水産動物肝臓中の脂肪酸について-I

Abstract

Many studies on the fatty acids of the marine animal livers have been done usually by the distillation of fatty acid esters extracted from high oil content livers. However, little effort has been made for quantitative determination of unsaturated fatty acids in low oil content livers. Kinds of animals used for the present study include bluefin tuna, bigeyed tuna, Indian tuna, Skipjack, fur-seal and fin whale. Free fatty acid and oil were extracted from the livers which had been minced and stored at about -10°C for 1 ?? 2 months. By saponifying the liver oil, mixed fatty acid which had formed glycerid and esters with vitamin A, sterol and other unsaponifiable alcohols, were separated from other components. In order to differentiate two groups of fatty acids, the authors propose to call the former “free type of fatty acids” (FFA) and the latter “ester type of fatty acids” (EFA). On each of the two types of fatty acids, iodine value and neutralisation value were determined (Table 3). Each of them was treated with lead acetate in 95 % alcohol, and separated into solid acid (SA) and liquid acid (LA). After brominated, the latter was separated into four fractions: oleic, linoleic, linolenic and arachidonic acid fractions, by making use of difference of solubility for petrol ether, ether and chloroform (Tables 2 and 4). The results of our experiments were as follows 1. During a long storage, glycerid was destroyed by the lipase in the tissues, but esters of unsaponifiable matters seemed to be hardly attacked by the enzyme (Table 1 and Fig. 1). Then in low oil content livers such as under report, unsaponifiable contents in the extracted oils ran up to 30 ?? 50 % (Table 3). 2. In those fish livers, SA content has been found 22 ?? 27 % in EFA and 24.2 ?? 35.5 % in FFA. The sum of SA and oleic acid was 61 ?? 76 %. Between the two types of FA, percentage of each other unsturated FA was almost the same. Accordingly it may be concluded that a greater portion of FA which forms esters with such unsaponifiable matters as vitamin A and sterols must be composed of oleic acid and SA likewise in glycerid (Table 4). 3. In fin whale, SA was found 41.4 % in FFA and 15.1 % in EFA, whereas in a specimen of fur-seal (B) it was 20.2 %-16.5 % in each type of FA. But the constitution percentages of unsaturated FA of the marine mammals were similar to those of fishes, with the sum of SA and oleic acid being also 61 ?? 76 %. However, the fur-seal (A) had an embryo and exceptionally low content of highly unsaturated FA. Some kinds of vitamins in the liver of fur-seal (A) and (B) were determined (Table 5).