Lecithin

LECITHIN (from Greek lekithos - yolk), in the ordinary sense, a mixture of lecithins and cephalins, substances classified as lipids (see), specifically as phosphatides (see). Lecithins are compounds that break down during hydrolysis to form higher fatty acids [mainly palmitic, stearic, oleic, and arachidonic (C₂₀H₃₂O₂)], glycerophosphoric acid, and choline. The possible structure of lecithins can be expressed by the formula: CH₂-O-CO.R* CH-O-CO.Ra CH₂-O-P-O-CH₂-CH₂-N⁺(CH₃)₃, where the alkaline hydroxyl of choline and the hydroxyl of phosphoric acid form an inner salt, splitting off water. The synthesis of lecithins has also been accomplished. Lecithins have also been obtained in crystalline form (they crystallize with difficulty). They are soluble in chloroform, ether, alcohol, gasoline, carbon disulfide. Unlike fats, they are insoluble in acetone and can be isolated from solutions in chloroform or alcohol or ether upon addition of acetone. They form an emulsion with water. They possess amphoteric properties: they form salts with both acids and bases; they form double salts with chloroplatinic acid, with CdCl₂. They are easily decomposed by alkalis. They rotate the plane of polarized light to the right. Cephalins are compounds constructed on the type of lecithins but containing instead of the choline residue a group of aminoethyl alcohol (colamine - NH₂.CH₂.CH₂.OH). Cephalins are similar in properties to lecithins; their mixtures with lecithins are difficult to separate; for separation, differences in solubility in alcohol and other solvents and the solubility of the cadmium salt of cephalins in ether (unlike lecithins) are used. The mixture of lecithins and cephalins - lecithin-containing - is present in all without exception studied animal and plant tissues and in almost all fluids of the animal organism; it is especially abundant in the brain, nerves, egg yolk, roe, semen, pus, and the electric organs of rays. In its pure form, L. is a white waxy mass that turns brown on exposure to air. L. gives with water under the microscope so-called myelin figures - twisted threads with club-shaped thickenings at the ends. Under the influence of intestinal juice, steapsin, takadiastase, L. is broken down. Under the influence of cobra venom, unsaturated fatty acids are split off from lecithins and cephalins, and so-called lysolecithins and lycephalins are formed. L. is also found in the organism in the form of compounds with proteins (see Lecithalbumins), with carbohydrates (?). L. forms the insulating sheath of the pulp nerves, has importance for the proper course of growth and nutrition of the organism, apparently has importance for the transport of Ca and P in the organism and for the construction of nucleoproteins and other complex phosphorus compounds. L. can apparently be synthesized in the organism with the participation of inorganic phosphorus (see also Metabolism, lipid; on the inclusion of lecithin in the composition of the boundary layer of protoplasm and on the importance of lecithin in the processes of osmosis between the cell and the environment - see Permeability). In addition to this, cephalins participate in the processes of blood clotting, apparently being one of the strongly acting thromboplastic substances. The anticoagulant effect of heparin (see) is eliminated by cephalin. The discovery and quantitative determination of L. is based on the determination of its P content: the ground organ is extracted with alcohol, the extract is evaporated at neutral reaction, the residue is extracted with a mixture of alcohol and ether; after evaporation of the solvent, the residue is extracted with ether (in addition to L., other phosphatides also pass into solution); the liquid is evaporated, the residue is dried and burned with a mixture of saltpeter and soda. When calculating, it is assumed that distearyl-L. gives 8.798% P₂O₅.

L. Brode. Experiments on animals have established (Danilevsky, Slovtsov, Muller and others) the important role of L. in the processes of nutrition and growth. Thus, young animals (rats, rabbits, dogs, guinea pigs, tadpoles) that received L. showed more rapid growth, more rapid development of the skeletal system, better utilization of proteins, better blood formation, greater liveliness and cheerfulness compared with control animals. The development of plants was also accelerated. However, other researchers (e.g. Yoshimoto) did not obtain clear results from the use of L. With a deficiency of L. in food, the processes of blood regeneration after bloodletting occur more slowly. In pernicious anemias, there is a sharp decrease in cholesterol and L. in the blood; with improvement in the pathological condition, their quantity always increases. Starting from the 3rd month of pregnancy, an increase in lipoids, particularly L. in the mother's blood, can be demonstrated. By introducing lecithin emulsion into the blood, it is possible to weaken the depth of chloroform anesthesia and maintain cardiac activity. When the blood plasma is depleted of lecithin, the process of blood clotting slows down and vice versa (Meyer, Gottlieb). By subcutaneous administration of L., it was possible to reduce the rate of growth of cancer tumors in rats (Sollmann). Literary data on the effect of L. on the heart and circulation are very contradictory. When lecithin emulsion is introduced into the blood, an increase in blood pressure is noted. The work of the isolated heart (Danilevsky, Clark) improves under the influence of small amounts of L. (concentration 1:50,000 - 1:10,000); larger amounts lead to weakening of heart function. There are indications (Sollmann) that L. weakens the effect on the heart of certain parasympathetic poisons, such as pilocarpine, choline, etc. On the other hand, Dresel, Sternheimer attribute to L. the role of a substance acting vagotropically - similarly to potassium salts, choline. - On the basis of all the above, L. must be assigned a significant role in the processes of growth, development and metabolism; apparently this role is especially great for the functions of the nervous system, blood formation and bone tissue. However, the therapeutic value of L. continues to remain not entirely clear, since the usual mixed food contains a sufficient amount (about 5 g) of L., and the same amount is contained in 2 egg yolks (Sollmann), while the daily dose of L. taken for treatment usually does not exceed 0.5 g. Consequently, with a deficiency of L. in ordinary food, its addition can undoubtedly be therapeutically very useful and experimentally justified. The therapeutic value of relatively small amounts of L., added to that already present in sufficient quantity in ordinary food, is still not entirely clear, all the more so since the possibility of the formation of organic phosphorus of the L. type in the body from inorganic phosphates, as well as the breakdown of L. in the digestive tract into its individual components, must be considered an experimentally proven fact. Main therapeutic indications: general weakness (physical and mental), scrofula, rickets, developmental retardation, functional disorders, as well as organic diseases of the nervous system. Preparations. 1. Lecithinum, Lecithinum ex ovo, Ovo lecithinum, lecithin; orally - 0.05-0.1 several times a day - up to 0.5 pro die; under the skin - 1-3 cm³ of 5% oil solution.--2. Hydrolecithinum, Hydrocithinum, L., in which, due to the action (catalytic) of hydrogen, unsaturated fatty acids are converted to saturated; doses - as for the previous preparation.-3. Bromlecithinum (Akt.-Gesellsch., Berlin), bromlecithin; similarly to the previous preparation, obtained by adding bromine to the unsaturated fatty acids of L.; a waxy, almost colorless mass; contains up to 20% bromine; in pills of 0.1-0.2 and tablets. Recommended especially for functional weakness of the nervous system.-4. Iodolecithinum, iodolecithin; obtained from L. by adding hydrogen iodide to its unsaturated fatty acids; iodine content up to 20%; in tablets - with up to 0.06 iodine; recommended especially for scrofula, anemias, chronic lymphadenitis.-5. Bilival Ingelheim, sodium lecithocholate; in pills - 0.15 g; recommended for gallstones. Preparations of Merck, Clin and others (in tablets, granules, etc.). m. gramenitsky.