Dinoxin B, a withanolide from Datura inoxia leaves with specific cytotoxic activities

A new withanolide, dinoxin B (12,21-dihydroxy-1-oxowitha-2,5,24-trienolide-27-O-β-D-glucopyranoside, 1), was isolated from a methanol extract of Datura inoxia leaves, using bioassay-guided fractionation. The structure was determined by spectroscopic techniques, including (1)H, (13)C, and 2D NMR experiments as well as by HRMS. Extracts and the purified compound were tested for their antiproliferative activities toward a panel of human normal and cancer cell lines. Dinoxin B (1) and its aglycone (2) exhibited submicromolar IC(50) values against multiple human cancer cell lines. Among the most sensitive were several breast cancer cell lines. Dinoxin B (1) was found only in D. inoxia and was not detected in D. metel or D. stramonium. The accumulation of this compound was limited largely to leaf tissue, with little to none detected in extracts from the flowers, fruits, roots, or stems of D. inoxia.     

Isolation, structures, and structure - cytotoxic activity relationships of withanolides and physalins from Physalis angulata

Phytochemical investigation of Physalis angulata was initiated following primary biological screening. Fractionation of CHCl3 and n-BuOH solubles of the MeOH extract from the whole plant was guided by in vitro cytotoxic activity assay using cultured HONE-1 and NUGC cells and led to the isolation of seven new withanolides, withangulatins B-H (1-7), and a new minor physalin, physalin W (8), along with 14 known compounds, including physaprun A, withaphysanolide, dihydrowithanolide E, physanolide A, withaphysalin A, and physalins B, D, F, G, I, J, T, U, and V. New compounds (1-8) were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS) and the relative stereochemical assignments based on NOESY correlations and analysis of coupling constants. Biological evaluation of these compounds against a panel of human cancer cell lines showed broad cytotoxic activity. Withangulatin B (1) and physalins D (10) and F (11) displayed potent cytotoxic activity against a panel of human cancer cell lines with EC50 values ranging from 0.2 to 1.6 microg/mL. Structure-activity relationship analysis indicated that withanolides and physalins with 4beta-hydroxy-2-en-1-one and 5beta,6beta-epoxy moieties are potential cytotoxic agents.     

Discorhabdins I and L, cytotoxic alkaloids from the sponge Latrunculia brevis

Two cytotoxic alkaloids, discorhabdins L (1) and I (2), were isolated from Latrunculia brevis and their structures assigned on the basis of detailed spectroscopic analysis and comparison with the known metabolites discorhabdins R (5), D (6), and B (4). Compounds 1 and 2 showed strong in vitro cytotoxicity against a panel of 14 tumor cell lines.     

Inhibition of tumor cells interacting with stromal cells by xanthones isolated from a Costa Rican Penicillium sp

CR1642D, an endophytic isolate of Penicillium sp. collected from a Costa Rican rainforest, was identified through a high-throughput approach to identify natural products with enhanced antitumor activity in the context of tumor-stromal interactions. Bioassay-guided separation led to the identification of five xanthones (1-5) from CR1642D. The structures of the xanthone dimer penexanthone A (1) and monomer penexanthone B (2) were elucidated on the basis of spectroscopic analyses, including 2D NMR experiments. All of the compounds were tested against a panel of tumor cell lines in the presence and absence of bone marrow stromal cells. Compound 3 was the most active, with IC(50) values of 1-17 μM, and its activity was enhanced 2-fold against tumor cell line RPMI8226 in the presence of stromal cells (IC(50) 1.2 μM, but 2.4 μM without stromal cells).     

Antimalarial β-carboline and indolactam alkaloids from Marinactinospora thermotolerans, a deep sea isolate

Four new β-carboline alkaloids, designated marinacarbolines A-D (1-4), two new indolactam alkaloids, 13-N-demethyl-methylpendolmycin (5) and methylpendolmycin-14-O-α-glucoside (6), and the three known compounds 1-acetyl-β-carboline (7), methylpendolmycin (8), and pendolmycin (9) were obtained from the fermentation broth of Marinactinospora thermotolerans SCSIO 00652, a new actinomycete belonging to the family Nocardiopsaceae. Their structures were elucidated by extensive MS and 1D and 2D NMR spectroscopic data analyses. The structure of compound 1 was further confirmed by single-crystal X-ray crystallography. The new compounds 1-6 were inactive against a panel of eight tumor cell lines (IC50>50 μM) but exhibited antiplasmodial activities against Plasmodium falciparum lines 3D7 and Dd2, with IC50 values ranging from 1.92 to 36.03 μM.     

Antineoplastic agents. 587. Isolation and structure of 3-epipancratistatin from Narcissus cv. Ice Follies

Bioassay-guided (cancer cell line) separation of an extract prepared from Narcissus cv. Ice Follies (from The Netherlands) led to the isolation of a new Amaryllidaceae isocarbostiryl, 3-epipancratistatin (1b), as well as narciclasine (2). This Narcissus cultivar was found to be a good source of narciclasine. The structure of 1b was established by high-resolution mass and high-field 2D NMR spectroscopic analyses. Against a panel of murine and human cancer cell lines, 3-epipancratistatin (1b) led to cell growth inhibition (GI(50) 2.2-0.69 μg/mL) some 100× less than that found for pancratistatin (1a) and narciclasine (2), thereby revealing an important configurational requirement in 1a for strong cancer cell growth inhibition.     

New cytotoxic 1-azaanthraquinones and 3-aminonaphthoquinone from the stem bark of Goniothalamus marcanii.

Guided by brine shrimp toxicity and human tumor cell toxicity, fractionation of the alcoholic extract from the stem bark of Goniothalamus marcanii led to the isolation of four new 1-azaanthraquinones: marcanines B (3), C (4), D (5), and E (6), along with two known derivatives: marcanine A and dielsiquinone. A new 5-hydroxy-3-amino-2-aceto-1,4-naphthoquinone (7), a possible 1-azaanthraquinone biosynthetic precursor, was also isolated. The structures of the compounds were elucidated by spectroscopic analyses, mainly 1D and 2D NMR techniques ((1)H, (13)C, NOEDS, COSY, HMQC, and HMBC), as well as comparison with literature data. All the compounds except 6 were evaluated for cytotoxic activity. They exhibited significant cytotoxicity against several human tumor cell lines, A-549, HT-29, MCF7, RPMI, and U251 with the ED(50) in the range of 0.04-3.03 microM.     

New cytotoxic cembranes from the sea pen Gyrophyllum sibogae

Two new cembrane-type diterpenoids have been isolated from the 2-propanol extract of the sea pen Gyrophyllum sibogae collected in South Africa: 7,8-dihydroflabellatene A (1) and 7,8-dihydroflabellatene B (2). Their structures were determined on the basis of detailed spectroscopic analysis and by single-crystal X-ray analysis of the major metabolite 1, which showed strong in vitro cytotoxicity against a panel of 13 tumor cell lines.     

Antineoplastic agents. 529. Isolation and structure of nootkastatins 1 and 2 from the Alaskan yellow cedar Chamaecyparis nootkatensis

The yellow cedar tree, Chamaecyparis nootkatensis, collected in southeast Alaska was evaluated as a potential source of new anticancer agents. Two new diterpene anticancer constituents termed nootkastatins 1 (4) and 2 (5) were isolated along with three previously known diterpene cancer cell growth inhibitors where two were reported as synthetic modifications of totarol and not previously found in nature. All five diterpene structures were established by HRMS and 1D and 2D NMR spectroscopic analyses combined with three X-ray crystal structure determinations (2, 3, and 5). Against a panel of six human cancer cell lines, this series of diterpenes exhibited inhibition over the range GI(50) 0.75-2.0 microg/mL, and all inhibited the growth of Gram-positive bacteria and fungi.     

Lagunamides A and B: cytotoxic and antimalarial cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula

Lagunamides A (1) and B (2) are new cyclic depsipeptides isolated from the marine cyanobacterium Lyngbya majuscula obtained from Pulau Hantu Besar, Singapore. The planar structural characterization of these molecules was achieved by extensive spectroscopic analysis, including 2D NMR experiments. In addition to Marfey's method and (3)J(H-H) coupling constant values, a modified method based on Mosher's reagents and analysis using LC-MS was deployed for the determination of the absolute configuration. Lagunamides A and B displayed significant antimalarial properties, with IC(50) values of 0.19 and 0.91 μM, respectively, when tested against Plasmodium falciparum. Lagunamides A and B also possessed potent cytotoxic activity against P388 murine leukemia cell lines, with IC(50) values of 6.4 and 20.5 nM, respectively. Furthermore, these cyanobacterial compounds exhibited moderate antiswarming activities when tested against Pseudomonas aeruginosa PA01.     

5,6:8,9-diepoxy and other cytotoxic sterols from the marine sponge Homaxinella sp

Four new (1, 2, 4, and 5) and 14 known (3 and 6-18) polyoxygenated sterols have been isolated from the MeOH extract of the marine sponge Homaxinella sp. by bioactivity-guided fractionation. The planar structures of the sterols were established by 1D and 2D NMR and MS spectroscopic analysis. 5,6:8,9-Diepoxy sterols (1-3) were isolated from a marine organism for the first time. The isolated sterols were tested against a panel of five human solid tumor cell lines and exhibited varying degrees of cytotoxicity.     

Antineoplastic agents. 534. isolation and structure of sansevistatins 1 and 2 from the African Sansevieria ehrenbergii

Using bioactivity-directed isolation procedures, three new spirostanol saponins designated sansevierin A (1), sansevistatin 1 (2), and sansevistatin 2 (3) were isolated (10(-5) % yield) from the CH3OH-CH2Cl2 extract of Sansevieria ehrenbergii, accompanied by three known steroidal saponins (4-6). The structures were determined on the basis of chemical methods and spectroscopic analysis, especially 1D and 2D NMR experiments. Each of the saponins was evaluated against the P388 lymphocytic leukemia cell line and a panel of human cancer cell lines. Except for 1, all were found to cause inhibition of cancer cell growth. In addition, most of the saponins exhibited antimicrobial activity, particularly against the pathogenic fungi Candida albicans and Cryptococcus neoformans.     

Guaiane sesquiterpene lactones and amino acid-sesquiterpene lactone conjugates from the aerial parts of Saussurea pulchella

Two new guaiane sesquiterpene lactones ( 1 and 2) and seven new amino acid-sesquiterpene lactone conjugates ( 3- 9), together with six known sesquiterpene lactones ( 10- 15), were isolated from the methanol extract of the aerial parts of Saussurea pulchella. Their structures were determined on the basis of spectroscopic and chemical methods to be 8alpha- O-(3'-hydroxy-3'-methylbutyryl)desacylcynaropicrin ( 1), 8alpha- O-(2', 3'-dihydroxyisobutyryl)11beta,13-dihydrodesacylcynaropicrin ( 2), and pulchellamines A, B, C, D, E, F, and G ( 3- 9). The structures of the new amino acid-sesquiterpene lactone conjugates, pulchellamines A, B, C, D, E, F, and G ( 3- 9), were confirmed by synthesis. The isolated compounds were evaluated for cytotoxic activity against four human tumor cell lines. Compounds 11 and 12 exhibited cytotoxicity against skin melanoma (SK-MEL-2) and ovary malignant ascites (SK-OV-3) human tumor cell lines with ED 50 values of 1.53 and 4.07 microM, and 2.49 and 7.42 microM, respectively.     

Granulatamides A and B, cytotoxic tryptamine derivatives from the soft coral Eunicella granulata

Two new tryptamine derivatives, granulatamides A (1) and B (2), were isolated from the 2-propanol extract of the soft coral Eunicella granulata. Their structures were determined on the basis of detailed spectroscopic analysis and comparison with previously published data for similar compounds. Both compounds showed moderate in vitro cytotoxicity against a panel of 16 human tumor cell lines.     

Indole alkaloids from Cephalanceropsis gracilis

Purification of CHCl3 and EtOAc solubles of the MeOH extract of Cephalanceropsis gracilis afforded seven new indole alkaloids, cephalinones A (1), B (2), C (3), and D (4) and cephalandoles A (5), B (6), and C (7), besides eight known compounds. The structures of the new compounds were determined by spectroscopic analysis. All 15 indole alkaloids were evaluated for their cytotoxic effects on MCF-7, NCI-H460, and SF-268 cell lines by the MTT method. Only cephalinone-F (6) showed significant cytotoxicity.     

Antiausterity agents from Uvaria dac and their preferential cytotoxic activity against human pancreatic cancer cell lines in a nutrient-deprived condition

Human pancreatic cancer cell lines are known for their inherent tolerance to nutrition starvation, which enables them to survive under a hypovascular (austerity) tumor microenvironment. The search for agents that preferentially retard the survival of cancer cells under low nutrition conditions (antiausterity agent) is a novel approach to anticancer drug discovery. In this study, it was found that a dichloromethane extract of the stem of Uvaria dac preferentially inhibited PANC-1 human pancreatic cancer cells survival under nutrition-deprived conditions at a concentration of 10 μg/mL. Workup of this bioactive extract led to the discovery of (+)-grandifloracin (8) as a potent antiausterity agent as evaluated in a panel of four human pancreatic cancer cell lines, PANC-1 (PC(50), 14.5 μM), PSN-1 (PC(50), 32.6 μM), MIA PaCa-2 (PC(50), 17.5 μM), and KLM-1 (32.7 μM). (+)-Grandifloracin (8) has been isolated from a natural source for the first time. Its absolute stereochemistry was established by single-crystal X-ray crystallography and circular dichroism spectroscopic analysis. In addition to this, seven other new highly oxygenated cyclohexene derivatives, named uvaridacanes A (1) and B (2), uvaridacols A-D (3, 4, 6, 7), and uvaridapoxide A (5), were also isolated and structurally characterized.     

Renierosides, cerebrosides from a marine sponge Haliclona (Reniera) sp

Guided by the brine shrimp lethality assay, eight new cerebrosides (1-8) have been isolated from an extract of the marine sponge Haliclona (Reniera) sp. A novel feature of these cerebrosides was the presence of unprecedented amide-linked long-chain fatty acid moieties. The planar structures of the cerebrosides (1-8) were established by 1D and 2D NMR spectroscopic techniques, mass spectrometric analyses, and chemical degradation methods. The isolated compounds did not display cytotoxicity to a panel of five human solid tumor cell lines.     

Suberosols A-D,four new sesquiterpenes with beta-caryophyllene skeletons from a Taiwanese gorgonian coral Subergorgia suberosa

Four new beta-caryophyllene-derived sesquiterpenes alcohols, suberosols A (1), B (2), C (3), and D (4), along with two known beta-caryophyllene-derived sesqueterpene ketones, buddledins C (5) and D (6), were isolated from a Taiwanese gorgonian coral Subergorgia suberosa. The structures of 1-4 were determined on the basis of extensive spectroscopic analyses. Cytotoxicity of these compounds toward various cancer cell lines is also described.     

Nonterpenoid C15 acetogenins from Laurencia marilzae

Eight new halogenated C(15) acetogenins, 1-8, were isolated from the organic extract of the red alga Laurencia marilzae. The structure elucidation and the assignments of the relative configurations were established by extensive use of spectroscopic studies, particularly 1D and 2D NMR data, while the absolute configurations of compounds 1 and 5 were determined by single-crystal X-ray diffraction analysis. Compounds 1, 2, 4, 5, and 7, along with the previously reported related cyclic ether obtusallene IV (9), were evaluated against six human solid tumor cell lines. All compounds were found to be essentially inactive (GI(50) > 10 μg/mL).     

Sesquiterpene benzoxazoles and sesquiterpene quinones from the marine sponge Dactylospongia elegans

A new sesquiterpene benzoxazole, nakijinol B (3), its acetylated derivative, nakijinol B diacetate (6), and two new sesquiterpene quinones, smenospongines B (4) and C (5), were isolated from the methanol extract of the marine sponge Dactylospongia elegans. Also isolated were the known compounds dactyloquinone B and a 1:1 mixture of ilimaquinone and 5-epi-ilimaquinone. Their structures were determined on the basis of spectroscopic analyses and comparison with literature data. The isolated compounds were assessed for their cytotoxicity against a panel of human tumor cell lines (SF-268, H460, MCF-7, and HT-29) and a normal mammalian cell line (CHO-K1). All compounds were found to have activities in the range 1.8-46 μM and lacked selectivity for tumor versus normal cell lines.