New polyoxygenated briarane diterpenoids, briaexcavatolides O-R, from the gorgonian Briareum excavatum.

Four new polyoxygenated briarane-type diterpenoids, briaexcavatolides O-R (1-4), have been isolated from a gorgonian octocoral Briareum excavatum. Their structures were determined using spectroscopic and chemical methods. Metabolites 1-3 were found to contain oxygenated substituents at C-2, C-3, and C-4, and the relative configurations were assigned as 2R*,3R*,4R* at these three positions. Briaranes containing this type of stereochemistry are reported for the first time. The structures of metabolites 1 and 2 were further confirmed by single-crystal X-ray analyses. Compound 2 has been shown to exhibit significant cytotoxicity toward P-388 and HT-29 cancer cells.

Junceol A, a new sesquiterpenoid from the sea pen Virgularia juncea.

A new sesquiterpenoid, junceol A(1), as well as two known diterpenoids, sclerophytin A (2) and cladiellisin (3), have been isolated from the sea pen octocoral Virgularia juncea. The structure of metabolite 1 was determined by extensive spectral analysis. Compounds 1-3 have been shown to exhibit cytotoxicity toward P-388 cancer cells.

Briaexcavatolides K-N, new briarane diterpenes from the gorgonian Briareum excavatum.

Four new briarane diterpenes, briaexcavatolides K-N (1-4), along with a known diterpene, 5, have been isolated from the Taiwanese gorgonian Briareum excavatum. The structures of the new metabolites were established by extensive spectral analyses. Furthermore, the structure, including the relative configuration of briaexcavatolide K (1), was confirmed by a single-crystal X-ray analysis. Briaexcavatolides K and L (1 and 2) are the only briarane diterpenes known to possess hydroxyl groups at the C-8beta and C-17alpha positions, respectively. Cytotoxicity of these metabolites toward various cancer cell lines also is described.

Junceellolides E-G, new briarane diterpenes from the West Pacific Ocean gorgonian Junceella fragilis.

Three new diterpenes, junceellolides E-G (1-3), along with an unnamed known diterpene 4, possessing the briarane carbon skeleton, have been isolated from the gorgonian Junceella fragilis collected in Taiwanese tropical waters. The structures of the new metabolites 1-3 were elucidated by extensive spectral analyses. The six-membered rings in junceellolides E and F (1 and 2) were found to exist in boat conformations. The structure, including the relative configuration of junceellolide E (1) was further confirmed by a single-crystal X-ray analysis.

A cytotoxic 5alpha,8alpha-epidioxysterol from a soft coral Sinularia species.

A new sterol, (22R,23R,24R)-5alpha,8alpha-epidioxy-22, 23-methylene-24-methylcholest-6-en-3beta-ol (1), as well as two known sterols, numersterol A (2) and pregnenolone (3), have been isolated from a soft coral Sinularia sp. The structure of metabolite 1 was determined by spectral analysis. Cytotoxicity of sterols 1-3 toward various cancer cell lines is also reported.

New cytotoxic sesquiterpenes from the gorgonian Isis hippuris.

Five new suberosane sesquiterpenes, suberosenol A (1), suberosenol B (2), suberosanone (3), suberosenol A acetate (4), and suberosenol B acetate (5), along with the known sesquiterpene subergorgic acid (6), have been isolated from the gorgonian Isis hippuris. The structures of these metabolites were established by spectroscopic and chemical methods. Metabolites 1 and 3-5 were found to exhibit potent cytotoxicity toward P-388, A549, and HT-29 cancer cell lines.

Structures and cytotoxicity relationship of isoaaptamine and aaptamine derivatives.

A series of 9-O-acylisoaaptamine (3-14) and 4-N-acyl-dihydroaaptamine (16-19) derivatives have been prepared and evaluated for antitumor activity against murine P-388 and human tumor cells including KB16, A549, and HT-29 cell lines. All of compounds showed significant cytotoxicity against P-388 cells. Among them, compounds 9-11 showed potent activity as isoaaptamine (1). There was an apparent lack of linear relationship between cytotoxicity and carbon number of the side chain. The structure and activity relationship for these particular compounds are discussed.

Bioactive sesquiterpenes from a Taiwanese marine sponge Parahigginsia sp.

Five new sesquiterpenes, parahigginols A-D (1-4) and parahigginic acid (5), have been isolated from a Taiwanese marine sponge Parahigginsia sp. The structural assignments of the new compounds were based on their spectral data, including 1D and 2D NMR. Biological studies revealed that compounds 2-5 exhibited cytotoxicity against murine P-388 and human KB16, A549, and HT-29 tumor cells.

New cytotoxic oxygenated fucosterols from the brown alga Turbinaria conoides.

Fucosterol (1), 24xi-hydroperoxy-24-vinylcholesterol (2), 29-hydroperoxystigmasta-5,24(28)-dien-3beta-ol (3), 24-ethylcholesta-4,24(28)-dien-3-one (4), 24xi-hydroperoxy-24-ethylcholesta-4,28(29)-dien-3-one (5), 24-ethylcholesta-4,24(28)-dien-3,6-dione (6), 24xi-hydroperoxy-24-ethylcholesta-4,28(29)-dien-3,6-di one (7), 6beta-hydroxy-24-ethylcholesta-4,24(28)-dien-3-one (8), and 24xi-hydroperoxy-6beta-hydroxy-24-ethylcholesta-4,28(2 9)-dien-3-one (9) were isolated from the marine brown alga Turbinaria conoides. The structures of these compounds were established by spectral analysis. Isolated for the first time from a natural source, the oxygenated fucosterols 4-9 exhibit cytotoxicity against various cancer cell lines.

Excavatolides F-M, new briarane diterpenes from the gorgonian Briareum excavatum.

Eight new briarane-type diterpenes, excavatolides F-M (1-8), have been isolated from the gorgonian Briareum excavatum. The structures and relative stereochemistry of these compounds were established by spectral analysis and chemical methods. The cytotoxicity of these compounds toward various cancer cell lines has also been determined.

Cytotoxic sterols from the soft coral Nephthea erecta.

Two new cytotoxic sterols, 24-methylcholesta-5,24(28)-diene-3beta, 15beta,19-triol (1) and 24-methylcholesta-5,24(28)-diene-3beta, 19-diol-7-one (2), as well as four cytotoxic sterols, 24-methylcholesta-5,24(28)-diene-3beta,19-diol (3), 24-methylcholesta-5,24(28)-diene-3beta,19-diol-7beta-mono aetate (4), 24-methylcholesta-5,24(28)-diene-3beta,7beta,19-triol (5), and 24-methylcholesta-24(28)-ene-3beta,5alpha,6beta,19-tet raol (6), have been isolated from the soft coral Nephthea erecta. The structures of compounds 1 and 2 were determined by spectral analysis.

Novel cytotoxic diterpenes, excavatolides A-E, isolated from the Formosan gorgonian Briareum excavatum.

The chemistry of Briareum excavatum, a Formosan gorgonian coral, was investigated. This study has led to the isolation of five novel marine natural products, excavatolides A-E (1-5), together with brianolide (6). The structures of the above compounds were established by spectral and chemical methods. The relative configuration of excavatolide B (2) was further confirmed by a single-crystal X-ray structure analysis. Cytotoxicity of these compounds toward various cancer cell lines also is described.

Novel cytotoxic cembranoids from the soft coral Sinularia flexibilis.

Three new cytotoxic cembranoid diterpenes, sinuflexolide (1), dihydrosinuflexolide (2), and sinuflexibilin (3), have been isolated from the soft coral Sinularia flexibilis. The structures of compounds 1-3 were determined by spectral and X-ray crystallographic analysis.

Study on cytotoxic oxygenated desmosterols isolated from the red alga Galaxaura marginata.

Four novel oxygenated desmosterols, 24 zeta-hydroperoxy-6 beta-hydroxycholesta-4,25-dien-3-one (1), 25-hydroperoxy-6 beta-hydroxycholesta-4,23(E)-dien-3-one (2), 24 zeta-hydroperoxycholesta-4,25-diene-3,6-dione (3), and 25-hydroperoxycholesta-4,23(E)-diene-3,6-dione (4) were isolated from the marine red alga Galaxaura marginata. Steroids 1-4 and three synthetic oxygenated desmosterols 5-7 were shown to exhibit significant cytotoxicity against several cancer cell lines.

Cytotoxic sterols from the formosan brown alga Turbinaria ornata.

Two hydroperoxysterols 24-hydroperoxy-24-vinyl-cholesterol (1) and 29-hydroperoxystigmasta-5,24(28)-dien-3beta-ol (2), and fucosterol (3) were isolated from the brown alga Turbinaria ornata (Sargassaceae). Hydroperoxide 2 is a new natural compound and was converted into 29-hydroxystigmasta-5,24 (28)-dien-3beta-ol (4) by reaction with LAH. Sterols 1, 2, and 4 exhibited cytotoxicity against various cancer cell lines.

Cytotoxic oxygenated desmosterols of the red alga Galaxaura marginata.

Desmosterol (1), 24,25-epoxycholesterol (2), 24-hydroperoxycholesta-5,25-dien-3 beta-ol (3), 25-hydroperoxycholesta-5,23(E)-dien-3 beta-ol (4), cholesta-5,25-diene-3 beta,24-diol (5), and 24,25-epoxy-6 beta-hydroxycholest-4-en-3-one (7) were isolated from the marine red alga Galaxaura marginata; sterols 3, 4, and 7 were isolated for the first time from a natural source. Sterols 3-7 exhibited significant cytotoxicity toward several cancer cell lines.