Lecithin

Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues, which are amphiphilic - they attract both water (and so are hydrophilic) and fatty substances (lipophilic), and are used for smoothing food textures, dissolving powders (emulsifiers), homogenizing liquid mixtures, and repelling sticking materials.

Lecithins are usually phospholipids, composed of phosphoric acid with choline, glycerol or other fatty acids usually glycolipids or triglyceride. Glycerophospholipids in lecithin include phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidic acid.

Lecithin was first isolated in 1845 by the French chemist and pharmacist Theodore Gobley. In 1850, he named the phosphatidylcholine lécithine. Gobley originally isolated lecithin from egg yolk—λέκιθος lekithos is "egg yolk" in Ancient Greek—and established the complete chemical formula of phosphatidylcholine in 1874; in between, he had demonstrated the presence of lecithin in a variety of biological matters, including venous blood, bile, human brain tissue, fish eggs, fish roe, and chicken and sheep brain.

1-Lysophosphatidylcholine

2-acyl-sn-glycero-3-phosphocholines are a class of phospholipids that are intermediates in the metabolism of lipids. Because they result from the hydrolysis of an acyl group from the sn-1 position of phosphatidylcholine, they are also called 1-lysophosphatidylcholine (or 1-lysoPC, in short). The synthesis of phosphatidylcholines with specific fatty acids occurs through the synthesis of 1-lysoPC. The formation of various other lipids generates 1-lysoPC as a by-product.

Other synonyms for this class of compounds are 2-acylglycero-3-phosphocholine, 1-lyso-2-acyl-sn-glycero-3-phosphocholine, β-lysophosphatidylcholine, 2-acylglycerophosphocholine, L-1-lysolecithin and 1-lecithin.

Chemical properties

1-LysoPC can convert to the structurally similar 2-lysoPC. This happens by the migration of the acyl group from the sn-1 position of the glycerol backbone to the sn-2 position.

The lowest rate of isomerization is at pH 4-5. Starting from either 1-lysoPC or 2-lysoPC, an equilibrium mixture of 90% 2-lysoPC and 10% 1-lysoPC is obtained with a half-time of about 10 minutes under physiological conditions and about 1 hour under typical laboratory conditions. Thus, unless special care is taken to slow this isomerization reaction, characterization of either of these lipids using laboratory assays that take a significant amount of time is likely to produce results on a mixture of the two lipids.