Lipid component solubility

When liposomes are prepared from a molecular mixture of lipid components it is important that all lipids be homogeneously dissolved in an organic solvent in order to obteiin bilayers with evenly distributed lipids after hydration. For example, the solubilities of phosphatidylcholine and cholesterol in chloroform are similar their solubility in benzene differs. Upon removal of benzene from the lipid solution an inhomogeneous lipid film is formed on the glass wall and... 

In this book we will focus on physicochemical profiling in support of improved prediction methods for absorption, the A in ADME. Metabolism and other components of ADME will be beyond the scope of this book. Furthermore, we will focus on properties related to passive absorption, and not directly consider active transport mechanisms. The most important physicochemical parameters associated with passive absorption are acid-base character (which determines the charge state of a molecule in a solution of a particular pH), lipophilicity (which determines distribution of a molecule between the aqueous and the lipid environments), solubility (which limits the concentration that a dosage form of a molecule can present to the solution and the rate at which the molecule dissolves from... 

Alpha hydroxy acids (AHAs) are water-soluble substances and thereby penetrate the outermost epidermal skin layers. In contrast, beta hydroxy acids (BHAs) are lipid (fat) soluble and are capable of penetrating to the underlying layers of skin (the dermis) located 1-5 mm below the surface of the skinJ2 Most AHAs are derived from plant materials and marine sources. Commonly used AHAs include malic acid (found in apples), ascorbic acid (a common ingredient in numerous fruits), glycolic acid (a constituent of sugar cane), lactic acid (a component of milk), citric acid (naturally abundant in citrus fruits), and tartatic acid (found in red wine). A common BHA is salicylic acid (an ingredient in aspirin). 

Gujlii-Ustundag O and Temelli F. 2004. Correlating the solubility behavior of minor lipid components in supercritical carbon dioxide. J Supercrit Fluids 31(3) 227-234. 

It should be noted that all three are lethal, however, and so the acute toxicity of these compounds is not entirely due to C-40 substituent effects. Potency does follow the oxidation series from alcohol to aldehyde to acid vivo, suggesting that perhaps these substituents influence the degree of accessibility of each lipid-solvent soluble toxin to its membrane site of action. Being that the toxins in their natural forms are so soluble in non-polar solvents, and tend to bind to or solubilize in the lipid components of membrane... 

Since the PC group is a polar head of a major lipid component of the cell membrane of red blood cell which is the only nonadherent cell among various blood cell types, a biomimetic approach to incorporating the PC group on the surface at the terminal end of water-soluble graft polymers has been... 

Methods of extracting the fat-soluble vitamin from food matrices include alkaline hydrolysis, enzymatic hydrolysis, alcoholysis, direct solvent extraction, and supercritical fluid extraction of the total lipid component. 

Once the nucleic acids are in solution, they must be separated from the other constituents of the cell. First, the protein molecules must be removed. Many of the proteins of the cell are strongly associated with nucleic acids. The addition of sodium perchlorate (NaC104) dissociates the proteins from nucleic acids. When the mixture is shaken with the organic solvent, chloroform-isoamyl alcohol, the proteins are denatured, and they precipitate at the interface. At the same time, the lipid components of the cells are dissolved in the organic solvent. Thus the aqueous layer will contain nucleic acids, small water-soluble molecules, and even some proteins as contaminants. 

HMG-CoA reductase, the enzyme that catalyses the formation of mevalonate [MVA, (2)] from HMG by an irreversible reaction that is considered rate-limiting with respect to the formation of cholesterol, has received much attention. Details of the purification of the enzyme from chicken liver and baker s yeast are available,15 and the solubilized enzyme from rat liver microsomes is readily and reversibly inactivated at temperatures below 19°C.16 Cold-inactivation is an uncommon phenomenon, and all the enzymes that have been found to exhibit this behaviour have been soluble proteins. Native HMG-CoA reductase is a particulate enzyme that is probably bound to protein or lipid of the microsomal membrane, although it is not known whether the solubilized enzyme contains a lipid component. Microsomal reductase is not cold-sensitive, and the cold-inactivation of the solubilized enzyme can be completely prevented by addition to the preparation of NADP+ or (more effectively) of NAD PH.17... 

With such major developments in the field of SCF technology, the objective of this chapter is to provide a critical overview of the solubility behavior of lipid components in SCCO2, which is fundamental for optimal process design as well as the unit operations of extraction, fractionation, and reactions using SCCO2 as applied to fats and oils processing. 

Available literature solubility data of pure lipids belonging to major (fatty acids, mono-, di- and triacylglycerols, and fatty acid esters) and minor lipid classes (pigments, sterols, vitamins, and hydrocarbons) in SCCO2 were compiled (26, 27). These references (26, 27) contain exhaustive bibliography on lipid + SCCO2 binary systems. Literature data were correlated using Chrastil s equation, which is an empirical model used quite commonly to correlate the solubility of lipid components (30). This model is based on the formation of a solute-solvent complex on association of the solute and solvent molecules and establishes a linear relationship between In(solubility) and In(density) as follows ... 

Chrastil s equation was adopted in the systematic study of binary solubility behavior because it is easy to use and it does not require information on the properties of lipid components. Its parameters can then be used to interpret the effect of operating conditions on solubility. Its value, however, is limited for predictive modeling of solubility data, which should involve in-depth thermodynamic models (e.g., using an Equation of State (EOS) approach), describing all the phases present at equilibrium. 

When the solubility of various minor lipid components were compared with that of selected components of other major lipid classes, it was found that a-tocopherol, oleic acid (a liquid fatty acid), and squalene were the most soluble solutes and p-carotene had the lowest solubility in SCCO2 (Figure 5, solubility isotherms constructed using Equation 2). 

Figure 5. Solubility isotherms of lipid components at 323 K plotted using model parameters estimated using Equation 2.

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