Lecithin specifications

Minimally Acetylated, Commercial, Liquid Lecithin Specification... 

The identity of the moiety (other than glycerol) esterified to the phosphoric group determines the specific phosphoHpid compound. The three most common phosphoHpids in commercial oils are phosphatidylcholine or lecithin [8002-45-5] (3a), phosphatidylethanolamine or cephalin [4537-76-2] (3b), and phosphatidjlinositol [28154-49-7] (3c). These materials are important constituents of plant and animal membranes. The phosphoHpid content of oils varies widely. Laurie oils, such as coconut and palm kernel, contain a few hundredths of a percent. Most oils contain 0.1 to 0.5%. Com and cottonseed oils contain almost 1% whereas soybean oil can vary from 1 to 3% phosphoHpid. Some phosphoHpids, such as dipaLmitoylphosphatidylcholine (R = R = palmitic R" = choline), form bilayer stmetures known as vesicles or Hposomes. The bdayer stmeture can microencapsulate solutes and transport them through systems where they would normally be degraded. This property allows their use in dmg deHvery systems (qv) (8). 

The US. Pharmacopeia (USP XXII) or National Formula (NFXVII) (20) also provide a similar description however, the peroxide value is not defined (Table 9). These specifications are also given in the Handbook of Pharmaceutical Excipients (HPE), pubhshed jointiy by the American Pharmaceutical Association and The Pharmaceutical Society of Great Britain (21), which defines lecithins both from plants and eggs. The Merck Index (22) specifies a slightiy lower acid value. The Japanese Monograph (ISCI-II) (23) specifies a slightiy lower acetone-insoluble matter and a lower heavy-metal content. 

Liposomes. Lecithin, and mote specifically purified phosphohpids, ate used to produce liposomes (39) for the food (40), cosmetics, pharmaceutical, agrochemical, and technical fields. 

Figure 3. Tissue distribution of lecithinized i25I-IgG (specific activity 0.01 xC / Xg) in C3H mice (4 hours after 200 p L/mouse iv injection) ( p<0.01 p<0.001 in relation to IgG only and IgG-lecithin mixture).

Y Kawano, T Noma. Inhibition by lecithin-bound iodine (LBI) of inducible allergen-specific T lymphocytes responses in allergic diseases. Int J Immunopharmacol 18(4) 241-249, 1996. 

F2. Fielding, C. J., and Fielding, P. E., Purification and substrate specificity of lecithin-cholesterol acyltransferase from hiunan plasma. FEBS (Fed. Eur. Biochem. Soc.), Lett. 15, 355-358 (1971). 

In the bile cholesterol is kept soluble by fats, phospholipids like lecithin and by bile acids. The important bile acids in human bile are cholic acid, chen-odeoxycholic acid or chenodiol and ursodeoxycholic acid or ursodiol. Bile acids increase bile production. Dehydrocholic acid, a semisynthetic cholate is especially active in this respect. It stimulates the production of bile of low specific gravity and is therefore called a hydrocholeretic drug. Chenodiol and ursodiol but not cholic acid decrease the cholesterol content of bile by reducing cholesterol production and cholesterol secretion. Ursodiol also decreases cholesterol reabsorption. By these actions chenodiol and ursodiol are able to decrease the formation of cholesterolic gallstones and they can promote their dissolution. 

Lecithin used by the USA armed forces is covered by a military specification (Ref 3) contg the following requirements (1) moisture, 1.0% max, (2) benz insol matter, 0.1% max,... 

Kobori K, Saito K, Ito S, Kotani K, Manabe M, Kanno T (2002) A new enzyme-linked immunosorbent assay with two monoclonal antibodies to specific epitopes measures human lecithin-cholesterol acyltransferase. J Lipid Res 43 325-334... 

The experimental methods have been described (1). Films are drawn by passing a hole in a Teflon screen through the oil-water interphase. The oil is a 0.5% solution of purified egg lecithin in a 3 1 vol./vol. heptane-chloroform mixture. By varying the heptane-chloroform ratio the specific density may be varied and thereby the drainage time of the film. The temperature is 23 °C. throughout. 

Although glycosphingolipids are the specific lipid components in the antigen-antibody complex, their activity is markedly enhanced by other (auxiliary) lipids such as lecithin and lecithin-cholesterol mixtures (15). The present study deals with the effect of lipid composition on the penetration of lactoside—cholesterol and lactoside—lecithin monolayers by rabbit y-globulin. We also investigated the lecithin-cholesterol system. Furthemore, since criteria for the existence of lipid-lipid complexes in monolayers are still few (8, 17), we have used infrared spectroscopy to examine lipid mixtures for the presence of complexes. 

The role of lecithin as an auxiliary lipid in the specific interaction of lactosides with globulin in monolayers is related to two processes complex formation between 3 or 4 molecules of lactoside and each lecithin molecule, and the protection of the lactoside molecules in surface micelles from nonspecific interaction. The location of lecithin at the periphery of the surface micelle would explain why the mixed micelle behaves as lecithin in nonspecific interaction. Lactoside molecules, located in the center of the surface micelle, would be in a position to interact specifically with antibody in the aqueous subphase (5). 

Recently Bourges, Small, and Dervichian (5) reported that a para-crystalline lamellar structure of egg lecithin can solubilize cholesterol up to a maximum of one molecule of cholesterol per molecule of lecithin. However, they conclude that this should not be considered as a molecular association but rather the consequence of the relative arrangement of the molecules in the lamellar structure which is a mutual (solid) solution of lecithin and cholesterol. They also reported that the state of compression in the lamellar structure corresponds to that of a highly compressed mixed monolayer of lecithin-cholesterol. The NMR results of Chapman and Penkett (8) also appear to indicate that solubilization of cholesterol in egg lecithin dispersions results in a highly packed structure in which fatty acyl chains possess little molecular motion. Our results from lecithin-cholesterol monolayers also suggest that these mixed mono-layers are two-dimensional solutions with no specific interaction and that the apparent condensation in some instances is caused by the steric factors of the fatty acyl chains and not by the interaction or association between lecithin and cholesterol. 

The phosphoric acid esters of diacyl glycerides, phospholipids, are important constituents of cellular membranes. Lecithins (phosphatidyl cholines) from egg white or soybeans are often added to foods as emulsifying agents or to modify flow characteristics and viscosity. Phospholipids have very low vapor pressures and decompose at elevated temperatures. The strategy for analysis involves preliminary isolation of the class, for example by TLC, followed by enzymatic hydrolysis, derivatization of the hydrolysis products, and then GC of the volatile derivatives. A number of phospholipases are known which are highly specific for particular positions on phospholipids. Phospholipase A2, usually isolated from snake venom, selectively hydrolyzes the 2-acyl ester linkage. The positions of attack for phospholipases A, C, and D are summarized on Figure 9.7 (24). Appropriate use of phospholipases followed by GC can thus be used to determine the composition of phospholipids. 

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