Synthesis, structure-activity relationships and preliminary mechanism of action of novel water-soluble 4-quinolone-3-carboxamides as antiproliferative agents

Developing our knowledge of the quinolone scaffold and its value to anticancer drug design

INTRODUCTION

The quinolone scaffold is a bicyclic benzene-pyridinic ring scaffold with nitrogen at the first position and a carbonyl group at the second or fourth position. It is endowed with a diverse spectrum of pharmacological activities, including antitumor activity, and has progressed into various development phases of clinical trials for their target-specific anticancer activity.

AREAS COVERED

The present review covers both classes of quinolones, i.e. quinolin-2(H)-one and quinolin-4(H)-one as anticancer agents, along with their possible mode of binding. Furthermore, their structure-activity relationships, molecular mechanisms, and pharmacokinetic properties are also covered to provide insight into their structural requirements for their rational design as anticancer agents.

EXPERT OPINION

Synthetic feasibility and ease of derivatization at multiple positions, has allowed medicinal chemists to explore quinolones and their chemical diversity to discover newer anticancer agents. The presence of both hydrogen bond donor (-NH) and acceptor (-C=O) functionality in the basic scaffold at two different positions, has broadened the research scope. In particular, substitution at the -NH functionality of the quinolone motif has provided ample space for suitable functionalization and appropriate substitution at the quinolone's third, sixth, and seventh carbons, resulting in selective anticancer agents binding specifically with various drug targets.

Recent advances in the synthesis of pharmaceutically active 4-quinolone and its analogues: a review

4-Quinolone and its analogs are heterocyclic classes of organic compounds displaying biologically active and a broad spectrum of pharmaceutical drug scaffolds. 4-Quinolone is the first-line chemotherapeutic treatment for a wide spectrum of bacterial infections. Recently, 4-quinolone and its derivatives have been shown to have the potential to cure and regulate various acute and chronic diseases, including pain, ischemia, immunomodulation, inflammation, malarial, bacterial infection, fungal infection, HIV, and cancer, based on several reports. This review highlights and provides brief information to better understand the development of experimental progress made to date in the synthetic protocol towards 4-quinolone and its analogs. Thus, classical synthesis protocol, metal-free reaction protocol, and transition metal-catalyzed reaction procedures are briefly discussed along with the pharmaceutical activities of selected 4-quinolone derivatives.

A green and efficient synthetic methodology towards the synthesis of 1-allyl-6-chloro-4-oxo-1,4-dihydroquinoline-3-carboxamide derivatives

Quinolone is a privileged scaffold in medicinal chemistry and 4-Quinolone-3-Carboxamides have been reported to harbor vast therapeutic potential. However, conversion of N-1 substituted 4-Quinolone 3-Carboxylate to its corresponding carbamates is highly restrictive. This motivated us to adopt a much simpler, scalable and efficient methodology for the synthesis of highly pure N-1 substituted 4- Quinolone-3-Carboxamides with excellent yields. Our adopted methodology not only provides a robust pathway for the convenient synthesis of N-1 substituted 4- Quinolone-3-Carboxamides which can then be explored for their therapeutic potential, this may also be adaptable for the derivatization of other such less reactive carboxylate species.

Iridium-Catalyzed Borylation of 6-Fluoroquinolines: Access to 6-Fluoroquinolones

The Ir-catalyzed C–H borylation of fluoroquinolines has been realized. The quinoline boronic ester formed undergoes a range of important transformations of relevance to medicinal chemistry. Judicious choice of the substituent at C4 on the quinoline facilitated the unmasking of a fluoroquinolone—the core structure of many antibiotics.

8-Geranyloxycarbostyril as a potent 15-LOX-1 inhibitor showed great anti-tumor effects against prostate cancer

Carbostyrils are quinolone derivatives, with possible growth inhibition properties on cancer cells. Unlike many tumors, 15-Lipoxygenase-1 (15-LOX-1) is highly expressed in prostate cancer (PCa) cells and has oncogenic properties. Here, with the hypothesis that 6-, 7- and 8-geranyloxycarbostyril (GQ) have inhibitory properties on 15-LOX-1, their effects were assessed on PCa cells. Their cytotoxic effects were evaluated by MTT assay and mechanism of cell death was investigated using annexin V/PI staining. Finally, the anti-tumor properties of 8-GQ were assessed in immunocompromised C57BL/6 mice bearing human PCa cells. Accordingly, these compounds could effectively inhibit 15-LOX activity in PCa cells. MTT and flow cytometry tests confirmed their toxic effects on PCa cells, with no significant toxicity on normal cells, and apoptosis was the main mechanism of cell death. In vivo results indicated that use of 8-GQ at 50 mg/kg had stronger anti-tumor effects than 5 mg/kg cisplatin, with fewer side effects on normal tissues. Therefore, 8-GQ can be introduced as a potential drug candidate with 15-LOX-1 inhibitory potency, which can be effective in treatment of prostate cancer, and should be considered for further drug screening investigations.

Bivalent β-Carbolines Inhibit Colorectal Cancer Growth through Inducing Autophagy

In this study, a series of alkyl diamine linked bivalent β-carbolines was synthesized and evaluated as antitumor agent. The results demonstrated that most compounds displayed good antiproliferative activities with IC₅₀ value lower than 10 µM against a panel of human tumor cell lines, and compound 8 was found to be the most potent antiproliferative agent with IC₅₀ value of 1.39, 1.96, 1.42, 1.49, 1.32, 1.96 and 1.63 µM against human breast cancer cell line (MCF-7), human adenocarcinoma cell line (769-P), human malighant melanoma cell line (A375), human ovarian cancer cell line (SK-OV-3), human colon carcinoma cell line (HCT-116), human gastric cancer cell line (BGC-823) and human esophageal squamous carcinoma cell line (Eca-109), respectively. Further investigations on mechanism of action of this class of compound demonstrated that the representative compound 8 inhibited colorectal cancer growth through inducing autophagy.

Current Pharmaceutical Aspects of Synthetic Quinoline Derivatives

Quinoline derivatives are considered broad-spectrum pharmacological compounds that exhibit a wide range of biological activities. Integration of quinoline moiety can improve its physical and chemical properties and also pharmacological behavior. Due to its wide range of pharmaceutical applications, it is a very popular compound to design new drugs for the treatment of multiple diseases like cancer, dengue fever, malaria, tuberculosis, fungal infections, AIDS, Alzheimer's disease and diabetes. In this review, our major focus is to pay attention to the biological activities of quinoline compounds in the treatment of these diseases such as anti-viral, anti-cancer, anti-malarial, antibacterial, anti-fungal, anti-tubercular and anti-diabetic.

Exploring quinolone scaffold: Unravelling the chemistry of anticancer drug design

Globally, cancer is considered as the major leading cause in decreasing the patient health care system of human beings. The growing threat from drug-resistant cancers makes heterocyclic moieties as an urgent need to develop more successful candidates for anti-cancer therapy. In view of outstanding pharmacological activities Quinolone and its derivatives have attracted more attention towards drug designing and biological evaluation in the search of new drug molecules. The inspired researchers attempted efforts in order to discover quinolone based analogs due to its wide range of biological activities. Due to immense pharmacological importance, distinct synthetic methods have been executed to attain new drug entities from quinolones and all the reported molecules have shown constructive anticancer activity. Some of the synthetic protocol like, one pot synthesis, post-Ugi-transformation, catalysed based synthesis, enzyme-based synthesis and nano-catalyst based synthetic procedures are also discussed as recent advancement in production of quinolone derivatives. In this review, recent synthetic approaches in the medicinal chemistry of quinolones and potent quinolone derivatives on the basis of structural activity relationship are outlined. Moreover, their major methods and modifications are discussed.

Design and Synthesis of 4(1H)-quinolone Derivatives as Autophagy Inducing Agents by Targeting ATG5 Protein

Background:

Quinolines have been characterized as a class of potential antitumor agents, and a large number of natural and synthetic quinolines acting as antitumor agents were reported.

Methods:

A series of 7-chloro-4(1H)-quinolone derivatives were synthesized. The antiproliferative effect of these compounds was evaluated by MTT assay against five human tumor cell lines. The mechanism of action of the selected compound 7h was also investigated.

Results and Discussion:

Most of the compounds had more potent antiproliferative activities than the lead compound 7-chloro-4(1H)-quinolone 6b. Compound 7h was found to be the most potent antiproliferative agent against human tumor cell lines. Further investigation demonstrated that compound 7h triggered ATG5-dependent autophagy of colorectal cancer cells by promoting the functions of LC3 proteins.

Conclusion:

These results were useful for designing and discovering more potent novel antitumor agents endowed with better pharmacological profiles.

Design, synthesis, and biological evaluation of novel arylcarboxamide derivatives as anti-tubercular agents

Our group has previously reported several indolecarboxamides exhibiting potent antitubercular activity. Herein, we rationally designed several arylcarboxamides based on our previously reported homology model and the recently published crystal structure of the mycobacterial membrane protein large 3 (MmpL3). Many analogues showed considerable anti-TB activity against drug-sensitive (DS) Mycobacterium tuberculosis (M. tb) strain. Naphthamide derivatives 13c and 13d were the most active compounds in our study (MIC: 6.55, 7.11 μM, respectively), showing comparable potency to the first line anti-tuberculosis (anti-TB) drug ethambutol (MIC: 4.89 μM). In addition to the naphthamide derivatives, we also identified the quinolone-2-carboxamides and 4-arylthiazole-2-carboxamides as potential MmpL3 inhibitors in which compounds 8i and 18b had MIC values of 9.97 and 9.82 μM, respectively. All four compounds retained their high activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) M. tb strains. It is worth noting that the two most active compounds 13c and 13d also exhibited the highest selective activity towards DS, MDR and XDR M. tb strains over mammalian cells [IC₅₀ (Vero cells) ≥ 227 μM], indicating their potential lack of cytotoxicity. The four compounds were docked into the MmpL3 active site and were studied for their drug-likeness using Lipinski's rule of five.

Synthesis and pharmacological evaluation of arylcarboxamide derivatives based on an antimycobacterial indole-2-carboxamide scaffold. The most active compounds demonstrated activities against MDR and XDR M. tb strains.

Effect of a newly synthesized quinoline-based compound (PPQ-8) on murine schistosomiasis mansoni

Schistosomiasis represents a public health problem and praziquantel is the only drug used for treatment of all forms of the disease. Thus, the development of new anti-schistosomal agents is of utmost importance to increase the effectiveness, reduce side effects and delay the emergence of resistance. The present study was conducted to report the therapeutic efficacy of PPQ-8, a new synthetic quinoline-based compound against Schistosoma mansoni. Mice were treated with PPQ-8 at day 49 post infection using two treatment regimens (20 and 40 mg/kg). Significant reductions were recorded in hepatic (62.9% and 83.6%) and intestinal tissue egg load (57.4% and 73.5%), granuloma count (75.4% and 89.1%) and diameter (26.2% and 47.3%), in response to the drug regimens, respectively. In addition, both treatment regimens induced significant decrease in liver (23.3% and 32.8%) and spleen (37.5% and 45.3%) indices. Also, there were significant reductions in mature ova, total worm and female count, which were more prominent with the higher dose. The reduction in the level of nitric oxide in the liver by both therapeutic regimens to 22.5% and 47.2% indicates the anti-oxidant activity of PPQ-8. Bright field microscopic examination of worms recovered from infected and PPQ-8-treated mice showed nearly empty intestinal caeca with no observable changes in the tegument. Our findings hold promise for the development of a novel anti-schistosomal drug using PPQ-8, but further in vitro and in vivo studies are needed to elucidate the possible mechanism/s of action and to study the effect of PPQ-8 on other human schistosomes.

Dimerization–cyclization reactions of isocyanoaryl-tethered alkylidenecyclobutanes via a triplet biradical mediated process

A triplet biradical mediated dimerization–cyclization reaction of isocyanoaryl-tethered alkylidenecyclobutanes to construct macrocyclic skeletons including dihydroquinoline and quinoline units has been reported.

Electroreductive Intermolecular Coupling of 4-Quinolones with Benzophenones: Synthesis of 2-Substituted 4-Quinolones

The electroreductive coupling of 1-alkoxycarbonyl-4-quinolones with benzophenones in the presence of trimethylsilyl chloride gave adducts reacted at the 2-position of 4-quinolones as trimethylsilyl ethers. The adducts were transformed to 2-(diarylhydroxymethyl)-4-quinolones. The electroreduction of 1,3-diethoxycarbonyl-4-quinolones and polyhalogenated 3-alkoxycarbonyl-1-alkyl-4-quinolones with benzophenones also gave adducts reacted at the 2-position of 4-quinolones. On the contrary, the electroreductive coupling of 1,3-diethooxycarbonyl-8-methoxy-4-quinolones occurred at the 4-position of 4-quinolones to give 4-substituted quinolines.

Recent advances in the synthetic and medicinal perspective of quinolones: A review

In the modern scenario, the quinolone scaffold has emerged as a very potent motif considering its clinical significance. Quinolones possess wide range of pharmacological activities such as anticancer, antibacterial, antifungal, antiprotozoal, antiviral, anti-inflammatory, carbonic anhydrase inhibitory and diuretic activity etc. The versatile synthetic approaches have been successfully applied and several of the resulted synthesized compounds exhibit fascinating biological activities in numerous fields. This has prompted to discover quinolone-based analogues among the researchers due to its great diversity in biological activities. In the past few years, various new, efficient and convenient synthetic approaches (including green chemistry and microwave-assisted synthesis) have been designed and developed to synthesize diverse quinolone-based scaffolds which represent a growing area of interest in academic and industry as well as to explore their biological activities. In this review, an attempt has been made by the authors to summarize (1) One of the most comprehensive listings of quinolone-based drugs or agents in the market or under various stages of clinical development; (2) Recent advances in the synthetic strategies for quinolone derivatives as well as their biological implications including insight of mechanistic studies. (3) Further, the biological data is correlated with structure-activity relationship studies to provide an insight into the rational design of more active agents.

A novel templates of piperazinyl-1,2-dihydroquinoline-3-carboxylates: Synthesis, anti-microbial evaluation and molecular docking studies

A series of piperazinyl-1,2-dihydroquinoline carboxylates were synthesized by the reaction of ethyl 4-chloro-1-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylates with various piperazines and their structures were confirmed by ¹H NMR, ¹³C NMR, IR and mass spectral analysis. All the synthesized compounds were screened for their in vitro antimicrobial activities. Further, the in silico molecular docking studies of the active compounds was performed to explore the binding interactions between piperazinyl-1,2-dihydroquinoline carboxylate derivatives and the active site of the Staphylococcus aureus (CrtM) dehydrosqualene synthase (PDB ID: 2ZCQ). The docking studies revealed that the synthesized derivatives showed high binding energies and strong H-bond interactions with the dehydrosqualene synthase validating the observed antimicrobial activity data. Based on antimicrobial activity and docking studies, the compounds 9b and 10c were identified as promising antimicrobial lead molecules. This study might provide insights to identify new drug candidates that target the S. aureus virulence factor, dehydrosqualene synthase.