Lecithin ternary systems

An experimental complication is the difficulty in effecting molecular interaction between the components. The usual technique for preparing lipid-protein phases in an aqueous environment is to use components of opposite charge. This in turn means that the lipid should be added to the protein in order to obtain a homogeneous complex since a complex separates when a certain critical hydrophobicity is reached. If the precipitate is prepared in the opposite way, the composition of the complex can vary since initially the protein molecule can take up as many lipid molecules as its net charge, and this number can decrease successively with reduction in available lipid molecules. It is thus not possible to prepare lipid— protein—water mixtures, as in the case of other ternary systems, and to wait for equilibrium. Systems were prepared that consisted of lecithin-cardiolipin (L/CL) mixtures with (a) a hydrophobic protein, insulin, and with (b) a protein with high water solubility, bovine serum albumin (BSA). 

Ternary systems consisting of lecithin/water/tri-glyceride oil described by Rydhag and Wilton (1981) are dominated by a three-phase region where water, oil and the lamellar L -phase exist in equilibrium. 

For mixtures of lecithin plus Na cholate it appears possible to infer the molecular arrangement in the dispersed micelles from the most likely structure of the liquid crystalline phase suggested by x-ray analysis. However, there are cases where dispersion is not possible because neither component is sufficiently hydrophilic to be dispersed even when alone in water. This is shown by the association of cholesterol and lecithin in the presence of water. The ternary diagram of Figure 4 is relative to these systems. Here only the lamellar liquid crystalline phase is obtained (region 1< in Figure 4). This phase is already given by lecithin alone, which can absorb up to 55% water. Cholesterol can be incorporated within this lamellar phase up to the proportion of one molecule of choles-... 

Figure 4. Ternary phase diagram for system lecithin (L), cholesterol (Choi), and water (W)...

Aboofazeli, R., Lawrence, C. B., Wicks, S. R., and Lawrence, M. J. (1994), Investigations into the formation and characterization of phospholipid microemulsions. Part 3. Pseudo-ternary phase diagrams of systems containing water-lecithin-isopropyl myristate and either an alkanoic acid, amine, alkanediol, polyethylene glycol alkyl ether or alcohol as cosurfactant, Int. J. Pharm., Ill, 63-72. 

Oxidative stability of 00-3 fatty acids can be increased using free radical scavengers. TBHQ (t-butyUiydroquinone) at a concentration of 0.02% has successfully slowed down the oxidation of menhaden oil for up to 40 days, compared with 3 days for the control group (83). a-Tocopherol and butylated hydroxytoluene (BHT) alone or in combination increased the oxidative stability of EPA and DHA (84). The most notable success in fish oil stabilization has been achieved with ternary antioxidant systems, which contain a- or y-tocopherol concentrates, ascorbic acid (or ascorbyl palmitate), and lecithin (85). 

Small, D. M., Bourges, M., and Dervichian, D. G., Ternary and quartemary aqueous systems containing bile salt, lecithin and cholesterol. Nature (London) 211, 816-818... 

In an earlier review [3], mixed micelles formed by bile salts were classified into those with (i) non-polar lipids (e.g., linear or cyclic hydrocarbons) (ii) insoluble amphiphiles (e.g., cholesterol, protonated fatty acids, etc.) (iii) insoluble swelling amphiphiles (e.g., phospholipids, monoglycerides, acid soaps ) and (iv) soluble amphiphiles (e.g., mixtures of bile salts with themselves, with soaps and with detergents) and the literature up to that date (1970) was critically summarized. Much recent work has appeared in all of these areas, but the most significant is the dramatic advances that have taken place in our understanding of the structure, size, shape, equilibria, and thermodynamics of bile salt-lecithin [16,18,28,29,99-102,127, 144,218,223,231-238] and bile salt-lecithin-cholesterol [238,239] micelles which are of crucial importance to the solubihty of cholesterol in bile [1]. This section briefly surveys recent results on the above subclasses. Information on solubilization, solubilization capacities or phase equilibria of binary, ternary or quaternary systems or structures of liquid crystalline phases can be found in several excellent reviews [5,85,207,208,210,211,213,216,217] and, where relevant, have been referred to earlier. 

Aboofazeli R and LawrenceMJ. (1993). Pseudo-ternary phase diagrams of systems containing water-lecithin-alcohol-isopropyl myristate. International Journal of Pharmaceutics, 93,161-175. 

Figure 1 Pseudo ternary phase diagrams at room temperature of (a) quaternary systems containing lecithin, butanol, isopropyl myristate, and water or (b) a 10 wt% aqueous solution of sodium salicylate, at a lecithin/butanol ratio of 1 1. (Adapted from Ref. 9.)...

Ternary and quaternary systems of lecithin, cholesterol, and bile salts... 

The ternary diagrams in Fig. 4.37 indicate the complexity of the bile salt-lecithin systems especially in the presence of cholesterol which limits the extent of the isotropic micellar phase (IV) in particular. Intense interest in these systems has been generated in the search for the cause of cholelithiasis. Of great importance in understanding gallstone formation is how cholesterol, which is a major... 

---