References: Lecithin
J Pharm Sci. 2003 Nov;92(11):2217-28.
Partitioning of halofantrine hydrochloride between water, micellar solutions, and soybean oil: Effects on its apparent ionization constant.
Taillardat-Bertschinger A, Perry CS, Galland A, Prankerd RJ, Charman WN.
Centre for Drug Candidate Optimisation, Victorian College of Pharmacy, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia.
Recent studies in a conscious dog model demonstrated intestinal lymphatic transport to be a significant contributor to the bioavailability of the highly lipid-soluble free-base of halofantrine (Hf), and surprisingly, also the poorly lipid-soluble hydrochloride salt (Hf. HCl). Partial conversion of solubilized Hf. HCl to Hf base within the intestinal lumen prior to the lymphatic uptake seemed to be the most likely explanation for these results. This hypothesis was supported by studies exploring the partitioning behavior of Hf. HCl between soybean oil (SBO) and aqueous micellar solutions containing different ionic and nonionic surfactants. Mixed micelles prepared from sodium taurodeoxycholate (NaTC) and lecithin (PC) were chosen to represent fed-state intestinal fluids. The apparent ionization constants derived from the partitioning versus pH profiles showed marked shifts when compared with the likely aqueous pK(a) value. In the present paper, the apparent pK(a) values of Hf in aqueous micellar phases, without a coexisting oil phase, were investigated to further probe the mechanisms underlying the effect of micellar media on the apparent ionization equilibrium, and subsequently, on its partitioning behavior in the triphasic systems. Another aim of this study was to further evaluate the aqueous pK(a) value of Hf. The results indicate that the aqueous pK(a) of Hf is most probably in the range approximately 8-9, and that the ionization equilibrium is highly dependent on the solution environment. For example, marked pK(a) shifts of several units were observed for Hf in the presence of di
J Cosmet Sci. 2003 Sep-Oct;54(5):451-62.
O/W microemulsion as a vehicle for sunscreens.
Carlotti ME, Gallarate M, Rossatto V.
Dipartimento di Scienza e Tecnologia del Farmaco, Universita degli Studi di Torino, via Giuria 9, 10125 Turin, Italy.
In recent years, transparent dispersions or diluted milks have been used as sunscreens. These products contain water-soluble sunscreen agents, and quite frequently are washed away from the skin. However, O/W microemulsions are now being prepared as transparent vehicles for sunscreens. They are waterproof, nonsticky, and easily spreadable. The microemulsions are prepared by using pseudoternary diagrams, by combining lipids with surfactant blends and a polar phase. Soya lecithin and decylpolyglucose produce transparent systems with the lowest percentage of surfactants. These microemulsions contain 4-methylbenzilidene camphor or octylmethoxycinnamate as sunscreen agents. Cyclomethicone, menthol, and allantoin give products a good skin feel, and stearyl methicone gives the waterproof effect. These systems show a Newtonian flux. Little permeation of the sunscreens' trough lipophilic and hydrophilic membrane is evidenced.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14605687&dopt=Abstract lecithin
Biosci Biotechnol Biochem. 1993 Sep;57(9):1445-9.
Encapsulation of chicken egg yolk immunoglobulin G (IgY) by liposomes.
Shimizu M, Miwa Y, Hashimoto K, Goto A.
School of Food and Nutritional Sciences, University of Shizuoka, Japan.
Encapsulation of antibodies isolated from chicken egg yolk (IgY) in egg lecithin/cholesterol liposomes was attempted. IgY was successfully encapsulated into the liposomes by using the dehydration-rehydration method. Electron microscopic observation demonstrated that the liposomes prepared by this method were large multilamellar vesicles with a diameter of several microns. The encapsulation efficiency was improved by increasing the rehydration temperature to 60 degrees C. The cholesterol/lecithin ratio also affected the efficiency, giving the highest value at a ratio of 1/4 (mol/mol). Some efflux of glucose through the liposomal membranes was observed, particularly for the liposome with a low cholesterol content, but that of IgY was not detected, irrespective of the cholesterol content. Encapsulation reduced the activity loss of the IgY antibodies under acidic conditions. IgY encapsulated in the liposomes was also markedly resistant to pepsin hydrolysis, which usually results in complete loss of activity with unencapsulated IgY, suggesting that liposomal encapsulation is an effective means for protecting IgY under gastric conditions.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7764217&dopt=Abstract lecithin
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