Preparation of novel (Z)-4-ylidenebenzo[b]furo[3,2-d][1,3]oxazines and their biological activity

A reaction of 2-acetyl-3-acylaminobenzo[b]furans (9d–o) with Vilsmeier (VM) reagent afforded a mixture of (E)- and (Z)-{(E)-2-aralkenylbenzo[b]furo[3,2-d][1,3]oxazin-4-ylidene}acetaldehydes (5) with a characteristic exo-formylmethylene group on the oxazine ring. The Z-isomer was more stable than the E-isomer. The Z-isomers ((Z)-5) were reacted with phosphonate reagents under two different conditions to obtain various butadiene derivatives (12) containing benzo[b]furo[3,2-d][1,3]oxazine skeleton. Typical compounds (5 and 12) were evaluated for their anti-osteoclastic bone resorption activity, antagonistic activity for the cysLT1 receptor and growth inhibitory activity for MIA PaCa-2 and MCF-7. Compounds 12f and 12j showed potent anti-osteoclastic bone resorption activity comparable to E₂ (17β-estradiol).     

Phenylpropenamide derivatives: anti-hepatitis B virus activity of the Z isomer, SAR and the search for novel analogs

Phenylpropenamides have been reported to be a class of non-nucleoside inhibitors of the hepatitis B virus (HBV). This class of compounds was explored with the objective of developing potent anti-HBV agents, with a novel mechanism of action, that could be combined with nucleos(t)ide analogs currently used to treat HBV infection. To accomplish this objective a series of substituted arylpropenamide derivatives were prepared and the E and Z geometrical isomers were separated. The structural identity of each of the E and Z isomers was determined by single crystal X-ray crystallography. Contrary to previous reports, the activity of this class of molecules resides in the Z isomer. Further structure-activity relationship studies around the active Z isomer identified compounds that displayed potent antiviral activity against HBV with EC₉₀ value of approximately 0.5 μM in vitro. Attempts to develop ring constrained analogs did not lead to active HBV inhibitors.     

Novel (E)-1-(4-methyl-2-(alkylamino)thiazol-5-yl)-3-arylprop-2-en-1-ones as potent antimicrobial agents

New (E)-1-(4-methyl-2-(alkylamino)thiazol-5-yl)-3-arylprop-2-en-1-ones, unsubstituted or carrying fluoro, bromo, methoxy, nitro, methyl and chloro groups on the benzene ring, were synthesized and assayed in vitro for their antimicrobial activity against Gram positive and Gram negative bacteria and fungi. The compounds were very potent towards all tested microorganisms and in most cases their activity was better than that of reference drugs.     

Development of indolequinone mechanism-based inhibitors of NAD(P)H:quinone oxidoreductase 1 (NQO1): NQO1 inhibition and growth inhibitory activity in human pancreatic MIA PaCa-2 cancer cells

NAD(P)H:quinone oxidoreductase 1 (NQO1) is currently an emerging target in pancreatic cancer. In this report, we describe a series of indolequinones, based on 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936), and evaluate NQO1 inhibition and growth inhibitory activity in the human pancreatic MIA PaCa-2 tumor cell line. The indolequinones with 4-nitrophenoxy, 4-pyridinyloxy, and acetoxy substituents at the (indol-3-yl)methyl position were NADH-dependent inhibitors of recombinant human NQO1, indicative of mechanism-based inhibition. However, those with hydroxy and phenoxy substituents were poor inhibitors of NQO1 enzyme activity, due to attenuated elimination of the leaving group. The ability of this series of indolequinones to inhibit recombinant human NQO1 correlated with NQO1 inhibition in MIA PaCa-2 cells. The examination of indolequinone interactions in complex with NQO1 from computational-based molecular docking simulations supported the observed biochemical data with respect to NQO1 inhibition. The design of both NQO1-inhibitory and noninhibitory indolequinone analogues allowed us to test the hypothesis that NQO1 inhibition was required for growth inhibitory activity in MIA PaCa-2 cells. ES936 and its 6-methoxy analogue were potent inhibitors of NQO1 activity and cell proliferation; however, the 4-pyridinyloxy and acetoxy compounds were also potent inhibitors of NQO1 activity but relatively poor inhibitors of cell proliferation. In addition, the phenoxy compounds, which were not inhibitors of NQO1 enzymatic activity, demonstrated potent growth inhibition. These data demonstrate that NQO1 inhibitory activity can be dissociated from growth inhibitory activity and suggest additional or alternative targets to NQO1 that are responsible for the growth inhibitory activity of this series of indolequinones in human pancreatic cancer.     

Leishmania donovani pteridine reductase 1: comparative protein modeling and protein–ligand interaction studies of the leishmanicidal constituents isolated from the fruits of Piper longum

Visceral leishmaniasis or kala-azar is caused by the dimorphic parasite Leishmania donovani in the Indian subcontinent. Treatment options for kala-azar are currently inadequate due to various limitations. Currently, drug discovery for leishmaniases is oriented towards rational drug design; the aim is to identify specific inhibitors that target particular metabolic activities as a possible means of controlling the parasites without affecting the host. Leishmania salvages pteridin from its host and reduces it using pteridine reductase 1 (PTR1, EC 1.5.1.33), which makes this reductase an excellent drug target. Recently, we identified six alkamides and one benzenoid compound from the n-hexane fraction of the fruit of Piper longum that possess potent leishmanicidal activity against promastigotes as well as axenic amastigotes. Based on a homology model derived for recombinant pteridine reductase isolated from a clinical isolate of L. donovani, we carried out molecular modeling and docking studies with these compounds to evaluate their binding affinity. A fairly good agreement between experimental data and the results of molecular modeling investigation of the bioactive and inactive compounds was observed. The amide group in the conjugated alkamides and the 3,4-methylenedioxystyrene moiety in the benzenoid compound acts as heads and the long aliphatic chain acts as a tail, thus playing important roles in the binding of the inhibitor to the appropriate position at the active site. The remarkably high activity of a component containing piperine and piperine isomers (3.36:1) as observed by our group prompted us to study the activities of all four isomers of piperine—piperine (2E,4E), isopiperine (2Z,4E), isochavicine (2E,4Z), and chavicine (2Z,4Z)—against LdPTR1. The maximum inhibitory effect was demonstrated by isochavicine. The identification of these predicted inhibitors of LdPTR1 allowed us to build up a stereoview of the structure of the binding site in relation to activity, affording significant information that should prove useful during the structure-based design of leishmanicidal drugs.     

Identification of the stereochemical requirements in the 4-aryl-2-cycloalkylidenhydrazinylthiazole scaffold for the design of selective human monoamine oxidase B inhibitors

Exploring the effect that substituents on the cycloaliphatic ring had on the inhibitory activity against human monoamine oxidase B of a series of 4-aryl-2-cycloalkylidenhydrazinylthiazoles led to the synthesis of a new series of 2-methylcyclopentyl and 3-methylcyclopentyl derivatives which were tested in vitro as mixtures of diastereoisomers. In fact, due to the presence of a chiral center on the cycloaliphatic ring and a trisubstituted CN bond, they exist as four diastereoisomers ((E)-(R), (E)-(S), (Z)-(R), (Z)-(S)). 4-(2,4-Difluorophenyl)-2-(2-(3-methylcyclopentylidene)hydrazinyl)thiazole was chosen as a model to investigate the influence of stereochemical requirements on the inhibitory activity against hMAO-B of these derivatives after a stereoconservative synthesis and semi-preparative HPLC diastereoseparation. (R)-(Z) isomer of this compound was endowed with a potent and selective hMAO-B inhibition higher than that of reference drugs as also corroborated by molecular modeling studies.     

Functionalized 3-benzylidene-indolin-2-ones: Inducers of NAD(P)H-quinone oxidoreductase 1 (NQO1) with antiproliferative activity

Functionalized benzylidene-indolin-2-ones are widely associated with antiproliferative activity. The scaffold is not normally associated with chemoprevention in spite of the presence of a nitrogen-linked Michael acceptor moiety that may predispose members to induction of NQO1, a widely used biomarker of chemopreventive potential. To investigate this possibility, we have synthesized and evaluated a series of functionalized 3-benzylidene-indolin-2-ones for induction of NQO1 in murine Hepa1c1c7 cells as well as antiproliferative activity against two human cancer cell lines (MCF-7, HCT116). The benzylideneindolinones were found to be good inducers of NQO1 activity, with 85% of test compounds able to increase basal NQO1 activity by more than twofold at concentrations of ?10 μM. By contrast, fewer compounds (11%) tested at the same concentration were able to reduce cell viability by more than 50%. Structure activity relationships showed that the nitrogen linked Michael acceptor moiety was an essential requirement for both activities. This common feature notwithstanding, substitution of the 3-benzylidene-indolin-2-one core structure affected NQO1 induction and antiproliferative activities in dissimilar ways, underscoring different structural requirements for these two activities. Nonetheless, promising compounds (10, 42, 45–48) were identified that combine selective induction of NQO1 with potent antiproliferative activity. A potential advantage of such agents would be the ability to provide added protection to normal cells by the up-regulation of NQO1 and other phase II enzymes while simultaneously targeting neoplastic cells.     

Discovery of novel inhibitors of phosphodiesterase 4 with 1-phenyl-3,4-dihydroisoquinoline scaffold: Structure-based drug design and fragment identification

Currently, it is in urgent need to develop novel selective PDE4 inhibitors with novel structural scaffolds to overcome the adverse effects and improve the efficacy. Novel 1-phenyl-3,4-dihydroisoquinoline amide derivatives were developed as potential PDE4 inhibitors based on the structure-based drug design and fragment identification strategy. A SARs analysis was performed in substituents attached in the C-3 side chain phenyl ring, indicating that the attachment of methoxy group or halogen atom substitution at the ortho-position of the phenyl ring was helpful to enhance both inhibitory activity toward PDE4B and selectivity. Compound 15 with excellent selectivity, exhibited the most potent inhibition in vitro and in vivo, which is a promising lead for development of a new class of selective PDE4 inhibitors.     

Design,synthesis and evaluation of 2-(indolylmethylidene)-2,3-dihydro-1-benzofuran-3-one and 2-(indolyl)-4H-chromen-4-one derivatives as novel monoamine oxidases inhibitors

A series of 2-(indolylmethylidene)-2,3-dihydro-1-benzofuran-3-ones (aurone-indole hybrids) and 2-(indolyl)-4H-chromen-4-ones (flavone-indole hybrids) were designed, synthesized, and their monoamine oxidase (MAO) A and B inhibitory activities were evaluated. Compounds 5b and 11b showed potent inhibitory activities against MAO-A, comparable to that of pargyline used as a positive control, and most of the compounds, except for 2a and 10b, showed potent inhibitory activities against MAO-B. Compound 9a was the most potent and highly selective inhibitor of MAO-B (IC₅₀ value for MAO-B: 0.0026 μM, and MAO-A: >100 μM). Comparison of the inhibitory activities of 1a vs. 9a vs. 13a and 1b vs. 7b vs. 11b suggested that methoxy substitution at R¹ on the A-rings of flavonoids increases MAO-A inhibition whereas methoxy substitution at R² increased MAO-B inhibition. Comparison of 4a vs. 10a, 6a vs. 11a, 3b vs. 8b and 4b vs. 9b showed incremental increases in MAO-B inhibitory activity by R² substitution on the A ring. Comparison of the MAO-B inhibitory effects of the flavone-indole hybrids and aurone-indole hybrids showed that most of the aurone-indole hybrids were stronger inhibitors than the corresponding flavone-indole hybrids. Molecular docking analysis of compounds 1a and 9a with MAO-B further supported the above structural effects of these compounds on MAO-B inhibitory activity.This is the first report identifying aurone-indole hybrids as potent MAO-B inhibitors. The results reported here suggest that 2-(1H-indol-1-ylmethylene)-6-methoxy-3(2H)-benzofuranone (9a) might be a useful lead for the design and development of novel MAO-B inhibitors     

Structure and activity relationship of 2-(substituted benzoyl)-hydroxyindoles as novel CaMKII inhibitors

A series of novel 2-substituted-5-hydroxyindoles were synthesized and evaluated for their inhibitory activity against CaMKII. Structure and activity relationship results indicated that potent inhibitory activity could be achieved by modification at the para-position of the phenyl ring of the high throughput screening hit compound 2. Among the prepared compounds, we identified 14 as a novel CaMKII inhibitor with an activity stronger than that of KN-93, a known CaMKII inhibitor.     

Design and synthesis of novel benzimidazole derivatives as phosphodiesterase 10A inhibitors with reduced CYP1A2 inhibition

A novel class of phosphodiesterase 10A (PDE10A) inhibitors with reduced CYP1A2 inhibition were designed and synthesized starting from 2-{[(1-phenyl-1H-benzimidazol-6-yl)oxy]methyl}quinoline (1). Introduction of an isopropyl group at the 2-position and a methoxy group at the 5-position of the benzimidazole ring of lead compound 1 resulted in the identification of 2-{[(2-isopropyl-5-methoxy-1-phenyl-1H-benzimidazol-6-yl)oxy]methyl}quinoline (25b), which exhibited potent PDE10A inhibitory activity with reduced CYP1A2 inhibitory activity compared to compound 1.     

NADPH: Quinone oxidoreductase 1 (NQO1) mediated anti-cancer effects of plumbagin in endocrine resistant MCF7 breast cancer cells

BackgroundPLB is a natural naphthoquinone compound isolated from the roots of Plumbago indica plant. Our previous study reported the inhibitory effect of Plumbagin (PLB) on human endocrine resistant breast cancer cell growth and cell invasion.Hypothesis/PurposeSince PLB is a naphthoquinone compound, it can be reduced by the cytosolic NADPH: quinone oxidoreductase 1 (NQO1) enzyme. NQO1 expression is upregulated in various types of aggressive cancer including breast cancer. This study investigated the impact of NQO1 on anti-cancer effects of PLB in endocrine-resistant breast cancer cells.Study DesignThis study was an in vitro study using ER-positive cell line (MCF7) and endocrine-resistant cell lines (MCF7/LCC2 and MCF7/LCC9 cells).MethodsThe roles of NQO1 in anti-cancer activity of PLB were investigated by using NQO1 knockdown cells, NQO1 inhibitor and NQO1 overexpressed cells. To study the impact of NQO1 on the effects of PLB on cell viability, apoptosis, invasion and generation of ROS, the following assays were used: MTT assays, annexin V-PE/7-ADD staining flow cytometry, matrigel invasion assays and DCFHDA assays. To study the mechanism of how NQO1 mediated PLB effects in tamoxifen response and apoptosis, we assessed the levels of mRNA expression by using qRT-PCR.Results1. In this study, NQO1 was upregulated in endocrine-resistant cells.2. PLB did not change the expression of NQO1 but it was able to increase NQO1 activity.3. The inhibitory effects of PLB on cell proliferation, cell invasion and expression of tamoxifen resistant gene were attenuated in NQO1 knockdown cells or in the presence of NQO1 inhibitor.4. The effects of PLB to induce apoptosis and generate ROS were also decreased when NQO1 activity was inhibited or when the NQO1 expression was reduced.5. The anti-cancer effects of PLB increased when NQO1 was upregulated.ConclusionThe effects of PLB in endocrine-resistant breast cancer cells is dependent on NQO1’s activity.     

Inhibitory activity of prostaglandin E2 production by the synthetic 2′-hydroxychalcone analogues: Synthesis and SAR study

A series of 2′-hydroxychalcones has been synthesized and screened for their in vitro inhibitory activities of cyclooxygenase-2 catalyzed prostaglandin production from lipopolysaccharide-treated RAW 264.7 cells. Structure–activity relationship study suggested that inhibitory activity against prostaglandin E₂ production was governed to a greater extent by the substituent on B ring of the chalcone, and most of the active compounds have at least two methoxy or benzyloxy groups on B ring. The relationship between chalcone structures and their PGE₂ inhibitory activities was also interpreted by docking study on cyclooxygenase-2.     

Metacytofilin has potent anti-malarial activity

Metacytofilin (MCF) was isolated from the fungus Metarhizium sp. TA2759. Although MCF possesses anti-Toxoplasma activity, the effects of this compound against other parasites are unknown. Here, we evaluated the in vitro anti-malarial activity of MCF against the 3D7 strain and the chloroquine-resistant K1 strain of Plasmodium falciparum. The half maximal inhibitory concentrations (IC₅₀) of MCF against the 3D7 and K-1 strains following culture for 48 h were 666 nM and 605 nM, respectively. Artemisinin was more potent than MCF against both strains (3D7 IC₅₀: 17.4 nM; K-1 IC₅₀: 18.3 nM), while chloroquine was ineffective against the chloroquine-resistant strain (3D7 IC₅₀: 39.1 nM; K-1 IC₅₀: 1.62 μM). MCF affected the ring stage of the parasites, resulting in their death as shown by spots within red blood cells. MCF also inhibited parasite growth following culture for 72 h (3D7 IC₅₀, 285 nM). Four optical isomers of cyclo[Leu-Phe]-diketopiperazine derivatives with modified methoxy and/or hydroxyl groups lost anti-malarial activity, suggesting that the spatial positions of the methoxy and hydroxyl groups in MCF play an important role in its anti-malarial effects. Together, these data suggest that MCF may represent a promising lead compound for treatment of drug-resistant malarial parasites.     

Ortho-metalation, rotational isomerization, and hydride-hydride coupling at rhenium (V) polyhydride complexes stabilized by aromatic amine ligands

An ortho-metalated rhenium (V) polyhydride complex has been prepared through the reaction of ReH₇(PPh₃)₂ with 2-phenylpyridine. Additionally, a small series of neutral rhenium (V) pentahydride complexes, each of which is stabilized by an aromatic amine ligand, has been prepared. E and Z rotational isomers of the ReH₅(PPh₃)₂(aromatic amine) complexes have been observed at low temperatures by NMR spectroscopy. The E and Z rotational isomers arise from a combination of the lack of a mirror plane symmetry element orthogonal to the aromatic ring in the aromatic amine ligands and the restricted rotation about the Re-N bond in such complexes. Restricted rotation about the Re-N bond in the related complex, ReH₅(PPh₃)₂(Py) has previously been observed by Crabtree et al. The restricted rotation about the Re-N bond seems to result from π-donation of the lone electron pair on the rhenium (V) center to the π∗ system of the aromatic amine ligands. Different populations of the E and Z rotational isomers arise from interactions of substituents on the aromatic ring with the other ligands bound to rhenium. The values of ΔG^‡ for the restricted rotation about the Re-N bonds, for the complexes containing 4-phenylpyrimidine, 2-aminopyrimidine, or 2-aminopyridine, range from 9.9 to 11.3 kcal/mole. One of the new compounds reported herein, ReH₅(PPh₃)₂[1-(2-NH₂Pyr)] is the first rhenium (V) polyhydride complex to display hydride-hydride coupling in its ¹H NMR spectrum.     

Resveratrol Inhibits the Growth of Gastric Cancer by Inducing G1 Phase Arrest and Senescence in a Sirt1-Dependent Manner

Resveratrol, a naturally occurring polyphenolic compound, has been reported to exert anticancer activity by affecting diverse molecular targets. In this study, we examined the effects and the underlying mechanisms of resveratrol on gastric cancer. We found that resveratrol inhibited the proliferation of gastric cancer cells in a dose-dependent manner. At the concentration of 25 and 50 µM, resveratrol inhibited the cell viability and diminished the clonogenic potential of gastric cancer cells. Resveratrol treatment arrested gastric cancer cells in the G1 phase and led to senescence instead of apoptosis. Regulators of the cell cycle and senescence pathways, including cyclin D1, cyclin-dependent kinase (CDK4 and 6), p21 and p16, were dysregulated by resveratrol treatment. The inhibitory effects of resveratrol on gastric cancer were also verified in vivo using a nude mice xenograft model. Resveratrol (40 mg/kg/d) exerted inhibitory activities on gastric cancer development and significantly decreased the fractions of Ki67-positive cells in the tumor specimens from the nude mice. After resveratrol treatment, the induction of senescence and the changes in the expression of the regulators involved in the cell cycle and senescence pathways were similar to what we observed in vitro. However, the depletion of Sirtuin (Sirt)1 reversed the above-described effects of resveratrol both in vitro and in vivo. Our data suggest that resveratrol inhibits gastric cancer in a Sirt1-dependent manner and provide detailed evidence for the possibility of applying resveratrol in gastric cancer prevention and therapy.     

Synthesis and evaluation of 1,4-diphenylbutadiene derivatives as inhibitors of plasminogen activator inhibitor-1 (PAI-1) production

Butadiene-imide 1 (T-686) derivatives were synthesized and evaluated for their inhibitory activity against PAI-1 production and their ADMET (DMPK and toxicology) profiles. Among these derivatives, compound 15k (T-2639) showed good antithrombotic activity in two rat thrombosis models without affecting bleeding time, indicating reduction of haemorrhagic risk. We also describe in this report a practical synthesis of 15k suitable for scale-up using Z,E-selective Stobbe condensation.     

Acid-catalyzed transformation of 13(S)-hydroperoxylinoleic acid into epoxyhydroxyoctadecenoic and trihydroxyoctadecenoic acids

Acid treatment of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadienoic acid in tetrahydrofuran-water solvent afforded mainly (11R,12R,13S)-(Z)-12,13-epoxy-11-hydroxy-9-octadecenoic acid, diastereomeric (Z)-11,12,13-trihydroxy-9-octadecenoic acids and four isomers of (E)-9,12,13(9,10,13)-trihydroxy-10(11)-octadecenoic acid. Other minor products were oxooctadecadienoic, (E)-9(13)-hydroxy-13(9)-oxo-10(11)-octadecenoic and (E)-12-oxo-10-dodecenoic acids. A heterolytic mechanism for acid catalysis was indicated, even though most of the products characterized also have been observed as a result of homolytic decomposition of the hydroperoxide via an oxy radical. Most of the products found in this study have been observed as metabolites of (13S)-(9Z,11E)-13-hydroperoxy-9,11-octadecadenoic acid in biological systems, and analogous compounds have been reported as metabolites of (12S)-(5Z,8Z,10E, 14Z)-12-hydroperoxy-5,8,10,14-hydroperoxy-5,8,10,14-eicosatetraenoic acid in either blood platelets or lung tissue.     

Structural insight into the active site of mushroom tyrosinase using phenylbenzoic acid derivatives

So far, many inhibitors of tyrosinase have been discovered for cosmetic and clinical agents. However, the molecular mechanisms underlying the inhibition in the active site of tyrosinase have not been well understood. To explore this problem, we examined here the inhibitory effects of 4′-hydroxylation and methoxylation of phenylbenzoic acid (PBA) isomers, which have a unique scaffold to inhibit mushroom tyrosinase. The inhibitory effect of 3-PBA, which has the most potent inhibitory activity among the isomers, was slightly decreased by 4′-hydroxylation and further decreased by 4′-methoxylation against mushroom tyrosinase. Surprisingly, 4′-hydroxylation but not methoxylation of 2-PBA appeared inhibitory activity. On the other hand, both 4′-hydroxylation and methoxylation of 4-PBA increased the inhibitory activity against mushroom tyrosinase. In silico docking analyses using the crystallographic structure of mushroom tyrosinase indicated that the carboxylic acid or 4′-hydroxyl group of PBA derivatives could chelate with cupric ions in the active site of mushroom tyrosinase, and that the interactions of Asn260 and Phe264 in the active site with the adequate-angled biphenyl group are involved in the inhibitory activities of the modified PBAs, by parallel and T-shaped π-π interactions, respectively. Furthermore, Arg268 could fix the angle of the aromatic ring of Phe264, and Val248 is supposed to interact with the inhibitors as a hydrophobic manner. These results may enhance the structural insight into mushroom tyrosinase for the creation of novel tyrosinase inhibitors.