Phospholipids emulsion

Another apolipoprotein, Pa-glycoprotein-1, or apoH, is a glycoprotein of Mr 54,000 found in all major lipoprotein density fractions, especially VLDL where it forms about 4% of the protein mass. Serum concentration is about 15-30 mg/100 ml. Two-thirds to three-quarters is found in the d > 1.21 g/ml fraction after ultracentrifugation (P19, P20). ApoH is taken up readily by a triglyceride-phospholipid emulsion (Intralipid) (P20) and it activates lipoprotein lipase (Nl). Lipoprotein lipase activation by either apoH or apoC-II is inhibited by apoC-III (Nl). 

Dellinger, R.P., Tomayko, J.F., Angus, D.C., Opal, S., Cupo, M.A., McDermott, S., Ducher, A., Calandra, T., Cohen, J. Efficacy and safety of a phospholipid emulsion (GR270773) in Gramnegative severe sepsis Results of a phase II multicenter, randomized, placebo-controlled, dosefinding clinical trial. Crit Care Med 37 (2009) 2929-2938. 

Entrapment of drug substances in liposomes and micelles can lead to changes in their stability. When entrapment reduces the degradation rate, it can be used as a method for stabilizing pharmaceuticals. Aspirin can be partially stabilized by incorporation in L-a-dimyristoylphosphatidylcholine (DMPC)-based liposomes.489-491 Anesthetics such as procaine are also stabilized by incorporation in liposomes.490 Physostigmine salicylate in a phospholipid emulsion is stabilized through interaction with phospholipids at the oil-water interface and through incorporation into the internal phase of the emulsion (Fig. 131).549... 

Figure 131. Stabilization of physostigmine salicylate degradation by incorporation into a phospholipid emulsion at pH 5.0. Solution phospholipid emulsion. (Reproduced from Ref. 549 with permission.)...

Similar inhibitory activity was observed for cobra venom phospholipase A2 and the mixture of bacterial alkylresorcinols in lecithin black lipid membrane and phospholipid emulsion systems. Almost complete inhibition (95%) of the enzyme studied was observed at a concentration of about 8 mM of resorcinolic lipids [351]. 

Lysophospholipids, obtained by complete or partial hydrolysis of lecithins, constitute another class of industrially important surfactants that are currently prepared on a large scale. This hydrolytic reaction, catalyzed by phospholipase A2, is typically carried out in 30% phospholipid emulsion in water. However, the process suffers from several complications, one of which is the necessity to inactive phospholipase A2 after completion of the hydrolysis because it is practically impossible to recover and reuse the enzyme from the heterogeneous reaction mixture. Irreversible inactivation of the phospholipase is achieved either by a combination of alkalization and heat treatment... 

Figure 14-22. Formation of lipid membranes, micelles, emulsions, and liposomes from am-phipathic lipids, eg, phospholipids.

Phospholipids are amphiphilic compoimds with high surface activity. They can significantly influence the physical properties of emulsions and foams used in the food industry. Rodriguez Patino et al. (2007) investigated structural, morphological, and surface rheology of dipalmitoylpho-sphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers at air-water interface. DPPC monolayers showed structural polymorphisms at the air-water interface as a function of surface pressure and the pH of the aqueous phase (Fig. 6.18). DOPC monolayers showed a... 

Intravenous lipid emulsions differ in their concentration (10%, 20%, and 30%), caloric density, natural source of lipids, and ratio of phospholipids to triglycerides (PL TG). Table 97-2 shows a comparison of commercially available intravenous lipid emulsions in the United States. The 10%, 20%, and 30% lipid emulsions provide 1.1 kcal/mL (4.6 kJ/mL), 2 kcal/mL (8.4 kJ/mL), and 3 kcal/mL (12.6 kJ/mL) with a PL TG of 0.12, 0.06 and 0.04 respectively. The lower PL TG indicates a lower phospholipid content and translates to abetter clearance of the 20% and 30% lipid emulsions compared with the 10% lipid emulsion.9 The 30% lipid emulsion is only approved for infusion in a TNA and should not be infused directly into patients. 

A higher PL TG ratio in the 10% lipid emulsion has been proposed to cause the appearance of the abnormal lipoprotein X particles [rich in phospholipids (-60%) and cholesterol (-25%), small amounts of triglycerides] in the blood.9,35 Lipoprotein X... 

Experiments with monkeys given intramuscular injections of a mineral oil emulsion with [l-14C] -hexa-decane tracer provide data illustrating that absorbed C-16 hydrocarbon (a major component of liquid petrolatum) is slowly metabolized to various classes of lipids (Bollinger 1970). Two days after injection, substantial portions of the radioactivity recovered in liver (30%), fat (42%), kidney (74%), spleen (81%), and ovary (90%) were unmetabolized -hexadecane. The remainder of the radioactivity was found as phospholipids, free fatty acids, triglycerides, and sterol esters. Essentially no radioactivity was found in the water-soluble or residue fractions. One or three months after injection, radioactivity still was detected only in the fat-soluble fractions of the various organs, but 80-98% of the detected radioactivity was found in non-hydrocarbon lipids. 

MJ Parnham. Safety and tolerability of intravenously administered phospholipids and emulsions. In RH Muller, S Benita, BHL Bohm, eds. Emulsions and Nanosuspensions for the Formulation of Poorly Soluble Drugs. Stuttgart Medpharm Scientific Publishers, 1998, pp 131-140. 

Reverse-phase evaporation in a nitrogen atmosphere was used to prepare lipids. A lipid film previously formed was redissolved in diethyl ether and an aqueous phase containing the dyebath components added to the phospholipid solution. The resulting two-phase system was sonicated at 70 W and 5 °C for 3 minutes to obtain an emulsion. The solvent was removed at 20 °C by rotary evaporation under vacuum, the material forming a viscous gel and then an aqueous solution. The vesicle suspension was extruded through a polycarbonate membrane to obtain a uniform size distribution (400 nm). 

Azuma K, Ippoushi K, Ito H, Higashio H and Terao J. 1999. Evaluation of antioxidative activity of vegetable extracts in linoleic acid emulsion and phospholipid bilayers. J Sci Food Agric 79(14) 2010-2016. 

When oxidized, 1 g of fat yields 9 kcal. Because of the caloric contribution from egg phospholipid and glycerol, caloric content of IVFE is 1.1 kcal/mL for the 10%, 2 kcal/mL for the 20%, and 3 kcal/mL for the 30% emulsions. 

Liposphere formulations are prepared by solvent or melt processes. In the melt method, the active agent is dissolved or dispersed in the melted solid carrier (i.e., tristearin or polycaprolactone) and a hot buffer solution is added at once, along with the phospholipid powder. The hot mixture is homogenized for about 2 to 5 min, using a homogenizer or ultrasound probe, after which a uniform emulsion is obtained. The milky formulation is then rapidly cooled down to about 20°C by immersing the formulation flask in a dry ice-acetone bath, while homogenization is continued to yield a uniform dispersion of lipospheres. 

The digestion and absorption of fat is considerably more complex than that of carbohydrate or protein because it is insoluble in water, whereas almost aU enzymes catalyse reactions in an aqueous medium. In such media, fat can form small droplets, an emulsion, which is stable in this medium. Formation of an emulsion is aided by the presence of detergents these possess hydrophobic and hydrophilic groups, so that they associate with both the fat and the aqueous phases. Such compounds are known as emulsifying agents and those involved in digestion are mainly the bile salts and phospholipids. 

The basis for contrast agents derived from nutrional products was Intralipid, which had been prepared from phospholipids obtained from soy bean oil and egg yolk [86]. Intralipid was chemically modified by iodination into Intraiodol, which contained 50 mgl mbThe particles formed in the emulsion were mostly taken up by the hepatocytes and to a lesser extent by the RES [87,88]. Intraiodol was better tolerated than EOE-13 or its precursor, AG 60.99. The addition of cholesterol to Intraiodol resulted in NRI 757 with an iodine concentration of 42 mg mL b Further modifications by replacing the iodinated triglycerides of Intraiodol by ethiodized poppy seed oil and reducing the cholesterol content to... 

The separation of oil and water (B) can be prevented by adding a strongly amphipathic substance. During shaking, a more or less stable emulsion then forms, in which the surface of the oil drops is occupied by amphipathic molecules that provide it with polar properties externally. The emulsification of fats in food by bile acids and phospholipids is a vital precondition for the digestion of fats (see p.314). 

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