Forced Oxidative Degradation Pathways of the Imidazole Moiety of Daclatasvir.

Daclatasvir hydrochloride (DCV) is the active pharmaceutical ingredient of Daklinza, a marketed product for the treatment of hepatitis C viral infection. The intrinsic stability of daclatasvir was evaluated via a forced degradation study. DCV was found to be stable in the solid state.

Concise asymmetric synthesis of a (1R,2S)-1-amino- 2-vinylcyclopropanecarboxylic acid-derived sulfonamide and ethyl ester.

The development and demonstration of short, robust and chromatography-free sequences for the preparation of a (1R,2S)-1-amino-2-vinylcyclopropane-carboxylic acid-derived sulfonamide and ethyl ester in ≥99% ee are described. Both compounds are common building blocks in multiple preparations of potent HCV NS3 protease inhibitors. The robustness of the asymmetric cyclopropanation of (E)-N-benzylideneglycine ethyl ester under phase transfer catalysis conditions is significantly improved based on a detailed mechanistic investigation that included an analysis of the catalyst decomposition pathway, a postulated model for the stereo-selectivity that was guided by calculations and rigorous quality control of the starting materials and reagents.

Improving the efficiency of quantitative (1)H NMR: an innovative external standard-internal reference approach.

The classical internal standard quantitative NMR (qNMR) method determines the purity of an analyte by the determination of a solution containing the analyte and a standard. Therefore, the standard must meet the requirements of chemical compatibility and lack of resonance interference with the analyte as well as a known purity. The identification of such a standard can be time consuming and must be repeated for each analyte.

The novel plant-derived agent silvestrol has B-cell selective activity in chronic lymphocytic leukemia and acute lymphoblastic leukemia in vitro and in vivo.

Therapeutic options for advanced B-cell acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL) are limited. Available treatments can also deplete T lymphocytes, leaving patients at risk of life-threatening infections. In the National Cancer Institute cell line screen, the structurally unique natural product silvestrol produces an unusual pattern of cytotoxicity that suggests activity in leukemia and selectivity for B cells.

Dioxadispiroketal Compounds and a Potential Acyclic Precursor from Amomum aculeatum.

Four new compounds having an unusual 1,7-dioxadispiro[5.1.5.

Silvestrol, a potential anticancer rocaglate derivative from Aglaia foveolata, induces apoptosis in LNCaP cells through the mitochondrial/apoptosome pathway without activation of executioner caspase-3 or -7.

The novel cyclopenta[b]benzofuran, silvestrol, isolated from the fruits and twigs of Aglaia foveolata, has been found to exhibit very potent in vitro cytotoxic activity against several human cancer cell lines. Furthermore, it was active in the in vivo P388 murine leukemia model. In this study, the mechanism of cytotoxicity mediated by silvestrol in the LNCaP (hormone-dependent human prostate cancer) cell line was investigated.

Anti-oxidant constituents of the roots and stolons of licorice (Glycyrrhiza glabra).

As part of a search for new cancer chemopreventive agents, a new chalcone derivative (1), a novel group of neolignan lipid esters (2), and seven known phenolic compounds (formononetin, glabridin, hemileiocarpin, hispaglabridin B, isoliquiritigenin, 4'-O-methylglabridin, and paratocarpin B) (3-9) were isolated from the roots and stolons of licorice (Glycyrrhiza glabra). The structures of compound 1 and the individual components of isolate 2 were elucidated using various spectroscopic and chemical methods. All isolates were tested in an authentic peroxynitrite anti-oxidant assay.

Ixocarpalactone A isolated from the Mexican tomatillo shows potent antiproliferative and apoptotic activity in colon cancer cells.

Physalis philadelphica Lam, commonly known as a tomatillo, is a staple of the Mesoamerican cuisine. In our laboratory, an ethyl acetate-soluble extract and four withanolides [ixocarpalactone A (IxoA), ixocarpalactone B, philadelphicalactone B, and withaphysacarpin] were isolated. Studies conducted on Hepa-1c1c7 hepatoma cells revealed that withanolides were potent inducers of quinone reductase, suggesting possible cancer chemoprotective activity.

Cytotoxic flavaglines and bisamides from Aglaia edulis.

Two new cyclopenta[b]benzofurans, aglaroxin A 1-O-acetate (2) and 3'-methoxyaglaroxin A 1-O-acetate (3), a new benzo[b]oxepine, 19,20-dehydroedulisone A (4), and five new cyclopenta[bc]benzopyrans, edulirin A (5), edulirin A 10-O-acetate (6), 19,20-dehydroedulirin A (7), isoedulirin A (8), and edulirin B (9), were isolated from the bark of Aglaia edulis, along with one known cyclopenta[b]benzofuran, aglaroxin A (1). Additionally, four new amides, aglamides A-D (10-13), as well as three known compounds, aglalactone, scopoletin, and 5-hydroxy-3,6,7,4'-tetramethoxyflavone, were isolated from the leaves and/or twigs of this species. The structures of the new compounds (2-13) were elucidated by interpretation of their spectroscopic data.

Silvestrol regulates G2/M checkpoint genes independent of p53 activity.

As previously reported, silvestrol, a rocaglate derivative isolated from Aglaia foveolata, has similar potency to paclitaxel and camptothecin against cultured human cancer cells. Furthermore, silvestrol can inhibit cancer cell growth in mice without noticeable toxicity when administered up to 5 mg/kg body weight (the highest dose tested). The purpose of the current study was to evaluate the mechanism of silvestrol's cytotoxicity in human prostate cancer cells (LNCaP).

Beccaridiol, an unusual 28-nortriterpenoid from the leaves of Diplectria beccariana.

A C29-triterpene, beccaridiol (1), a dihydrochalcone natural product, 2',4'-dihydroxy-3-(4-methoxyphenyl)-propiophenone (2), as well as three known compounds, 4'-hydroxy-1',2'-dihydro-beta-ionone, 4'-O-methyldavidigenin (3), and ursolic acid, have been isolated from an EtOAc-soluble extract of the leaves of Diplectria beccariana. Beccaridiol (1) was characterized as an ursane-type 28-nortriterpene possessing an unusual aromatic E-ring by spectroscopic data interpretation. The relative configuration of this unusual isolate was established by analyzing the observed NOESY NMR correlations, and the absolute stereochemistry of 1 was then determined based on the circular dichroism (CD) spectrum of its 2,3-di-p-bromobenzoate (1b) derivative.

An anthraquinone with potent quinone reductase-inducing activity and other constituents of the fruits of Morinda citrifolia (noni).

Morinda citrifolia, commonly known as noni, has a long history of utilization throughout much of tropical Polynesia and is considered to be the second most important medicinal plant in the Hawaiian Islands. Recently, the use of noni as a dietary supplement in the United States has greatly increased. Bioassay-guided fractionation of a dichloromethane-soluble partition of a MeOH extract of noni fruits has led to the isolation of an extremely potent quinone reductase inducer, 2-methoxy-1,3,6-trihydroxyanthraquinone (1).

Activity-guided isolation of cytotoxic constituents from the bark of Aglaia crassinervia collected in Indonesia.

Activity-guided fractionation of a CHCl(3)-soluble partition of the MeOH extract of the bark of Aglaia crassinervia collected in Indonesia led to the isolation of three new glabretal-type triterpenoids, aglaiaglabretols A-C (1-3), as well as nine known compounds, 3-epi-cabraleahydroxylactone (4), cabraleahydroxylactone (5), rocaglaol (6), 2beta,3beta-dihydroxy-5alpha-pregn-17(20)-(E)-16-one, scopoletin, and mixtures of cabraleadiol and epicotillol and of beta-sitosterol and stigmasterol. The structures of compounds 1-3 were determined on the basis of spectroscopic and chemical methods. The structure of aglaiaglabretol A (1) was confirmed by single-crystal X-ray analysis, and the absolute stereochemistry of this isolate was established by the Mosher ester method.

Limnophilaspiroketone, a highly oxygenated phenolic derivative from Limnophila geoffrayi.

A highly oxygenated phenolic spiroketone, limnophilaspiroketone (1), was isolated from the aerial parts of Limnophila geoffrayi collected in Thailand. The structure of 1 was determined based on spectroscopic data interpretation. This novel isolate, obtained as a major secondary metabolite constituent, was verified as a racemate using the Mosher ester method.

Chemical constituents of the fruits of Morinda citrifolia (Noni) and their antioxidant activity.

Purification of a n-BuOH-soluble partition of the MeOH extract of Morinda citrifolia (Noni) fruits led to the isolation of two new iridoid glucosides, 6alpha-hydroxyadoxoside (1) and 6beta,7beta-epoxy-8-epi-splendoside (2), as well as 17 known compounds, americanin A (3), narcissoside (4), asperuloside, asperulosidic acid, borreriagenin, citrifolinin B epimer a, citrifolinin B epimer b, cytidine, deacetylasperuloside, dehydromethoxygaertneroside, epi-dihydrocornin, d-glucose, d-mannitol, methyl alpha-d-fructofuranoside, methyl beta-d-fructofuranoside, nicotifloroside, and beta-sitosterol 3-O-beta-d-glucopyranoside. The structures of the new compounds were determined by spectroscopic data interpretation. Compound 4, borreriagenin, cytidine, deacetylasperuloside, dehydromethoxygaertneroside, epi-dihydrocornin, methyl alpha-d-fructofuranoside, and methyl beta-d-fructofuranoside were isolated for the first time from M.

Constituents of the leaves and twigs of Calyptranthes pallens collected from an experimental plot in Southern Florida.

Fractionation of the chloroform-soluble extract of the leaves and twigs of Calyptranthes pallens, collected from an experimental plot in a hardwood forest of southern Florida, using a hormone-dependent human prostate carcinoma (LNCaP) tumor cell line, led to the isolation of a phloroglucinol derivative with a novel carbon skeleton, pallenic acid (1), and a new triterpenoid, 3beta-hydroxy-18alpha,19alpha-urs-20-en-28-oic acid (2). The known compound methylene-bis-aspidinol (3) was selectively active against the human oral epidermoid carcinoma (KB) cell line. Several known compounds of the ellagic acid, lignan, phloroglucinol, sterol, and triterpene types were also obtained in the present investigation.

Activity-guided fractionation of the leaves of Ormosia sumatrana using a proteasome inhibition assay.

Activity-guided fractionation of a chloroform-soluble extract of the leaves of Ormosia sumatrana, using a proteasome inhibition assay, led to the isolation of a new A-type proanthocyanidin derivative, 3'-O-cinnamoylprocyanidin A-2 (1), and a new cerebroside, sumatranoside (2). The structures of these two isolates were determined as epicatechin-(2 beta-->O-->7',4 beta-->8')-epicatechin-3'-O-cinnamate (1) and 1-O-(beta-d-glucopyranosyl)-(2S,3S,4R)-2N-[(2'R)-2'-hydroxy-tetracosanoyl]-9Z-octadecene-1,3,4-triol (2), respectively, by spectroscopic and chemical methods. Sumatranoside (2) exhibited proteasome inhibitory activity with an IC(50) value of 30 microM.

Constituents of the stems of Macrococculus pomiferus and their inhibitory activities against cyclooxygenases-1 and -2.

As part of our program directed towards the discovery of new cancer chemopreventive agents from plants, the EtOAc-soluble extract of the stems of M. pomiferus was found to inhibit the enzyme cyclooxygenase-2 (COX-2). Bioassay-directed fractionation of this extract led to the isolation of two dibenzylbutyrolactone lignans, (8R,8'R)-3'-O-demethyl-5-hydroxymatairesinol (1) and (8R,8'R)-3'-O-demethyl-5-methoxymatairesinol (2), as well as seven known compounds, (-)-5'-methoxyyatein (3), blumenol A, (-)-deoxypodophyllotoxin (anthricin), (-)-deoxypodorhizone, 2,6-dimethoxyhydroquinone, 4-hydroxybenzaldehyde, and beta-sitosterol glucoside.

Constituents of the seeds of Hernandia ovigera with inhibitory activity against cyclooxygenase-2.

A new dibenzylbutyrolactone lignan, (2 R,3 R)-5'-methoxyguayarol (1), was isolated from an EtOAc-soluble extract of the seeds of Hernandia ovigera using an in vitro activity-guided fractionation procedure based on the inhibition of cyclooxygenase-2. Also obtained were three known fatty acid derivatives, (S)-coriolic acid, (+/-)-12,13-epoxyoleic acid, and (+/-)-glycerol 1-monolinolate, and seven known lignans, epiashantin, dehydrodesoxypodophyllotoxin, dehydropodophyllotoxin, (-)-hernolactone, (-)-pinoresinol, (-)-syringaresinol, and (-)-yatein. The structure, including absolute stereochemistry, of compound 1 was determined using spectroscopic methods.

Natural inhibitors of carcinogenesis.

Previous collaborative work by our group has led to the discovery of several plant isolates and derivatives with activities in in vivo models of cancer chemoprevention, including deguelin, resveratrol, bruceantin, brassinin, 4'-bromoflavone, and oxomate. Using a panel of in vitro bioassays to monitor chromatographic fractionation, a diverse group of plant secondary metabolites has been identified as potential cancer chemopreventive agents from mainly edible plants. Nearly 50 new compounds have been isolated as bioactive principles in one or more in vitro bioassays in work performed over the last five years.

Silvestrol and episilvestrol, potential anticancer rocaglate derivatives from Aglaia silvestris.

Two cytotoxic rocaglate derivatives possessing an unusual dioxanyloxy unit, silvestrol (1) and episilvestrol (2), were isolated from the fruits and twigs of Aglaia silvestris by bioassay-guided fractionation monitored with a human oral epidermoid carcinoma (KB) cell line. Additionally, two new baccharane-type triterpenoids, 17,24-epoxy-25-hydroxybaccharan-3-one (3) and 17,24-epoxy-25-hydroxy-3-oxobaccharan-21-oic acid (4), as well as eleven known compounds, 1beta,6alpha-dihydroxy-4(15)-eudesmene (5), ferulic acid (6), grasshopper ketone (7), apigenin, cabraleone, chrysoeriol, 1beta,4beta-dihydroxy-6alpha,15alpha-epoxyeudesmane, 4-hydroxy-3-methoxyacetophenone, 4-hydroxyphenethyl alcohol, ocotillone, and beta-sitosterol 3-O-beta-D-glucopyranoside, were also isolated and characterized. The structures of compounds 1-4 were elucidated by spectroscopic studies and by chemical transformation.