Phosphatidylcholines hydrogenation

Several phospholipid-based excipients are finding increased application as solubilizing agents, emulsifying agents, or as components of liposomal formulation. The phospholipids occur naturally and are biocompatible and biodegradable. Examples include egg phosphatidylcholine, soybean phosphatidylcholine, hydrogenated soybean phosphatidylcholine (HSPC),... 

LEH is primarily composed of a combination of saturated high-carbon phospholipids and cholesterol. Synthetic phospholipids replaced hydrogenated soy lecithin when the latter was found to induce several untoward biological responses (40). Current choice of a saturated high-carbon phospholipid is mostly between distearoyl phosphatidylcholine (DSPC, 55°C) and... 

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. 

Fig. 3. Structure of 1-stearoyl-2-oleoyl-3-phosphatidylcholine showing the saturated stearoyl (C18 0) and the mono-unsaturated oleoyl (C18 1) hydrocarbon chains. The hydrogen atoms surrounding the C=C bond are in the cis configuration.

MPEG = methyl PEG HSPC = hydrogenated soy phosphatidylcholine DSPG = disteroylphosphatidyl-glycerol DOPC = dioleoylphosphatidylcholine DPPG = dipalmitoylphosphatidylglycerol. 

Using diffuse reflectance Fourier transform infrared spectroscopy, Adhikari et al. studied the binding of oleic acid (88), triacylglycerol (89), and phosphatidylcholine (90) on silica gel at room temperature. Their interpretation was that oleic acid and triacylglycerols bind to silica surface hydroxyls via hydrogen bonding interactions between the carboxylate and ester carbonyls of these molecules, respectively. In contrast, phospholipids hydrogen bond to silica surface hydroxyls via the phosphate... 

Hydrogenated soy phosphatidylcholine (HSPC) Distearoylphosphatidylglycerol (DSPG) L-a-Dimyristoylphos-phatidylcholine (DMPC) L-a-Dimyristoylphos-phatidylglycerol (DMPG) Phosphatidylglycerol... 

Phospholipids are essential components of cell membranes and liposomes, which are closed spherical vesicles with an inner aqueous core and an outer shell composed of phospholipid bilayer membranes. Depending on the level of hydrophobicity, moderately hydrophobic drugs can be solubilized by liposomes if the drug becomes encapsulated or intercalated within the liposome. The phospholipids in commercially available injectable formulations include hydrogenated soy phosphatidylcholine, dimyristoylphosphatidyl-choline, egg phosphatidylglycerol, distearoylphospha-tidylglycerol, and dimyristoylphosphatidylglycerol. 

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