Studies on Lipids of Barracuda, Sphyraena pinguis

(1) The characteristics of the lipids (acetone-soluble lipid, lecithin, cephalin and sphingolipid) obtained from barracuda, Sphyraena pinguis GUNTHER, were studied from the view point of fat metabolism of fish. (2) Forty-one fresh sample fish caught in the Komekami fishing ground near Odawara City (west part of Kanagawa Prefecture, Japan) on the 4th of October, 1959, were extracted with acetone. The acetone extract was further treated with acetone to yield the fatty oil as acetone-soluble lipid. The above mentioned fish, previously treated with acetone, were successively extracted with ethanol, petroleum ether and finally with boiling ethanol to yield lecithin fraction, cephalin fraction and sphingolipid fraction as shown in Fig. -1. (3) The acetone-soluble lipid was obtained in the yield of 0.50% from the fresh fish. This lipid had the characteristics as given in Table-3. The unsaponifiable material contained 21.38% of sterols. The conjugated fatty acids, prepared from the acetone-soluble lipid by alkali-hydrolysis, were separated into three portions, solid, slightly unsaturated and highly unsaturated acids, with a combination of lead salt-ethanol and lithium salt-acetone fractionations. Individual acids were identified with paper chromatography, saturated acids and hydrogenated polyenoic acids as their 2, 4-dinitrophenylhydrazones, and mono-and dienoic acids as their mercuric acetate complexes. The paper chromatography indicated the presence of myristic, palmitic, stearic, arachidic, behenic, zoomaric, oleic, eicosenoic, erucic and linoiic acids in the acetone-soluble lipid. The composition of the conjugated fatty acids of the acetone-soluble lipid was found to be as shown in Table-9. According to brief calculation, the acetone-souble lipid from barracuda contains 22.9% saturated acids, 55.2% mono-and dienoic acids and 21.9% polyenoic acids (trienoic 6.0%, tetraenoic 7.8%, pentaenoic 5.7% and hexaenoic acid 2.4%). (4) Lecithin purified from the lecithin fraction mentioned above was obtained in the yield of 0.14% from the fresh barracuda. The characteristics of the purified lecithin are shown in Table-10. The conjugated fatty acids, prepared from the lecithin by alkali-hydrolysis, were separated into solid and liquid fatty acids by the lead salt-ethanol method modified by HILDITCH. Spectrophotometry of the alkali-isomerized liquid fatty acids indicated the presence of conjugated tri-to pentaenoic acids in the lecithin. According to simple calculation, the composition of the conjugated fatty acids of the lecithin from the sample fish seems to consist of 34.2% saturated acids and 65.8% unsaturated acids. (5) Cephalin purified from the above mentioned cephalin fraction with petroleum ether was obtained in the yield of 0.60% from the fresh sample fish. Fractional precipitation of the purified cephalin from chloroform with absolute ethanol yielded five groups and showed the presence of phosphatidyl serine, phosphatidyl ethanolamine and inositol-containing lipid in the cephalin from the sample fish. The characteristics of the fractionated cephalins are summarized in Table-11. The conjugated fatty acids, prepared from the cephalin by alkali-hydrolysis, were separated into two portions (solid and liquid acids) by the lead salt-ethanol fractionation. Spectrophotometry of the alkali-isomerized liquid fatty acids showed no presence of polyenoic acids. According to rough calculation, the conjugated fatty acids of the cephalin from the sample fish consist of 40.4 % saturated acids and 59.6% of unsaturated acids. It shows that the component fatty acids of the lecithin are more unsaturated than those from cephalin.