Hydroxy fatty acid with ceramides

In contrast to the striking divergences in the carbohydrate parts, respective ceramide moieties resemble those of other cestode glycosphingolipids in so far as sphinganine (d18 0) and 4-hydroxy-sphingoid bases (tl 8 0, t20 0) as well as, in part hydroxylated, fatty acids with 16 to 28 carbon atoms, in particular C26 0 and C28 0, represent predominant ceramide constituents, which might be an indication of similar biosynthetic routes. 

We initially demonstrated that brain cerebrosides, galactosyl-ceramides containing hydroxy fatty acids (HFA) and nonhydroxy fatty acids (NFA), could be completely derivatized by reaction with 10% benzoyl chloride at 60°C for 1 hour (2). After removal of excess reagents by partition between hexane and alkaline aqueous methanol, the perbenzoyl derivatives were seen to separate into two completely resolved components (HFA and NFA... 

The derivatives obtained by reaction with benzoic anhydride have longer retention times when compared to the benzoyl chloride products. We have previously shown that galactosylceramide which contains a-hydroxy fatty acids is not N-benzoylated with benzoyl chloride and reaction with benzoic anhydride or benzoyl chloride results in an identical product. Similar results have been obtained with anhydride in the presence of DMAP as illustrated in Fig. 2. The behavior of peak "b" which we have shown to be derived from a-hydroxy fatty acid containing glucosyl and galactosylceramides is illustrative. The UV response from each of the standard GSLs benzoylated by the anhydride and by the benzoyl chloride method were compared. The relative responses (chloride/anhydride) for the mono, di, tri and tetra-hexosyl ceramide were found to be 1.18, 1.15, 0.94 and 1.03 respectively. These values were not significantly different from calculated rations 1.20, 1.12, 1.09, and 1.15, based on the assumption that the anhydride method avoids amide benzoylation. The yields of the per-O-benzoylated products were similar to those obtained for the products of the benzoyl chloride method reported previously. 

Based on the MS data only sphingosine is present in the ceramide moiety CMH-C , ceramide monohexosides from T. cruzi wilh n fatty acids CMH-Con, CMH with oc-hydroxy fatty acids from T. cruzi tr, trace... 

Figure 8.12. Schematic separation of ceramides by TLC on layers of silica gel G, impregnated with 2 % sodium arsenite (plate A) and 2 % sodium borate (plate B), using a solvent system of chloroform-methanol (95 5, v/v) for development [467], Abbreviations na, normal fatty acid ha, hydroxy fatty acid db, dihydroxy base tb, trihydroxy base sat, saturated.

Figure 8.15. GC separation of the TMS ethers of a ceramide fraction containing sphingosine and non-hydroxy fatty acids from brain cerebrosides [346]. A glass column (1.7 m x 3.5 mm), packed with 2.4 % OV-1 on Gas Chrom (100-120 mesh), was maintained at 300 C. Only the fatty acid component is identified. (Reproduced by kind permission of the authors and of the European Journal of Biochemistry, and redrawn from the original paper).

Hydroxy fatty acid (HFA) A fatty acid with a OH group linked to carbon C2 (also referred to as a). Ceramide with a hydroxyacyl chain is referred to as ceramide-HFA. If the acyl chain is nonhydroxylated, the ceramide is referred to as ceramide-NFA. 

Cholesterol is a major component of the alcoholic fraction of lanolin.15 It is also an essential constituent of the lipids of the stratum corneum, which form the epidermal permeability barrier.29,30 However, the other stratum corneum lipids (ceramides and fatty acids) are different from those of lanolin. Clark and Steel have suggested that the a-, ()-, and m-hydroxy lanolin acids are esterified with diols to form diesters with two long acyl chains, which are similar to those found in ceramides.16,31,32... 

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