Studies of lipid peroxidation in microsomes isolated from beef and pork muscles: and, Bioluminescent bacterial mutagenesis test for fatty acid derivatives, heated oils, mycotoxins and heterocyclic amines

The presence of an enzymatic lipid peroxidation system in microsomal fractions of beef or pork muscle has been demonstrated in this study. The enzymatic reaction required ADP, NADPH or NADH, and ferrous or ferric iron. When intact muscles or isolated microsomes were stored at -70°C for up to a month, the enzyme activity of the microsomes did not change. Metmyoglobin (MetMb) in the presence of hydrogen peroxide initiated microsomal lipid peroxidation, whereas no oxidation occurred in the presence of MetMb or hydrogen peroxide alone. With 10[mu]M to 50 [mu]M ferrous iron alone, there was significant stimulation of microsomal lipid peroxidation. From 100 [mu]M to 250 [mu]M, the ferrous iron alone caused no lipid peroxidation. The addition of hydrogen peroxide may have different effects on microsomal lipid peroxidation depending on the concentration of ferrous iron. Antioxidants such as BHT, EDTA, [alpha]-tocopherol and ascorbic acid in either enzymatic or non-enzymatic systems inhibited microsomal lipid peroxidation;The Mutatox°ler test has been shown to be a good alternative to the Ames test. The test provides a rapid, screening test which can be used to assay the mutagenicity of a large numbers of pure and complex compounds. Five different column fractions isolated from either autoxidized methyl linoleate or autoxidized methyl linolenate were not mutagenic with or without the activation by the S-9 (microsomal) fraction. Chlorinated fatty acids including chloroethyl caprate, laurate, palmitate and linoleate were mutagenic in the presence of S-9 activation. When heated at 180°C, after 32 hours soybean oil exhibited mutagenic activity with or without the S-9 activation. The addition of 1% cholesterol into the soybean oil increased the onset of the mutagenicity. This study indicated that aflatoxin B[subscript]1 (AFB[subscript]1), methyl-imidazo-quinoline (MeIQ), tryptophan pyrolysates (Trp-P-1 and Trp-P-2) were mutagenic in the presence of S-9 activation, while AFB[subscript]1 epoxide and fumonisin B[subscript]1 showed direct mutagenic activity and AFB[subscript]2 and ochratoxin A were not mutagenic