Phosphatidyl Derivatives

Figure 22.4 The head-group construction of the six commonly encountered phosphatidyl derivatives.

Recent work indicates that various methylarsenic compounds can be accumulated by marine organisms. These include arsenobetaine (2/0, 25/), trimethylarsoniumlactate [(CH3)3AsCH2CH(0H)C02] and its phosphatidyl derivatives (252-254), and arsenosugars (255), These compounds form from arsenate salts, and provide strong evidence for the biological formation of As-C bonds other than As-CH3. 

The fatty acid constituents of phosphodiglycerides can vary considerably in nature among a number of different chain lengths and points of unsaturation. A given isolated phosphatidyl derivative from a biological source usually possesses a range of fatty acid... 

Shuto S, Awano H, Shimazaki N, Hanaoka K, Matsuda A (1996) Nucleosides and nucleotides.150. Enzymatic synthesis of 5 -phosphatidyl derivatives of l-(2 -C-cyano-2-deoxy-P-D-ar i o-pentofuranosyl) cytosine (CNDAC) and their notable antitumor effects in mice. Bioorg Med Chem Lett 6 1021-1024... 

A series of S -phosphatidyl derivatives (11) of the potent anti tumour agent... 

Kojic acid and arbutin are tyrosinase inhibitors. Kojic acid inhibits tyrosinase activity by chelation and as an antioxidant, while arbutin is a competitive inhibitor of tyrosinase. To impart hydrophobicity to these compounds to prevent degradation, phosphatidyl-kojic acid and phosphatidyl-arbutin were synthesized from dipalmitic-PC (DPPC) [43]. Their inhibition of l-DOPA (3,4-dihydroxyphenylalanine) to dop-achrome (precursor of melanin), catalyzed by tyrosinase in vitro, was of a similar level to the parent compounds. These phosphatidyl derivatives show promise for application in the cosmetics industry. 

T. Koga, A. Nagao, J. Terao, K. Sawada, and K. Mukai Synthesis of a phosphatidyl derivative of vitamin E and its antioxidant activity in phospholipid bilayers. Lipids 29 (1994) 83-89. 

T. Koga and J. Terao Antioxidant activity of a novel phosphatidyl derivative of vitamin E in lard and its model system. Journal of Agricultural and Food Chemistry 42 (1994) 1291-1294. 

The most important phosphatides are the lecithins, cephalins, phosphatidylser-ines, and plasmalogens (a phosphatidyl derivative). Their general structures are shown in Table 23.5. 

Plasmalogens are phosphatidyl derivatives in which the fatty acid in the a position has been replaced by an unsaturated ether (10.50a). They are found in brain and nervous tissue. 

Modified neplanocin A analogues have been prepared, as well as anti-tumour 6 phosphatidyl derivatives, using an enzymic coupling procedure. ... 

Phosphatidyl derivatives and other P-containing lipids, e. g., plasmalogens, sphingomyelins. The abbreviations correspond to Formulas 3.26 - 3.29. 

Examples of foods which contain phosphatidyl derivatives are shown in Table 3.18. The differences to the data in Table 3.17 are caused by the biological range of variations. 

Phospholipids are sensitive to autoxidation since they contain an abundance of linoleic acid. The other acid commonly present is palmitic acid. Phospholipids are soluble in chloroform-methanol and poorly soluble in water-free acetone. The pKs value of the phosphate group is between 1 and 2. Phosphatidyl choline and phosphatidyl ethanolamine are zwitter-ions at pH 7. Phospholipids can be hydrolyzed stepwise by alcoholic KOH. Under mild conditions, only the fatty acids are cleaved, whereas, with strong alkalies, the base moiety is released. The bonds between phosphoric acid and glycerol or phosphoric acid and inositol are stable to alkalies, but are readily hydrolyzed by acids. Phosphatidyl derivatives, together with triacylglycerols and sterols, occur in the lipid fraction of lipoproteins (cf. 3.5.1). 

Fatty acid composition is determined after methanolysis of the lipid. For positional analysis of acyl residues (positions 1 or 2 in glycerol), phosphatidyl derivatives are selectively hydrolyzed with phospholipases (cf. 3.7.1.2.1) and the fatty acids liberated are analyzed by gas chromatography. 

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