Synthetic lecithin

PE, PS, lecithin, synthetic phosphatides Ox brain cephalin, egg yolk Folch Recalcification time of human and chicken plasma PS active at low and inhibitory at high concentrations lecithin inactive maximal activity with combination of PS and PE PS and lecithin almost as active combinations of synthetic phosphatides active Hecht and Slotta (1962)... 

CjHiaNO, [Mc3NCH= CH2] OH. A liquid forming a crystalline trihydrate, It is present free and combined in brain and other animal and vegetable products and is formed as a product of putrefaction of lecithin. It can be prepared synthetically from choline and decomposes easily to trimethylamine. neutralization, heat of The amount of heat evolved when I g equivalent of an acid is neutralized by 1 g equivalent of a base. For strong acids and strong bases in dilute solution the only reaction which occurs is H -h OH ---> H2O and the heat of neutral-... 

Fig. XV-6. Pressure-area isotherms for a synthetic lecithin at the indicated temperatures in degrees Celsius. [From H. E. Ries, Jr., M. Matsumoto, N. Uyeda, and E. Suito, Adv. Chem. Ser, No. 144, ACS, 1975, p. 286 (Ref. 37). Copyright 1975, American Chemical Society.]...

Choline occurs widely in nature and, prepared synthetically, it is available as an article of commerce. Soybean lecithin and egg-yolk lecithin have been used as natural sources of choline for supplementing the diet. Other important natural-food sources include Hver and certain legumes (18—22). 

Emulsifiers. Natural lecithin is one of the most widely used emulsifiers because it is metabolized in the body. However, type I allergic reaction to soybean lecithin emulsified in lipid solutions has been observed [195], Among the synthetic emulsifying agents, block copolymers of polyoxyethylene-polyoxypropylene (poloxamer) have attracted increasing interest for parenteral emulsions. Other examples of emulsifiers commonly found in parenteral formulations are given in Table 9 [190]. 

Tocopherols are not as effective as antioxidants as the synthetic antioxidants, e.g. BHA or BHT. The antioxidant effect of tocopherols is increased by mixing them with ascorbyl palmitate, ascorbic acid, lecithin or citric acid. Typical confectionery applications are the use of tocopherols with ascorbyl palmitate or lecithin or citric acid in the fat phase of toffees or caramels. Chewing gum base can be treated with a- and y-tocopherol to extend the shelf life. 

Totally synthetic bilayers show liquid crystalline properties similar to those of lecithin bilayers (Nagamura et al., 1978 Kano et al., 1979). Bilayer formation has also been observed for dialkyl compounds with anionic head groups such as [2] and [3] (Kunitake and Okahata, 1978a Mortara et al., 1978), and with nonionic and zwitterionic head groups as in [4] and [5] (Okahata et al., 1978a). 

LEH is primarily composed of a combination of saturated high-carbon phospholipids and cholesterol. Synthetic phospholipids replaced hydrogenated soy lecithin when the latter was found to induce several untoward biological responses (40). Current choice of a saturated high-carbon phospholipid is mostly between distearoyl phosphatidylcholine (DSPC, 55°C) and... 

Ipratropium Atrovent HFA, Atrovent Nasal) [Bronchodilotor/ Anticholinergic] Uses Bronchospasm w/ COPD, rhinitis, rhinorrhea Action Synthetic anticholinergic similar to atropine antagonizes acetylcholine receptors, inhibits mucous gland secretions Dose Adults Feds >12 y. Nebuliza-tion 500 meg in 2.5-3.0 mL NS Feds. Nebulization 125-250 meg in 2.5-3.0 mL NS Caution [B, +/-] w/ inhal insulin Contra Allergy to soya lecithin/related foods Disp HFAmet-dose inhal 18 meg/dose inhal soln 0.02% nasal spray 0.03,... 

The appearance of tubular myelin-like structures in swollen lecithin was observed by light microscopy well before the systematic investigation of liposomes [351-352]. Similarly, it was also demonstrated some time ago that the addition of calcium ions converted phospholipid liposomes to cochleate cylinders [353]. Subsequent studies have, however, revealed that the system is extremely complex. For example, examination of the phase-transition behavior of synthetic sodium di-n-dodecyl phosphate [(C12H2sO)2PO2Na+ or NaDDP] and calcium di-n-dodecyl phosphate [Ca(DDP)2] showed the presence of many diverse structures [354]. In particular, hydrated NaDDP crystals were shown to form lyotropic liquid-crystalline phases which transformed, upon heating to 50 °C, to myelin-like tubes. Structures of the tubes formed were found... 

PE), usually present in the ratio of approximately 3 1 and making up about 90% of the total weight of the lecithin phospholipids (Table 9.1). It is known that the two main phospholipids account for most of the stabilization and emulsification activity of the lecithin, but it is thought that minor components such as sphingomyelin and phosphatidic acid also play some as yet undefined role in the process. It might be emphasized here that the natural mixture of components is more effective at stabilizing emulsions than any of the major components in either purified or synthetic form, alone or in artificial admixtures. 

Materials. The water used for all purposes was double-distilled (once with glassware) and deionized (final conductance was less than 1 X 10"6 ohm1 cm."1). Stearic acid (obtained from Sigma Chemical Co.) was at least 99% pure as determined by silica gel thin-layer chromatography (4), and the synthetic L-a(/ ,y-dipalmitoyl) lecithin was about 90% pure (see Ref. 13 for analysis). The ATP-14C and its derivatives were obtained from Nuclear-Chicago or New England Nuclear Corp. and were found to be 95-98% pure as determined by cellulose thin-layer chromatography (16). 

Figure 5. P-A curves for synthetic lecithin monolayer and AV-A curve for beef brain lipid at pH 7.8. (O), [Ca2+] =...

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The phase behavior of a synthetic lecithin, dipalmitoyllecithin, as analyzed by Chapman and co-workers (5), is diagrammed in Figure 3. The main features are the same as in the phase diagram of egg lecithin a mixture of numerous homologs. As a consequence of the variation in fatty acid chain length, the chain melting point is lowered which means that the critical temperature for formation of liquid crystalline phases is reduced. This temperature is about 42 °C for dipalmitoyllecithin, and, if the lamellar liquid crystal is cooled below this temperature, a so-called gel phase is formed. The hydrocarbon chains in the lipid bilayers of this phase are extended, and they can be regarded as crystalline. The gel phase and the transitions between ordered and disordered chains are considered separately. 

Sigma Chemical Co., St. Louis, MO. Dimyristoyl and distearoyl lecithins (DML and DSL) and synthetic dipalmitoyl phosphatidic acid (DPPA) were products of Applied Science, State College, Pa. 

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