > 0.05) affect lipid oxidation at all the concentrations (1, 10, or 100 mu M) studied. Morin, luteolin (flavonoids), butein (chalcone), tannic acid, ellagic acid (polyphenol s), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) (synthetic antioxidants) were potent antioxidants (producing < 50% TB ARS compared to control) of Fe2+-catalyzed lipid oxidation. Morin, lut eolin, and butein possess two hydroxyl substituents, a C-4 ketone stru cture and a 2-3 double bond, all of which contributed to their antioxi dative potential. Fe2+ caused some losses of polyunsaturated fatty aci ds (PUFA), whereas tannic acid protected the oxidation of several of t he PUFA including C 16:1 (Palmitoleic acid), C 18:3 (Linolenic acid), C 20:4 (Arachidonic acid), C 20:5 (Eicosapentaenoic acid), and C 22:6 (Docosahexaenoic acid).