Antibacterial activity of noscapine analogs.

The antibacterial properties of close noscapine analogs have not been previously reported. We used our pDualrep2 double-reporter High Throughput Screening (HTS) platform to identify a series of noscapine derivatives with promising antibacterial activity. The platform is based on RPF (SOS-response/DNA damage) and Katushka2S (inhibition of translation) proteins and simultaneously provides information on antibacterial activity and the mechanism of action of small-molecule compounds against E. coli. The most potent compound exhibited an MIC of 13.5 µM(6.25 µg/ml) and a relatively low cytotoxicity against HEK293 cells (CC50 = 71 µM, selectivity index: ~5.5). Some compounds from this series induced average Katushka2S reporter signals, indicating inhibition of translation machinery in the bacteria; however, these compounds did not attenuate translation in vitro in a luciferase-based translation assay. The most effective compounds did not significantly arrest the mitotic cycle in HEK293 cells, in contrast to the parent compound in a flow cytometry assay. Several molecules showed activity against clinically relevant gram-negative and gram-positive bacterial strains. Compounds from the discovered series can be reasonably regarded as good templates for further development and evaluation.

Discovery of noscapine derivatives as potential ß-tubulin inhibitors.

Twenty novel 1,2,3-triazole noscapine derivatives were synthesized starting from noscapine by consecutive N-demethylation, reduction of lactone ring, N-propargylation and Huisgen 1,3-dipolar cycloaddition reaction. In order to select the most promising molecules to subject to further biophysical and biological evaluation, a molecular docking analysis round was performed using noscapine as reference compound. The molecules featuring docking predicted binding affinity better than that of noscapine were then subjected to MTT assay against MCF7 cell line. The obtained results disclosed that all the selected triazole derivatives exhibited a remarkably lower cell viability compared to noscapine in the range of 20 µM in 48 h. In an attempt to correlate the biological activity with the ability to bind tubulin, the surface plasmon resonance (SPR) assay was employed. Compounds 8a, 8h, 9c, 9f and 9j were able to bind tubulin with affinity constant values in the nanomolar range and higher if compared to noscapine. Integrating computational predictions and experimental evaluation, two promising compounds (8h and 9c) were identified, whose relevant cytotoxicity was supposed to be correlated with tubulin binding affinity. These findings shed lights onto structural modifications of noscapine toward the identification of more potent cytotoxic agents targeting tubulin.

N-substituted noscapine derivatives as new antiprotozoal agents: Synthesis, antiparasitic activity and molecular docking study.

Novel N-substituted noscapine derivatives were synthesized by a three-component Strecker reaction of cyclic ether of N-nornoscapine with varied aldehydes, in the presence of cyanide ion. Moreover, the corresponding amides were synthesized by the oxidation of cyanide moieties in good yields. The in vitro antiprotozoal activity of the products was also investigated. Interestingly, some analogues did put on display promising antiparasitic activity against Trypanosoma brucei rhodesiense with IC50 values between 2.5 and 10.0 µM and selectivity index (SI) ranged from 0.8 to 13.2. Eight compounds exhibited activity against Plasmodium falciparum K1 strain with IC50 ranging 1.7-6.4 µM, and SI values between 2.8 and 10.5 against L6 rat myoblast cell lines. Molecular docking was carried out on trypanothione reductase (TbTR, PDB ID: 2WOW) and UDP-galactose 4' epimerase (TbUDPGE PDB: 1GY8) as targets for studying the envisaged mechanism of action. Compounds 6j2 and 6b2 displayed excellent docking scores with -8.59 and -8.86 kcal/mol for TbTR and TbUDPGE, respectively.

Design, synthesis and biological evaluation of di-substituted noscapine analogs as potent and microtubule-targeted anticancer agents.

Noscapine is an opium-derived kinder-gentler microtubule-modulating drug, currently in Phase I/II clinical trials for cancer chemotherapy. Here, we report the synthesis of four more potent di-substituted brominated derivatives of noscapine, 9-Br-7-OH-NOS (2), 9-Br-7-OCONHEt-NOS (3), 9-Br-7-OCONHBn-NOS (4), and 9-Br-7-OAc-NOS (5) and their chemotherapeutic efficacy on PC-3 and MDA-MB-231 cells. The four derivatives were observed to have higher tubulin binding activity than noscapine and significantly affect tubulin polymerization. The equilibrium dissociation constant (KD) for the interaction between tubulin and 2, 3, 4, 5 was found to be, 55±6µM, 44±6µM, 26±3µM, and 21±1µM respectively, which is comparable to parent analog. The effects of these di-substituted noscapine analogs on cell cycle parameters indicate that the cells enter a quiescent phase without undergoing further cell division. The varying biological activity of these analogs and bulk of substituent at position-7 of the benzofuranone ring system of the parent molecule was rationalized utilizing predictive in silico molecular modeling. Furthermore, the immunoblot analysis of protein lysates from cells treated with 4 and 5, revealed the induction of apoptosis and down-regulation of survivin levels. This result was further supported by the enhanced activity of caspase-3/7 enzymes in treated samples compared to the controls. Hence, these compounds showed a great potential for studying microtubule-mediated processes and as chemotherapeutic agents for the management of human cancers.

Design, synthesis and biological evaluation of 1-phenanthryl-tetrahydroisoquinoline derivatives as novel p21-activated kinase 4 (PAK4) inhibitors.

Functional versatility and elevated expression in cancers have promoted p21-activated kinase 4 (PAK4) as one of the first-in-class anti-cancer drug targets. In this study, a series of novel 1-phenanthryl-tetrahydroisoquinoline analogues have been designed and synthesized as a novel class of small-molecule PAK4 inhibitors to fit into the cavity of PAK4. All of the target compounds were evaluated for their in vitro PAK4 inhibitory activities and antiproliferative activities. Lead optimization identified all the derivatives with more potency than the lead compound, especially compound 21a. Moreover, compound 21a significantly induced the cell cycle in the G1/S phase, and inhibited migration and invasion of MCF-7 cells via the regulation of the PAK4-LIMK1-cofilin signaling pathway. A molecular modeling study showed possible novel binding modes between 21a and PAK4 and provided a structural basis for further structure-guided design of PAK4 inhibitors.

Synthesis and biological evaluation of novel biaryl type α-noscapine congeners.

Natural α-noscapine, a known antitussive drug, is also now known to possess weak anticancer efficacy with relatively safe toxicity profile. In this study, we report synthesis and evaluation of novel biaryl type α-noscapine congeners designed by adding aryl unit to the tetrahydroisoquinoline part of natural α-noscapine core. Palladium catalyzed Suzuki cross coupling of 9-bromo α-noscapine with aryl boronic acids was employed using mild and inexpensive reagents to attain desired noscapinoids 5a-g in excellent yields. Screening anti-proliferative activity for new noscapinoids 5b-g, on human cancer cell lines resulted three compounds 5b, 5d and 5f as potent analogues, active against human breast epithelial (MCF-7), human cervix cancer (HeLa) and human lung adenocarcinoma epithelial (A549) cell lines.

Copper(I) mediated facile synthesis of potent tubulin polymerization inhibitor, 9-amino-α-noscapine from natural α-noscapine.

Facile synthesis of natural α-noscapine analogue, 9-amino-α-noscapine, a potent inhibitor of tubulin polymerization for cancer therapy, is achieved via copper(I) iodide mediated in situ aromatic azidation and reduction of 9-bromo-α-noscapine (obtained by bromination of natural α-noscapine) with NaN(3) in DMSO at 130°C in the presence of L-proline as an amino acid promoter. The protocol developed here avoided isolation of 9-azido-α-noscapine and did not cleave the sensitive C-C bond between two heterocyclic phthalide and isoquinoline units.

In silico inspired design and synthesis of a novel tubulin-binding anti-cancer drug: folate conjugated noscapine (Targetin).

Our screen for tubulin-binding small molecules that do not depolymerize bulk cellular microtubules, but based upon structural features of well known microtubule-depolymerizing colchicine and podophyllotoxin, revealed tubulin binding anti-cancer property of noscapine (Ye et al. in Proc Natl Acad Sci USA 95:2280-2286, 1998). Guided by molecular modelling calculations and structure-activity relationships we conjugated at C9 of noscapine, a folate group-a ligand for cellular folate receptor alpha (FRα). FRα is over-expressed on some solid tumours such as ovarian epithelial cancers. Molecular docking experiments predicted that a folate conjugated noscapine (Targetin) accommodated well inside the binding cavity (docking score -11.295 kcal/mol) at the interface between α- and ß-tubulin. The bulky folate moiety of Targetin is extended toward lumen of microtubules. The binding free energy (ΔG (bind)) computed based on molecular mechanics energy minimization was -221.01 kcal/mol that revealed favourable interaction of Targetin with the receptor. Chemical synthesis, tubulin-binding experiments, and anti-cancer activity in vitro corroborate fully well with the molecular modelling experiments. Targetin binds tubulin with a dissociation constant (K (d) value) of 149 ± 3.0 µM and decreases the transition frequencies between growth and shortening phases of microtubule assembly dynamics at concentrations that do not alter the total polymer mass. Cancer cells in general were more sensitive to Targetin compared with the founding compound noscapine (IC(50) in the range of 15-40 µM). Quite strikingly, ovarian cancer cells (SKOV3 and A2780), known to overexpress FRα, were much more sensitive to targetin (IC(50) in the range of 0.3-1.5 µM).

Synthesis and biological evaluation of noscapine analogues as microtubule-interfering agents.

A series of noscapine analogues have been synthesized via 13-step reaction starting from 2-hydroxy-3-methoxybenzaldehyde. Anti-tumor activities of these compounds were evaluated against HL-60 cell lines in vitro by the standard MTT assay. It was found that most of these derivatives showed appreciable inhibitory activity against HL-60 and tubulin polymerization. The results also indicated that the potency of compound 31 is about three times more than that ofnoscapine against HL-60 cell line and tubulin polymerization. Moreover, it induced a massive accumulation of cells in G2/M phase. These results showed noscapine and its derivatives were worth to be intensively studied further.

Rational design, synthesis and biological evaluations of amino-noscapine: a high affinity tubulin-binding noscapinoid.

Noscapine and its derivatives are important microtubule-interfering agents shown to have potent anti-tumor activity. The binding free energies (ΔG (bind)) of noscapinoids computed using linear interaction energy (LIE) method with a surface generalized Born (SGB) continuum solvation model were in agreement with the experimental ΔG (bind) with average root mean square error of 0.082 kcal/mol. This LIE-SGB model guided us in designing a novel derivative of noscapine, amino-noscapine [(S)-3-((R)-9-amino-4-methoxy-6-methyl-5,6,7,8-tetrahydro [1, 3] dioxolo[4,5-g]isoquinolin-5-yl)-6,7-dimethoxy isobenzo-furan-1(3H)-one] that has higher tubulin binding activity (predicted ΔG (bind) = -6.438 kcal/mol and experimental ΔG (bind) = -6.628 kcal/mol) than noscapine, but does not significantly change the total extent of the tubulin subunit/polymer ratio. The modes of interaction of amino-noscapine with the binding pocket of tubulin involved three hydrogen bonds and are distinct compared to noscapine which involved only one hydrogen bond. Also the patterns of non-bonded interactions are albeit different between both the lignads. The 'blind docking' approach (docking of ligand with different binding sites of a protein and their evaluations) as well as the reasonable accuracy of calculating ΔG (bind) using LIE-SGB model constitutes the first evidence that this class of compounds binds to tubulin at a site overlapping with colchicine-binding site or close to it. Our results revealed that amino-noscapine has better anti-tumor activity than noscapine.

Novel noscapine derivatives stabilize the native state of insulin against fibrillation.

Protein aggregation to form amyloid is associated with many human diseases, increasing the need to develop inhibitors of this process. Here we evaluate the ability of derivatives of the small organic compound noscapine, derived from the opium poppy, to inhibit fibrillation of the model protein insulin. We combined biophysical methods to assess insulin stability and aggregation with computational docking and cell viability studies to identify the most potent derivatives. The best aggregation inhibitor (a phenyl derivative of N-nornoscapine) also demonstrated the highest ability to stabilize native insulin against thermal denaturation. This compound maintained insulin largely in the monomeric and natively folded state under fibrillation conditions and also decreased insulin aggregate toxicity against human neuroblastoma SH-SY5Y cells. The inhibitory effects were specific for insulin fibrillation, as the noscapine compounds did not inhibit fibrillation of other proteins such as α-synuclein, Aß, and FapC. Our data demonstrate that compounds which stabilize the folded native state of a protein can not only inhibit fibrillation but also decrease the toxicity of the mature fibrillar aggregates of insulin protein.

A Novel Class of N-Sulfonyl and N-Sulfamoyl Noscapine Derivatives that Promote Mitotic Arrest in Cancer Cells.

Noscapine displays weak anticancer efficacy and numerous research efforts have attempted to generate more potent noscapine analogues. These modifications included the replacement of the N-methyl group in the 6'-position with a range of substituents, where N-ethylcarbamoyl substitution was observed to possess enhanced anticancer activity. Herein, we describe advances in this area, namely the synthesis and pharmacological evaluation of a series of N-sulfonyl and N-sulfamoyl noscapine derivatives. A number of these sulfonyl-containing noscapinoids demonstrated improved activities compared to noscapine. ((R)-5-((S)-4,5-Dimethoxy-1,3-dihydroisobenzofuran-1-yl)-4-methoxy-6-((1-methyl-1H-imidazol-4-yl)sulfonyl)-5,6,7,8-tetrahydro[1,3]dioxolo[4,5-g]isoquinoline) (14 q) displayed sub-micromolar activities of 560, 980, 271 and 443 nM against MCF-7, PANC-1, MDA-MB-435 and SK-MEL-5 cells, respectively. This antiproliferative effect was also maintained against drug-resistant NCI/AdrRES cells despite high expression of the multidrug efflux pump, P-glycoprotein.

Insights into the structure and tubulin-targeted anticancer potential of N-(3-bromobenzyl) noscapine.

BACKGROUND: Noscapine is a non-narcotic, antitussive alkaloid isolated from plants of Papaveraceae family. This benzylisoquinoline alkaloid and its synthetic derivatives, called noscapinoids, are being evaluated for their anticancer potential. METHODS: The structure of a novel analogue, N-(3-bromobenzyl) noscapine (N-BBN) was elucidated by X-ray crystallography. Effect of N-BBN on cancer cell proliferation and cellular microtubules were studied by sulphorhodamine B assay and immunofluorescence, respectively. Binding interactions of the alkaloid with tubulin was studied using spectrofluorimetry. RESULTS: N-BBN, synthesized by introducing modification at site B ('N' in isoquinoline unit) and a bromo group at the 9th position of the parent compound noscapine, was found to be superior to many of the past-generation noscapinoids in inhibiting cancer cell viability and it showed a strong inhibition of the clonogenic potential of an aggressively metastatic breast tumour cell line, MDA-MB-231. The compound perturbed the tertiary structure of purified tubulin as indicated by an anilinonaphthalene sulfonic acid-binding assay. However, substantiating the common feature of noscapinoids, it did not alter microtubule polymer mass considerably. In cells, the drug-treatment showed a peculiar type of disruption of normal microtubule architecture. CONCLUSION: N-BBN may be considered for further investigations as a potent antiproliferative agent.

Elucidation of the Tubulin-targeted Mechanism of Action of 9-(3-pyridyl) Noscapine.

We have recently reported the synthesis and antiproliferative potential of a series of biaryl type α-noscapine congeners. Among them, 9-(3-pyridyl) noscapine 3f (9-PyNos, henceforth), which was synthesized by adding pyridine unit to the tetrahydroisoquinoline part of natural α-noscapine core, was found to be the most effective one to inhibit proliferation of a variety of cancer cell lines. However, details of its interactions with its cellular target, tubulin, remain poorly understood. In this report, we examined the nature of interactions of 9-PyNos with tubulin based on the methodologies of spectrofluorimetry, circular dichroism, and turbidimetry techniques. Far-UV circular dichroism spectra indicated perturbation of tubulin secondary structure in the presence of 9-PyNos, not amounting, however, to the perturbation induced by noscapine. The noscapinoid nevertheless altered the surface configuration of the protein considerably, as indicated by an anilinonaphthalene sulphonate binding assay, and promoted colchicine binding to tubulin, the latter indicating its adjacent binding site with colchicine. 9-PyNos however, did not alter microtubule assembly considerably. Investigating the possible reason behind this apparent lack of strong inhibition of microtubule assembly, we found that the binding interactions of tubulin with 9-PyNos do not involve modification of cysteine residues of tubulin. Taken together, our data suggest that the antiproliferative mechanism of action of 9-PyNos involves disruption of structural integrity of tubulin without strong inhibition of tubulin assembly.

Synthesis of microtubule-interfering halogenated noscapine analogs that perturb mitosis in cancer cells followed by cell death.

We have previously identified the naturally occurring non-toxic antitussive phthalideisoquinoline alkaloid, noscapine as a tubulin-binding agent that arrests mitosis and induces apoptosis. Here we present high-yield efficient synthetic methods and an evaluation of anticancer activity of halogenated noscapine analogs. Our results show that all analogs display higher tubulin-binding activity than noscapine and inhibit proliferation of human cancer cells (MCF-7, MDA-MB-231 and CEM). Surprisingly, the bromo-analog is approximately 40-fold more potent than noscapine in inhibiting cellular proliferation of MCF-7 cells. The ability of these analogs to inhibit cellular proliferation is mediated by cell cycle arrest at the G2/M phase, in that all analogs except 9-iodonoscapine, caused selective mitotic arrest with a higher efficiency than noscapine followed by apoptotic cell death as shown by immunofluorescence and quantitative FACS analyses. Furthermore, our results reveal the appearance of numerous fragmented nuclei as evidenced by DAPI staining. Thus, our data indicate a great potential of these compounds for studying microtubule-mediated processes and as chemotherapeutic agents for the management of human cancers.

Discovery of S-phase arresting agents derived from noscapine.

Analogues of the natural product noscapine were synthesized, and their potential as antitumor agents were examined. The discovery of a novel regio- and stereoselective O-demethylation led to the synthesis of several O-alkylated analogues that induced an unexpected S-phase arrest of mammalian cells. Compound 4a was the most potent analogue inhibiting cell proliferation at an EC(50) of 1.9 microM.

Identification of novel and improved antimitotic agents derived from noscapine.

Analogues of the natural product noscapine were synthesized and their potential as antitumor agents evaluated. The discovery of a novel regioselective O-demethylation facilitated the synthesis of the potent aniline 6, which arrests mammalian cells in the G2/M phase of the cell cycle at 0.1 microM and also affects tubulin polymerization. Aniline 6 is orally bioavailable and is 250-fold more potent than noscapine in reducing cell proliferation in rapidly dividing cells.

Noscapine comes of age.

Noscapine is a phthalideisoquinoline alkaloid, which represents a class of plant specialized metabolites within the large and structurally diverse group of benzylisoquinoline alkaloids. Along with the narcotic analgesic morphine, noscapine is a major alkaloid in the latex of opium poppy (Papaver somniferum) that has long been used as a cough suppressant and has undergone extensive investigation as a potential anticancer drug. Cultivated opium poppy plants remain the only commercial source of noscapine. Despite its isolation from opium more than two centuries ago, the almost complete biosynthesis of noscapine has only recently been established based on an impressive combination of molecular genetics, functional genomics, and metabolic biochemistry. In this review, we provide a historical account of noscapine from its discovery through to initial investigations of its formation in opium poppy. We also describe recent breakthroughs that have led to an elucidation of the noscapine biosynthetic pathway, and we discuss the pharmacological properties that have prompted intensive evaluation of the potential pharmaceutical applications of noscapine and several semi-synthetic derivatives. Finally, we speculate on the future potential for the production of noscapine using metabolic engineering and synthetic biology in plants and microbes.

Tubulin binding, protein-bound conformation in solution, and antimitotic cellular profiling of noscapine and its derivatives.

Noscapine and its 7-hydroxy and 7-amino derivatives were characterized for their binding to tubulin. A solution NMR structure of these compounds bound to tubulin shows that noscapine and its 7-aniline derivative do not compete for the same binding site nor does its small molecule crystal structure match its tubulin-bound conformation. These compounds were also tested for their antiproliferative effects on a panel hepatocellular carcinoma cell lines.

Synthesis and biological evaluation of N-substituted noscapine analogues.

Noscapine is a phthalideisoquinoline alkaloid isolated from the opium poppy Papaver somniferum. It has long been used as an antitussive agent, but has more recently been found to possess microtubule-modulating properties and anticancer activity. Herein we report the synthesis and pharmacological evaluation of a series of 6'-substituted noscapine derivatives. To underpin this structure-activity study, an efficient synthesis of N-nornoscapine and its subsequent reduction to the cyclic ether derivative of N-nornoscapine was developed. Reaction of the latter with a range of alkyl halides, acid chlorides, isocyanates, thioisocyanates, and chloroformate reagents resulted in the formation of the corresponding N-alkyl, N-acyl, N-carbamoyl, N-thiocarbamoyl, and N-carbamate derivatives, respectively. The ability of these compounds to inhibit cell proliferation was assessed in cell-cycle cytotoxicity assays using prostate cancer (PC3), breast cancer (MCF-7), and colon cancer (Caco-2) cell lines. Compounds that showed activity in the cell-cycle assay were further evaluated in cell viability assays using PC3 and MCF-7 cells.