Enhancer Phosphatidylcholine

The rate of production of DAG in the cell does not occur linearly with time, but rather it is biphasic. The first peak is rapid and transient and coincides with the formation of IP3 and the release of Ca2+ this DAG is therefore derived from the PI-PLC catalyzed hydrolysis of phosphatidylinositols [1]. There is then an extended period of enhanced DAG production that is now known to be derived from the more abundant phospholipid phosphatidylcholine (PC), which has a different composition of fatty acid side chains [9]. Although DAG may be generated directly from PC through the action of PC-PLC, it can also be formed indirectly from PC. In this pathway, PC is first hydrolyzed by PLD to give choline and phosphatidic acid, which is then converted to DAG by the action of a phos-phatidic acid phosphatase [10,11 ]. 

The bioavailability of silibinin from the extract is low and seems to depend on several factors such as (i) the content of accompanying substances with a solubilizing character such as other flavonoids, phenol derivatives, aminoacids, proteins, tocopherol, fat, cholesterol, and others found in the extract and (ii) the concentration of the extract itself (132,133). The systemic bioavailability can be enhanced by adding solubilizing substances to the extract (11,134). The bioavailability of silibinin can also be enhanced by the complexation with phosphatidylcholine or p-cyclodextrin, and possibly by the choice of the capsule material (135-137). The variations in content, dissolution, and (oral) bioavailability of silibinin between different commercially available silymarin products—despite the same declaration of content—are significant (138). 

The realization that tubules may be formed on temperature reduction of polymerized SUVs, prepared from polymerizable diacetylenic phosphatidylcholines (21 where n = 7-16 and m = 5-11), represented a major breakthrough in obtaining the desired supramolecular structure [355-360]. In the initial experiments, 0.4- to 1.0-pm-diameter and 10- to 1000-pm-long tubules were prepared by the gradual lowering of the temperature (to about 38 °Q of 21 (m = 8, n = 9) SUVs [358]. The walk of the tubules had thickness of 10-40 nm and were coated by spiral ripples and helical bilayer strips. Many tubules contained trapped SUVs. Polymerization of the acetylenic moieties greatly enhanced the mechanical and thermal stabilities of the tubules [355-360]. 

Pharmaceuticals. Lecithin and especially purified phosphatidylcholine can act as excipients in pharmaceutical (drug) formulation to enhance and control the Unavailability of the active component. Moreover, phosphatidylcholine can be utilized as a diedelic source, as it involved in the cholesterol metabolism and the metabolism of fats in the liver also, it can be utilized as a precursor of brain acetylcholine, as neurotransmiticr. 

Electrophoretic mobility and 31P-NMR measurements were made to investigate the binding of the alkaline earth cations to membranes formed from phosphatidyl choline molecules with either saturated or unsaturated hydrocarbon chains. Calcium and magnesium bind to the same degree to membranes formed from lipids with unsaturated chains. These phosphatidylcholine molecules are present in the liquid crystalline state at all temperatures under consideration. Calcium binds more strongly than magnesium to membranes formed from lipids with saturated chains, even when the lipids are in the liquid crystalline state. The selectivity is enhanced when the temperature is lowered and the saturated chain lipids are in the gel state. 

We report here the results of a study of the adsorption of the alkaline earth cations to bilayer membranes formed from phosphatidylcholines with saturated chains dipalmitoyl phosphatidyl choline (DPPC) and dimyristoyl phosphatidyl choline (DMPC). Our salient result is that the adsorption of calcium is distinct from the other alkaline earth cations in two respects. First, only calcium adsorbs significantly more strongly to PCs with saturated chains than to phosphatidyl cholines with unsaturated chains, even when all lipids are present in the liquid crystalline state. Second, when the membranes are present in the frozen or gel state, the binding of calcium is significantly enhanced. We used two independent techniques to demonstrate this unique behavior of calcium. 

Figure 3. Physicochemical features of mixed aggregates of phosphatidylcholine, phosphatidylethanolamine (PE, used as surface marker), and gangliosides (Gut, G ,a, GTlb, Gt),b) at increasing proportions of ganglioside. Highest value of the outer PE/total PE ratio corresponds to liposomes. Lowering of turbidity and concurrent enhancement of ratio indicate presence of micelles. Break point is indicated as the transition ganglioside/ phospholipid molar ratio. ...

Lecithin (phosphatidylcholine) is a phospholipid, which may be isolated from either egg yolk or soybeans. It is commercially available in high purity for medical uses and has been used to enhance the absorption of insulin in vivo [26]. The antibiotic sodium fusidate, a steroid similar in molecular structure to bile salts has also been shown to have permeation enhancing properties for insulin in vitro [41]. 

Many studies have employed phospholipids as liposomes (vesicles) to transport drugs into and through human skin. However, a few investigations have also employed phospholipids in a nonvesicular form as penetration enhancers. For example, 1% phosphatidylcholine in PG, a concentration at which liposomes would not form, enhanced theophylline penetration through hairless mouse skin [64]. Similarly, indomethacin flux was enhanced through rat skin by the same phospholipid and hydrogenated soybean phospholipids increased diclofenac permeation through rat skin in vivo. 

Koo, S.I. and Noh, S.K. 2001. Phosphatidylcholine inhibits and lysophosphatidylcholine enhances the lymphatic absorption of a-tocopherol in adult rats. J. Nutr. 131, 717-722. 

Moschetta, A., van Berge-Henegouwen, G.P., Portincasa, P., Palasciano, G., Groen, A.K., van Erpecum, K.J. 2000. Sphingomyelin exhibits greatly enhanced protection compared with egg yolk phosphatidylcholine against detergent bile salts. J. Lipid Res. 41, 916-924. 

Another set of studies from this laboratory examined the assembly of symmetric and asymmetric phosphatidylcholines at the CCfr/water interface [50]. In these studies, a series of saturated symmetric and asymmetric chain PCs were examined. Symmetric PCs with 16 or fewer carbons per acyl chain and highly asymmetric PCs were found to produce relatively disordered films at the CCU/water interface as measured by VSFS. However, the longest chain PCs studied, 1,2-distearoyl-sn-PC (C18 C18), l-stearoyl-2-palmitoyl-sn-PC (C18 C16) and l-palmitoyl-2-stearoyl-sn-PC (C16 C18), formed well-ordered crystalline phase monolayers at room temperature. These results have been explained in terms of enhanced chain-chain interactions among the longer, nearly symmetric hydrocarbon chains that reduce the intercalation of solvent. 

In the bacterial PI-PLC structures, the top of the barrel rim has several hydrophobic residues that are fully exposed to solvent and poorly defined in the crystal structures (implying significant mobility). The active site of PI-PLC is accessible and well-hydrated, and these mobile elements at the top of the barrel offer a different motif for interactions of the protein with phospholipid interfaces. The PI-PLC from B. thuringiensis (nearly identical in sequence to the enzyme from B. cereus whose crystal structure was determined) exhibits the property of interfacial activation, where enhanced activity is observed when the substrate PI is present in an interface compared to monomeric substrate (Lewis et al., 1993). However, other non-substrate lipids such as phosphatidylcholine (PC), phosphatidic acid (PA), and other anionic lipids have an effect on the activity of PI-PLC toward both substrates PI and water-soluble cIP (Zhou et al., 1997). In particular, the presence of PC enhances the catalytic activity of... 

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