Natural phospholipids

Lecithin

Lecithin is the generic term describing the mixture of fatty acids, glycolipids and phospholipids mainly consisting of phosphatidylcholine (PC) and other minor fractions including phosphatidylethanolamine (PE) and phosphatidylinositol (PI). Lecithin was first isolated from egg yolk by Gobley in 1846, and it is typically derived from egg yolk, soybean, sunflower seed or rapeseed. Lecithin and phospholipids are widely applied in various chemical industries mostly as emulsifiers and release agents.

Phosphatidylcholine

A purified phospholipid, commonly called phosphatidylcholine is a vital component of the cell membrane in all living organisms and its water-like polar head and oil-like non-polar tail makes it amphipathic. Natural phosphatidylcholine can be obtained from animal (e.g. chicken egg) and plant (e.g. soybean, sunflower seed) sources, and owing to its particular chemical properties and biocompatibilities, phosphatidylcholine has been used as emulsifier, solubiliser, wetting agent and precursor of liposome.

Egg phospholipids

Compared to phospholipids obtained from soybeans, egg phospholipids are highly biocompatible and classified as safe for intravenous administration routes. Therefore, they have been used as the emulsifier of choice in the manufacture of pharmaceutical emulsions for parenteral nutrition. Egg phospholipids contain about 80% phosphatidylcholine (PC) and other minor phospholipids including phosphatidylethanolamine (PE), lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE) and sphingomyelin (SM).

Phosphatidylcholine in drug delivery systems

Liposomes are vesicles, mainly composed of phospholipids, with a structure similar to the cellular membrane that can be used as drug delivery systems (DDS) for encapsulating and delivering therapeutic compounds. Phosphatidylcholine’s exceptional biocompatibility and amphiphilicity make these phospholipids most suitable for use in DDS. The applications of phospholipids in DDS have advantage of enhancing bioavailability of drugs with low aqueous solubility, reducing toxicity and improving drug stability. Other examples of DDS based on phospholipids include intravenous lipid emulsions, micelle, drug phospholipids complexes and cochleates.