Cytotoxic and antimalarial beta-carboline alkaloids from the roots of Eurycoma longifolia

Three new [n-pentyl beta-carboline-1-propionate (1), 5-hydroxymethyl-9-methoxycanthin-6-one (2), and 1-hydroxy-9-methoxycanthin-6-one (3)] and 19 known beta-carboline alkaloids were isolated from the roots of Eurycoma longifolia. The new structures were determined by comprehensive analyses of their 1D and 2D NMR and mass spectral data and by chemical transformation. These compounds were screened for in vitro cytotoxic and antimalarial activities, and 9-methoxycanthin-6-one (4) and canthin-6-one (5) demonstrated significant cytotoxicity against human lung cancer (A-549) and human breast cancer (MCF-7) cell lines.     

Cytotoxic and antimalarial constituents of the roots of Eurycoma longifolia.

By bioactivity-directed fractionation, five cytotoxic constituents have been characterized from the roots of Eurycoma longifolia collected in Kalimantan, Indonesia. Four canthin-6-one alkaloids, namely, 9-methoxycanthin-6-one, 9-methoxycanthin-6-one-N-oxide, 9-hydroxycanthin-6-one, and 9-hydroxycanthin-6-one-N-oxide, and one quassinoid, eurycomanone, were found to be cytotoxic principles. Each of these compounds was evaluated against a panel of cell lines comprising a number of human cancer cell types [breast, colon, fibrosarcoma, lung, melanoma, KB, and KB-V1 (a multi-drug resistant cell line derived from KB)] and murine lymphocytic leukemia (P-388). The canthin-6-ones 1-4 were found to be active with all cell lines tested except for the KB-V1 cell line. Eurycomanone was inactive against murine lymphocytic leukemia (P-388) but was significantly active against the human cell lines tested. Two additional isolates, the beta-carboline alkaloids beta-carboline-1-propionic acid and 7-methoxy-beta-carboline-1-propionic acid, were not significantly active with these cultured cells. However, compounds 5 and 7 were found to demonstrate significant antimalarial activity as judged by studies conducted with cultured Plasmodium falciparum strains. The structures of the novel compounds 2-4 and 7 were established by spectral and chemical methods.     

Production of cytotoxic canthin-6-one alkaloids by Ailanthus altissima plant cell cultures

Ailanthus altissima (Mill.) Swingle was established as callus- and cell-suspension cultures. Canthin-6-one and 1-methoxycanthin-6-one were isolated by a combination of preparative tlc and preparative hplc. The two alkaloids were identified by their uv, ms, and 1H-nmr spectra. The combined yield of the two alkaloids was 1.38% of dry weight from callus and 1.27% of dry weight from cell suspensions. The cytotoxicities of canthin-6-one, 1-methoxycanthin-6-one, 5-methoxycanthin-6-one, and canthin-6-one-3-N-oxide to guinea pig ear keratinocytes have been compared, and the IC50 values range from 1.11 to 5.76 micrograms/ml. There is no significant difference in activity among these four cytotoxic alkaloids.     

苦树化学成分研究

目的:对苦木科苦树属植物苦树Picrasma quassioides的化学成分进行研究.方法:采用各种柱色谱和重结晶等技术进行分离纯化,综合运用紫外光谱(UV)、红外光谱(IR)、质谱(MS)及核磁共振光谱(1H-NMR,13C-NMR)等现代波谱学方法和技术进行化合物的结构鉴定.结果:从苦树中鉴定得到了14个化合物,分别为高丽槐素-3-O-β-D-葡萄糖苷(1),maack-iain(2),3',7-二羟基4-甲氧基异黄酮(3),7-羟基香豆素(4),大黄素(5),nigakilactone F(6),picrasin B(7),picraquaGde B(8),4-甲氧基-5-羟基-铁屎米-6-酮(9),4,5-二甲氧基-铁屎米-6-酮(10),5-甲氧基-铁屎米-6-酮(11),11-羟基-铁屎米-6-酮(12),1-甲氧甲酰基-β-咔巴啉(13),1-羟甲基-β-咔巴啉(14).结论:化合物1-5在苦树属中为首次报道.     

Effects of canthin-6-one alkaloids from Zanthoxylum chiloperone on Trypanosoma cruzi-infected mice

Canthin-6-one (1), isolated from Zanthoxylum chiloperone (Rutaceae), possesses a broad sprectum of antifungal and leishmanicidal activities. In this study, we have examined the antiparasitic effects of canthin-6-one (1), 5-methoxycanthin-6-one (2), canthin-6-one N-oxide (3), as well as that of the total alkaloids of Zanthoxylum chiloperone stem bark, in Balb/c mice infected either acutely or chronically with Trypanosoma cruzi. The compounds were administered orally or subcutaneously at 5mg/kg/day for 2 weeks, whereas the alkaloidal extract was given at 50mg/kg/day for 2 weeks. The antiparasitic activity was compared with that of benznidazole given at 50mg/kg/day for 2 weeks. In the case of acute infection, parasiteamia was significantly reduced following oral treatment with canthin-6-one (1). Moreover, the total alkaloids of Zanthoxylum chiloperone stem bark led to high levels of parasitological clearance. Seventy days post-infection, the serological response in the acute model was significantly different between oral canthin-6-one (1) and benznidazole-treated mice. Chronic model of the disease showed that both canthin-6-one (1) and the alkaloidal extract at the above dosage induced 80-100% animal survival compared to untreated controls. These results indicate that canthin-6-one (1) exhibits trypanocidal activity in vivo in the mouse model of acute or chronic infection. This is the first demonstration of anti-Trypanosoma cruzi activity for a member of this chemical group (canthinones). Considering the very low toxicity of canthin-6-one (1), our results suggest that long-term oral treatment with this natural product could prove advantageous compared to the current chemotherapy of Chagas disease.     

Bromophenol derivatives from the red alga Rhodomela confervoides

Eight new bromophenol derivatives, 2,3-dibromo-4,5-dihydroxybenzyl methyl sulfoxide (1), 4-(2,3-dibromo-4,5-dihydroxyphenyl)-3-butene-2-one (2), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid (3), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid methyl ester (4), 2-phenyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid (5), 4'-methoxy-2',3',3'-tribromo-4',5',5'-trihydroxydiphenylacetic acid (6), and 3-bromo-5-hydroxy-4-methoxyphenylacetic acid (7) and its methyl ester (8), together with a known bromophenol, 3-bromo-5-hydroxy-4-methoxybenzoic acid (9), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by spectroscopic methods including IR, EIMS, FABMS, ESIMS, HRFABMS, HRESIMS, 1D and 2D NMR, and single-crystal X-ray structure analysis. Compounds 1-4, 8, and 9 were found inactive against several human cancer cell lines and microorganisms.     

Leishmanicidal activity of two canthin-6-one alkaloids,two major constituents of Zanthoxylum chiloperone var. angustifolium

The crude alkaloidal extract of Zanthoxylum chiloperone stem bark exhibited in vitro activity against various strains of Leishmania ssp. at 100 μg/ml. Two active major constituents were isolated and identified as canthin-6-one and 5-methoxycanthin-6-one. The effect of these compounds was also tested in an in vivo assay using BALB/c mice infected with Leishmania amazonensis. The mice were treated for 5 weeks postinfection with these alkaloids by oral (14 days) or intralesional route (4 days) at 10 mg/kg daily. The reference drug, N-methylglucamine antimonate was administered by subcutaneous injections at 100 mg/kg for 10 days. Intralesional administration of canthin-6-one reduced the parasite burden but not significantly when it was compared with the untreated group, while the reference drug reduced by 91% the parasite loads in the lesion.     

Cytotoxic effects of the root extracts of Eurycoma longifolia Jack

The methanol, n-butanol, chloroform and water extracts obtained from the root of Eurycoma longifolia Jack were assayed using methylene blue assay to evaluate its cytotoxic effect against KB, DU-145, RD, MCF-7, CaOV-3, MDBK cell lines. The results showed that all the root extracts except the water extract of E. longifolia produced significant cytotoxic effect on these cell lines. However, no significant cytotoxic effect was detected on MDBK (kidney) normal cell line. 9-methoxycanthin-6-one, an alkaloid, was detected in each extract with different intensities by reversed-phase high performance liquid chromatography.     

Norsesquiterpenes from the brown alga Dictyopteris divaricata

Three bisnorsesquiterpenes (1-3) with novel carbon skeletons and a norsesquiterpene (4) have been isolated from the brown alga Dictyopteris divaricata. By means of spectroscopic data including IR, HRMS, 1D and 2D NMR techniques, single-crystal X-ray diffraction, and CD, their structures including absolute configurations were proposed as (+)-(1R,6S,9R)-1-hydroxyl-6-isopropyl-9-methylbicyclo[4.3.0]non-4-en-3-one (1), (-)-(1S,6S,9R)-1-hydroxyl-6-isopropyl-9-methylbicyclo[4.3.0] non-4-en-3-one (2), (+)-(5S,6R,9S)-5-hydroxyl-6-isopropyl-9-methylbicyclo[4.3.0]non-1-en-3-one (3), and (-)-(1R,7S,10R)-1-hydroxy-11-norcadinan-5-en-4-one (4). Biogenetically, the carbon skeleton of 1-3 may be derived from the co-occurring cadinane skeleton by ring contraction and loss of two carbon units, and compound 4 from the oxidation of cadinane derivatives. Compounds 1-4 were inactive (IC50 > 10 microg/mL) against several human cancer cell lines including lung adenocarcinoma (A549), stomach cancer (BGC-823), breast cancer (MCF-7), hepatoma (Bel7402), and colon cancer (HCT-8) cell lines.     

Dibenzyl bromophenols with diverse dimerization patterns from the brown alga Leathesia nana

Six novel dibenzyl bromophenols (1-6) with different dimerization patterns and two propyl bromophenol derivatives (7 and 8), together with 11 known bromophenol derivatives, were isolated from the ethanolic extract of the brown alga Leathesia nana. On the basis of spectroscopic methods the structures of the new compounds were determined as 5,6'-diethyloxymethyl-3,4,2'-tribromo-2,3',4'-trihydroxydiphenyl ether (1), 2-(2,3-dibromo-4,5-dihydroxybenzyl)-3,5-dihydroxy-4-methoxybenzyl alcohol (2), 6-(2,3-dibromo-4,5-dihydroxybenzyl)-2,3-dibromo-4,5-dihydroxy benzyl methyl ether (3), 9,10-dihydro-9,10-dimethoxy-3,4,7,8-tetrabromo-1,2,5,6-tetrahydroxyanthracene (4), (+)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroisobenzofuran (5), rel-(4aS,10aR)-(+/-)-6,7-dibromo-4a-hydroxy-3,8-dihydroxymethyl-10a-methoxy-1,4,4a,10a-tetrahydrodibenzo[b,e][1,4]dioxin-1-one (6), (E)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propenal (7), and 2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)-1-propanol (8). Some compounds including 3 showed in vitro selective cytotoxicity against several human cancer cell lines. This is the first brown alga to be reported containing bromophenols.     

Mono-, Bi-, and triphenanthrenes from the tubers of Cremastra appendiculata

Six newphenanthrene derivatives, including three monophenanthrenes (1-3), two biphenanthrenes (4 and 5), and a triphenanthrene (6), have been isolated from an ethanolic extract of the tubers of Cremastra appendiculata. Using spectroscopic methods, the structures of compounds 1-6 were determined as 1-hydroxy-4,7-dimethoxy-1-(2-oxopropyl)-1H-phenanthren-2-one (1), 1,7-dihydroxy-4-methoxy-1-(2-oxopropyl)-1H-phenanthren-2-one (2), 2-hydroxy-4,7-dimethoxyphenanthrene (3), 2,7,2'-trihydroxy-4,4',7'-trimethoxy-1,1'-biphenanthrene (4), 2,2'-dihydroxy-4,7,4',7'-tetramethoxy-1,1'-biphenanthrene (5), and 2,7,2',7',2' '-pentahydroxy-4,4',4' ',7' '-tetramethoxy-1,8,1',1' '-triphenanthrene (6), respectively. Compounds 1-6 and two known compounds, cirrhopetalanthin (7) and flavanthrinin (8), obtained previously from this plant, were evaluated against six human cancer cells and a normal cell line.     

Antineoplastic agents. 522. Hernandia peltata (Malaysia) and Hernandia nymphaeifolia (Republic of Maldives)

Bioassay (P388 lymphocytic leukemia cell line and human tumor cell lines)-guided separation of the extracts prepared from the tropical and coastal trees Hernandia peltata (Malaysia) and Hernandianymphaeifolia (Republic of Maldives) led to the isolation of a new lignan designated as hernanol (1) and 12 previously known lignans: (-)-deoxypodophyllotoxin (2), deoxypicropodophyllin (3), (+)-epiaschantin (4), (+)-epieudesmin (5), praderin (6), 5'-methoxyyatein (7), podorhizol (8), deoxypodorhizone (9), bursehernin (10), kusunokinol (11), clusin (12), and (-)-maculatin (13). The oxidative cyclization (with VOF(3)) of lignans 8, 9, and 10 resulted in a new and unusual benzopyran (14), isostegane (15), and a new dibenzocyclooctadiene lactone (16), respectively. The structure and relative stereochemistry of hernanol (1) and lignans 3, 7, 8, 9, 10, 11, and 12 were determined by 1D and 2DNMR and HRMS analyses. The structures and absolute stereochemistry of structures 2, 4, 5, 6, 13, 14, 15, and 16 were unequivocally determined by single-crystal X-ray diffraction analyses. Evaluation against the murine P388 lymphocytic leukemia cell line and human tumor cell lines showed podophyllotoxin derivatives 2 and 3 to be strong cancer cell line growth inhibitors and substances 4, 5, 8, and 15 to have marginal cancer cell line inhibitory activities. Seven of the lignans and one of the synthetic modifications (14) inhibited growth of the pathogenic bacterium Neisseria gonorrhoeae.     

Antifungal compounds from Zanthoxylum chiloperone var. angustifolium

An alkaloidal extract of the stem barks of Zanthoxylum chiloperone var. angustifolium exhibited antifungal activity against Candida albicans, Aspergillus fumigatus and Trichophyton mentagrophytes var. interdigitale using a TLC bioautographic method. Bioassay-guided fractionation of this extract resulted in the isolation of two active compounds identi fi ed as canthin-6-one and 5-methoxycanthin-6-one. Canthin-6-one exhibited a broad spectrum of activities against Aspergillus fumigatus, A. niger, A. terreus, Candida albicans, C. tropicalis, C. glabrata, Cryptococcus neoformans, Geotrichum candidum, Saccharomyces cerevisiae, Trichosporon beigelii, Trichosporon cutaneum and Trichophyton mentagrophytes var. interdigitale with MICs values between 5.3 and 46 micro mol/L. 5-methoxy-canthin-6-one was active against only Trichophyton mentagrophytes var. interdigitale with a MIC value of 12.3 micro mol/L.     

Bromophenols coupled with methyl gamma-ureidobutyrate and bromophenol sulfates from the red alga Rhodomela confervoides

Four new bromophenols C-N coupled with methyl gamma-ureidobutyrate (1-4), a phenylethanol bromophenol (5), and three phenylethanol sulfate bromophenols (6-8) have been isolated from polar fractions of an ethanolic extract of the red alga Rhodomela confervoides. On the basis of spectroscopic evidence including HRMS and 2D NMR data, the structures of the new compounds were determined as methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (1), methyl N,N'-bis(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (2), methyl N'-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (3), methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-N'-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (4), 2,3-dibromo-4,5-dihydroxyphenylethanol (5), 2,3-dibromo-4,5-dihydroxyphenylethanol sulfate (6), 3-bromo-4,5-dihydroxyphenylethanol sulfate (7), and 3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxyphenylethanol sulfate (8). The cytotoxicity of all compounds was evaluated against several human cancer cell lines including human colon cancer (HCT-8), hepatoma (Bel7402), stomach cancer (BGC-823), lung adenocarcinoma (A549), and human ovarian cancer (A2780). Among them, the phenylethanol and the phenylethanol sulfate bromophenols (5-8) showed moderate cytotoxicity against all tested cell lines.     

Phelligridins C-F: cytotoxic pyrano[4,3-c][2]benzopyran-1,6-dione and furo[3,2-c]pyran-4-one derivatives from the fungus Phellinus igniarius

Three unique pyrano[4,3-c][2]benzopyran-1,6-dione derivatives and a new furo[3,2-c]pyran-4-one, named phelligridins C-F (2-5), together with hispolon (8), (E)-4-(3,4-dihydroxyphenyl)but-3-en-2-one (9), 4-hydroxybenzaldehyde, protocatechualdehyde, syringic acid, protocatechuic acid, caffeic acid, isoergosterone, and octadecyl ferulate were isolated and identified from the ethanolic extract of Phellinus igniarius. Their structures were determined by spectroscopic methods including IR, MS, and 1D and 2D NMR experiments. The structures of the new compounds were characterized as 3-(4-hydroxystyryl)-8,9-dihydroxypyrano[4,3-c]isochromene-4-one (2), 3-(3,4-hydroxystyryl)-8,9-dihydroxypyrano[4,3-c]isochromene-4-one (3), 8,9-dihydroxy-3-[5',6'-dihydroxy-5' '-methyl-3' '-oxo-spiro[fural-2' '(3' 'H),1'-indene]-2'-yl]-1H,6H-pyrano[4,3-c][2]benzopyran-1,6-dione (4), and (3Z)-3-(3,4-dihydroxybenzylidene)-6-(3,4-dihydroxystyryl)-2,3-dihydro-2-methoxy-2-(2-oxo-propyl)furo[3,2-c]pyran-4-one (5), respectively. Some compounds including 2 and 3 showed in vitro selective cytotoxicity against a human lung cancer cell line (A549) and a liver cancer cell line (Bel7402). Possible biogenetic sequences to the formation of 1-9 are postulated.     

Microbial transformation and butyrylcholinesterase inhibitory activity of (-)-caryophyllene oxide and its derivatives

Microbial transformation of the sesquiterpene (-)-caryophyllene oxide (1) [(1R,4R,5R,9S)-4,5-epoxycaryophyllan-8(13)-ene] by a number of fungi, using a standard two-stage fermentation technique, has afforded as products (1R,4R,5R,9S)-4,5-dihydroxycaryophyllan-8(13)-ene (2), (1S,4R,5R,8S,9S)-clovane-5,9-diol (3), (1R,4R,5R,9S,11R)-4,5-epoxycaryophyllan-8(13)-en-15-ol (4), (1R,4R,5R,9S,11S)-4,5-epoxycaryophyllan-8(13)-en-14-ol (5), (1R,2S,4R,5R,9S)-4,5-epoxy-13-norcaryophyllan-8-one (6), (1R,4R,5R,8S,9S)-4,5-epoxycaryophyllan-13-ol (7), (1R,4R,5R,8S, 9S,13S)-caryolane-5,8,13-triol (8), (1R,3R,4R,5R,8S,9S)-4,5-epoxycaryophyllan-3,13-diol (9), and (1S,4R,5R,8S,9S)-clovane-5,9,12-triol (10). Metabolites 6 and 8-10 were found to be new compounds, as deduced on the basis of spectroscopic techniques. Compounds 1-10 were evaluated for butyrylcholinesterase inhibitory activity, and compound 5 exhibited an IC50 value of 10.9 +/- 0.2 microM.     

Diterpenoids from the roots of Suregada glomerulata

Six new diterpenoids, 7beta,8alpha-dihydroxy-12-oxo- ent-abietan-16,14-olide ( 1), 3,4,18beta-cyclopropa-7beta,17-dihydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 2), 3alpha,7beta-dihydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 3), 3-oxo-8beta,14beta-epoxy- ent-abieta-11,13(15)-dien-16,12-olide ( 4), 17-hydroxy- ent-pimara-8(14),15-dien-3-one ( 5), and 3alpha,6beta-dihydroxy- ent-kaur-16-ene ( 6), and two known compounds, 7beta-hydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 7) and jolkinolide B, were isolated from roots of Suregada glomerulata. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR and other spectroscopic studies. The structure of compound 1 was confirmed by X-ray crystallography. Cytotoxic activities were evaluated against five human tumor cell lines.     

New bisbenzylisoquinolines, fatty acid amidic aporphines, and a protoberberine from Formosan Cocculus orbiculatus

Two new bisbenzylisoquinoline alkaloids, (+)-coccuorbiculatine A (2) and (+)-10-hydroxyisotrilobine (3), two new amidic aporphines, a mixture of (+)-laurelliptinhexadecan-1-one (6) and (+)-laurelliptinoctadecan-1-one (7), and one new protoberberine (-)-4-methoxy-13,14-dihydrooxypalmatine (8) have been isolated from the stems of Taiwanese Cocculus orbiculatus. The structures were established on the basis of extensive analysis of spectroscopic data and by comparison with known related metabolites. Cytotoxicity of the isolated compounds was examined toward HepG2, Hep3B, MCF-7, and MDA-MB-231 cancer cell lines. Alkaloids 1 and (-)-sinococuline (9) showed significant inhibitory activity against the target cell lines.     

Antibacterial activity of two canthin-6-one alkaloids from Allium neapolitanum

The emergence of multidrug-resistant strains of many human pathogens has led to an urgent need for the discovery and development of new antimicrobial agents. As part of an ongoing investigation into the antibacterial properties of the Alliaceae, the isolation of 1 (canthin-6-one), 2 (8-hydroxy-canthin-6-one) and 3 (5(zeta)-hydroxy-octadeca-6(E)-8(Z)-dienioc acid)) from A. neapolitanum, a perennial bulbous herb found in open pastures of the Mediterranean is reported. Compounds 1 and 2 were isolated by Sephadex LH-20 from fractions exhibiting a positive reaction with Dragendorff's reagent on TLC, compound 3 was isolated after HPLC purification of Sephadex fractions. Structures were elucidated by extensive 1D and 2D NMR experiments and are in accordance with published data, however, the 13C NMR data for compound 2 and the 1H and 13C NMR data for compound 3 are reported here for the first time. Canthin-6-one alkaloids are well-known constituents of the Simaroubaceae and Rutaceae, and display a wide range of biological activities. These metabolites are reported as constituents of the Alliaceae here for the first time, and displayed minimum inhibitory concentrations (MICs) in the range 8-32 microg/mL against a panel of fast-growing Mycobacterium species and 8-64 microg/mL against multidrug-resistant (MDR) and methicillin-resistant (MRSA) strains of Staphylococcus aureus. Compound 3 displayed antimycobacterial activity in the range of 16-32 microg/mL.     

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.