Toxic Character of Rancid Oil. XVII.

Abstract

It is known that natural antioxidants are usually contained in vegetable oil and fats, and tocopherol (Toc) is the most abundant substance in those oils. Toc decomposes on heating, so it may be conceivable that the toxic effect of thermally oxidized oil (TO) is enhanced by the decrease of Toc. In the previous papers, the authors reported that Toc reduces the toxicity of TO in rats. The present paper deals with the influence of Toc on lipid component and triglyceride composition of rat tissues of rats fed fresh oil (FO) or TO. Toc-free FO was prepared by aluminium oxide column chromatography from fresh soybean oil and TO was prepared from the same oil by heating at 180°C for 50hr. Rats were fed on the diets containing FO and TO with or without Toc. The total lipids extracted from each tissue of rats were separated into neutral lipid (NL) and phospholipid fractions by column chromatography and triglyceride (TG) was isolated from (NL) fraction by thin-layer chromatography. Fatty acid distribution in TG was investigated by pancreatic lipase hydrolysis. The results indicated that total lipids and percentage of their phospholipids in liver, kidney and testicle of rats fed on Toc-free TO decreased markedly compared with those fed on FO or Toc-free FO. TG in tissues of rats fed on Toc-free TO decreased, but cholesterol increased. Significant difference on component fatty acids and 2-position of TG was observed. TG in each tissue (except kidney-TG after 30 days feeding) of rats fed on FO or Toc-free FO showed higher proportion of C18 : 2 than C18 : 1. On the contrary, C18 : 2 content in TG of rats fed on Toc-free TO was lower. The percentage of unsaturated fatty acids at the 2-position in each tissue TG was high compared to saturated fatty acids at the same position and/or component fatty acids in TG. Percentage of C18 : 1 and C18 : 2 at 2-position of TG was about 80 mole % in each tissue. C16 : 0, C18 : 0 and C18 : 1 at this position in TG of rats fed on Toc-free TO increased but C18 : 2 decreased to compare with those of FO or Toc-free FO groups. Toc was effective for prevention of toxicity induced by TO as described above, but no significant effect was not observed for FO. These results suggest that Toc has some biological antioxidative and protective activities aganist the toxicity induced by TO.