Quinolines, a perpetual, multipurpose scaffold in medicinal chemistry

Copper/Zinc-Catalyzed Stitching of 2-Carbonylanilines with Bis(ynamides): Access to Pyrrolo[2,3-b]quinolines and Its Photophysical Studies

Herein, a one-pot desulfonylative protocol enabled by copper(II)/zinc(II) salts to access pyrrolo[2,3-b]quinolines in good to excellent yields from 2-carbonylanilines and ynamide-derived buta-1,3-diynes has been reported. Significantly, various 2-carbonylanilines carrying reactive functional groups are well tolerated. Moreover, a gram-scale synthesis and synthetic application highlight the practical utility of the current protocol. Notably, the fluorescence properties of pyrrolo[2,3-b]quinolines have been recorded, and their potential use as a fluorescent probe in the imaging of live cells has been demonstrated.

Design, synthesis and cytotoxic activity of molecular hybrids based on quinolin-8-yloxy and cinnamide hybrids and their apoptosis inducing property

The present work aims at design and synthesis of a congeneric series of small hybrids 5 and 6a-i featuring the privileged quinoline scaffold tethered with 2-(arylamido)cinnamide moiety as potential anticancer tubulin polymerization inhibitors. Most of the synthesized hybrids 5 and 6a-i significantly inhibited the growth of the HepG2 cell line, with IC50 ranged from 2.46 to 41.31 μM. In particular, 2-(3,4,5-trimethoxybenzamido)-4-methoxycinnamide-quinoline hybrid 6e displayed potent IC50 value toward the examined cell line, and hence chosen for further mechanistic investigations. It is noteworthy that the antiproliferative action of compound 6e highly correlated well with its ability to inhibit tubulin polymerization. In addition, the most potent hybrid 6e demonstrated a significant modification in the cellular cycle distribution, in addition to provoke of apoptotic death within the tested HepG2 cell line. Furthermore, the mechanistic approach was confirmed by a substantial upregulation in the quantity of active caspase 9 by 5.81-fold relative to untreated control cells.

Inhibition of cancer cells by Quinoline-Based compounds: A review with mechanistic insights

This article includes a thorough examination of the inhibitory potential of quinoline-based drugs on cancer cells, as well as an explanation of their modes of action. Quinoline derivatives, due to their various chemical structures and biological activity, have emerged as interesting candidates in the search for new anticancer drugs. The review paper delves into the numerous effects of quinoline-based chemicals in cancer progression, including apoptosis induction, cell cycle modification, and interference with tumor-growth signaling pathways. Mechanistic insights on quinoline derivative interactions with biological targets enlightens their therapeutic potential. However, obstacles such as poor bioavailability, possible off-target effects, and resistance mechanisms make it difficult to get these molecules from benchside to bedside. Addressing these difficulties might be critical for realizing the full therapeutic potential of quinoline-based drugs in cancer treatment.

Design and synthesis of forsythin derivatives as anti-inflammatory agents for acute lung injury

Acute lung injury (ALI) is a clinically high mortality disease, which has not yet been effectively treated. The development of anti-ALI drugs is imminent. ALI can be effectively treated by inhibiting the inflammatory cascade and reducing the inflammatory response in the lung. Forsythia suspense is a common Chinese herbal medicine with significant anti-inflammatory activity. Using forsythin as the parent, 27 Forsythin derivatives were designed and synthesized, and the anti-AIL activity of these compounds was evaluated. Among them, compound B5 has the best activity to inhibit the release of IL-6, and the inhibition rate reaches 91.79% at 25 μM, which was 7.5 times that of the parent forsythin. In addition, most of the compounds have no significant cytotoxicity in vitro. Further studies showed that compound B5 had a concentration-dependent inhibitory effect on NO, IL-6 and TNF-α. And the IC50 values of compound B5 for NO and IL-6 are 10.88 μM and 4.93 μM, respectively. We also found that B5 could significantly inhibit the expression of some immune-related cytotoxic factors, including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, B5 inhibits NF-κB/MAPK signaling pathway. In vivo experiments showed that B5 could alleviate lung inflammation in LPS-induced ALI mice and inhibit IL-6, TNF-α, COX-2 and iNOS. In summary, B5 has anti-inflammatory effects and alleviates ALI by regulating inflammatory mediators and inhibiting MAPK and NF-κB signaling pathways.

Visible-light-induced synthesis of 2,4-disubstituted quinolines from o-vinylaryl isocyanides and oxime esters

A visible-light-induced radical cyclization reaction of o-vinylaryl isocyanides and oxime esters to access various 2,4-disubstituted quinolines was disclosed. Oxime esters were employed as acyl radical precursors via the carbon-carbon bond cleavage. It provided an effective way for the synthesis of 2-acyl-4-arlysubstituted quinolines under mild conditions and exhibited good functional group tolerance and substrate applicability.

Target identification, and optimization of dioxygenated amide derivatives as potent antibacterial agents with FabH inhibitory activity

The enzyme FabH plays a critical role in the initial step of fatty acid biosynthesis, which is vital for the survival of bacteria. As a result, FabH has emerged as an appealing target for the development of novel antibacterial agents. In this study, employing the chemical proteomics method, we validated the previously identified skeleton amide derivatives bearing dioxygenated rings, potentially formed through metabolic processes. Building upon the proteomics findings, we then synthesized and evaluated 32 compounds containing N-heterocyclic amides for their antimicrobial activity for future optimizing the deoxygenated amides. Several compounds demonstrated potent antimicrobial properties with low toxicity, particularly compound 25, which exhibited remarkable potential as an agent with an MIC range of 1.25-3.13 μg/mL against the tested bacterial strains and an IC50 of 2.0 μM against E. coli-derived FabH. Furthermore, we evaluated nine analogues with relatively low MIC values through cytotoxicity and hemolytic activity assessments, Lipinski's rule-of-five criteria, and in silico ADMET predictions to ascertain their druggability potential. Notably, a detailed docking simulation was performed to investigate the binding interactions of compound 25 within the binding pocket of E. coli FabH, which encouragingly revealed strong binding interactions. Based on our findings, compound 25 emerges as the optimal candidate for in vivo therapy aimed at treating infected skin defects. Remarkably, the application of compound 25 demonstrated a significant reduction in the duration of wound infection and notably accelerated the healing process of infected wounds, achieving an impressive 94 % healing rate by day 10.

Synthesis and biological evaluation of novel 2-morpholino-4-anilinoquinoline derivatives as antitumor agents against HepG2 cell line

Cancer is a life-threatening illness all over the world, and developing anticancer treatments with high efficacy and low side effects remains a challenge. The quinoline ring structure has long been recognized as a flexible nucleus in the design and synthesis of physiologically active chemicals. In this study, five new 2-morpholino-4-anilinoquinoline compounds were synthesized and their biological anticancer potential against the HepG2 cell line was assessed. The compounds produced demonstrated varying responses against HepG2 cells, with compounds 3c, 3d, and 3e exhibiting the highest activity, with IC50 values of 11.42, 8.50, and 12.76 μM, respectively. It is a critical requirement that anticancer medications are able to selectively decrease cancer growth while not causing damage to normal cells. Compound 3e exhibited increased activity while maintaining adequate selectivity. It was also the most effective chemical against cell migration and adhesion, which could play an important role in drug resistance and cell metastasis. In total, the findings revealed good possibilities for anticancer therapy, suggesting a target for future development of anticancer medication.

Photoredox radical cyclization reaction of o-vinylaryl isocyanides with acyl chlorides to access 2,4-disubstituted quinolines

We herein report an efficient photoredox radical cyclization reaction of o-vinylaryl isocyanides with acyl chlorides to access a wide range of 2,4-disubstituted quinolines. Preliminary mechanism experiment results suggested that this reaction was initiated by an acyl radical generated from acyl chlorides through a single-electron-transfer (SET) process. This transformation showed good substrate suitability and functional group compatibility at room temperature.

Identification of new potential candidates to inhibit EGF via machine learning algorithm

One of the cost-effective alternative methods to find new inhibitors has been the repositioning approach of existing drugs. The advantage of computational drug repositioning method is saving time and cost to remove the pre-clinical step and accelerate the drug discovery process. Hence, an ensemble computational-experimental approach, consisting of three steps, a machine learning model, simulation of drug-target interaction and experimental characterization, was developed. The machine learning type used here was a different tree classification method, which is one of the best randomize machine learning model to identify potential inhibitors from weak inhibitors. This model was trained more than one-hundred times, and forty top trained models were extracted for the drug repositioning step. The machine learning step aimed to discover the approved drugs with the highest possible success rate in the experimental step. Therefore, among all the identified molecules with more than 0.9 probability in more than 70% of the models, nine compounds, were selected. Besides, out of the nine chosen drugs, seven compounds have been confirmed to inhibit EGF in the published articles since 2019. Hence, two identified compounds, in addition to gefitinib, as a positive control, five weak-inhibitors and one neutral, were considered via molecular docking study. Finally, the eight proposed drugs, including gefitinib, were investigated using MTT assay and In-Cell ELISA to characterize the drugs' effect on A431 cell growth and EGF-signaling. From our experiments, we could conclude that salicylic acid and piperazine could play an EGF-inhibitor role like gefitinib.

MedGAN: optimized generative adversarial network with graph convolutional networks for novel molecule design

Generative Artificial Intelligence can be an important asset in the drug discovery process to meet the demand for novel medicines. This work outlines the optimization and fine-tuning steps of MedGAN, a deep learning model based on Wasserstein Generative Adversarial Networks and Graph Convolutional Networks, developed to generate new quinoline-scaffold molecules from complex molecular graphs, including hyperparameter adjustments and evaluations of drug-likeness attributes such as pharmacokinetics, toxicity, and synthetic accessibility. The best model was capable of generating 25% valid molecules, 62% fully connected, from which 92% were quinolines, 93% were novel, and 95% unique, preserving chirality, atom charge, and favorable drug-like properties while generating 4831 novel quinolines. These results provide valuable insights into how activation functions, optimizers, learning rates, neuron units, molecule size and constitution, and scaffold structure affect the performance of generative models and their potential to create new molecular structures, enhancing deep learning applications in computational drug design.

Developing a new multi-featured chitosan-quinoline Schiff base with potent antibacterial, antioxidant, and antidiabetic activities: design and molecular modeling simulation

A new chitosan Schiff base was developed via the reaction of chitosan (CH) with 2-chloro-3-formyl-7-ethoxy quinoline (Q) derivative. The alteration in the chemical structure and morphology of CHQ derivative was confirmed by 1H NMR, FT-IR spectroscopy and SEM analysis. The antibacterial activity was considerably promoted with increasing quinoline concentration up to 1 M with maximal inhibition reached 96 and 77% against Staphylococcus haemolyticus and Escherichia coli, respectively. Additionally, CHQ derivative afforded higher ABTS·+ radical scavenging activity reached 59% compared to 13% for native chitosan, approving its acceptable antioxidant activity. Moreover, the developed CHQ derivative can stimulate the glucose uptake in HepG-2 and yeast cells, while better inhibition of α-amylase and α-glucosidase was accomplished with maximum values of 99.78 and 92.10%, respectively. Furthermore, the molecular docking simulation clarified the binding mode of CHQ derivative inside the active site of α-amylase and α-glucosidase, suggesting its potential use as diabetes mellitus drug. The DFT calculations indicated an improvement in the electronic properties of CHQ with a lower energy band gap reached 4.05eV compared to 5.94eV for CH. The cytotoxicity assay revealed the safety of CHQ towards normal HSF cells, hypothesizing its possible application as non-toxic antibacterial, antioxidant, and antidiabetic agent for biomedical applications.

Six-Membered Aromatic Nitrogen Heterocyclic Anti-Tumor Agents: Synthesis and Applications

Cancer stands as a serious malady, posing substantial risks to human well-being and survival. This underscores the paramount necessity to explore and investigate novel antitumor medications. Nitrogen-containing compounds, especially those derived from natural sources, form a highly significant category of antitumor agents. Among these, antitumor agents with six-membered aromatic nitrogen heterocycles have consistently attracted the attention of chemists and pharmacologists. Accordingly, we present a comprehensive summary of synthetic strategies and clinical implications of these compounds in this review. This entails an in-depth analysis of synthesis pathways for pyridine, quinoline, pyrimidine, and quinazoline. Additionally, we explore the historical progression, targets, mechanisms of action, and clinical effectiveness of small molecule inhibitors possessing these structural features.

Photoactivated Pyridine Directed Fluorination through Hydrogen Atom Transfer

We have established hydrogen atom transfer (HAT) as the key player in a directed, photopromoted fluorination of pyridylic groups. The Lewis basic pyridyl nitrogen directs amine radical dication propagated HAT and Selectfluor fluorination of various ortho substituents in a highly regioselective manner with little to no side product formation. A variety of pyridines and quinolines were employed to showcase the directing capability of the nitrogen atom. Additionally, both experimental and computational data are provided that illuminate how this mechanism differs from and complements prior work in the area.

Enhanced Method for the Synthesis and Comprehensive Characterization of 1-(4-Phenylquinolin-2-yl)propan-1-one

We present an enhanced method for synthesizing a novel compound, 1-(4-phenylquinolin-2-yl)propan-1-one (3), through the solvent-free Friedländer quinoline synthesis using poly(phosphoric acid) as an assisting agent. The crystal structure of compound 3 is analyzed using FT-IR, and the chemical shifts of its 1H- and 13C NMR spectra are measured and calculated using B3LYP/6-311G(d,p), CAM-B3LYP/6-311G(d,p), and M06-2X/6-311G(d,p) basis sets in the gas phase. Additionally, the optimized geometry of quinoline 3 is compared with experimental X-ray diffraction values. Through density functional theory calculations, we explore various aspects of the compound's properties, including noncovalent interactions, Hirshfeld surface analysis, nonlinear optical properties, thermodynamic properties, molecular electrostatic potential, and frontier molecular orbitals. These investigations reveal chemically active sites within this quinoline derivative that contribute to its chemical reactivity.

Lewis Acid Catalyzed [4 + 2] Annulation of Propargylic Alcohols with 2-Vinylanilines

An elegant Lewis acid catalyzed, protection-free, and straightforward synthetic strategy for the assembly of a series of sophisticated polycyclic quinoline skeletons employing propargylic alcohols and 2-vinylanilines as the substrates in the presence of Yb(OTf)3 (10 mol %) and AgOTf (10 mol %) in tetrahydrofuran has been described. This annulation protocol, which proceeds through a sequential Meyer-Schuster rearrangement/nucleophilic substitution/deprotonation sequence, provides a versatile, practical, and atom-economical approach for accessing quinoline derivatives in moderate-to-good yields.

Therapeutic Activity of a Topical Formulation Containing 8-Hydroxyquinoline for Cutaneous Leishmaniasis

Cutaneous leishmaniasis exhibits a wide spectrum of clinical manifestations; however, only a limited number of drugs are available and include Glucantime® and amphotericin B, which induce unacceptable side effects in patients, limiting their use. Thus, there is an urgent demand to develop a treatment for leishmaniasis. Recently, it was demonstrated that 8-hydroxyquinoline (8-HQ) showed significant leishmanicidal effects in vitro and in vivo. Based on that, this work aimed to develop a topical formulation containing 8-HQ and assess its activity in experimental cutaneous leishmaniasis. 8-HQ was formulated using a Beeler base at 1 and 2% and showed an emulsion size with a D50 of 25 and 51.3 µm, respectively, with a shear-thinning rheological behaviour. The creams were able to permeate artificial Strat-M membranes and excised porcine skin without causing any morphological changes in the porcine skin or murine skin tested. In BALB/c mice infected with L. (L.) amazonensis, topical treatment with creams containing 1 or 2% of 8-HQ was found to reduce the parasite burden and lesion size compared to infected controls with comparable efficacy to Glucantime® (50 mg/kg) administered at the site of the cutaneous lesion. In the histological section of the skin from infected controls, a diffuse inflammatory infiltrate with many heavily infected macrophages that were associated with areas of necrosis was observed. On the other hand, animals treated with both creams showed only moderate inflammatory infiltrate, characterised by few infected macrophages, while tissue necrosis was not observed. These histological characteristics in topically treated animals were associated with an increase in the amount of IFN-γ and a reduction in IL-4 levels. The topical use of 8-HQ was active in decreasing tissue parasitism and should therefore be considered an interesting alternative directed to the treatment of leishmaniasis, considering that this type of treatment is non-invasive, painless, and, importantly, does not require hospitalisation, improving patient compliance by allowing the treatment to be conducted.

Progression and expansion of quinoline as bioactive moiety: a patent review

Quinoline inhibitors are appealing medicinal products for a range of illnesses and problems. It is bicyclic heterocyclic scaffold has been intensively employed in pharmacological research and is well known for its wide range of biological purposes. Biological activities exhibited by quinoline derivatives, such as anti-inflammatory properties, antioxidant, antimicrobial, anti-tubercular, antidiabetic, anti-malarial and others are covered in detail in this review. The IC50 of patented inhibitors might range from nm to μM range, based on the experiments used. It presents an outline of patents file between 2002 and 2023 concerning to biological activities by quinoline derivatives. As a result, it is critical to develop additional chemical quinoline core alterations for novel chemical compounds and enhanced pharmacological impacts.

Quinoline Derivatives: Promising Antioxidants with Neuroprotective Potential

Quinoline has been proposed as a privileged molecular framework in medicinal chemistry. Although by itself it has very few applications, its derivatives have diverse biological activities. In this work, 8536 quinoline derivatives, strategically designed using the CADMA-Chem protocol, are presented. This large chemical space was sampled, analyzed and reduced using selection and elimination scores that combine their properties of bioavailability, toxicity and manufacturability. After applying several filters, 25 derivatives were selected to investigate their acid-base, antioxidant and neuroprotective properties. The antioxidant activity was predicted based on the ionization potential and bond dissociation energies, parameters directly related to the transfer of hydrogen atoms and of a single electron, respectively. These two mechanisms are typically involved in the radical scavenging processes. The antioxidant efficiency was compared with reference compounds, and the most promising antioxidants were found to be more efficient than Trolox but less efficient than ascorbate. In addition, based on molecular docking simulations, some derivatives are expected to act as inhibitors of catechol-O methyltransferase (COMT), acetylcholinesterase (AChE) and monoamine oxidase type B (MAO-B) enzymes. Some structural insights about the compounds were found to enhance or decrease the neuroprotection activity. Based on the results, four quinoline derivatives are proposed as candidates to act as multifunctional antioxidants against Alzheimer's (AD) and Parkinson's (PD) diseases.

Novel 1,2,3-Triazole-Containing Quinoline-Benzimidazole Hybrids: Synthesis, Antiproliferative Activity, In Silico ADME Predictions, and Docking

The newly synthesized quinoline-benzimidazole hybrids containing two types of triazole-methyl-phenoxy linkers were characterized via NMR and elemental analysis. Additional derivatization was achieved by introducing bromine at the C-2 position of the phenoxy core. These novel hybrids were tested for their effects on the growth of the non-tumor cell line MRC-5 (human fetal lung fibroblasts), leukemia and lymphoma cell lines: Hut78, THP-1 and HL-60, and carcinoma cell lines: HeLa and CaCo-2. The results obtained, presented as the concentration that achieves 50% inhibition of cell growth (IC50 value), show that the compounds tested affect tumor cell growth differently depending on the cell line and the dose applied (IC50 ranged from 0.2 to >100 µM). The quinoline-benzimidazole hybrids tested, including 7-chloro-4-(4-{[4-(5-methoxy-1H-1,3-benzo[d]imidazol-2-yl)phenoxy]methyl}-1H-1,2,3-triazol-1-yl)quinoline 9c, 2-(3-bromo-4-{[1-(7-chloroquinolin-4-yl)-1H-1,2,3-triazol-4-yl]methoxy}phenyl)-N-propyl-1H-benzo[d]imidazol-5-carboximidamide trihydrochloride 10e, 2-{4-[(1-{2-[(7-chloroquinolin-4-yl)amino]ethyl}-1H-1,2,3-triazol-4-yl)methoxy]phenyl}-N-propyl-1H-benzo[d]imidazol-5-carboximidamide trihydrochloride 14e and 2-{3-bromo-4-[(1-{2-[(7-chloroquinolin-4-yl)amino]ethyl}-1H-1,2,3-triazol-4-yl)methoxy]phenyl}-N-propyl-1H-benzo[d]imidazol-5-carboximidamide trihydrochloride 15e, arrested the cell cycle of lymphoma (HuT78) cells. The calculated ADMET properties showed that the synthesized compounds violated at most two of Lipinski's rules, making them potential drug candidates, but mainly for parenteral use due to low gastrointestinal absorption. The quinoline-benzimidazole hybrid 14e, which was shown to be a potent and selective inhibitor of lymphoma cell line growth, obtained the highest binding energy (-140.44 kcal/mol), by docking to the TAO2 kinase domain (PDB: 2GCD).

Discovery of novel 2-(trifluoromethyl)quinolin-4-amine derivatives as potent antitumor agents with microtubule polymerization inhibitory activity

In this work, a series of 2-(trifluoromethyl)quinolin-4-amine derivatives were designed and synthesized through structural optimization strategy as a microtubule-targeted agents (MTAs) and their cytotoxicity activity against PC3, K562 and HeLa cell lines were evaluated. The half maximal inhibitory concentration (IC50) of 5e, 5f, and 5o suggested that their potency of anti-proliferative activities against HeLa cell lines were better than the combretastatin A-4. Compound 5e showed the higher anti-proliferative activity against PC3, K562 and HeLa in vitro with IC50 values of 0.49 µM, 0.08 µM and 0.01 µM, respectively. Further mechanism study indicated that the representative compound 5e was new class of tubulin inhibitors by EBI competition assay and tubulin polymerization assays, it is similar to colchicine. Immunofluorescence staining revealed that compound 5e apparently disrupted tubulin network in HeLa cells, and compound 5e arrested HeLa cells at the G2/M phase and induced cells apoptosis in a dose-dependent manner. Molecular docking results illustrated that the hydrogen bonds of represented compounds reinforced the interactions in the pocket of colchicine binding site. Preliminary results suggested that 5e deserves further research as a promising tubulin inhibitor for the development of anticancer agents.

Indole derivatives targeting colchicine binding site as potential anticancer agents

Microtubules are appealing as intracellular targets for anticancer activity due to their importance in cell division. Three important binding sites are present on the tubulin protein: taxane, vinca, and colchicine binding sites (CBS). Many USFDA-approved drugs such as paclitaxel, ixabepilone, vinblastine, and combretastatin act by altering the dynamics of the microtubules. Additionally, a large number of compounds have been synthesized by medicinal chemists around the globe that target different tubulin binding sites. Although CBS inhibitors have proved their cytotoxic potential, no CBS-targeting drug had been able to reach the market. Several studies have reported design, synthesis, and biological evaluation of indole derivatives as potential anticancer agents. These compounds have been shown to inhibit cancer cell proliferation, induce apoptosis, and disrupt microtubule formation. Moreover, the binding affinity of these compounds to the CBS has been demonstrated using molecular docking studies and competitive binding assays. The present work has reviewed indole derivatives as potential colchicine-binding site inhibitors. The structure-activity relationship studies have revealed the crucial pharmacophoric features required for the potent and selective binding of indole derivatives to the CBS. The development of these compounds with improved efficacy and reduced toxicity could potentially lead to the development of novel and effective cancer therapies.

Synthesis of 4-(Phenylchalcogenyl)tetrazolo[1,5-a]quinolines by Bicyclization of 2-Azidobenzaldehydes with Phenylchalcogenylacetonitrile

A general methodology to access valuable 4-(phenylchalcogenyl)tetrazolo[1,5-a]quinolines was developed by the reaction of 2-azidobenzaldehyde with phenylchalcogenylacetonitriles (sulfur and selenium) in the presence of potassium carbonate (20 mol%) as a catalyst. The reactions were conducted using a mixture of dimethylsulfoxide and water (7:3) as solvent at 80 °C for 4 h. This new methodology presents a good functional group tolerance to electron-deficient and electron-rich substituents, affording a total of twelve different 4-(phenylchalcogenyl)tetrazolo[1,5-a]quinolines selectively in moderate to excellent yields. The structure of the synthesized 4-(phenylselanyl)tetrazolo[1,5-a]quinoline was confirmed by X-ray analysis.

Design, synthesis, molecular dynamics simulation, MM/GBSA studies and kinesin spindle protein inhibitory evaluation of some 4-aminoquinoline hybrids

The discovery of novel chemotherapeutic agents is always challenging for researchers in industry and academia. Among the recent promising anticancer therapeutic targets, an important modulatory factor in mitosis is the expression of the kinesin family motor protein (Eg5). In terms of chemotherapy treatment, mitosis has gained significant attention due to its role as one of the biological processes that can be intervened in it. This study was undertaken to design, synthesise and evaluation of 4-aminoquinoline hybrid compounds as potential Eg5 inhibitors. Based on data collected from Malachite green and steady state ATPase assays, it has been determined that compounds such as 6c, 6d, 6g, and 6h are sensitive to Eg5 inhibition. In special mention, compounds 4 and 6c showed promising inhibitory activity in Malachite green assay with IC₅₀ values of 2.32 ± 0.23 µM and 1.97 ± 0.23 µM respectively. Compound 4 showed favourable inhibitory potential Steady state ATPase Assay with IC₅₀ value of 5.39 ± 1.39 µM. We performed molecular docking, MM/GBSA calculations, and molecular dynamic simulations to evaluate the interactions between ligands and the binding site of the kinesin spindle protein to evaluate the functional consequences of these interactions. As a result of these findings, it can be concluded that these 4-amioquinoline Schiff's base hybrids may prove to be promising candidates for development as novel inhibitors of Eg5. Further in-vivo research in this area is required.

Favorable Preclinical Pharmacological Profile of a Novel Antimalarial Pyrrolizidinylmethyl Derivative of 4-amino-7-chloroquinoline with Potent In Vitro and In Vivo Activities

The 4-aminoquinoline drugs, such as chloroquine (CQ), amodiaquine or piperaquine, are still commonly used for malaria treatment, either alone (CQ) or in combination with artemisinin derivatives. We previously described the excellent in vitro activity of a novel pyrrolizidinylmethyl derivative of 4-amino-7-chloroquinoline, named MG3, against P. falciparum drug-resistant parasites. Here, we report the optimized and safer synthesis of MG3, now suitable for a scale-up, and its additional in vitro and in vivo characterization. MG3 is active against a panel of P. vivax and P. falciparum field isolates, either alone or in combination with artemisinin derivatives. In vivo MG3 is orally active in the P. berghei, P. chabaudi, and P. yoelii models of rodent malaria with efficacy comparable, or better, than that of CQ and of other quinolines under development. The in vivo and in vitro ADME-Tox studies indicate that MG3 possesses a very good pre-clinical developability profile associated with an excellent oral bioavailability, and low toxicity in non-formal preclinical studies on rats, dogs, and non-human primates (NHP). In conclusion, the pharmacological profile of MG3 is in line with those obtained with CQ or the other quinolines in use and seems to possess all the requirements for a developmental candidate.

Development of 2-chloroquinoline based heterocyclic frameworks as dual inhibitors of SARS-CoV-2 MPro and PLPro

Evolution of new variants of SARS-CoV-2 warrant the need for the continued efforts in identifying target-oriented new drugs. Dual targeting agents against M^Pro and PL^Pro not only overcome the incomplete efficacy but also the drug resistance, which is common problem. Since both these are cysteine proteases, we designed 2-chloroquinoline based molecules with additional imine moiety in the middle as possible nucleophilic warheads. In the first round of design and synthesis, three molecules (C3, C4 and C5) inhibited (Ki < 2 μM) only M^Pro by binding covalently to C145 and one molecule (C10) inhibited both the proteases non-covalently (Ki < 2 μM) with negligible cytotoxicity. Further conversion of the imine in C10 to azetidinone (C11) improved the potency against both the enzymes in the nanomolar range (820 nM against M^Pro and 350 nM against PL^Pro) with no cytotoxicity. Conversion of imine to thiazolidinone (C12), reduced the inhibition by 3-5 folds against both the enzymes. Biochemical and computational studies suggest that C10-C12 bind in the substrate binding pocket of M^Pro and in the BL2 loop of the PL^Pro. Since these dual inhibitors have least cytotoxicity, they could be further explored as therapeutics against the SARS-CoV-2 and other analogous viruses.

Anti-inflammatory efficacy and relevant SAR investigations of novel chiral pyrazolo isoquinoline derivatives: Design, synthesis, in-vitro, in-vivo, and computational studies targeting iNOS

Isoquinoline alkaloids are a rich source of multimodal agents with distinctive structural specificity and various pharmacological activities. In the present report, we propose a combination of design, synthesis, computational study, primary in-vitro screening using the lipopolysaccharide (LPS)-induced RAW 264.7 cell line, and in-vivo evaluation in mice models as a novel approach to speed up anti-inflammatory drugs discovery. The nitric oxide (NO) inhibitory effect of new compounds revealed that all of them displayed the potent NO inhibitory ability in a dose-dependent manner with no obvious cytotoxicity. A series of the model compounds 7a, 7b, 7d, 7f, and 7g have been identified as the most promising, with IC₅₀ values of 47.76 μM, 33.8 μM, 20.76 μM, 26.74 μM, and 47.8 μM respectively in LPS-induced RAW 264.7 cell line. Structure-activity relationship (SAR) studies on a range of derivatives aided in identifying key pharmacophores in the lead compound. Western blotting data of 7d identified that our synthesized compounds can down-regulate and suppress the expression of the key inflammatory enzyme, inducible nitric oxide synthase (iNOS). These results suggested that synthesized compounds may be potent anti-inflammatory agents, inhibiting the NO-release, in turn, iNOS inflammatory pathways. Furthermore, in-vivo anti-inflammatory detection via xylene-induced ear edema in mice revealed that these compounds could also inhibit swelling in mice, with model compound 7h showing an inhibition activity (64.4%) at a concentration of 10 mg/kg comparable to the reference drug celecoxib. Molecular docking results showed that shortlisted compounds (7b, 7c, 7d, 7e, and 7h) had a potential binding affinity for iNOS with low energies, with S-Score to be -7.57, -8.22, -7.35, -8.95, -9.94 kcal/mol, respectively. All results demonstrated that the newly synthesized chiral pyrazolo isoquinoline derivatives are highly potential anti-inflammatory agents.

Copper(II)-Catalyzed Synthesis of Pyrrolo[3,4-b]quinolinediones from o-Amino Carbonyl Compounds and Maleimides

A copper(II)-catalyzed cascade synthesis of 1H-pyrrolo[3,4-b]quinoline-1,3(2H)-diones has been achieved from readily available o-amino carbonyl compounds and maleimides. This one-pot cascade strategy involves a copper-catalyzed aza-Michael addition followed by condensation and oxidation to deliver the target molecules. The protocol features a broad substrate scope and excellent functional group tolerance and affords products in moderate to good (44-88%) yields.

Conversion of 2-methyl-4-styrylquinolines into 2,4-distyrylquinolines: synthesis, and spectroscopic and structural characterization of five examples

Four new 2,4-distyrylquinolines and one 2-styryl-4-[2-(thiophen-2-yl)vinyl]quinoline have been synthesized using indium trichloride condensation reactions between aromatic aldehydes and the corresponding 2-methylquinolines, which were themselves prepared using Friedländer annulation reactions between mono- or diketones and (2-aminophenyl)chalcones: the products have all been fully characterized by spectroscopic and crystallographic methods. 2,4-Bis[(E)-styryl]quinoline, C₂₅H₁₉N, (IIa), and its dichloro analogue, 2-[(E)-2,4-dichlorostyryl]-4-[(E)-styryl]quinoline, C₂₅H₁₇Cl₂N, (IIb), exhibit different orientations of the 2-styryl unit relative to the quinoline nucleus. In each of the 3-benzoyl analogues {2-[(E)-4-bromostyryl]-4-[(E)-styryl]quinolin-3-yl}(phenyl)methanone, C₃₂H₂₂BrNO, (IIc), {2-[(E)-4-bromostyryl]-4-[(E)-4-chlorostyryl]quinolin-3-yl}(phenyl)methanone, C₃₂H₂₁BrClNO, (IId), and {2-[(E)-4-bromostyryl]-4-[(E)-2-(thiophen-2-yl)vinyl]quinolin-3-yl}(phenyl)methanone, C₃₀H₂₀BrNOS, (IIe), the orientation of the 2-styryl unit is similar to that in (IIa), but the orientation of the 4-arylvinyl units show considerable variation. The thiophene unit in (IIe) is disordered over two sets of atomic sites having occupancies of 0.926 (3) and 0.074 (3). There are no hydrogen bonds of any kind in the structure of (IIa), but in (IId), a single C-H...O hydrogen bond links the molecules into cyclic centrosymmetric R₂²(20) dimers. A combination of C-H...N and C-H...π hydrogen bonds links the molecules of (IIb) into a three-dimensional framework structure. A combination of three C-H...π hydrogen bonds links the molecules of (IIc) into sheets, and a combination of C-H...O and C-H...π hydrogen bonds forms sheets in (IIe). Comparisons are made with the structures of some related compounds.

Copper-Catalyzed Cyclization of 2-Alkynylanilines to Give 2-Haloalkoxy-3-alkyl(aryl)quinolines

Herein we describe a method to produce 2-haloalkoxy-3-substituted quinolines via the cyclization of 2-alkynylanilines with TMSCF₃ and THF. This synthetic method uses inexpensive and easy-to-handle TMSCF₃ and employs a commercially available CuI catalyst to transform a broad range of 2-alkynylanilines into versatile 2-difluoromethoxy-3-substituted quinolines and 2-iodoalkoxy-3-substituted quinolines with excellent chemoselectivity.

Visible Light-Mediated Cyclisation Reaction for the Synthesis of Highly-Substituted Tetrahydroquinolines and Quinolines

Condensation of 2-vinylanilines and conjugated aldehydes followed by an efficient light-mediated cyclisation selectively yields either substituted tetrahydroquinolines with typically high dr, or in the presence of an iridium photocatalyst the synthesis of quinoline derivatives is demonstrated. These atom economical processes require mild conditions, with the substrate scope demonstrating excellent site selectivity and functional group tolerance, including azaarene-bearing substrates. A thorough experimental mechanistic investigation explores multiple pathways and the key role that imine and iminium intermediates play in the absorption of visible light to generate reactive excited states. The synthetic utility of the reactions is demonstrated on gram scale quantities in both batch and flow, alongside further manipulation of the medicinally relevant products.

Recent advances in functionalized quinoline scaffolds and hybrids-Exceptional pharmacophore in therapeutic medicine

Quinoline is one of the most common nitrogen-containing heterocycles owing to its fascinating pharmacological properties and synthetic value in organic and pharmaceutical chemistry. Functionalization of this moiety at different positions has allowed for varying pharmacological activities of its derivative. Several publications over the last few decades have specified various methods of synthesis. This includes classical methods of synthesizing the primary quinoline derivatives and efficient methods that reduce reaction time with increased yield employing procedures that fulfill one of the twelve green chemistry principles, "safer solvent". The metal nanoparticle-catalyzed reaction also serves as a potent and effective technique for the synthesis of quinoline with excellent atom efficiency. The primary focus of this review is to highlight the routes to synthesizing functionalized quinoline derivatives, including hybrids that have moieties with predetermined activities bound to the quinoline moiety which are of interest in synthesizing drug candidates with dual modes of action, overcoming toxicity, and resistance amongst others. This was achieved using updated literature, stating the biological activities and mechanisms through which these compounds administer relief. The ADMET studies and Structure-Activity Relationship (SAR) of novel derivatives were also highlighted to explore the drug-likeness of the quinoline-hybrids and the influence of substituent characteristics and position on the biological activity of the compounds.

Molecular Target Interactions of Quinoline Derivatives as Anticancer Agents: A Review

One of the leading causes of death worldwide is cancer, which poses substantial risks to both society and an individual's life. Cancer therapy is still challenging, despite developments in the field and continued research into cancer prevention. The search for novel anticancer active agents with a broader cytotoxicity range is therefore continuously ongoing. The benzene ring gets fused to a pyridine ring at two carbon atoms close to one another to form the double ring structure of the heterocyclic aromatic nitrogen molecule known as quinoline (1-azanaphthalene). Quinoline derivatives contain a wide range of pharmacological activities, including antitubercular, antifungal, antibacterial, and antimalarial properties. Quinoline derivatives have also been shown to have anticancer properties. There are many quinoline derivatives widely available as anticancer drugs that act via a variety of mechanisms on various molecular targets, such as inhibition of topoisomerase, inhibition of tyrosine kinases, inhibition of heat shock protein 90 (Hsp90), inhibition of histone deacetylases (HDACs), inhibition of cell cycle arrest and apoptosis, and inhibition of tubulin polymerization.

Ultrasound-Assisted Wittig Reaction for the Synthesis of 3-Substituted 4-Chloroquinolines and Quinolin-4(1H)-ones with Extended π-Conjugated Systems

3-(Vinyl-/buta-1,3-dien-1-yl/4-phenylbuta-1,3-dien-1-yl)-4-chloro quinolines and quinolin-4(1H)-ones were synthesized by ultrasound-assisted Wittig reaction of the corresponding 4-chloro-3-formylquinoline and 3-formylquinolin-4(1H)-ones with nonstabilized ylides. Ease execution, mild conditions, and high yields make this method exploitable for the generation of libraries of 3-substituted 4-chloroquinolines and quinolin-4(1H)-ones with extended π-conjugated systems. To demonstrate the usefulness of these compounds as precursors for the synthesis of more complex structures, 3-vinylquinolin-4(1H)-ones were used as dienes in the Diels–Alder reaction with N-methylmaleimide to produce novel acridone derivatives. The attempted Diels–Alder reaction with 3-(buta-1,3-dien-1-yl)quinolin-4(1H)-one did not afford the expected cycloadduct; instead, 2-methyl-2H-pyrano[3,2-c]quinoline was obtained. The structures and stereochemistry of the new compounds were established by NMR studies.

Friedlӓnder's synthesis of quinolines as a pivotal step in the development of bioactive heterocyclic derivatives in the current era of medicinal chemistry

In the current scenario of medicinal chemistry, quinoline plays a pivotal role in the design of new heterocyclic compounds with several pharmacological properties, so the search for new synthetic methodologies and their application in drug discovery has been widely studied. So far, many procedures have been performed for the preparation of quinoline scaffolds, among which Friedländer quinoline synthesis plays an important role in obtaining these heterocycles. The Friedländer reaction involves condensation between 2-aminobenzaldehydes and keto-compounds. The quinoline nucleus, once obtained through the Friedländer synthesis, has been extensively modified so that these derivatives can exhibit a large number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antituberculosis, and antileishmanial properties. In this work, the focus is on the applicability of the Friedländer reaction in the synthesis of various types of bioactive heterocyclic quinoline compounds, which to date has not been reported in the context of medicinal chemistry. The main part of this review selectively focuses on research from 2010 to date and will present highlights of the Friedländer quinoline synthesis procedures and findings to address biological and pharmacological activities.

2-Arylquinolines as novel anticancer agents with dual EGFR/FAK kinase inhibitory activity: synthesis, biological evaluation, and molecular modelling insights

In this study, different assortments of 2-arylquinolines and 2,6-diarylquinolines have been developed. Recently, we have developed a new series of 6,7-dimethoxy-4-alkoxy-2-arylquinolines as Topoisomerase I (TOP1) inhibitors with potent anticancer activity. Utilising the SAR outputs from this study, we tried to enhance anticancer and TOP1 inhibitory activities. Though target quinolines demonstrated potent antiproliferative effect, specifically against colorectal cancer DLD-1 and HCT-116, they showed weak TOP1 inhibition which may be attributable to their non-coplanarity. Thereafter, screening against kinase panel revealed their dual inhibitory activity against EGFR and FAK. Quinolines 6f, 6h, 6i, and 20f were the most potent EGFR inhibitors (IC50s = 25.39, 20.15, 22.36, and 24.81 nM, respectively). Meanwhile, quinolines 6f, 6h, 6i, 16d, and 20f exerted the best FAK inhibition (IC50s = 22.68, 14.25, 18.36, 17.36, and 15.36 nM, respectively). Finally, molecular modelling was employed to justify the promising EGFR/FAK inhibition. The study outcomes afforded the first reported quinolines with potent EGFR/FAK dual inhibition.

Preparation and antioxidant activity of novel chitosan oligosaccharide quinolinyl urea derivatives

In the present study, four new chitosan oligosaccharide derivatives bearing quinolinyl urea groups were synthesized by reaction between 2-methoxyformylated chitosan oligosaccharide and aminoquinoline. The chitosan oligosaccharide derivatives were characterized by Fourier Transform Infrared (FTIR) and 1H Nuclear Magnetic Resonance (1H NMR) spectroscopy. The obtained results confirmed that chitosan oligosaccharide quinolinyl urea derivatives were successfully synthesized. Meanwhile, the antioxidant activities of different chitosan oligosaccharide derivatives were examined in vitro. Experimentally, it was demonstrated that chitosan oligosaccharide quinolinyl urea derivatives had superior antioxidant activity compared with chitosan oligosaccharide and the antioxidant effects were concentration-dependent. Especially, when the concentration was 1.6 mg/mL, their superoxide anion radical scavenging rates could reach to 72.35 ± 0.49%, 100.00 ± 0.21%, 84.63 ± 0.49%, and 87.22 ± 0.32%, respectively. And the hydroxyl radical scavenging rates could reach to 100.00 ± 0.82%, 98.49 ± 4.08%, 100.00 ± 5.76%, and 92.07 ± 5.10%. In addition, the cytotoxic activity of the prepared chitosan derivatives against L929 cells was determined by CCK-8 assay. The cell survival rates were all higher than 90%, which intuitively indicated that the samples had almost no cytotoxicity. The findings indicated that the enhanced antioxidant property and biocompatibility of these chitosan oligosaccharide quinolinyl urea derivatives could enlarge the scope of the application of chitosan oligosaccharide, particularly as an antioxidant in food packaging, biomedical, pharmaceutical, cosmetics industries and other fields.

Synthesis, characterization and antimicrobial property in vitro of supramolecular coordination polymers bearing brominated Schiff base ligand

In this study, two supramolecular coordination polymers of Co(II) and Zn(II) based on brominated Schiff base (E)-4-bromo-2-((quinolin-6-ylimino)methyl)phenol (HL) were synthesized and characterized by using elemental analysis, IR spectroscopy and NMR spectroscopy. Furthermore, the crystal structures of HL, CoL₂ (І) and ZnL₂ (II) were determined by single crystal X-ray analysis. It was revealed that the bromine-related interaction played important role in the self-assembly of HL supramolecular network. The crystal structural investigations revealed that І and II were isomorphous with the same geometry around the metal atom and similar structural feature. The stable four-membered chelate structure resulted from coordination between the metal(II) ion and deprotonated bidentate ligand. And supramolecular coordination polymers of І and II formed diverse architecture through multiple hydrogen bondings, π···π interactions and halogen-related interactions. Antimicrobial activities of polymers were tested toward four bacteria and five phytopathogenic fungi. І and II showed higher activities toward the tested microorganisms than HL. Furthermore, the photoluminescence results indicated that HL and II accompanied with better fluorescence properties in the ultraviolet region.

The Anticancer Effect of a Novel Quinoline Derivative 91b1 through Downregulation of Lumican

Quinoline derivatives have been reported to possess a wide range of pharmaceutical activities. Our group previously synthesized a series of quinoline compounds, in which compound 91b1 showed a significant anticancer effect. The purpose of this study was to evaluate the anticancer activity of compound 91b1 in vitro and in vivo, and screen out its regulated target. A series of cancer cell lines and nontumor cell lines were treated with compound 91b1 by MTS cytotoxicity assay and cell-cycle assay. In vivo anticancer activity was evaluated by a xenografted model on nude mice. Target prediction of 91b1 was assessed by microarray assay and confirmed by pancancer analysis. Relative expression of the target gene Lumican was measured by qRT-PCR. 91b1 significantly reduced tumor size in the nude mice xenograft model. Lumican was downregulated after 91b1 treatment. Lumican was proven to increase tumorigenesis in vivo, as well as cancer cell migration, invasion, and proliferation in vitro. The results of this study suggest that the anticancer activity of compound 91b1 probably works through downregulating the gene Lumican.

Hybrids of 1,4-Quinone with Quinoline Derivatives: Synthesis, Biological Activity, and Molecular Docking with DT-Diaphorase (NQO1)

Hybrids 1,4-quinone with quinoline were obtained by connecting two active structures through an oxygen atom. This strategy allows to obtain new compounds with a high biological activity and suitable bioavailability. Newly synthesized compounds were characterized by various spectroscopic methods. The enzymatic assay used showed that these compounds were a suitable DT-diaphorase (NQO1) substrates as evidenced by increasing enzymatic conversion rates relative to that of streptonigrin. Hybrids were tested in vitro against a panel of human cell lines including melanoma, breast, and lung cancers. They showed also a high cytotoxic activity depending on the type of 1,4-quinone moiety and the applied tumor cell lines. It was found that cytotoxic activity of the studied hybrids was increasing against the cell lines with higher NQO1 protein level, such as breast (MCF-7 and T47D) and lung (A549) cancers. Selected hybrids were tested for the transcriptional activity of the gene encoding a proliferation marker (H3 histone), cell cycle regulators (p53 and p21) and the apoptosis pathway (BCL-2 and BAX). The molecular docking was used to examine the probable interaction between the hybrids and NQO1 protein.

Arylselenyl Radical-Mediated Cyclization of N-(2-Alkynyl)anilines: Access to 3-Selenylquinolines

An efficient and novel approach to accessing 3-selenylquinolines from diaryl diselenides and acyclic, selenium-free substrates is described. Preliminary mechanistic studies indicate that the combination of CuCl₂ and air affords an appropriate environment for producing arylselenyl radicals that initiate the cascade cyclization of N-(2-alkynyl)anilines, forming key Se-C and C-C bonds in a single step. Using this chemistry, a wide variety of 3-selenylquinolines were produced in moderate to excellent yield under mild conditions, highlighting the versatility and usefulness of this new method.

Synthesis and biological evaluation of new 2‑substituted‑4‑amino-quinolines and -quinazoline as potential antifungal agents

Aiming to discover novel antifungal agents, a series of 2‑substituted‑4‑amino-quinolines and -quinazoline were prepared and characterized using IR, ¹H NMR, ¹³C NMR, and HRMS spectroscopic techniques. Their antifungal activities against four invasive fungi were evaluated, and the results revealed that some of the target compounds exhibited moderate to excellent inhibitory potencies. The most promising compounds III₁₁, III₁₄, III_15, and III₂₃ exhibited potent and broad-spectrum antifungal activities with MIC values of 4-32 μg/mL. The mechanism studies showed that compound III₁₁ (N,2-di-p-tolylquinolin-4-amine hydrochloride) did not play antifungal potency by disrupting fungal membrane, which was quite different from many traditional membrane-active antifungal drugs. Meanwhile, III₁₁ also demonstrated a low likelihood of inducing resistance, and excellent stability in mouse plasma. In addition, some interesting structure-activity relationships (SARs) were also discussed. These results suggest that some 4‑aminoquinolines may serve as new and promising candidates for further antifungal drug discovery.

Benzamides Substituted with Quinoline-Linked 1,2,4-Oxadiazole: Synthesis, Biological Activity and Toxicity to Zebrafish Embryo

To develop new compounds with high activity, broad spectrum and low-toxicity, 17 benzamides substituted with quinoline-linked 1,2,4-oxadiazole were designed using the splicing principle of active substructures and were synthesized. The biological activities were evaluated against 10 fungi, indicating that some of the synthetic compounds showed excellent fungicidal activities. For example, at 50 mg/L, the inhibitory activity of 13p (3-Cl-4-Cl substituted, 86.1%) against Sclerotinia sclerotiorum was superior to that of quinoxyfen (77.8%), and the inhibitory activity of 13f (3-CF₃ substituted, 77.8%) was comparable to that of quinoxyfen. The fungicidal activities of 13f and 13p to Sclerotinia sclerotiorum were better than that of quinoxyfen (14.19 mg/L), with EC₅₀ of 6.67 mg/L and 5.17 mg/L, respectively. Furthermore, the acute toxicity of 13p was 19.42 mg/L, classifying it as a low-toxic compound.

Efficient removal of mefenamic acid and ibuprofen on organo-Vts with a quinoline-containing gemini surfactant: Adsorption studies and model calculations

To pursue the adsorptivity of versatile vermiculite (Na-Vt)-based adsorbent targeted at emerging pharmaceuticals (mefenamic acid and ibuprofen, corresponding to MEA and IBP, respectively), a quinoline-based gemini surfactant (DHQU) with multi-functional groups is applied as modifier on Na-Vt. Enhanced hydrophobicity, enlarged interlayer space and decreased surface area of DHQU-Vt are obtained, whose modifier availability (the mole ratio of modifier intercalated to added) reaches up to 84.18% as characterized by FT-IR, XRD, TG-DTG, EA and BET analysis. Efficient adsorption of MEA/IBP (123.71/240.69 mg/g) is achieved under an extremely low DHQU dosage (0.2 CEC lower than the usual saturated dosage of organo-Vts), with all the processes fitting satisfactorily with pseudo-second order and Freundlich isotherm models accompanied by an exothermic nature. Acid pickling testifies a stable and reliable reusability process of DHQU-Vt even after 3 cycles. Multiple interactions (i.e., partition process, XH-π interaction, π-π interaction, π-π stacking and electrostatic interaction) are revealed and compared from not only characterization results, but also simulation of frontier orbital analysis, the adsorption configuration and bonding analysis: (i) The greater molecular flexibility of the adsorbate, the greater intra particle diffusion effect. (ii) π-π stacking between isolated aromatic rings is stronger than that between parallelly connected aromatic rings. (iii) The strength of multiple active sites provided by quinoline (CH-π, NH-π and π-π interactions) are comparable but weaker than electrostatic interaction/intra particle diffusion.