Subroto Ghosh Ph.D.* *Fishery & Aquaculture Unit, Department of Zoology, Rishi Bankim Chandra College, Naihati 743165 West Bengal, India Contact email: firstname.lastname@example.org
Article submitted on April 8, 2008
Article published on June 8, 2008
◊An article by Subroto Ghosh Ph.D, (8 June 2008):Stearic acid – the unique saturated fatty acid in Clarias batrachus, an Indian lean fish. Published on biologyonline.com.(Abstract)All natural fats that make up the lipid part of the human diet has all the three types of fatty acids, viz., saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids. Most saturated ones are straight-chains even-numbered having 14 to 20 carbon atoms (Christie, 1982). They have a general formula CH3 (CH2) n COOH. Stearic acid whose systematic name is octadecanoic acid has the formula CH3 (CH2)16COOH and is a long-chain fatty acid consisting of 18 carbon atoms without double bonds. The uniqueness of stearic acid is that it does not, perhaps, behave like other saturated fatty acids. According to Ackman (2000) only 14 fatty acids are “really needed to describe the fatty acids of fish” and studies done on the composition of lipids in fishes have shown that of these important major fatty acids stearic acid is one. Fish normally store fat in the liver and the flesh rather than in the adipose tissue (Gurr and Harwood, 1991). It is important to distinguish between lean and fatty fish exclusively for cardio-protection. A very common Indian catfish, Clarias batrachus belonging to family Claridae of the order Siluriformes (Chondar, 1999), is prescribed more often as a lean fish because of its very little or no adipose tissue content. Saturated fatty acids with chain lengths of 12-16 have the most cholesterol-raising properties (Renaud and Delorgel, 1989). Stearic acid consisting of 18 carbon atoms does not fall in this category. This behaviour of stearic acid in spite of being a saturated fatty acid has been explained from the fact that stearic acid (18:0) is desaturated to oleic acid (18:1n-9) soon after its absorption and so does not raise the total cholesterol level (Bonanome and Grundy,1988; Denke and Grundy, 1992). Monsa and Ney (1993) examined the modes whereby stearic acid exerts its neutral or cholesterol- lowering effect. The amount of oleic acid (18:1n-9) in this fish is much higher than that of stearic acid in the total lipid, neutral lipid and in triacylglycerol in the breeding and in the post-breeding seasons. In the phospholipid it is not so and here oleic acid remains less to stearic acid also in the pre-breeding season. This fact can be explained from the typical utilization of stearic acid for membrane synthesis in the liver. Here it did not convert to oleic acid to a significant amount and made the fish ready in the pre-breeding season for an efficient process of membrane synthesis. ReferencesAckman R.G., 2000. Fatty acids in fish and shellfish. Fatty Acids in Foods and Their Health Implications, (ed. C. K. Chow) 2nd ed. pp. 153-173. Marcel Dekker, Inc. New York, Basel. Bonanome A, Grundy SM. Effect of dietary stearic acid on plasma cholesterol and lipoprotein levels. N Engl J Med 1988; 318:1244–1248 Chondar S.L.,1999. Biology of Finfish and Shellfish, pp. 337-350, 422-433. SCSC Publishers (India) Howrah. Christie W.W.,1982. Lipid Analysis, 2nd ed. Pergamon Press. Denke MA, Grundy SM. Comparison of effects of lauric acid and palmitic acid on plasma lipids and lipoproteins. Am J Clin Nutr 1992; 56: 895–898. Gurr M.I. and Harwood J.L.,1991. Lipid Biochemistry : An Introduction, 4th ed. Chapman & Hall. Monsma CC, Ney DM. Interrelationship of stearic acid content and triacylglycerol composition of lard, beef tallow and cocoa butter in rats. Lipids 1993; 28(6): 539-547. Renaud S, Delorgel M. Dietary lipids and their relation to ischemic heart disease from epidemiology to prevention. J Int Med 1989; 225 (Suppl): 39–46.