New triterpene glycosides, cucumariosides H₂ (1), H₃ (2) and H₄ (3), have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. The structures of 1-3 were elucidated using extensive NMR spectroscopy (¹H- and ¹³C-NMR, DEPT, ¹H-¹H COSY, 1D TOCSY, H2BC, HMBC, heteronuclear single-quantum coherence, and NOESY) and ESI-MS. Glycosides 1-3 are monosulphated branched pentaosides having rare 3-O-methyl-D-xylose as a terminal monosaccharide. Glycosides 1 and 3 contain holostane aglycones, whereas 2 has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone, which is also uncommon for the sea cucumbers. Glycoside 3 contains a very rare ethoxyl radical at C-25 of the aglycone side chain, and it is most probably an artefact that was formed during long storage of the ethanolic extract. Cytotoxic activities of 1-3 against mouse spleen lymphocytes, haemolytic activity against mouse erythrocytes and Ehrlich carcinoma cells have been studied. The presence of 25-hydroxy group in aglycone moiety significantly decreased the activities.
New steroidal oligoglycosides mycalosides B-I (2-9) have been isolated from the polar extract of the Caribbean sponge Mycale laxissima, and their structures have been elucidated by 1D and 2D NMR ((1)H, (13)C, DEPT, COSY-45, COSY-RCT, HSQC, HMBC, and NOESY spectra) and MALDI-TOF mass spectrometry. Mycalosides B (2) and C (3) were shown to be 27- and 28-nor derivatives of the previously known tetraoside mycaloside A (1). Mycaloside D (4) differs from 1 only in the presence of an additional acetyl group in the carbohydrate moiety. Mycaloside E (5) was structurally identified as a 28-nor-4-dehydroxy derivative of 1. Mycalosides F-H (6-8), differing from each other by the structures of their side chains and nonacetylated (7, 8) or acetylated (6) tetrasaccharide carbohydrate moieties, have new 5(6)-unsaturated 3 beta,4 beta,21-trihydroxy-15-keto-steroidal aglycons. Mycaloside I (9) is a tetraoside of a new 7,24(28)-diunsaturated 3beta,15 beta,29-trihydroxystigmastane aglycon. It was established that the total fraction of the mycalosides as well as mycalosides A (1) and G (7) inhibit the fertilization of eggs by sperm of the sea urchin Strongylocentrotus nudus preincubated with these compounds.
The new triterpene glycoside koreoside A (1) has been isolated from the sea cucumber Cucumaria koraiensis. Koreoside A (1) is the first glycoside reported from holothurians that presents a delta(7) nonholostane aglycon without a lactone group and with a shortened side chain. Its structure has been elucidated by 13C and 1H NMR as well as FABMS studies.
Three new minor triterpene glycosides, cucumariosides I 1 (1), I 3 (2) and I 4 (3) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1-3 belong to the group of cucumariosides I, having branched pentasaccharide carbohydrate moieties with two sulfate groups and possessing 3-O-methyl-D-xylose as a terminal monosaccharide unit that is a characteristic feature of all the glycosides isolated from E. fraudatrix. Glycosides 1 and 2 differ from each other by the side chain structures in the holostane aglycone moieties, while cucumarioside I 4 (3) has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone. Cytotoxic activities of glycosides 1-3 against mouse spleen lymphocytes and ascite form of mouse Ehrlich carcinoma cells, along with hemolytic activity against mouse erythrocytes and antifungal activity were studied. Glycoside 1, having an aglycone side chain with a 24(25)-double bond, possesses moderate activity in all the tests, while glycoside 2, having 23(24)-double bond and 25-hydroxy group in the side chain, and glycoside 3 with an aglycone with an 18(16)-lactone and shortened side chain have either low activity or are non-active.
Triterpene glycosides of three species of the Mediterranean sea cucumbers Holothuria polii, Holothuria tubulosa, and Holothuria sp. were studied. Three new monosulfated biosides, holothurins B(2) (1), B(3) (2), and B(4) (3), along with the previously known holothurins A (4) and B (5) were isolated from the sea cucumber H. polii. Triterpene glycosides belonging to holothurin A and B groups were found in H. tubulosa, while only one individual glycoside, holothurin A (4), was isolated from Holothuria sp. Structures of new substances were elucidated on the basis of spectral data (2D NMR and MS). The significance of holothurins as chemotaxonomic markers of the animals belonging to the genus Holothuria and taxonomic status of some representatives of the holothurians studied are discussed.
Seven new minor triterpene glycosides, cucumariosides A 1 (1), A 3 (2), A 4 (3), A 5 (4), A 6 (5), A 12 (6) and A 15 (7) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1-7 belong to the group of cucumariosides A, having linear tetrasaccharide carbohydrate moieties without any sulfate group and possessing 3-O-methyl-D-xylose as a terminal monosaccharide unit. The latter peculiarity is rare in sea cucumber glycosides, but typical for the glycosides from E. fraudatrix. Glycosides 1-7 differ from each other by side chain structures in the aglycone moieties; three of them have unique structural features. The first is the presence of a 25-butoxy-group in the side chain of cucumarioside A 3 (2), the second is a 23E,25-diene system in cucumarioside A 6 (5) and the third is a 25-keto-27-nor-holostane aglycone in cucumarioside A 12 (6); these were never previously found in sea cucumber glycosides. Cytotoxic activity of glycosides 1-7 against mouse spleen lymphocytes and the cells of the ascite form of mouse Ehrlich carcinoma, along with hemolytic activity against mouse erythrocytes and antifungal activity were studied. Glycosides 1 and 5 were the most active in all the tests.
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