Soybean phosphatidylcholine

The presence of impurities like free fatty acids in egg or soybean phosphatidylcholine, or in the (semi)synthetic phosphatidylcholines (e.g., DMPC, DPPC, DSPC) can be detected by monitoring the electrophoretic behavior of liposome dispersions of these phospholipids in aqueous media with low ionic strength a negative charge will be found on these liposomes when free fatty acids are present in the bilayers. 

Fr kjaer et al., 1984 Grit et al., 1989). An example of the pH dependency on the hydrolysis rate of liposomes consisting of soybean phosphatidylcholine is presented in Fig. 6. Hydrolysis kinetics changed rather abruptly around the phase transition temperature. 

P Therond, M Couturier, JF Demelier, F Lemonnier. Simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides obtained by lipoxygenase treatment. Lipids 28 245-249, 1993. 

Additional naturally occurring lipids may be minor components of oral lipid-based formulations. Terpenes such as peppermint oil (>50% menthol) are fairly hydrophobic but can provide some solvent capacity. Steroids such as cholesterol, while important in topical and in parenteral liposomal products, are not important as oral pharmaceutical adjuvants. Phospholipids (e.g., egg or soybean phosphatidylcholine) an essential component of cell membranes, are considered polar lipids, and have surfactant properties. 

Von Corswant, C. et al. (1997) Microemulsions based on soybean phosphatidylcholine and triglycerides. Phase behavior and microstructurbangmuir, 13 5061-5070. 

N8. Niki, S., Saito, M., Yoshikawa, Y., Yamamoto, Y., and Kamiya, Y., Oxidation of lipids. XII. Inhibition of oxidation of soybean phosphatidylcholine and methyl linoleate in aqueous dispersions by uric acid. Bull. Chem. Soc. Jpn. 59, 471-477 (1986). 

Several phospholipid-based excipients are finding increased application as solubilizing agents, emulsifying agents, or as components of liposomal formulation. The phospholipids occur naturally and are biocompatible and biodegradable. Examples include egg phosphatidylcholine, soybean phosphatidylcholine, hydrogenated soybean phosphatidylcholine (HSPC),... 

A variety of chemical penetration enhancers with or without protease inhibitors or colloidal vehicles (liposomes) have been investigated for their potential to enhance the skin permeability of peptides and pro-teins, but these approaches have only been limited to animal models or in vitro or in vivo models of human skin and have not progressed to human clinical studies. A notable exception is the use of so-called Transferosomes , ultraflexible liposomes, containing a mixture of soybean phosphatidylcholine and sodium... 

The nucleus 31P is useful in determining the micellization processes of phosphorus-containing surfactants. For the lithium ethyl (n-octyl) phosphate in D20, a critical micelle concentration was determined by 3IP NMR spectra.54 Three CMCs were detected by the inflection points in the concentration-dependent slopes of the 3IP chemical shift of a soybean phosphatidylcholine in n-butanol. They are 7.5%, 35% and 63% w/w soybean phosphatidylcholine.-55... 

FIGURE 4.7 Effects of phospholipid/polymer ratio on the cumulative release of leuprolide from lipospheres. Lipospheres were prepared from L-PLA and EPC (1 6, pluses), hydrogenated soybean phosphatidylcholine (1 3, open circles), HSPC (1 6, filled circles), or HSPC (1 10, filled triangles), as described in Figure 4.6. Microspheres release data (filled squares) are presented for comparison. (Adapted from [35] with permission from Elsevier.)... 

Figure 33. Arrhenius plots describing the degradation of soybean phosphatidylcholine at three pH values. Phosphatidylcholine concentration 0.05M (Reproduced from Ref. 309 with permission.)...

Schuler, I. A. Milon Y. Nakatani G. Ourisson A.M. Albrecht P. Benveniste M.A. Hartmann. Differential effects of plant sterols on water permeability and on acyl chain ordering of soybean phosphatidylcholine bilayers. Proc. Natl Acad. Sci. USA, 1991, 88, 6926-6930. 

Recently, a very extensive and we11-de.signed study was described by Ogi.so et al. (54). They compared gel systems in which /-limonene or lauracapram was present as penetration enhancer and studied the transport of -histine with and without liposomes in these gels. The liposomes were prepared from either egg phosphatidylcholine or hydrogenated soybean phosphatidylcholine. In vivo stud-... 

Table 1.2. Mean droplet diameter and polydispersity index of o/w emulsions resulting from dilution by water of a microemulsion consisting of a medium-chain triglyceride, soybean phosphatidylcholine, and poly(ethylene gly-col)(660)-12-hydroxystearate, poly(ethylene glycol) 400 and ethanol (from ref. (174) Reprinted by permission of Wiley-Liss, Inc., a subsidiary of John Wiley Sons, Inc)...

A number of kinetic studies were carried out to elucidate the interaction between a-tocopherol and ascorbic acid in liposomes. By using either water-soluble or oil-soluble diazo radical initiators, the effect of radicals can be compared when they are produced either in the phospholipid bilayer or in the aqueous phase. Oxidation of a soybean phosphatidylcholine liposome in the presence of radicals produced in the water phase with a water-soluble radical initiator [2,2 -azobis(2-amidinopropane) dihydrochloride, (AAPH)], showed an induction period with both a-tocopherol (vitamin E) and ascorbic acid (vitamin C) (Figure 10.9). With a mixture of vitamin E and vitamin C, the length of the induction was close to the sum of the individual induction periods. This result indicates an additive effect in suppressing oxidation by both vitamin E and vitamin C. Vitamin C apparently traps radicals in the water phase. When oxidation was induced by radicals produced in the lipid phase with an oil-soluble radical initiator [2,2 -azobis(2,4-dimethylvaleronitrile), (AMVN)] incorporated into the membrane, ascorbic acid alone had no effect, while a-tocopherol had a greater effect because it is lipophilic. However, the mixture... 

Figure 10.9. Effect of vitamin E (E) and vitamin C (C) and their mixtures on the oxidation of a soybean phosphatidylcholine (PC) liposome in the presence of a water-soluble radical initiator (AAPH) and oil-soluble radical initiator (AMVN). From Niki et al. (1985).

Soybean phosphatidylcholine (Phospholipon 80, Nattermann Phosphohpid, Germany), PRO from grape Vitis vinifera L.) seeds [18] and propylenghcol (Sigma, USA) were used for hposome preparation. Osmium tetraoxide and absolute ethanol (Merck, Germany) were used for scanning electron microscopy (SEM) sample preparation. All other chemicals were of analytical grade. 

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