Discover the world of phospholipids

 

Phospholipids are unique and versatile molecules. Phospholipids are of natural occurrence and the main components in cellular membranes. Arranged as a lipid bilayer, phospholipids play an important role in the structure and functionality of biological membranes.

They are amphiphilic (“both loving” [water and fat]) and consist of a hydrophilic as well as a lipophilic moiety. Phospholipids are esters of glycerol. The sn-1 and sn-2 positions of the glycerol backbone are esterified with fatty acids of varying length and degree of saturation (illustrated in the symbolic presentations of phospholipids by yellow lines). Position sn-3 is esterified with phosphoric acid which on its turn is esterified with a short-chain alcohol of varying chemical structure. Phospholipids are highly soluble in many organic solvents, whereas in water, they spontaneously form aggregates due to their amphiphilic nature. The structure of the aggregates depends on the head group, the length and degree of unsaturation of the fatty acid chains, and the pH and ionic strength of the aqueous surroundings.1

Due to their structural diversity, phospholipids are widely used in various pharmaceutical dosage forms. Below, we have illustrated some of the aggregates which can be formed, including those that are already successfully used in pharmaceutical dosage forms and others which have the potential to be used.

main categories

Unsaturated Phospholipid

Monoacyl Phospholipid

Saturated/Hydrogenated
Phospholipid

AGGREGATES

Micelle

Reverse Micelle

Bilayer

Lamellar Phase

o/w Emulsion

w/o Emulsion

Liposome

Mixed Micelle

Cochleate