Synthesis of novel curcumin analogues and their evaluation as selective cyclooxygenase-1 (COX-1) inhibitors

Curcumin, a major yellow pigment and active component of turmeric, has been shown to possess anti-inflammatory and anti-cancer activities. Recent studies have indicated that cyclooxygenase-1 (COX-1) plays an important role in inflammation and carcinogenesis. In order to find more selective COX-1 inhibitors a series of novel curcumin derivatives was synthesized and evaluated for their ability to inhibit this enzyme using in vitro inhibition assays for COX-1 and COX-2 by measuring PGE(2) production. All curcumin analogues showed a higher rate of COX-1 inhibition. The most potent curcumin compounds were (1E,6E)-1,7-di-(2,3,4-trimethoxyphenyl)-1,6-heptadien-3,5-dione (4) (COX-1: IC(50) = 0.06 microM, COX-2: IC(50) > 100 microM, selectivity index>1666) and (1E,6E)-methyl 4-[7-(4-methoxycarbonyl)phenyl]-3,5-dioxo-1,6-heptadienyl]benzoate (6) (COX-1: IC(50) = 0.05 microM, COX-2: IC(50) > 100 microM, selectivity index > 2000). Curcumin analogues therefore represent a novel class of highly selective COX-1 inhibitors and promising candidates for in vivo studies.     

CCR5 antagonists as anti-HIV-1 agents. 1. Synthesis and biological evaluation of 5-oxopyrrolidine-3-carboxamide derivatives

A novel lead compound, N-(3-[4-(4-fluorobenzoyl)piperidin-1-yl]propyl)-1-methyl-5-oxo-N-phenylpyrrolidine-3-carboxamide (1), was identified as a CCR5 antagonist by high-throughput screening using [(125)I]RANTES and CCR5-expressing CHO cells. The IC(50) value of 1 was 1.9 microM. In an effort to improve the binding affinity of 1, a series of 5-oxopyrrolidine-3-carboxamides was synthesized. Introduction of 3,4-dichloro substituents to the central phenyl ring (10i, IC(50)=0.057 microM; 11b, IC(50)=0.050 microM) or replacing the 1-methyl group of the 5-oxopyrrolidine moiety with a 1-benzyl group (12e, IC(50)=0.038 microM) was found to be effective for improving CCR5 affinity. Compound 10i, 11b, and 12e also inhibited CCR5-using HIV-1 envelope-mediated membrane fusion with IC(50) values of 0.44, 0.19, and 0.49 microM, respectively.     

Biotransformations of imbricatolic acid by Aspergillus niger and Rhizopus nigricans cultures

Microbial transformation of imbricatolic acid (1) by Aspergillus niger afforded 1alpha-hydroxyimbricatolic acid (2), while transformation with Rhizopus nigricans yielded 15-hydroxy-8,17-epoxylabdan-19-oic acid (3). When the diterpene 1 was added to a Cunninghamella echinulata culture, the main products were the microbial metabolites mycophenolic acid (4) and its 3-hydroxy derivative 5. All the structures were elucidated by spectroscopic methods. The cytotoxicity of these compounds towards human lung fibroblasts and AGS cells was assessed. While 4 and 5 showed low cytotoxicity, with IC50 values > 1000 microM against AGS cells and fibroblasts, 1alpha-hydroxyimbricatolic acid (2) presented moderate toxicity towards these targets, with IC50 values of 307 and 631 microM, respectively. The structure of 2 is presented for the first time.     

Probing sponge-derived terpenoids for human 15-lipoxygenase inhibitors

A human 15-lipoxygenase (15-HLO) assay has been employed to discover new marine-sponge-derived bioactive compounds. Extracts from two different sponges, Jaspis splendens (order Choristida, family Jaspidae) and Suberea sp. (order Verongida, family Aplysinellidae), exhibited potent IC(50) values of 0.4 and 0.1 microg/mL, respectively. Both are sources of terpenoids, and the former is a known source of (+)-jasplakinolide (7), which is inactive as a 15-HLO inhibitor. The terpenoids included (+)-(5S,6S)-subersin (1, IC(50) > 100 microM), (-)-(5R,10R)-subersic acid (2, IC(50) = 15 microM), jaspaquinol (3, IC(50) = 0.3 microM), and (-)-jaspic acid (4, IC(50) = 1.4 microM). Structure elucidations and lipoxygenase activity studies of these compounds are reported.     

Development of plasmin-selective inhibitors and studies of their structure-activity relationship

Various compounds were synthesized by combining three components at positions P1, P1' and P2'. Of these, N-(trans-4-aminomethylcyclohexanecarbonyl)-Tyr(O-2-bromobenzylo xycarbonyl)- octylamide inhibited plasmin selectively with IC50 values of 0.80 and 0.23 microM towards S-2251 and fibrin, respectively. This compound also inhibited plasma kallikrein, urokinase, thrombin and trypsin with IC50 values of 10, > 50, > 50 and 1.6 microM, respectively.     

Humulene derivatives from Zingiber zerumbet with the inhibitory effects on lipopolysaccharide-induced nitric oxide production

A new humulene sesquiterpene, 5-hydroxyzerumbone (5-hydroxy-2E,6E,9E-humulatrien-8-one) (1) and a known compound, zerumboneoxide (2) were isolated from the rhizomes of Zingiber zerumbet (Zingiberaceae), and found to inhibit lipopolysaccharide-induced nitric oxide production in murine macrophage RAW 264.7 cells with IC50 values of 14.1 and 23.5 microM, respectively, by bioassay-guided fractionation (positive control: N(omega)-monomethyl-L-arginine, IC50=21.3 microM). The structure of 1 was determined by spectroscopic methods including 1D and 2D-NMR.     

Golmaenone, a new diketopiperazine alkaloid from the marine-derived fungus Aspergillus sp

A new diketopiperazine alkaloid, golmaenone (1). and related alkaloids, neoechinulin A (2). and L-alanyl-L-tryptophan anhydride (3). have been isolated from the culture broth of the marine-derived fungus Aspergillus sp. The structure and absolute stereochemistry of the new compound (1). was assigned by spectroscopic methods and the advanced Marfey's method. Compounds 1 and 2 exhibited a significant radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC(50) values of 20 and 24 microM, respectively, which are similar to the positive control, ascorbic acid (IC(50), 20 microM). Compounds 1 and 2 also showed an ultraviolet-A (UV-A) (320--390 nm) protecting activity with ED(50) values of 90 and 170 microM, respectively, which are more active than oxybenzone (ED(50), 350 microM) currently being used as sunscreen.     

A new labdane diterpene from the flowers of Solidago canadensis

A new labdane diterpene, 9alpha,16xi-dihydroxy-6-oxo-7,13-labdadien-15,16-olide (solicanolide, 1) and six known compounds identified as quercetin (2), 3-O-caffeoylquinic acid (3, neochlorogenic acid), 5-O-caffeoylquinic acid (4, chlorogenic acid), 4,5-di-O-caffeoylquinic acid (5), 3,5-di-O-caffeoylquinic acid (6) and 3,4-di-O-caffeoylquinic acid (7) were isolated from the flowers of Solidago canadensis. To our knowledge, compound 7 was isolated for the first time in S. canadensis. This work describes the isolation of compounds 1-7 and the structure elucidation of a new compound identified as compound 1. Solicanolide (1) showed cytotoxic activity against A549 (IC(50): 13+/-2 microM), DLD-1 (IC(50): 26+/-2 microM) and WS1 (IC(50): 17+/-1 microM) cell lines.     

Liquid chromatography/tandem mass spectrometric determination of inhibition of human cytochrome P450 isozymes by resveratrol and resveratrol-3-sulfate

trans-Resveratrol, a phenolic phytoalexin occurring in grapes, wine, peanuts, and cranberries, has been reported to both have anticarcinogenic, antioxidative, phytoestrogenic, and cardioprotective activities, and to be a weak inhibitor of cytochrome P450 (CYP)3A4, which might have significance for drug-drug interactions. Since trans-resveratrol is rapidly converted in vivo to primarily trans-resveratrol-3-sulfate, a rapid, selective, and sensitive method using liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed to investigate human cytochrome P450 inhibition by trans-resveratrol-3-sulfate. Effects of trans-resveratrol and trans-resveratrol-3-sulfate on the metabolism of selective cytochrome P450 substrates (CYP1A2/ethoxyresorufin, CYP2C9/diclofenac, CYP2C19/(S)-mephenytoin, CYP2D6/bufuralol, CYP3A4/testosterone) were monitored using cDNA-expressed human recombinant isozymes. For method validation, LC/MS/MS was used to measure the inhibition of various cytochrome P450 isozymes by different concentrations (0-50 microM) of known selective inhibitors. IC(50) values of 3.2, 1.4, 8.9, 0.2, and 0.3 microM were obtained for the standard isozyme inhibitors CYP1A2/furafylline, CYP2C9/sulfaphenazole, CYP2C19/tranylcypromine, CYP2D6/quinidine, and CYP3A4/ketoconazole, respectively, which were in good agreement with literature values. trans-Resveratrol showed IC(50) values of 11.6 microM for CYP2C19 and 1.1 microM for CYP3A4, but the IC(50) values exceeded 50 microM for all the other CYP isozymes, which indicated no inhibition. No enzyme inhibition was observed for trans-resveratrol-3-sulfate. Our results indicate that trans-resveratrol is a marginal inhibitor of CYP3A4 and a weak inhibitor of CYP2C19, but its major metabolite trans-resveratrol-3-sulfate is not an inhibitor of any of the cytochrome P450 isozymes investigated.     

Influenza neuraminidase inhibitors possessing a novel hydrophobic interaction in the enzyme active site: design, synthesis, and structural analysis of carbocyclic sialic acid analogues with potent anti-influenza activity

The design, synthesis, and in vitro evaluation of the novel carbocycles as transition-state-based inhibitors of influenza neuraminidase (NA) are described. The double bond position in the carbocyclic analogues plays an important role in NA inhibition as demonstrated by the antiviral activity of 8 (IC50 = 6.3 microM) vs 9 (IC50 > 200 microM). Structure-activity studies of a series of carbocyclic analogues 6a-i identified the 3-pentyloxy moiety as an apparent optimal group at the C3 position with an IC50 value of 1 nM for NA inhibition. The X-ray crystallographic structure of 6h bound to NA revealed the presence of a large hydrophobic pocket in the region corresponding to the glycerol subsite of sialic acid. The high antiviral potency observed for 6h appears to be attributed to a highly favorable hydrophobic interaction in this pocket. The practical synthesis of 6 starting from (-)-quinic acid is also described.     

Fumimycin: a peptide deformylase inhibitor with an unusual skeleton produced by Aspergillus fumisynnematus

Fumimycin, an unusual metabolite incorporating an unusual alanine unit linked to a phenyl group at the alpha-carbon with both lactone and amide moieties, was isolated from cultures of Aspergillus fumisynnematus. Its structure was established by spectral analysis. Fumimycin was found to inhibit Staphylococcus aureus peptide deformylase with an IC50 value of 4.1 microM and also showed antibacterial activity against S. aureus.     

Acetylcholinesterase and butyrylcholinesterase inhibitory compounds from Corydalis cava (Fumariaceae)

Tubers of Corydalis cava were extracted with ethanol and fractionated using n-hexane, chloroform and ethanol. Repeated column chromatography, preparative TLC and crystallization led to the isolation of fifteen isoquinoline alkaloids. The chemical structures of the isolated compounds were determined on the basis of spectroscopic techniques and by comparison with literature data. All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibitory activity. (+)-Canadaline inhibited acetylcholinesterase as well as butyrylcholinesterase in a dose-dependent manner with IC50 values of 20.1 +/- 1.1 microM and 85.2 +/- 3.2 microM, respectively. (+)-Canadine, with an IC50 value of 12.4 +/- 0.9 microM, was the most potent inhibitor of acetylcholinesterase, whilst (+/-)-corycavidine and (+)-bulbocapnine were effective inhibitors of butyrylcholinesterase with IC50 values of 46.2 +/- 2.4 microM and 67.0 +/- 2.1 microM, respectively. The other isolated alkaloids were considered inactive (IC50 > 100 microM).     

Studies on the monoamine oxidase (MAO) inhibitory potency of TL-1, isolated from a fungus, Talaromyces luteus

The compound tentatively named TL-1 was isolated from Talaromyces luteus as a metabolite having monoamine oxidase (MAO) inhibitory potency. TL-1 showed mixed-type inhibition of MAO in mouse liver when kynuramine was used as a substrate, and the IC50 was 6.6 microM. The inhibition constants (Ki) for MAO-A and -B in mouse liver were 39.9 and 7.85 microM, respectively. On the other hand, the Ki values for MAO-A and -B in mouse brain were 74.0 and 0.71 microM, respectively. Despite the marked structural resemblance between TL-1 and 7-episclerotiorin, the latter compound had little inhibitory effect on MAO.     

Rational design,synthesis, and pharmacological evaluation of 2-azanorbornane-3-exo,5-endo-dicarboxylic acid: a novel conformationally restricted glutamic acid analogue

The design and synthesis of conformationally restricted analogues of alpha-amino acids is an often used strategy in medicinal chemistry research. Here we present the rational design, synthesis, and pharmacological evaluation of 2-azanorbornane-3-exo,5-endo-dicarboxylic acid (1), a novel conformationally restricted (S)-glutamic acid (Glu) analogue intended as a mimic of the folded Glu conformation. The synthesis of 1 was completed in its racemic form in eight steps from commercially available starting materials. As a key step, the first facially selective hydroboration of a 5-methylidene[2.2.1]bicyclic intermediate was investigated. In this transformation, the catalytic methodology of Wilkinson's/catechol borane proved superior to stoichiometric borane or dialkyl borane reagents, in terms of higher diastereomeric excess and chemical yield. To our surprise (+/-)-1 did not show affinity in binding studies on native 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) (IC(50) > 300 microM, [(3)H]AMPA) or kainic acid (IC(50) > 160 microM, [(3)H]kainic acid) receptors nor in binding studies on the cloned iGluR5,6 subtypes (IC(50) > 300 microM, [(3)H]kainic acid).     

Neoglycopeptide dendrimer libraries as a source of lectin binding ligands

[structure: see text] A 15 625-membered peptide dendrimer combinatorial library was acylated with an alpha-C-fucosyl residue at its four N-termini and screened for binding to fucose-specific lectins. Dendrimer FD2 (Fuc-alpha-CH2CO-Lys-Pro-Leu)4(Lys-Phe-Lys-Ile)2Lys-His-Ile-NH2 was identified as a potent ligand against Ulex europaeus lectin UEA-I (IC50 = 11 microM) and Pseudomonas aeruginosa lectin PA-IIL (IC50 = 0.14 microM).     

A new radical scavenging anthracene glycoside, asperflavin ribofuranoside, and polyketides from a marine isolate of the fungus microsporum

A new anthracene glycoside, asperflavin ribofuranoside (1), and the previously described polyketides, flavoglaucin (2), isodihydroauroglaucin (3), and citrinin (4) have been isolated from the marine-derived fungus Microsporum sp. The structure and absolute stereochemistry of a new compound (1) was assigned on the basis of physicochemical data. Compounds 1-3 exhibited a significant radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC(50) values of 14.2, 11.3, and 11.5 microM, respectively, which are more potent than the positive control, ascorbic acid (IC(50), 20 microM). Compound 1 also showed a moderate antibacterial activity against the methicillin-resistant and multidrug-resistant Staphylococcus aureus (MRSA and MDRSA) with MIC value of 50 microg/ml.     

Novel glycoconjugates of diospyrin, a quinonoid plant product: synthesis and evaluation of cytotoxicity against human malignant melanoma (A375) and laryngeal carcinoma (Hep2)

Glycoside derivatives of diospyrin (1) were synthesized for the first time, and the cytotoxicity of the novel compounds vis-à-vis their precursors were evaluated against two human cancer cell lines, viz. malignant melanoma (A375) and laryngeal carcinoma (Hep2). The IC(50) values were in the low micromolar range for all the compounds tested, and A375 cells showed comparatively greater sensitivity than Hep2. Most of the compounds exhibited enhanced activity as compared to the plant-derived quinonoid precursor of the series (1), while the aminophenyl mannosyl (6) was found to be the most effective derivative. In A375 cells, 6 (IC(50) = 0.02 microM) showed the maximum increase in cytotoxicity (approximately 35-fold) over that of 1 (IC(50) = 0.82 microM). Again, when the glycosides were evaluated at a given concentration (0.1 microM) for their relative capacity to generate ROS from A375 cells, the compound 6 could produce the highest amount of ROS. Incidentally, this derivative also showed a comparatively lower toxicity (IC(50) approximately 41 microM) when tested against normal human peripheral blood mononuclear cells, indicating a fair prospect of its development as a novel chemotherapeutic agent for the treatment of malignant melanoma.