In our continuing research on biologically active glycosphingolipids (GSLs) from echinoderms, a series of studies on the isolation and structural elucidation of the GSLs from sea cucumber species have been performed in our laboratory. [2][3][4][5][6][7][8][9][10][11] In the study of the GSLs of the sea cucumber Holothuria pervicax, we reported the isolation and structure of ten glucocerebrosides revealing a very close resemblance in structure.9) However, all these compounds still exist as a mixture of regio-isomers for terminal methyl groups in the side chain of the long-chain base (LCB) moiety, namely a mixture of iso and ante-iso isomers as shown in Fig. 1. Continuing the previous studies, the separation of the mixture of the regio-isomers was conducted. In this paper, we report on the isolation of an ante-iso type regio-isomer of glucocerebroside from its parent glucocerebroside molecular species HLC-2, an abundant compound obtained from the whole bodies of the sea cucumber Holothuria leucospilota (Nisekuronamako in Japanese).
12)The less polar lipid fraction, which was obtained from the chloroform/methanol extract of the whole bodies of H. leucospilota, was subjected to repeated silica gel column chromatography to give three cerebroside molecular species, HLC-1, HLC-2, and HLC-3, each showing a single spot on silica gel thin-layer chromatography (TLC).In the IR and positive-ion FAB mass spectra of HLC-1, HLC-2, and HLC-3, strong hydroxy and amide absorptions and a series of molecular ion peaks are observed. Their 13 C-NMR spectra (Fig. 1, Table 1) exhibit the characteristic signals of a sphingosine-type b-glucocerebroside possessing an unsubstituted fatty acid (HLC-1), a sphingosine-type b-glucocerebroside possessing a 2-hydroxy fatty acid (HLC-2), and a phytosphingosine-type b-glucocerebroside possessing a 2-hydroxy fatty acid (HLC-3), respectively. Therefore, they are suggested to be the molecular species of three typical types of glucocerebrosides. Their structures shown in Fig. 1 were characterized by comparison of their 13 C-NMR spectral data with those of known glucocerebrosides 2-4) hitherto obtained, and by means of the results of their chemical degradations, namely methanolysis followed by the GC-MS analysis of the methanolysis products, fatty acid methyl ester (FAM), and LCB, as shown in Fig. 2 and Experimental. The geometry (Z) of the double bond in the unsaturated fatty acyl moiety of HLC-1-HLC-3 was determined from the d value (27.4, 27.5) of the allylic carbon atoms obtained from their 1 H-detected heteronuclear multiple-bond connectivity (HMBC) spectra (Fig. 3) ; 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan: and b Department of Medical Electronics Engineering, Faculty of Engineering, Towa University; 1-1-1 Chikusigaoka, Minamiku, Fukuoka 815-0036, Japan. Received February 14, 2005; accepted March 22, 2005 An ante-iso type regio-isomer on the long chain base moiety of a glucocerebroside, HLC-2-A, has been isolated from its parent glucocerebroside molecular species HLC-2 composed of ...