Overview Oncologic, Endocrine & Metabolic: Oncologic, Endocrine & Metabolic :Ellipticine and related anticancer agents

Bioactive Olivacine Derivatives-Potential Application in Cancer Therapy

Olivacine and its derivatives are characterized by multidirectional biological activity. Noteworthy is their antiproliferative effect related to various mechanisms, such as inhibition of growth factors, enzymes, kinases and others. The activity of these compounds was tested on cell lines of various tumors. In most publications, the most active olivacine derivatives exceeded the effects of doxorubicin (a commonly used anticancer drug), so in the future, they may become the main new anticancer drugs. In this publication, we present the groups of the most active olivacine derivatives obtained. In this work, the in vitro and in vivo activity of olivacine and its most active derivatives are presented. We describe olivacine derivatives that have been in clinical trials. We conducted a structure-activity relationship (SAR) analysis that may be used to obtain new olivacine derivatives with better properties than the available anticancer drugs.

Small Molecules Targeting Mutant P53: A Promising Approach for Cancer Treatment

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More than half of all human tumors express mutant forms of p53, with the ovary, lung, pancreas, and colorectal cancers among the tumor types that display the highest prevalence of p53 mutations. In addition, the expression of mutant forms of p53 in tumors is associated with poor prognosis due to increased chemoresistance and invasiveness. Therefore, the pharmacological restoration of wild-type-like activity to mutant p53 arises as a promising therapeutic strategy against cancer. This review is focused on the most relevant mutant p53 small molecule reactivators described to date. Despite some of them have entered into clinical trials, none has reached the clinic, which emphasizes that new pharmacological alternatives, particularly with higher selectivity and lower adverse toxic side effects, are still required.

A catalyst-free aqueous mediated multicomponent reaction of isocyanide: expeditious synthesis of polyfunctionalized cyclo[b]fused mono-, di- and tricarbazoles

A new multi-component reaction is developed for the synthesis of cyclo[b]fused mono-, di- and tricarbazoles from o-alkenyl arylisocyanides, aldehydes, and cyclic diketones in ethanol/water (1 : 1) as the solvent system.

Novel 11-Substituted Ellipticines as Potent Anticancer Agents with Divergent Activity against Cancer Cells

Ellipticines have well documented anticancer activity, in particular with substitution at the 1-, 2-, 6- and 9-positions. However, due to limitations in synthesis and coherent screening methodology the full SAR profile of this anticancer class has not yet been achieved. In order to address this shortfall, we have set out to explore the anticancer activity of this potent natural product by substitution. We currently describe the synthesis of novel 11-substituted ellipticines with two specific derivatives showing potency and diverging cellular growth effects.

Direct access to substituted benzo[b]carbazoles through cascade annulation of 2-vinylbenzaldehydes with indoles

A highly efficient palladium-catalyzed cascade annulation of 2-vinylbenzaldehydes with indoles has been achieved to afford 6-(3-indolyl)benzo[b]carbazoles under mild conditions in good yield and with excellent regioselectivity.

Gold(I)-Catalyzed Formal Intramolecular Dehydro-Diels-Alder Reaction of Ynamide-ynes: Synthesis of Functionalized Benzo[ b]carbazoles

A gold-catalyzed cycloisomerization of ynamide-ynes via a formal dehydro-Diels-Alder reaction has been developed, providing an attractive route to diversely substituted benzo[ b]carbazoles. The reaction likely proceeds via regioselective attack of the pendant alkyne moiety to a keteniminium ion intermediate followed by benzannulation. The method offers several advantages such as high efficiency, mild reaction conditions, and wide functional group tolerance and serves as a highly useful complement to the thermal DDA reactions of ynamide-ynes.

Loading of an anti-cancer drug into mesoporous silica nano-channels and its subsequent release to DNA

Mesoporous silica nano-channel (MCM-41) based molecular switching of a biologically important anticancer drug, namely, ellipticine (EPT) has been utilized to probe its efficient loading onto MCM-41, and its subsequent release to intra-cellular biomolecules, like DNA. By exploiting various spectroscopic techniques (like, steady state fluorescence, time-resolved fluorescence and circular dichroism), it has been shown that EPT can be easily translocated from MCM-41 to DNA without using any external stimulant. Blue emission of EPT in a polar aprotic solvent, i.e., dichloromethane (DCM), completely switches to green upon loading inside MCM-41 due to the conversion from a neutral to a protonated form of the drug inside nano-pores. Powder X-ray diffraction (PXRD), N₂ gas adsorption and confocal fluorescence microscopy results confirm the adsorption of EPT inside the nano-pores of MCM-41. Here, the lysozyme (Lyz) protein has been utilized as a pore blocker of MCM-41 in order to prevent premature drug release. Interestingly, EPT is released to DNA even from the EPT-MCM-Lyz composite system, and results in intensification of green fluorescence. Electron microscopy results reveal the formation of a distinctive garland kind of morphology involving MCM-41 and DNA probably through non-covalent interactions, and this is believed to be responsible for the DNA assisted release of drug molecules from silica nano-pores. Confocal laser scanning microscopy (CLSM) imaging revealed that EPT-MCM is successfully internalized into the HeLa cervical cancer cells and localized into the nucleus. Cell viability assay results infer that EPT-MCM and EPT-MCM-Lyz showed much improved efficacy in HeLa cancer cells compared to free ellipticine.

Synthesis, structure and in vitro cytostatic activity of ferrocene-Cinchona hybrids

Exploring copper(I)- and ruthenium(II)-catalyzed azide-alkyne cycloadditions and a Sonogashira protocol, novel cytostatic ferrocene-cinchona hybrids were synthetized displaying significant in vitro activity on HepG-2 and HT-29 cells. Preliminary SAR studies disclosed that compounds incorporating linkers with 1,2,3-triazole and chalchone residues can be considered as promising lead structures. According to the best of our knowledge this is the first letter on the incorporation of ferrocene nucleus in the reputed cinchona family via triazole and chalcone linkers with established pharmaceutical profile.

Partitioning of prototropic species of an anticancer drug ellipticine in bile salt aggregates of different head groups and hydrophobic skeletons: a photophysical study to probe bile salts as multisite drug carriers

The entrapment of neutral and cationic species of an anticancer drug, namely ellipticine and their dynamic features in different bile salt aggregates have been investigated for the first time using steady state and time-resolved fluorescence spectroscopy. Because ellipticine exists in various prototropic forms under physiological conditions, we performed comparative photophysical and dynamical studies on these prototropic species in different bile salts varying in their head groups and hydrophobic skeletons. We found that the initial interaction between ellipticine and bile salts is governed by the electrostatic forces where cationic ellipticine is anchored to the head groups of bile salts. Bile salts having conjugated head groups are better candidates to bind with the cationic species than those having the non-conjugated ones. The fact implies that binding of cationic species to different bile salts depends on the pK(a) of the corresponding bile acids. The hydrophobic interaction dominates at higher concentrations of bile salts due to formation of aggregates and results in entrapment of neutral ellipticine molecules according to their hydrophobicity indices. Thus bile salts act as multisite drug carriers. The rotational relaxation parameters of cationic ellipticine were found to be dependent on head groups and the number of hydroxyl groups on the hydrophilic surface of bile salts. Cationic ellipticine exhibits a faster rotational relaxation in the tri-hydroxy bile salt aggregates than in di-hydroxy bile salts. We interpreted this observation from the fact that tri-hydroxy bile salts hold a higher number of water molecules in their hydrophilic surface offering a less viscous environment for ellipticine compared to di-hydroxy bile salts. Surprisingly, the neutral ellipticine molecules display almost the same rotational relaxation in all the bile salts. The observation indicates that after intercalation inside the hydrophobic pocket, neutral ellipticine molecules experience similar confinement in all the bile salts.

Excited state proton transfer dynamics of an eminent anticancer drug, ellipticine, in octyl glucoside micelle

Photophysics and proton transfer dynamics of an eminent anticancer drug, ellipticine (EPT), have been investigated inside a biocompatible octyl-β-D-glucoside (OBG) micellar medium using steady state and time-resolved fluorescence spectroscopic techniques. EPT exists as protonated form in aqueous solution of pH 7. When EPT molecules are encapsulated in OBG micelles, protonated form is converted to neutral form in the ground state due to the hydrophobic effect of the micellar environment. Interestingly, steady state fluorescence results indicate the existence of both neutral and protonated forms of EPT in the excited state, even though neutral molecules are selectively excited, and it is attributed to the conversion of neutral to protonated form of EPT by the excited state proton transfer (ESPT) process. A clear isoemissive point in the time-resolved area normalized emission spectra (TRANES) further supports the excited state conversion of neutral to protonated form of EPT. Notably, this kind of proton transfer dynamics is not observed in other conventional micelles, such as, SDS, Triton-X and CTAB. Therefore, the observed ESPT dynamics is believed to be an outcome of combined effects of the local dielectric constant felt by EPT and the local proton concentration at the OBG micellar surface.

pH responsive translocation of an anticancer drug between cyclodextrin and DNA

Herein, the pH triggered translocation of EPT in between γ-cyclodextrin and DNA is monitored using fluorescence switch of the drug.

An anticancer drug to probe non-specific protein-DNA interactions

A visible fluorescence switch of an eminent anti-carcinogen, ellipticine has been used to probe non-specific protein-DNA interaction. The unique pattern of protein-DNA complexation is depicted for the first time through field emission scanning electron microscopy (FE-SEM) images and spectroscopic techniques.

Total synthesis of ellipticine quinones, olivacine, and calothrixin B

A direct route to the synthesis of biologically active ellipticine quinones, olivacine, and calothrixin B is described. The prominent key steps involved are Friedel-Crafts hydroxyalkylation followed by oxidation and directed ortho-lithiation reactions of readily available indole-2-carboxylate esters with appropriately substituted pyridine and quinoline carboxaldehydes.

Acylated mono-, bis- and tris- cinchona-based amines containing ferrocene or organic residues: synthesis, structure and in vitro antitumor activity on selected human cancer cell lines

A series of novel functionalized mono-, bis- and tris-(S)-{[(2S,4R,8R)-8-ethyl-quinuclidin-2-yl](6-methoxyquinolin-4-yl)}methanamines including ferrocene-containing derivatives was obtained by the reaction of the precursor amine with a variety of acylation agents. Their in vitro antitumor activity was investigated against human leukemia (HL-60), human neuroblastoma (SH-SY5Y), human hepatoma (HepG2) and human breast cancer (MCF-7) cells by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-assay and the 50% inhibitory concentration (IC₅₀) values were determined. Our data indicate that the precursor amine has no antitumor activity in vitro, but the bis-methanamines with ureido-, thioureido and amide-type linkers display attractive in vitro cytotoxicity and cytostatic effects on HL-60, HepG2, MCF-7 and SH-SY5Y cells. Besides ¹H- and ¹³C-NMR methods the structures of the new model compounds were also studied by DFT calculations.

Spectral study of the interaction of DNA with benzothiazolyl-benz-alpha-chromene

Absorption and luminescence excitation and emission spectra of newly synthesized 2-(4-methylphenylimino)-3-(2 -benzothiazolyl)benz-alpha-chromene (BCBT) have been studied in the presence of various DNA concentrations. BCBT is characterized by the existence of two different fluorescent systems, exhibiting radiationless fluorescence resonance energy transfer between them. In the range of molar ratios of polynucleotide/dye concentrations from 0 to 50, BCBT preferentially intercalates into DNA due to its benz-alpha-chromene fragment, whereas the 2-benzothiazolyl fragment is responsible for fluorescence.

Synthesis and Biological Evaluation of Indoloquinolines and Pyridocarbazoles: A New Example of Unexpected Photoreduction Accompanying Photocyclization

Indoloquinoline alkaloid cryptolepine and pyridocarbazole alkaloid ellipticine are of great interest because in vitro and in vivo studies revealed their good cytotoxic properties. In order to obtain some biologically active analogs of these compounds, we developed a synthesis based on the photocyclization of tertiary N-substituted enaminones derived from 1,3-cyclohexandione and 3 or 6-aminoquinoline. The angular cyclized compounds thus obtained were tested in vitro on K 562 cells and A 2780 doxorubicin sensitive and resistant cells. All compounds were less effective than doxorubicin in sensitive cells but their activity wasn't decreased by MDR resistance.

Solvent Effect on the Photophysical Properties of the Anticancer Agent Ellipticine

This paper investigates how solution conditions, especially solvent polarity and hydrogen bonding, affect the fluorescence of ellipticine, a natural plant alkaloid with anticancer activity. A total of 16 solvents that cover a wide range of polarities were tested. The ultraviolet (UV) absorption and fluorescence emission of ellipticine were found to be solvent dependent. The absorption and emission maximum shifted to higher wavelengths (red shift) with increased solvent polarity. The difference in absorption and emission maximum (Stokes' shift) was large, approximately 10,000-11,000 cm-1, in polar solvents (with orientation polarizability Deltaf>0.2) but unusually small, approximately 8900 cm-1, in nonpolar solvents (hexane and cyclohexane). Large Stokes' shifts were due to an intramolecular charge transfer (ICT), which was enabled by large solvent polarity and hydrogen bonding of ellipticine with the solvents. Two transitions were found in the Lippert-Mataga plot between (1) nonpolar and semipolar solvents and between (2) semipolar and polar solvents. The first transition reflected the formation of hydrogen bonds between ellipticine and the solvents whereas the second transition indicated that ellipticine underwent an ICT. In addition, the larger extinction coefficients and the longer lifetime of ellipticine obtained in protic solvents were attributed to the formation of stronger hydrogen bonds. The photophysical response of ellipticine to changes in solvent polarity and hydrogen bond formation could be used to infer the location of ellipticine in a heterogeneous medium, namely liposomes in aqueous solution. A relatively large red shift of emission in liposomes indicated that ellipticine may be in a more polar environment with respect to the lipid bilayer, possibly close to the hydrophilic interface.

Molecular Property eXplorer: a novel approach to visualizing SAR using tree-maps and heatmaps

The tremendous increase in chemical structure and biological activity data brought about through combinatorial chemistry and high-throughput screening technologies has created the need for sophisticated graphical tools for visualizing and exploring structure-activity data. Visualization plays an important role in exploring and understanding relationships within such multidimensional data sets. Many chemoinformatics software applications apply standard clustering techniques to organize structure-activity data, but they differ significantly in their approaches to visualizing clustered data. Molecular Property eXplorer (MPX) is unique in its presentation of clustered data in the form of heatmaps and tree-maps. MPX employs agglomerative hierarchical clustering to organize data on the basis of the similarity between 2D chemical structures or similarity across a predefined profile of biological assay values. Visualization of hierarchical clusters as tree-maps and heatmaps provides simultaneous representation of cluster members along with their associated assay values. Tree-maps convey both the spatial relationship among cluster members and the value of a single property (activity) associated with each member. Heatmaps provide visualization of the cluster members across an activity profile. Unlike a tree-map, however, a heatmap does not convey the spatial relationship between cluster members. MPX seamlessly integrates tree-maps and heatmaps to represent multidimensional structure-activity data in a visually intuitive manner. In addition, MPX provides tools for clustering data on the basis of chemical structure or activity profile, displaying 2D chemical structures, and querying the data based over a specified activity range, or set of chemical structure criteria (e.g., Tanimoto similarity, substructure match, and "R-group" analysis).

Spectral Study of Interactions of 4,8,4′-Trimethylpsoralen and 4,4′-Dimethylangelicin Dyes with DNA

Absorption and fluorescence spectra for six new synthetic dyes of 4,8,4'-trimethylpsoralen and 4,4'-dimethylangelicin derivatives containing various terminal substituents at 5'-position have been investigated in different environments using a wide range of the DNA/ligand concentrations. Various spectral and binding characteristics of the DNA-ligand systems have been determined. General principles characterizing mechanisms responsible for changes in the fluorescent properties of nucleotide-specific dyes have been proposed; they take into consideration chemical structure of the dyes, properties of the environment, and degree of sorption on substrate.

Study of Applicability of the Bifunctional System “Ethidium Bromide + Hoechst-33258” for DNA Analysis

Changes in absorbance and fluorescence excitation and emission spectra in the ultraviolet and visible regions of the system containing ethidium bromide (EtBr) and Hoechst-33258 (Ht) were investigated depending on various DNA quantities and the composition of the medium. It is noted that spectral properties of this system are determined by interactions of EtBr and Ht both with nucleic acid and with one another (for example, joint sorption of EtBr and Ht on DNA may involve fluorescent resonance energy transfer between the dye molecules). Thus, different modes of EtBr and Ht specificity to substrate and assay conditions suggest that combined use of these dyes provides some additional effects that may be interesting in terms of structure-functional study of nucleic acid. Some of these effects are considered in this paper.

1,5-dimethyl-6H-pyridazino[4,5-b]carbazole, a 3-aza bioisoster of the antitumor alkaloid olivacine

A series of b-fused carbazoles structurally related to pyrido[4,3-b]carbazole-type alkaloids was prepared, utilizing the Diels-Alder reaction of 1-methylpyrano[3,4-b]indol-3(9H)-one with electron-deficient acetylenic dienophiles as the key step. The title compound (14) thus obtained in only four steps represents a new 3-aza analog of the antitumor natural product, olivacine.

LeadScope: software for exploring large sets of screening data

Modern approaches to drug discovery have dramatically increased the speed and quantity of compounds that are made and tested for potential potency. The task of collecting, organizing, and assimilating this information is a major bottleneck in the discovery of new drugs. We have developed LeadScope a novel, interactive computer program for visualizing, browsing, and interpreting chemical and biological screening data that can assist pharmaceutical scientists in finding promising drug candidates. The software organizes the chemical data by structural features familiar to medicinal chemists. Graphs are used to summarize the data, and structural classes are highlighted that are statistically correlated with biological activity.