Lignoceric acid 2-hydroxy

Five triplets of deprotonated molecules at m/z ranging from 908.6 to 1750.9, separately by a multiple of 162 was detected in the negative ion MALDI-TOF mass spectrum, suggested the presence of glycan chains containing 0, 1, 2, 4 or 5 hexose residues [74]. The lipid portion was characterized as a ceramide composed of C-18 phytosphingosine N-aeylated by hydroxy C24 fatty acid (80%), C24 (15%) or 2,3-hydroxy lignoceric acids (5%). 

SLs are also polar cell membrane lipids, but they are typically present in much lower concentration than PLs. Soybeans are a relatively rich source of SLs (Vesper et al., 1999), and ceramides and cerebrosides are the primary SL classes in soybeans. SLs contain a sphingoid long-chain (CIS) drhydroxy base and an a-hydroxy fatty acyl chain that is linked to the base by an amide bond. The main soybean ceramide molecular species is a trihydroxy base (4-hydroxy-trans 8-sphingenine) V -acylated with a-hydroxy lignoceric acid (C24 0). The main soybean cerebroside molecular species is a dihydroxy base trans A-trans 8-sphingediene) V acylated with a-hydroxy palmitic acid. The general molecular structures of ceramide and cerebroside are shown in Fig. 10.4. 

Moschidis et al. (1984) found small amounts of phosphonohpids in the egg yolk. The comparison of the FA composition of minor components shows that in sphingomyelins the amount of palmitic acid is twice that in the egg yolk lipids, whereas there is almost 40% less oleic acid. Linoleic acid at 30% is found at concentrations about three times higher in lysophosphatidylcholines than in egg yolk hpids, and twice as much as in the PC fraction. At 28%, docosanoic acid (C20 o = behenic acid) is present in considerable amounts in gangliosides, as opposed to lower concentrations of oleic and linoleic acids in comparison with the FA spectrum of egg yolk lipids. Momma et al. (1972) also found a high proportion of approximately 67% hydroxy FA in the cerebrosides. Many of the hydroxy FA have a chiral center. In any case. Momma et al. (1972) determined a relatively high concentration (15.7%) of tetracosanoic acid (C24 o = lignoceric acid), while smaller concentrations of the main FA of the egg yolk lipids were found in the cerebrosides. Table 14.5 shows an overview of the FA spectrum of the minor components. 

Cerebrosides differ also in the composition of the constituent fatty acids. Alpha-hydroxy fatty acids with chain lengths ranging between 18 and 25 carbon atoms have been obtained from cerebroside hydrolysates. The saturated fatty acids most frequently found are stearic and lignoceric acids. The unsaturated fatty acids found mainly in cerebroside hydrolysates are 24 carbons long. Sphingosine is present in 95% of the cerebrosides, but cerebrosides containing dihydro-sphingosine have also been reported. 

Had sjmthesis occurred via psychosine, the presence of a-hydroxy-lignoceryl-SCoA or (x-hydroxy-lignoceric acid, ATP, and the fatty acid activating system would have been required to convert the psychosine to the cerebroside. In addition more recent experiments have shown a stimulation of the incorporation of radioactivity from UDP-galactose-1- C into cerebroside by the addition of exogenous ceramide (isolated from cerebroside) in a reaction mixture containing brain microsomes and 2% n-butanol (Burton, unpublished data). 

Galactosylceramides usually contain large amounts of 2-hydroxy fatty acids, which are linked to the sphingosine base through the amino group. In addition, odd chain fatty acids may also present. Typical fatty acids reported are behenic (C22 0), lignoceric (C24 0), nervonic (C24 l), cerebronic (a-OH C24 0), and 2-hydroxynervonic (a-OH C24 l) (2). 

Chemical synthesis of the palmitoyl- and stearoyl-derivatives of dihydrosphingomyelin confirmed this structure (Shapiro et al. 1958). Long chain saturated fatty acids, mono- and even diunsaturated fatty acids (predominantly stearic, lignoceric and nervonic acids) have been isolated from sphingomyelin, but no hydroxy fatty acids (Sweeley 1963 Kishimoto et al. 1963 O Brien et al. 1964). 

Chemical analyses of white matter reveal decrease of total phospholipids, cholesterol, cerebrosides and sulphatides, increase of water content and near absence of cholesterol esters, as well as a ratio of cerebrosides sulphatides almost double that in controls [35]. Decrease of hydroxy fatty acids [36, 37] has been reported. A marked loss of lignoceric and nervonic acid also noted [38] cannot be considered specific since this... 

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