Phosphatidylcholine, diacyl 0-phosphocholine

Fig. 1. Chemical stmcture of phosphatidylcholine (PC) (1) and other related phosphohpids. R C O represents fatty acid residues. The choline fragment may be replaced by other moieties such as ethanolamine (2) to give phosphatidylethanolamine (PE), inositol (3) to give phosphatidylinositol (PI), serine (4), or glycerol (5). IfH replaces choline, the compound is phosphatidic acid (6). The corresponding lUPAC-lUB names ate (1), l,2-diacyl-t -glyceto(3)phosphocholine (2), l,2-diacyl-t -glyceto(3)phosphoethanolamine (3), 1,2-diacyl-t -glyceto(3)phosphoinositol (4), 1,2-diacyl-t -glyceto(3)phospho-L-serine and (5), l,2-diacyl-t -glyceto(3)phospho(3)-t -glycetol.

The chemical nomenclature and CAS Registry numbering of lecithin is complex. The commercially available lecithin, used in cosmetics, pharmaceuticals, and food products, is a complex mixture of phospholipids and other materials. However, it may be referred to in some literature sources as l,2-diacyl-s -glycero-3-phosphocholine (trivial chemical name, phosphatidylcholine). This material is the principal constituent of egg lecithin and has the same CAS Registry Number. The name lecithin and the CAS Registry Number above are thus used to refer to both lecithin and phosphatidylcholine in some literature sources. 

Synonyms Cholinphosphoric acid diglyceride ester 1,2-Diacyl-sn-glycero-3-phosphocholine Hydrogenated soya phosphatidylcholine Lecithin, hydrogenated (3-sn-Phosphatidyl) choline, soya, hydrogenated Definition End prod, of controlled hydrogenation of lecithin... 

Figure 14.1 Comparisons between the molecular species profiles of choline glycerophos-pholipids in the lipid extracts of CHO cells acquired in the full MS scan mode and neutral-loss mode. Lipid extracts of CHO cells were prepared by using a Bligh-Dyer extraction procedure. Each individual lipid extract was diluted to a lipid concentration of <50pmol total lipids/pL. A small amount of LiOH (25 pmol LiOH/pL) was added to the diluted solution. A positive-ion ESI mass spectrum in the full MS scan mode was acquired in the mass range from m/z 600 to 900 from the diluted lipid extract of CHO cells (a). Neutral-loss scans of 183.1 amu (i.e., phosphocholine) (b) and 189.1 amu (i.e., lithium cholinephosphate) (c) as indicated were also acquired from the diluted lipid extract in the mass range with a collision energy of 35 eV. IS denotes internal standards SM stands for sphingomyelin and dPC abbreviates diacyl phosphatidylcholine. Source Yang et al. [20]. Reproduced with permission of Elsevier.

Phospholipids are hydrolysed by pancreatic phospholipase Aj (phosphatidylcholine 1-acylhydrolase) and phospholipase A2 (phosphatidylcholine 2-acylhydrolase) present as a zymogen that requires activation by trypsin. The products of 1,2-diacyl-s -glycero-3-phosphocholine breakdown are fatty acids and lysophospholipids, that is, 2-acyl-s -glycero-3-phosphocholine and l-acyl-s -glycero-3-phosphocholine, respectively. Cholesterol esters are hydrolysed by pancreatic steryl ester acylhydrolase (cholesterol ester hydrolase) to give cholesterol and fatty acids. 

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