New Sphingolipids and a Sterol from a Lobophytum Species of the Indian Ocean

Abstract

As part of our continuous search for bioactive metabolites from marine organisms, [2][3][4][5][6] we have investigated a soft coral species belonging to the genus Lobophytum collected from the Indian Ocean. Earlier studies of the genus Lobophytum led to the isolation of several sesquiterpenoids, cembrane and lobane diterpenes, sterols and sphingolipids. 7,8) Several compounds from this genus showed cytotoxic, [9][10][11] anti-HIV, 12) antibacterial, 13) and ichthyotoxic [14][15][16][17] activities. In this paper we report the isolation and structural elucidation of three new sphingolipids and a sterol along with cytotoxic activity of a known sphingolipid isolated from the organism.Sphingolipids exist widely in the eukaryotic cell membranes of both terrestrial and marine organisms.18) Sphingolipids attracted much attention in recent years due to their involvement in various cellular processes including cell growth, survival, differentiation, and adhesion. 19,20) Results and DiscussionRepeated column chromatography of EtOAc solubles of the methanolic extract of the organism followed by purification by medium pressure liquid chromatography (MPLC) afforded compounds 1-5 as colourless solids. The IR spectra of 1-3 suggested the presence of hydroxyl and amide groups while the UV spectra had no characteristic signals above 210 nm. Close examination of 1 H-and 13 C-NMR spectra of 1-3 (Table 1) revealed the presence of NH, carbonyl, end methyls and long aliphatic chain suggesting sphingolipid skeleton. . The stereochemistries at C-2, C-3 and C-2Ј were assigned 2S, 3R and 2ЈR by comparing the NMR and optical rotation data with those of natural and synthetic sphingolipids. [24][25][26][27] The geometry of the double bonds was taken as trans (4E,8E) on the basis of large coupling constants (15.3, 15.0 Hz). Chemical investigation of a soft coral species of the genus Lobophytum has resulted in the isolation of three new sphingolipids- (2S,3S,4R)-2-nonadecanoylamino-octadecane-1,3,4-triol (1), (2S,3R,4E,8E)

Isolation and Enzyme‐Inhibition Studies of the Chemical Constituents from Ajuga bracteosa

“…1 þ ) in the EI-MS [16]. Methanolysis [7] of 1 with methanolic HCl gave the base and the methyl ester of the long-chain hydroxy acid. After acetylation [7] and subsequent GC/MS, the two fragments could be identified as 2-acetoxydodecanoate (m/z 272) and 2-acetamino-1,3,4-triacetoxytriacont-5-ene (m/z 651).…”

“…Methanolysis [7] of 1 with methanolic HCl gave the base and the methyl ester of the long-chain hydroxy acid. After acetylation [7] and subsequent GC/MS, the two fragments could be identified as 2-acetoxydodecanoate (m/z 272) and 2-acetamino-1,3,4-triacetoxytriacont-5-ene (m/z 651). It has been previously reported in literature that both the optical rotation and chemical shifts of the H-atoms attached to the stereogenic C-atoms provide a strong evidence for the absolute configuration of sphingolipids.…”

“…The length of the base was also determined by the characteristic ion at m/z 269 ([M À CH 3 (CH 2 ) 23 [20]. Methanolysis [7] of 2 yielded a fatty acid methyl ester, a sphingosine base, and a methylated sugar moiety. Both the methyl ester and the base on acetylation [7], and subsequent GC/MS could be identified as methyl 2-acetoxyhexacosanoate (m/z 468) and 2-(acetamino)-1,3,4,15-tetracetoxypentadeca-5,8-diene (m/z 497).…”

“…Methanolysis [7] of 2 yielded a fatty acid methyl ester, a sphingosine base, and a methylated sugar moiety. Both the methyl ester and the base on acetylation [7], and subsequent GC/MS could be identified as methyl 2-acetoxyhexacosanoate (m/z 468) and 2-(acetamino)-1,3,4,15-tetracetoxypentadeca-5,8-diene (m/z 497). The glycone from the aqueous layer was identified as methyl b-d-glucopyranoside by comparing the sign of its optical rotation and spectral data with those of an authentic sample [17] [18].…”

Cytotoxic Steroids from the Vietnamese Soft Coral <i>Sinularia leptoclados</i>

“…1) were isolated from a methanol extract of the soft coral S. leptoclados. The known compounds, 7-oxogorgosterol (3), 6) crassumsterol (4), 9) 7β-hydroxygorgosterol (5), 10) sarcophytosterol (6), 11) 3β-hydroxyergosta-5-ene-7-one (7), 12) ergost-5-en-3β,7β-diol (8), 13) ergost-5-en-3β,7α-diol (9), 14,15) ergosta-5,24(28)-diene-3β-ol (10), 16) 3β-hydroxyergost a-5,24(28)-diene-7-one (11), 17,18) ergosta-5,22,24(28)-trien-3β-ol (12), 19) 3β,7β-dihydroxyergosta-5,24(28)-diene (13), 20) 3β,7α-di hydroxyergosta-5,24(28)-diene (14), 20) and 3β,4α-dihydroxyergosta-5,24(28)-diene (15), 7) were identified by detailed analysis of their one and two dimensional (1-and 2D)-NMR and MS data as well as comparison of them with those reported in the literatures. Pos.…”