Structure-activity relationships and binding mode of styrylquinolines as potent inhibitors of HIV-1 integrase and replication of HIV-1 in cell culture

Quinolines and isoquinolines as HIV-1 inhibitors: Chemical structures, action targets, and biological activities

Human immunodeficiency virus type 1 (HIV-1), a lentivirus that causes acquired immunodeficiency syndrome (AIDS), poses a serious threat to global public health. Since the advent of the first drug zidovudine, a number of anti-HIV agents acting on different targets have been approved to combat HIV/AIDS. Among the abundant heterocyclic families, quinoline and isoquinoline moieties are recognized as promising scaffolds for HIV inhibition. This review intends to highlight the advances in diverse chemical structures and abundant biological activity of quinolines and isoquinolines as anti-HIV agents acting on different targets, which aims to provide useful references and inspirations to design and develop novel HIV inhibitors for medicinal chemists.

Microwave and Cs+-assisted chemo selective reaction protocol for synthesizing 2-styryl quinoline biorelevant molecules

The reaction protocols and their continuous development to achieve the desired selectivity remain a primary target of organic chemistry, which is addressed here with the specific role of the cesium ion. The pharmacophore “2-styryl quinoline” was taken as a reference here because of the continuation of our work, where it was found fit as fusion inhibitors and anti-viral agents. The present protocol defines its importance for the synthesis of O-alkylated products. However, in most cases, N-alkylation proceeds because of nitrogen atoms’ more nucleophilic nature and electronic density. The cesium effect makes this possible because of the large cationic size and its affection for the oxygen atom. The plausible mechanism and its progression were demonstrated here with the help of density function theory calculation by analyzing the energy of intermediates. The protocol is also found suitable with microwave irradiation. Moreover, it gives the product a better yield in less reaction time. The present reaction protocol and its importance will address some of the crucial issues related to the synthesis of the complex molecule, and the present protocol will open up hope, where the selectivity and product yield would be a concern.

Fragment-Based Lead Discovery Strategies in Antimicrobial Drug Discovery

Fragment-based lead discovery (FBLD) is a powerful application for developing ligands as modulators of disease targets. This approach strategy involves identification of interactions between low-molecular weight compounds (100-300 Da) and their putative targets, often with low affinity (K_D ~0.1-1 mM) interactions. The focus of this screening methodology is to optimize and streamline identification of fragments with higher ligand efficiency (LE) than typical high-throughput screening. The focus of this review is on the last half decade of fragment-based drug discovery strategies that have been used for antimicrobial drug discovery.

Analogue and structure based approaches for modelling HIV-1 integrase inhibitors

A set of 220 inhibitors belonging to different structure classes and having HIV-1 integrase activity were collected along with their experimental pIC50 values. Geometries of all the inhibitors were fully optimized using B3LYP/6-31 + G(d) level of theory. These ligands were docked against 4 different HIV-1 integrase receptors (PDB IDs: 4LH5, 5KRS, 3ZSQ and 3ZSV). 30 docked poses were generated for all 220 inhibitors and ligand interaction of the first docked pose and the docked pose with the highest score were analysed. Residue GLU170 of 4LH5 receptor shows the highest number of interactions followed by ALA169, GLN168, HIS171 and ASP167 residues. Hydrogen bonding and stacking are mainly responsible for the interactions of these inhibitors with the receptor. We performed Molecular Dynamics (MD) simulation to observe the root-mean-square deviation (RMSD), for measure the average change of displacement between the atoms for a particular frame with respect to a reference and The Root Mean Square Fluctuation (RMSF) for characterization of local changes along the protein chain of the docked complexes. Analogue based models were generated to predict the pIC50 values for integrase inhibitors using various types of descriptors such as constitutional, geometrical, topological, quantum chemical and docking based descriptors. The best models were selected on the basis of statistical parameters and were validated by training and test set division. A few new inhibitors were designed on the basis of structure activity relationship and their pIC50 values were predicted using the generated models. All the designed new inhibitors a very high potential and may be used as potent inhibitors of HIV integrase. These models may be useful for further design and development of new and potent HIV integrase inhibitors.Communicated by Ramaswamy H. Sarma.

Insights of metal 8-hydroxylquinolinol complexes as the potential anticancer drugs

8-Hydroxyquinoline and its derivatives, which belong to a well-known class of quinoline based drugs with varied biological activities, have been extensively explored for the treatments of cancer, Alzheimer's disease, neurodegenerative diseases and other life-threatening diseases. In virtue of the existence of bicyclic heterocyclic scaffold, their bidentate chelators can further bind to metal ions via O- and N-donors from 8-hydroxylquinolinol skeletons to yield a variety of metal 8-hydroxylquinolinol complexes appealing as the anticancer drugs with low toxicity, due to their better biological effects and higher anticancer activities than free 8-hydroxylquinolinol ligands and cis-diammine-dichloro-platinum. The present review summarizes the recent developments in the syntheses, crystal structures, and anticancer activities of metal 8-hydroxylquinolinol complexes, attempting to discover a correlation between their structures and anticancer activities, and to provide an evidence for their potential application perspectives. It means to offer the helpful and meaningful guidance for the researchers in the future syntheses of new and highly efficient anticancer metal 8-hydroxylquinolinol complexes based drugs.

A fragment-based drug discovery strategy applied to the identification of NDM-1 β-lactamase inhibitors

Hydrolysis of β-lactam drugs, a major class of antibiotics, by serine or metallo-β-lactamases (SBL or MBL) is one of the main mechanisms for antibiotic resistance. New Delhi Metallo-β-lactamase-1 (NDM-1), an acquired metallo-carbapenemase first reported in 2009, is currently considered one of the most clinically relevant targets for the development of β-lactam-β-lactamase inhibitor combinations active on NDM-producing clinical isolates. Identification of scaffolds that could be further rationally pharmacomodulated to design new and efficient NDM-1 inhibitors is thus urgently needed. Fragment-based drug discovery (FBDD) has become of great interest for the development of new drugs for the past few years and combination of several FBDD strategies, such as virtual and NMR screening, can reduce the drawbacks of each of them independently. Our methodology starting from a high throughput virtual screening on NDM-1 of a large library (more than 700,000 compounds) allowed, after slicing the hit molecules into fragments, to build a targeted library. These hit fragments were included in an in-house untargeted library fragments that was screened by Saturation Transfer Difference (STD) Nuclear Magnetic Resonance (NMR). 37 fragments were finally identified and used to establish a pharmacophore. 10 molecules based on these hit fragments were synthesized to validate our strategy. Indenone 89 that combined two identified fragments shows an inhibitory activity on NDM-1 with a K_i value of 4 μM.

Styrylquinolines Derivatives: SAR study and Synthetic Approaches

Abstract:

In the present-day scenario, heterocyclic derivatives have revealed the primary function of various medicinal agents precious for humanity. Out of a diverse range of heterocycles, Styrylquinolines scaffolds have been proved to play an essential role in a broad range of biological activities, includinganti-HIV-1, antimicrobial, anti-inflammatory, anti-Alzheimer activity with antiproliferative effects on tumor cell lines. Due to the immense pharmacological importance, distinct synthetic methods have been executed to attain new drug entities from Styrylquinolines. Various schemes for synthesizing Styrylquinolines derivatives like one-pot, ultrasound-promoted heterogeneous acid-catalysed, microwave-assisted, solvent-free, and green synthesis were discussed in the present review. Some products of Styrylquinolines are in clinical trials, and patents are also granted for the novel synthesis of Styrylquinolines. According to the structure-activity relationship, replacement at the R-7 and R-8 positions is required for various activities. In this review, recent synthetic approaches in the medicinal chemistry of Styrylquinolines and potent Styrylquinolines derivatives based on structural activity relationships (SAR) are outlined. Moreover, their primary methods and modifications are also discussed.

Inhibition of in vitro Ebola infection by anti-parasitic quinoline derivatives

There continues to be no approved drugs for the treatment of Ebola virus disease (EVD). Despite a number of candidate drugs showing limited efficacy in vitro and/or in non-human primate studies, EVD continues to plaque certain areas of Africa without any efficacious treatments yet available. Recently, we have been exploring the potential for anti-malarial drugs to inhibit an in vitro model of Ebola Zaire replication using a transcription-competent virus-like particle (trVLP) assay. We examined the efficacy of chloroquine, amodiaquine and 36 novel anti-parasite quinoline derivatives at inhibiting Ebola virus replication. Drug efficacy was tested by trVLP assay and toxicity by MTT assay. Both chloroquine and amodiaquine were effective for inhibition of Ebola virus replication without significant toxicity. The half-maximal inhibitory concentration (IC ₅₀) of chloroquine and amodiaquine to inhibit Ebola virus replication were IC _{50, Chl} = 3.95 µM and IC _{50, Amo} = 1.45 µM, respectively. Additionally, three novel quinoline derivatives were identified as having inhibitory activity and low toxicity for Ebola trVLP replication, with 2NH2Q being the most promising derivative, with an IC ₅₀ of 4.66 µM. Quinoline compounds offer many advantages for disease treatment in tropical climates as they are cheap to produce, easy to synthesize and chemically stable. In this report, we have demonstrated the potential of anti-parasite quinolines for further investigation for use in EVD.

Styrylquinoline – A Versatile Scaffold in Medicinal Chemistry

Background: :

Styrylquinolines are characteristic fully aromatic compounds with flat, rather lipophilic structures. The first reports on their synthesis and biological activity were published roughly a century ago. However, their low selectivity, unfavorable toxicity and problems with their mechanism of action significantly hampered their development. As a result, they have been abandoned for most of the time since they were discovered.

Objective: :

Their renaissance was observed by the antiretroviral activity of several styrylquinoline derivatives that have been reported to be HIV integrase inhibitors. Subsequently, other activities such as their antifungal and anticancer abilities have also been revisited.

Methods:

In the present review, the spectrum of the activity of styrylquinolines and their use in drug design is presented and analyzed.

Results:

New properties and applications that were reported recently have re-established styrylquinolines within medicinal and material chemistry. The considerable increase in the number of published papers regarding their activity spectrum will ensure further discoveries in the field.

Conclusions:

Styrylquinolines have earned a much stronger position in medicinal chemistry due to the discovery of their new activities, profound mechanisms of action and as drug candidates in clinical trials.

Antifungal Styryloquinolines as Candida albicans Efflux Pump Inhibitors: Styryloquinolines are ABC Transporter Inhibitors

Styrylquinolines are heterocyclic compounds that are known for their antifungal and antimicrobial activity. Metal complexation through hydroxyl groups has been claimed to be a plausible mechanism of action for these types of compounds. A series of novel structures with protected hydroxyl groups have been designed and synthesized to verify the literature data. Their antifungal activity against wild-type Candida albicans strain and mutants with silenced efflux pumps activity has been determined. Combinations with fluconazole revealed synergistic interactions that were dependent on the substitution pattern. These results open a new route for designing active antifungal agents on a styrylquinoline scaffold.

A general three-step one-pot synthesis of novel (E)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acids

In this work, a facile and general three-step one-pot synthesis of structurally new (E)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acid derivatives has been achieved from easily available ethyl 6-chloro-2-(chloromethyl) quinoline-3-carboxylate and aromatic or heteroaromatic aldehydes. This strategy features simple one-pot operation, tolerance of a wide range of substituents, and good yields. Moreover, these newly synthesized compounds belong to a new class of quinoline derivatives and could be good candidates for the development of more complex quinoline compounds for use in medicinal chemistry.

Different Pathways Leading to Integrase Inhibitors Resistance

Integrase strand-transfer inhibitors (INSTIs), such as raltegravir (RAL), elvitegravir, or dolutegravir (DTG), are efficient antiretroviral agents used in HIV treatment in order to inhibit retroviral integration. By contrast to RAL treatments leading to well-identified mutation resistance pathways at the integrase level, recent clinical studies report several cases of patients failing DTG treatment without clearly identified resistance mutation in the integrase gene raising questions for the mechanism behind the resistance. These compounds, by impairing the integration of HIV-1 viral DNA into the host DNA, lead to an accumulation of unintegrated circular viral DNA forms. This viral DNA could be at the origin of the INSTI resistance by two different ways. The first one, sustained by a recent report, involves 2-long terminal repeat circles integration and the second one involves expression of accumulated unintegrated viral DNA leading to a basal production of viral particles maintaining the viral information.

Dual Behavior of Iodine Species in Condensation of Anilines and Vinyl Ethers Affording 2-Methylquinolines

A metal-free, mild and efficient method for the synthesis of 2-methylquinolines was successfully developed by condensation of anilines with vinyl ethers in the presence of catalytic amount of iodine. Modification of both pyridine and benzene moieties was easily achieved by changing only the vinyl ether and aniline. In this reaction, the iodine species was revealed to show dual behavior; molecular iodine serves as an oxidant, while its reduced form, hydrogen iodide, activates the vinyl ether. The redox reaction between these iodine species enables the use of a catalytic amount of iodine in this synthetic method.

Comparison of Newly Assembled Full Length HIV-1 Integrase With Prototype Foamy Virus Integrase: Structure-Function Prospective

Background

Drug design against human immunodeficiency virus type 1 (HIV-1) integrase through its mechanistic study is of great interest in the area in biological research. The main obstacle in this area is the absence of the full-length crystal structure for HIV-1 integrase to be used as a model. A complete structure, similar to HIV-1 of a prototype foamy virus integrase in complex with DNA, including all conservative residues, is available and has been extensively used in recent investigations.

Objectives

The aim of this study was to determine whether the above model is precisely representative of HIV-1 integrase. This would critically determine the success of any designed drug using the model in deactivation of integrase and AIDS treatment.

Materials and Methods

Primarily, a new structure for HIV-1 was constructed, using a crystal structure of prototype foamy virus as the starting structure. The constructed structure of HIV-1 integrase was simultaneously simulated with a prototype foamy virus integrase on a separate occasion.

Results

Our results indicate that the HIV-1 system behaves differently from the prototype foamy virus in terms of folding, hydration, hydrophobicity of binding site and stability.

Conclusions

Based on our findings, we can conclude that HIV-1 integrase is vastly different from the prototype foamy virus integrase and does not resemble it, and the modeling output of the prototype foamy virus simulations could not be simply generalized to HIV-1 integrase. Therefore, our HIV-1 model seems to be more representative and more useful for future research.

Benzylation of heterocyclic N-oxides via direct oxidative cross-dehydrogenative coupling with toluene derivatives

A novel cross-dehydrogenative coupling (CDC) of heterocyclic N-oxides with toluene derivatives has been disclosed.

In(OTf)3-catalyzed synthesis of 2-styryl quinolines: scope and limitations of metal Lewis acids for tandem Friedländer annulation–Knoevenagel condensation

Investigation of metal Lewis acids for one-pot tandem Friedländer annulation–Knoevenagel condensation and exploration of In(OTf)₃for synthesis of 2-styryl quinolines.

Targeting HIV-1 integrase with strand transfer inhibitors

HIV-1 integrase (IN) is a retroviral enzyme essential for integration of genetic material into the DNA of the host cell and hence for viral replication. The absence of an equivalent enzyme in humans makes IN an interesting target for anti-HIV drug design. This review briefly overviews the structural and functional properties of HIV-1 IN. We analyze the binding modes of the established drugs, clinical candidates and a comprehensive library of leads based on innovative chemical scaffolds of HIV-1 IN strand transfer inhibitors (INSTIs). Computational clustering techniques are applied for identifying structural features relating to bioactivity. From bio- and chemo-informatics analyses, we provide novel insights into structure-activity relationships of INSTIs and elaborate new strategies for design of innovative inhibitors.

Computational models on quantitative prediction of bioactivity of HIV-1 integrase 3' processing inhibitors

In this study, four computational quantitative structure-activity relationship (QSAR) models were built to predict the bioactivity of 3' processing (3'P) inhibitors of HIV-1 integrase. Some 453 inhibitors whose bioactivity values were detected by the radiolabelling method were collected. The molecular structures were represented with MOE descriptors. In total, 21 descriptors were selected for modelling. All inhibitors were divided into a training set and a test set with two methods: (1) by a Kohonen's self-organizing map (SOM); (2) by a random selection. For every training set and test set, a multilinear regression (MLR) analysis and a support vector machine (SVM) were used to establish models, respectively. For the training/test set divided by SOM, the correlation coefficients (r) were over 0.84, and for the training/test set split randomly, the r values were over 0.86. Some molecular properties such as hydrogen bond donor capacity, atomic partial charge properties, molecular refractivity, the number of aromatic bonds and molecular surface area, volume and shape properties played important roles for inhibiting 3' processing step of HIV-1 integrase.

Bioactivity-guided isolation of anticancer agents from Bauhinia kockiana Korth

BACKGROUND

Flowers of Bauhinia kockiana were investigated for their anticancer properties.

METHODS

Gallic acid (1), and methyl gallate (2), were isolated via bioassay-directed isolation, and they exhibited anticancer properties towards several cancer cell lines, examined using MTT cell viability assay. Pyrogallol (3) was examined against the same cancer cell lines to deduce the bioactive functional group of the phenolic compounds.

RESULTS

The results showed that the phenolic compounds could exhibit moderate to weak cytotoxicity towards certain cell lines (GI50 30 - 86 µM), but were inactive towards DU145 prostate cancer cell (GI50 > 100 µM).

CONCLUSION

It was observed that pyrogallol moiety was one of the essential functional structures of the phenolic compounds in exhibiting anticancer activity. Also, the carboxyl group of compound 1 was also important in anticancer activity. Examination of the PC-3 cells treated with compound 1 using fluorescence microscopy showed that PC-3 cells were killed by apoptosis.

Past and future. Current drugs targeting HIV-1 integrase and reverse transcriptase-associated ribonuclease H activity: single and dual active site inhibitors

Catalytic HIV type-1 (HIV-1) integrase (IN) and ribonuclease H (RNase H) domains belong to the polynucleotidyl transferase superfamily and are characterized by highly conserved motifs that coordinate two divalent Mg(2+) cations and are attractive targets for new antiviral agents. Several structural features of both domains are now available. Drugs targeting the HIV-1 IN are currently approved for anti-HIV therapy, while no drug targeting the HIV-1 RNase H function is yet available. This review describes HIV-1 IN and the RNase H function and structures, compounds targeting their active sites and dual inhibition as a new approach for drug development.

Synthesis, spectroscopy and computational studies of selected hydroxyquinolines and their analogues

Synthetic, spectroscopy and mechanistic aspects of preparation of selected hydroxyquinolines and their analogues or derivatives contained methoxy, fluoro, chloro, carboxylic, carbodithioic and phosphinate or dioxaphosphinane groups were elaborated. The multinuclear NMR and five single crystal X-ray characteristics of the series of quinolines have been determined. The molecular orbitals of the selected hydroxyquinolines have been calculated by density functional theory. The X-ray and NMR studies of 8-[(5,5-dimethyl-2-oxido-1,3,2-dioxaphosphinan-2-yl)oxy]-5,7-dibromo-2-methylquinoline and 8-[(5,5-dimethyl-2-oxido-1,3,2-dioxaphosphinan-2-yl)oxy]-5-fluoro-2-methylquinoline indicate the appearance of anomeric effect.

Green chemical approach: microwave assisted, titanium dioxide nanoparticles catalyzed, convenient and efficient C–C bond formation in the synthesis of highly functionalized quinolines and quinolinones

TiO₂ nanoparticles was effectively applied in the microwave assisted synthesis of quinolines and quinolones.

A convenient and efficient C–OH bond activation, PdCl2(PPh3)2catalyzed, C–C bond formation of tautomerizable quinolinones with the aid of BOP reagent and boronic acids

C–C bond formation of tautomerizable quinolinones. C–OH bond activation using BOP reagent and boronic acids.

Metal-free oxidative olefination of primary amines with benzylic C–H bonds through direct deamination and C–H bond activation

An oxidative olefination reaction between aliphatic primary amines and benzylic sp³ C–H bonds has been achieved using N-bromosuccinimide as catalyst and tert-butyl hydroperoxide as oxidant.

Prediction of bioactivity of HIV-1 integrase ST inhibitors by multilinear regression analysis and support vector machine

In this study, four computational quantitative structure-activity relationship models were built to predict the biological activity of HIV-1 integrase strand transfer (ST) inhibitors. 551 Inhibitors whose bioactivities were detected by radiolabeling method were collected. The molecules were represented with 20 selected MOE descriptors. All inhibitors were divided into a training set and a test set with two methods: (1) by a Kohonen's self-organizing map (SOM); (2) by a random selection. For every training set and test set, a multilinear regression (MLR) analysis and a support vector machine (SVM) were used to establish models, respectively. For the test set divided by SOM, the correlation coefficients (rs) were over 0.91, and for the test set split randomly, the rs were over 0.86.

Contribution to investigation of antimicrobial activity of styrylquinolines

Series of new ring-substituted styrylquinolines and two oxorhenium complexes were prepared and characterized. The compounds were analyzed using RP-HPLC to determine lipophilicity. Primary in vitro screening of the synthesized compounds was performed against fungal and bacterial strains. Some compounds were active against bacteria at micromolar level and against fungi at submicromolar level. Compounds 5,7-dichloro-2-[2-(2-ethoxyphenyl)vinyl]quinolin-8-ol expressed excellent antifungal activity comparable with or higher than the standard fluconazole as well as antibacterial activity against Staphylococcus strains comparable with or higher than the standards bacitracin, penicillin and ciprofloxacin. The structure-activity relationships are discussed.

3D-QSAR studies of quinoline ring derivatives as HIV-1 integrase inhibitors

In the process of HIV-1 virus replication, integrase plays a quite important role. Integrase inhibitors of quinoline ring derivatives were analysed by the Comparative Molecular Field Analysis (CoMFA), Comparative Molecular Similarity Induces Analysis (CoMSIA) and Topomer CoMFA methods. Firstly, 77 compounds were selected to form the training and test sets. Secondly, predictive models were constructed with the CoMFA, CoMSIA and Topomer CoMFA methods. The CoMFA model yielded the best model with q (2) of 0.76 and [Formula: see text] of 0.99, the CoMSIA model has q (2 )= 0.70 and [Formula: see text] of 0.99, while the Topomer CoMFA model has q (2) of 0.66 and [Formula: see text] of 0.97. These results provide a helpful contribution to the design of novel highly active HIV-1 integrase inhibitors.

Bicyclic hydroxy-1H-pyrrolopyridine-trione containing HIV-1 integrase inhibitors

HIV-1 integrase (IN) is a validated therapeutic target for the treatment of AIDS. However, the emergence of resistance to raltegravir, the sole marketed FDA-approved IN inhibitor, emphasizes the need to develop second-generation inhibitors that retain efficacy against clinically relevant IN mutants. We report herein bicyclic hydroxy-1H-pyrrolopyridine-triones as a new family of HIV-1 integrase inhibitors that were efficiently prepared using a key 'Pummerer cyclization deprotonation cycloaddition' cascade of imidosulfoxides. In in vitro HIV-1 integrase assays, the analogs showed low micromolar inhibitory potencies with selectivity for strand transfer reactions as compared with 3'-processing inhibition. A representative inhibitor (5e) retained most of its inhibitory potency against the three major raltegravir-resistant IN mutant enzymes, G140S/Q148H, Y143R, and N155H. In antiviral assays employing viral vectors coding these IN mutants, compound 5e was approximately 200- and 20-fold less affected than raltegravir against the G140S/Q148H and Y143R mutations, respectively. Against the N155H mutation, 5e was approximately 10-fold less affected than raltegravir. Thus, our new compounds represent a novel structural class that may be further developed to overcome resistance to raltegravir, particularly in the case of the G140S/Q148H mutations.

Authentic HIV-1 integrase inhibitors

HIV-1 integrase (IN) is indispensable for HIV-1 replication and has become a validated target for developing anti-AIDS agents. In two decades of development of IN inhibition-based anti-HIV therapeutics, a significant number of compounds were identified as IN inhibitors, but only some of them showed antiviral activity. This article reviews a number of patented HIV-1 IN inhibitors, especially those that possess high selectivity for the strand transfer reaction. These compounds generally have a polar coplanar moiety, which is assumed to chelate two magnesium ions in the binding site. Resistance to those compounds, when given to patients, can develop as a result of IN mutations. We refer to those compounds as authentic IN inhibitors. Continued drug development has so far delivered one authentic IN inhibitor to the market (raltegravir in 2007). Current and future attention will be focused on the development of novel authentic IN inhibitors with the goal of overcoming viral resistance.