Bone lipids and fatty acids of Peru fish

The neurocranium of the vieja, Pimelometopon darwini, and the cojinoba, Seriolella violacea, contained 29.5 and 26% lipid (as percent dry weight), mostly as triacylglycerol. The anchoveta, Engraulis ringens; sardina, Sardinops sagax sagax; doncella, Halichoeres dispilis; and mackerel, Scomber japonicus, contained less lipid in the neurocranium (3.3–18.4%). Polyunsaturated fatty acids, dominated by 20:5 and 22:6, were highest for S. violacea (10.6–56.1%) and P. darwini (12.2–28.9%). Lower levels of polyunsaturated fatty acids were found in E. ringens. The major monosaturated fatty acids in all Peruvian fish included 16:1n7, 18:1n9 + 11, and 18:n7, whereas the major saturated fatty acids were 14:0 and 16:0 with lesser amounts of 18:0.     

Extraction of lipids and lipophilic antioxidants from fish tissues: a comparison among different methods.

1. Lipids, phospholipids and lipid soluble antioxidants were extracted from Sparus auratus liver and white muscle by three different methods and the yields obtained were compared. 2. None of the three procedures can recover the above components with the same efficiency. 3. For comparison the methods were also applied to rat liver homogenates. 4. The choice of the extraction procedures depends on the tissue investigated and on specific research requirements.     

Composition, accumulation and utilization of yolk lipids in teleost fish

Lipid reserves in teleost eggs are stored in lipoprotein yolk and, in some species, a discrete oil globule. Lipoprotein yolk lipids are primarily polar lipids, especially phosphatidylcholine and phosphatidylethanolamine (PE), and are rich in (n–3) polyunsaturated fatty acids, especially 22:6(n–3) (docosahexaenoic acid, DHA). Oil consists of neutral lipids and is rich in monounsaturated fatty acids (MUFA). Egg lipids are derived from dietary fatty acid, fatty acid mobilized from reserves and possibly fatty acid synthesized de novo. There is selective incorporation of essential fatty acids, particularly DHA, into yolk lipids and discrimination against incorporation of 22:1(n–11). Lipid is delivered to the oocyte by vitellogenin, which is rich in polar lipids, and likely also by other lipoproteins, especially very low density lipoprotein, which is rich in triacylglycerol (TAG). All classes of lipid may be used as fuel during embryonic and larval development and MUFA are preferred fatty acids for catabolism by embryos. Catabolism of oil globules is frequently delayed until latter stages of development. In some species, DHA derived from hydrolysis of phospholipid may be conserved by transfer to the neutral lipid. Recent work has expanded knowledge of the role of DHA in membrane structure, especially in neural tissue, and molecular species analysis has indicated that PE containing sn-1 oleic acid is a prime contributor to membrane fluidity. The results of this type of study provide an explanation for the selection pressures that influence yolk lipid composition. Future work ought to expand knowledge of specific roles of individual fatty acids in embryos along with knowledge of the ecological physiology of ovarian recrudescence, environmental influences on vitellogenin and yolk lipid composition, and the control of yolk lipid accumulation and utilization.     

Study of lipid changes in freeze-dried fish during storage. I. The interaction of relative humidity and tissue lipids.

Several studies on lipid stability of freeze-dried fish pointed out the relationship between relative humidity (RH) and autoxidation of highly unsaturated fatty acids. The present study shows the changes of tissue lipids in two different fish, freeze-dried and stored under various RH conditions. Fillets of Scomber scomber L and Sardina pilchardus sardina were freeze-dried and stored for 1, 3, 6 and 9 months. periodically, the sample of both fish were analyzed to evaluate the autoxidation of lipids. The results show that the autoxidation of lipids is quicker during 1st-3rd month of storage, while in a high humidity environment the tissue lipids change slower. According to these results both time of storage and relative humidity must be controlled to maintain the nutritive value of freeze-dried fish.     

Effects of ammonia on hydrolysis of proteins and lipids from fish residues

This study investigated the influence of ammonia on the hydrolysis rates of proteins and lipids in fish residues under mesophilic anaerobic incubation at a neutral pH. The hydrolysis kinetics of the fish residues, which contained primarily proteins and lipids, were examined at initial ammonia concentrations of 0–16 g N l⁻¹. Carbon hydrolysis was suppressed more by ammonium in the acidogenesis phase than in the acidogenesis/methanogenesis period of a single-stage anaerobic digestion. Conversely, hydrolysis of compounds containing nitrogen was similarly suppressed by ammonia during acidogenesis and acidogenesis/methanogenesis phases of a single-stage anaerobic digestion. Parameter uncertainty analysis demonstrated that the proteins fraction in the fish residues was entirely biodegradable. Model fitting demonstrated that two fractions of lipid substrates exist, namely, easy and hard to biodegrade with hydrolysis rates that were affected differently by ammonia content.     

Metabolism of glycerol ether-containing lipids in dog fish (Squalus acanthias)

Dogfish (Squalus acanthias) received intrahepatic injections of either palmitic acid-1-(14)C or chimyl alcohol-1-(14)C. The lipids of the liver were then analyzed for incorporated radioactivity. The experiments with labeled palmitic acid demonstrated that fatty acids are reductively incorporated into the alkyl and alkenyl ether chains of glycerolipids. Significantly lower specific activities were found for the diacyl alk-1'-enyl ethers and diacyl glycerol ethers than for other glycerol ether-containing lipids. These compounds may therefore represent terminal points in ether-lipid metabolism. The studies with labeled chimyl alcohol indicate that dogfish liver contains enzymes that have a high capacity for oxidatively cleaving alkyl ether linkages. Furthermore, it is probable that alkyl ethers are converted directly to alkenyl ethers, possibly via a biodehydrogenation reaction.     

Lipase-catalyzed synthesis of phenolic lipids from fish liver oil and dihydrocaffeic acid

The enzymatic synthesis of phenolic lipids by lipase-catalyzed transesterification of dihydrocaffeic acid (DHCA) with fish liver oil was investigated in a selected organic solvent medium. These synthesized phenolic lipids have potential use as nutraceutical products. Using a molar ratio of 1:8 DHCA to fish liver oil in hexane:2-butanone mixtures of 75:25 and 85:15 (v/v), the lipase-catalyzed reaction resulted in maximum conversion of 55.8 and 65.4%, respectively. The maximum conversion of phenolic monoacylglycerols in hexane:2-butanone mixture of 75:25 and 85:15 (v/v) was 40.3 and 37.7%, respectively; using the same solvent mixtures, the conversions of the phenolic diacylglycerol were 15.8 and 36.8%, respectively. Hexane:2-butanone mixture of 75:25 (v/v) was, therefore, the best organic solvent mixture for the production of phenolic monoacylglycerols, while that of 85:15 (v/v) was best for the production of phenolic diacylglycerols. The phenolic lipids produced from the fish liver oil and DHCA demonstrated antioxidant property as indicated by its free radical scavenging capacity.