Cerebrosides of frog brain. Structure of the ceramide part of the cerebrosides
Twelve cerebrosides were isolated from the brain tissues of the bullfrog (Rana catesbeiana) and they were characterised as 1-o-β-D-galactopyranosyl ceramides. On the basis of chemical and spectral evidence, the ceramide parts of six of them were found to be composed of a sphingosine as a long-chain base and six fatty acids consisting of C18:0, C22:1, C24:1 and their 2-hydroxy derivatives. The ceramide parts of the others were found to be composed of a dihydrosphingosine and the six fatty acids. The configurations at C-2 and C-3 of the two long-chain bases were determined to be S and R, respectively, on the basis of the NMR spectra of their acetates and the exciton chiralities of the benzoate-benzamide derivatives. Further, the chiral centre of the three 2-hydroxy fatty acids was determined to be R in all cases by means of CD measurements. A different distribution of the cerebrosides was seen among the hemisphere, diencephalon and mixed tissue from the optic lobe, cerebellum and medulla oblongata of the brain.