Plasmalogen phospholipid

Hahnel D., Beyer K., and Engelmann B. (1999). Inhibition of peroxyl radical-mediated lipid oxidation by plasmalogen phospholipids and a-tocopherol. Free Radic. Biol. Med. 27 1087-1094. 

Engelmann, B, Brautigam, C and Thiery, J (1994) Plasmalogen phospholipids as potential protectors against lipid peroxidation of low density lipoproteins. Biochem Biophys Res Commun, 204,1235-1242. 

Mandel, H, Sharf, R, Berant, M, Wanders, RJA, Vreken, P and Aviram, M (1998) Plasmalogen phospholipids are involved in HDL-mediated cholesterol efflux Insights frominvestigationswithplasmalogen-deficientcells.Bloc/zemBiop/zys Rei CommMn, 250,... 

Murphy, RC (2001) Free-radical-induced oxidation of arachidonoyl plasmalogen phospholipids Antioxidant mechanism and precursor pathway for bioactive eicosanoids. Chem Res Toxicol, 14,463-472. 

Berry, K.A.Z. and Murphy, R.C., Electrospray ionization tandem mass spectrometry of glyc-erophosphoethanolamine plasmalogen phospholipids. J. Am. Soc. Mass Spectrom., 15,... 

The Hoveyda group worked out an elegant cross metathesis of terminal alkenes with vinyl ethers or allylic amides [63]. Functionalized vinyl ethers and allylic amides can be directly accessed with unprecedented Z-selectivity, which have been applied to the total synthesis of two highly valuable natural products including an anti-oxidant plasmalogen phospholipid (Fig. 29) and a potent immunostimulant KRN7000. 

Fig. 29 Z-Selective cross metathesis of vinyl ethers for synthesis of plasmalogen phospholipid...

In 2011, Hoveyda et al. reported the total syntheses of two natural products, C18 (plasm)-16 0 (PC) (162) and KRN7000 (163), an anti-oxidant plasmalogen phospholipid and a potent immunostimulant, respectively, through catalytic Z-selective olefin cross metathesis (CM) [97]. In this study (Fig. 41), the corresponding disubstituted aUcenes were efficiently formed in good yields and excellent Z-selectivity (up to >96%) by the treatment of a molybdenum aUcylidene complex. 

We mentioned the occurrence of glyceride ethers in section 4.2. The mechanism of formation of this ether bond is precisely the same as in the plasmalogen phospholipids (section 7.1.9). 

These compounds constimte as much as 10% of the phospholipids of brain and muscle. StmcmraUy, the plasmalogens resemble phosphatidylethanolamine but possess an ether link on the sn- carbon instead of the ester link found in acylglycerols. Typically, the alkyl radical is an unsamrated alcohol (Figure 14-10). In some instances, choline, serine, or inositol may be sub-stimted for ethanolamine. 

In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels. 

Plasmalogens and platelet-activating factor (PAF) are ether phospholipids formed from dihydroxyacetone phosphate. 

Some animal tissues and some unicellular organisms are rich in ether lipids, in which one of the two acyl chains is attached to glycerol in ether, rather than ester, linkage. The ether-linked chain may be saturated, as in the alkyl ether lipids, or may contain a double bond between C-l and C-2, as in plasmalogens (Fig. 10-9). Vertebrate heart tissue is uniquely enriched in ether lipids about half of the heart phospholipids are plasmalogens. The membranes of halophilic bacteria, ciliated protists, and certain invertebrates also contain high proportions of... 

Ether phospholipids, analogous to the ether lipids described in Section 2, are also widely distributed. Tire alkenyl ether analogs of phosphatidylcholine (Fig. 8-2) are called plasmalogens.17 In neutrophils the 1-O-alkyl ethers contain the major share of the cell s arachidonic acid, which is esterified in the 2 position.1819... 

Inclusion of other molecules of irregular shape within membranes also lowers Tm. However, a molecule of cholesterol can pack into a bilayer with a cross-sectional area of 0.39 nm2, just equal to that of two hydrocarbon chains.49 It tends to harden membranes above Tm but increases mobility of hydrocarbon chains below Tm.97 -100 A complex of cholesterol and phosphatidylcholine may form a separate phase within the membrane.101102 The ether-linked plasmalogens may account for over 30% of the phosphoglycerides of the white matter of the brain and of heart and ether linked phospholipids are the major lipids of many anaerobic bacteria.103 Their Tm values are a few degrees higher than those of the corresponding acyl phospholipids.104... 

Farooqui A. A., Rapoport S. I., and Horrocks L. A. (1997). Membrane phospholipid alterations in Alzheimer disease deficiency of ethanolamine plasmalogens. Neurochem. Res. 22 523-527. 

Studies by Johnston and Roots (1964), Roots (1968) and Kreps (1981) have revealed an increased ratio between the plasmalogenic and diacyl forms of phosphatidyl ethanolamine in oceanic fish from low-temperature waters. During cold adaptation, the ratios between the main phospholipid fractions alter the relative proportion of phosphatidyl choline decrease and phosphatidyl ethanolamine, phosphatidyl serine and sphingomyelin, all of which contain large amounts of polyenoic acids, increase (Caldwell and Vemberg, 1970 Miller etal, 1976 Wodke, 1978 Hazel, 1979 Brichon et al., 1980 van den Thillart and de Bruin, 1981 Zabelinsky and Shukolyukova, 1989). 

Most phospholipids are essentially disubstituted phosphates (Figure 1.27). They may be initially classified as phosphatidyl compounds, plasmalogens, ether phospholipids and sphingomyelins depending on the nature of the Ri group attached to the phosphate residue (Table 1.6). 

The a-phosphatidyl lipids are further subdivided according to the nature of their R2 residues (Table 1.7). The R2 groups of plasmalogens and ether phospholipids are similar to the R2 groups of the phosphatidyl lipids, whilst the sphingomyelins have a choline residue. 

Phospholipid molecules form the lipid bilayer of cell membranes (Appendix 3). Plasmalogens and sphingomyelins are particularly abundant in brain tissue. 

The complex lipids in milk fat are comprised of the phosphoglycerides, phosphatidyl choline, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidylinositol and plasmalogens. Also, the non-glyceride phospholipid, sphingomyelin, occurs in important amounts (Jensen, 2002). Bitman and Wood (1990) described the distribution of phospholipid classes in bovine milk and their fatty acid composition. The phospholipids comprise about 1% and cholesterol 0.4—0.5% of the total milk fat. These occur almost completely in the milk fat globule membrane. 

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