Synthesis and Evaluation of the Antibacterial and Antioxidant Activities of Some Novel Chloroquinoline Analogs

Quinoline heterocycle is a useful scaffold to develop bioactive molecules used as anticancer, antimalaria, and antimicrobials. Inspired by their numerous biological activities, an attempt was made to synthesize a series of novel 7-chloroquinoline derivatives, including 2,7-dichloroquinoline-3-carbonitrile (5), 2,7-dichloroquinoline-3-carboxamide (6), 7-chloro-2-methoxyquinoline3-carbaldehyde (7), 7-chloro-2-ethoxyquinoline-3-carbaldehyde (8), and 2-chloroquinoline-3-carbonitrile (12) by the application of Vilsmeier–Haack reaction and aromatic nucleophilic substitution of 2,7-dichloroquinoline-3-carbaldehyde. )e carbaldehyde functional group was transformed into nitriles using POCl3 and NaN3, which was subsequently converted to amide using CH3CO2H and H2SO4. )e compounds synthesized were screened for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes. Compounds 6 and 8 showed good activity against E. coli with an inhibition zone of 11.00± 0.04 and 12.00± 0.00mm, respectively. Compound 5 had good activity against S. aureus and P. aeruginosa with an inhibition zone of 11.00± 0.03mm relative to standard amoxicillin (18± 0.00mm). Compound 7 displayed good activity against S. pyogenes with an inhibition zone of 11.00± 0.02mm. )e radical scavenging activity of these compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), and compounds 5 and 6 displayed the strongest antioxidant activity with IC50 of 2.17 and 0.31 μg/mL relative to ascorbic acid (2.41 μg/mL), respectively. )e molecular docking study of the synthesized compounds was conducted to investigate their binding pattern with topoisomerase IIβ and E. coli DNA gyrase B. Compounds 6 (−6.4 kcal/mol) and 8 (−6.6 kcal/mol) exhibited better binding affinity in their in silicomolecular docking against E. coliDNA gyrase.)e synthesized compounds were also found to haveminimum binding energy ranging from −6.9 to −7.3 kcal/ mol against topoisomerase IIβ. )e SwissADME predicted results showed that the synthesized compounds 5–8 and 12 satisfy Lipinski’s rule of five with zero violations. )e ProTox-II predicted organ toxicity results revealed that all the synthesized compounds were inactive in hepatotoxicity, immunotoxicity, mutagenicity, and cytotoxicity. )e findings of the in vitro antibacterial and molecular docking analysis suggested that compound 8might be considered a hit compound for further analysis as antibacterial and anticancer drug. )e radical scavenging activity displayed by compounds 5 and 6 suggests these compounds as a radical scavenger.


Introduction
Pathogenic microorganisms, including bacteria, viruses, fungi, and protozoan, are the major cause of public health problems in developed and developing countries [1,2]. Cancer and bacterial diseases are the leading cause of death all over the world. So far, numerous types of drugs have been developed and used to treat of various types of infections [3]. However, various reports have disclosed that pathogenic microorganisms develop resistance against most of commercially available drugs. e problem is exacerbated due to the emergence of new pathogenic microorganisms at an alarming rate [4]. In addition to pathogenic microorganism, free radicals also attack body's cells causing deleterious diseases including cancer, cataract, premature aging, and other degenerative diseases [5,6]. us, the treatment of infectious diseases and cancer remains challenging in this era and demand a continuous research to develop new, effective, and safe antibiotics [4].
Quinoline is an aromatic heterocyclic compound characterized by having a double-ring structure composed of benzene and a pyridine ring. For the last ten decades, quinoline moiety has been used as a scaffold for drug design and development. Even today, compounds containing this scaffold represent an inexhaustible inspiration for the design and development of novel semisynthetic or synthetic agents exhibiting a broad spectrum of bioactivities. Both natural and synthetic analogs of quinolines were reported to have several biological activities, including anticancer [7], antimalarial [8], antibacterial [7], antiviral [9], antifungal [10], and anti-inflammatory [10]. In drug development, choosing a correct molecular scaffold is one of the most important roles of chemists. Among several scaffolds, quinoline, with its good chemical reactivity and enormous biological activities, has been used as a starting point for drug synthesis or modification [11,12]. Various types of functional groups can be introduced using relatively simple reactions [13]. Because of these attractive properties, to date, there are antibacterial [14], anticancer [15], and antimalarial [16] commercial quinoline-based drugs. e broad spectrum biological activities of quinolinebased compounds urge the generation of a large number of structurally diverse derivatives. In this regard, quinoline-3-carbonitrile derivatives were reported as a valuable starting material for the development of broad-spectrum antibacterial agents [17]. e good antibacterial activities of derivatives of quinoline-3-carbonitrile were also reported by Khan et al. [17]. ese reports further necessitate the synthesis of several analogs derived from the substitution of the 2-chloro in 2-chloroquinoline-3-carbaldehydes using various nucleophiles. In fact, the synthesis and biological activities of 2-chloro and 2,7-dichloroquinoline-3-carbaldehydes were also reported in the literature [18]. Inspired by the good biological activities of 2-chloroquinoline-3-carbaldehydes, we have previously reported the synthesis and antibacterial activities of various derivatives of quinoline-3-carbaldehydes [17]. Indeed, compounds with better antibacterial and antioxidant activities were synthesized [17]. e side chains of the benzene ring of quinolines are the other key focus area to build novel compounds with better biological activities. Owing to such significance and keeping in view the wide range of biological activities of chloroquinoline, we are interested in the synthesis of derivatives of quinolines having chlorine in the benzene ring. Herein, we reported the synthesis and biological activities of some novel 7-chloroquinoline derivatives. e in silico molecular docking analysis against E. coli DNA gyrase B and human topoisomerase IIβ and pharmacokinetic properties of the synthesized compounds were also incorporated for the first time in this paper.

General.
e chemicals used in this study were bought from Loba Chemie Pvt., Ltd. e iele tube was used to determine the melting point. e synthesized compounds were purified by column chromatography using silica gel (60-120 mesh) Merck. e progress of the reaction was monitored by TLC, and spots were detected using UV lamp. NMR analyses were carried out on Bruker Avance 400 MHz spectrometer using CDCl 3 , MeOD-d4, and DMSO-d6 as a solvent. Coupling constants J in Hz were directly calculated from the spectra. Splitting patterns are designated as s (singlet), d (doublet), t (triplet), q (quartet), and m (multiplet). Low-resolution electron impact mass spectra were obtained at 70 eV using a double focusing sector field mass spectrometer Finnigan MAT 95.

Synthesis of Acetanilide.
In a 250 mL round flask, aniline (25 mL), acetic anhydride (25 mL), zinc powder (0.2 g), and acetic acid (25 mL) were added. e mixture was boiled under reflux using a water condenser for 2 hours. en, it was cooled to room temperature and poured into 300 mL of crushed ice water. e solid product was collected by suction filtration (white crystals; yield 89%, mp 112-113°C (Lit. mp 114.3°C)) [19].

Synthesis of 3-Chloroacetanilide.
In a 250 mL round flask, 3-chloroaniline (25 mL), acetic anhydride (25 mL), zinc powder (0.2 g), and acetic acid (25 mL) were added. e mixture was boiled under reflux using a water condenser for 2 hours. en, it was cooled to room temperature and poured into 300 mL of crushed ice water. e solid product was collected by suction filtration (white crystals; yield 91%, mp 72-74°C (Lit. mp 76°C)) [20]. 3-carbaldehyde. N,N-Dimethylformamide (21.1 mL, 0.27 mol) was added to a 250 mL round-bottom flask guarded with a drying tube; it was cooled to 0°C using an ice bath. en, phosphorus oxychloride (60 mL, 0.64 mol) was added dropwise from the separatory funnel guarded by a drying tube while stirred by a magnetic stirrer. is addition was done for 30 minutes. en, acetamide (12.34 g, 0.09 mol) was added. After 5 minutes, the dropper funnel was replaced by an air condenser with guarding tube at its end, and the mixture was heated for 22 hours on an oil bath at 94-98°C. en, it was cooled to room temperature, poured into a beaker containing 400 mL crushed ice water, and stirred for 20 minutes. e yellow solid product was collected by suction filtration and washed with cold water. e crude yield was 14.6 g (83%) and recrystallized from ethyl acetate (yellow crystals; yield 5.2 g (30%), mp 146-148°C (Lit. mp 146-148°C)) [19]. (4). N,N-Dimethylformamide (16.5 mL, 0.21 mol) was added to a 250 mL round bottom flask guarded with a drying tube; it was cooled to 0°C using an ice bath. en, phosphorus oxychloride (46.5 mL, 0.50 mol) was added dropwise from the separatory funnel guarded by a drying tube while stirred by a magnetic stirrer. is addition was done for 30 minutes. en, N-(3-chlorophenyl)-acetamide (12 g, 0.07 mol) was added to it. After 5 minutes, the dropper funnel was replaced by an air condenser with guarding tube at its end, and the mixture was heated for 22 hours on an oil bath at 100-105°C. en, it was cooled to room temperature, poured into a beaker containing 300 mL crushed ice water, and stirred for 20 minutes. e yellow solid product was collected by suction filtration and washed with cold water. e crude yield was 4.5 g (28%) and recrystallized from ethyl acetate; yellow crystals; mp 170-174°C; yield 2.38 g (15%); UV-Vis:

Synthesis of 2,7-Dichloroquinoline-3-carboxamide (6).
A 100 mL round-bottom flask was charged with 2,7-dichloroquinoline-3-carbonitrile (0.19 g, 0.85 mmol), acetic acid (2 mL), and sulfuric acid (1 mL). e mixture was refluxed using a water condenser with stirring for 3 hrs, and the progress of the reaction was monitored with TLC. After completion of the reaction, the mixture was cooled and poured into a beaker containing 100 mL of ice water. e

2.2.7.
Synthesis of 7-Chloro-2-methoxyquinoline-3carbaldehyde (7). A 100 mL round-bottom flask was charged with 2,7-dichloroquinoline-3-caraldehyde (0.99 g, 4.4 mmol), methanol (10 mL), N,N-dimethylformamide (13 mL), and potassium carbonate (0.57 g, 8.8 mmol). e mixture was refluxed using a water condenser with stirring for 4 hrs, and the progress of the reaction was monitored by TLC. After completion of the reaction, the mixture was cooled to room temperature and poured into 60 ml crushed ice water. e yellow crystal was collected using suction filtration and mp 102-104°C; yield 74% with R f � 0.71 (nhexane:ethyl acetate  (8). A 100 mL round bottom flask was charged with 2,7-dichloroquinoline-3-carbaldehyde (0.5 g, 2.2 mmol), potassium carbonate (0.6 g, 4.3 mmol), ethanol (10 mL), and N,N-dimethylformamide (10 mL). e mixture was refluxed using a water condenser with stirring for 4 hrs, and the progress of the reaction was monitored by TLC. At the end, ethanol was removed by distillation, and the remaining cooled mixture was poured into 80 mL crushed ice water. e solid product was collected by suction filtration, and the yield was 0.

Synthesis of 2-Chloroquinoline-3-carbonitrile (12).
In a test tube, 2-chloroquinoline-3-carbaldehyde (1 g, 5.2 mmol), sodium azide (0.68 g, 10.5 mmol), and phosphorus oxychloride (4 mL, 42.7 mmol) of ratio 1 : 1: 5 were added and stirred for 30 minutes in a hood. e mixture was heated in a water bath for 6 hrs, and the reaction progress was monitored by TLC. After completion of the reaction, the mixture was cooled to room temperature and poured into a Journal of Chemistry beaker containing 60 mL of crushed ice water. e yellow crystal was collected by suction filtration, mp 132-134°C; yield 89% with R f � 0.66 (n-hexane: ethyl acetate � 5 : 1). e product was purified over silica gel column chromatography n-hexane: ethyl acetate (

Antibacterial Activity.
e in vitro antibacterial activity of the compounds synthesized was determined by the disc diffusion method against four strains of bacterial species: two Gram-positive (S. aureus (ATCC25923), S. pyogenes (ATCC19615)) and two Gram-negative (E. coli (ATCC25922), P. aeruginosa (ATCC27853)). e medium was prepared by dissolving Mueller Hinton Agar (MHA) in distilled water and then autoclaved at 121°C for 15 min. It was poured into sterile plates (20-25 mL/plate), and the plates were allowed to solidify under a sterile condition at room temperature.
e synthesized compounds at the concentrations of 100 and 200 µg/mL were prepared by dissolving the samples in dimethyl sulphoxide (DMSO). e sterile discs (6 mm) were infused with the synthesized compounds, positioned on the surface of the medium with sterile forceps, and gently pressed down to ensure contact with the MHA [21]. After incubation for 24 hrs at 37°C, the inhibition zone produced by the synthesized compounds was evaluated by measuring the diameter (mm) of the clear zone around the disc against the test organisms using a ruler. Amoxicillin was used as a standard antibiotic, and DMSO was used as a control.

Radical Scavenging Activity.
e diphenyl picryl hydride (DPPH) radical scavenging activity of the synthesized compounds was assessed following the previously reported procedure [22]. In short, 0.04 mg/mL (0.004% (w/v)) solution of DPPH in methanol was prepared and used as control solution. e synthesized compounds were serially diluted in DPPH solution to furnish four different concentrations (1.25, 2.50, 5.00, and 10.00 μg/mL).
is was repeated for ascorbic acid, used as standard. After a 30 min incubation period at room temperature, the absorbance was measured against blank at λ max 517 nm [23]. e activity was expressed as % inhibition and IC 50 , the concentration of the sample that can scavenge 50% of DPPH free radical. e percent DPPH inhibition (%I) of the compounds synthesized and ascorbic acid was calculated by the following formula: where A control is the absorbance of the control reaction and A sample is the absorbance of the test compound.

In Silico Molecular Docking Analysis.
AutoDock Vina with the standard protocol was used to dock the proteins (PDB ID : 6F86; PDB ID : 4FM9, and PDB ID :1HD2) and synthesized compounds incorporated into the active site of proteins. e chemical structures of compounds were drawn using the ChemOffice tool (ChemDraw 16.0) assigned with proper 2D orientation, and the energy of each molecule was minimized using ChemBio3D. e energy-minimized ligand molecules were then used as input for AutoDock Vina to carry out the docking simulation. e crystal structures of receptor molecule E. coli gyrase B (PDB ID : 6F86) and human topoisomerase IIβ (4fm9) were downloaded from the protein data bank. e protein preparation was done using the reported standard protocol by removing the cocrystallized ligand, selected water molecules, and cofactors; the target protein file was prepared by leaving the associated residue with protein using Auto preparation of target protein file AutoDock 4.2 (MGLTools 1.5.6). e graphical user interface program was used to set the grid box for docking simulations. e graphical user interface program was used to set the grid box for docking simulations. e grid box was constructed using 40, 40, and 40, pointing in x, y, and z directions, respectively, with a grid point spacing of 0.375Å. e center grid box was (13.52Å, 15.68Å, and 19.12Å), (16.40Å, 39.73Å, and 23.10Å), and (18.04Å, 20.67Å, and 17.69Å), for 6f86, 4fm9, and 1hd2, respectively. e docking algorithm provided with AutoDock Vina was used to search for the best-docked conformation between ligand and protein. During the docking process, a maximum of nine conformers were considered for each ligand. e conformations with the most favorable (least) free binding energy were selected for analyzing the interactions between the target receptor and ligands by Discovery Studio Visualizer and PyMOL. e ligands are represented in different colors. H-bonds and the interacting residues are represented in ball and stick model representation [24].

In Silico Drug-Likeness and Toxicity Predictions.
Drug-likeness properties of the compounds synthesized were predicted based on an already established concept by Lipinski's rule [25]. e structures of the synthesized compounds were converted to their canonical simplified molecular-input line-entry system (SMILE). ese compounds were submitted to the SwissADME and PreADMET tool to estimate in silico pharmacokinetics, such as the number of hydrogen donors, hydrogen acceptors, rotatable bonds, and total polar surface area of a compound. e organ toxicities and toxicological endpoints of the synthesized compounds were predicted using PreADMET and OSIRIS Property. e analyses of the compounds were compared with that of the clinical drug (vosaroxin/ciprofloxacin), and only compounds without violation of any screening were used for the molecular docking analysis.

Antibacterial Activity.
Quinolines are pharmacologically active compounds used to treat various life-threatening diseases [19]. In an attempt to find bioactive quinoline analogs, a series of quinoline derivatives were synthesized and tested for their antibacterial activity against some Grampositive and Gram-negative bacterial pathogens by measuring the inhibitory effect of such compounds. e results are described in Table 1 and Figure 1.
All synthesized compounds displayed weak-to-moderate activities against all tested bacterial strains when compared with amoxicillin, a standard drug used in the present study. e mean inhibition zone exhibited by the synthesized compounds ranged from 7.00 ± 0.04 to 12.00 ± 0.00 mm. Compounds 6 and 8 showed good activities against E. coli with mean inhibition zones of 11.00 ± 0.04 and 12.00 ± 0.00 mm, respectively, while compound 5 exhibited good activity against S. aureus and P. aeruginosa with 11.00 ± 0.03 mm at 200 µg/mL. e activity shown by compound 8 is superior to the other compounds synthesized in the present study but modest compared with standard amoxicillin. On the contrary, compound 7 showed better activity against S. pyogenes with mean inhibition of 11.00 ± 0.02 mm compared with the other synthesized compounds at 200 µg/mL. Compound 7 also displayed a medium inhibition zone against all strains of bacteria used in this study except for S. pyogenes. Compounds 5 and 8 showed medium activities against other tested strains of bacteria, while compound 12 showed a medium mean inhibition zone against three other tested bacterial strains such as S. aureus, P. aeruginosa, and S. pyogenes. e activity displayed by compound 12 against P. aeruginosa in this work contradicted with previous work reported as inactive by Kamal et al. [27]. e synthesized compounds have stronger activities when compared with related compounds reported in [19], which differ in substituents and functional groups. e better activity shown by these compounds might be due to chlorine at 7-position and the amide and nitrile functional groups.

Radical Scavenging Activity.
Antioxidants are substances that prevent and stabilize the damage caused by free radicals via supplying their own electrons to these damaged cells. Antioxidants also turn free radicals into waste by-products, which are eliminated from the body [28]. DPPH assay is a quick method to evaluate the radical scavenging activity of the samples. Compounds exhibiting antioxidant activity reduced the absorbance at 517 nm, which is due to DPPH radical. Furthermore, antioxidants turn the purple color due to DPPH radical to yellow or colorless. In this work, the radical scavenging activity of the compounds synthesized was evaluated using DPPH, and the findings are depicted in Table 2 and Figure 2. Moreover, the IC 50 values of the synthesized compounds were calculated using Microsoft Excel, and the results are summarized in Figure 3. e DPPH radical scavenging activity of the synthesized compounds was compared with ascorbic acid, which was used as standard, and the result is graphically presented in Figure 2.
Generally, the antioxidant activities of the synthesized compounds in this work were medium to high relative to ascorbic acid at the same concentration. e radical scavenging activity of compound 6 was found to be 68.82%. e result was better than the activity displayed by the other synthesized compounds. Moreover, the percentage free radical inhibition of compound 6 at 2.50 and 1.25 µg/mL was much significant compared with the results shown by ascorbic acid.
is was supported by the low IC 50 of compound 6 (0.31 µg/mL) compared with ascorbic acid (2.41 µg/mL). e percentage inhibition of compound 8 at 10.00 µg/mL, 5.00 µg/mL, and 2.50 µg/mL is medium when compared with that of ascorbic acid and high in 1.25 µg/mL concentration. e IC 50 value shown by compound 5 was 2.17 µg/mL. is is superior relative to ascorbic acid used as the positive control. is might be because of the presence of free electrons in the amide functional group in compound 5. e percentage inhibition of compound 7 is almost low in all concentrations relative to ascorbic acid. Compound 12 does not have percentage inhibition at all tested concentrations. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) is a stable free radical accepting hydrogen from a corresponding donor, which causes it to lose the characteristic deep purple (λ max 517 nm) color. Compound 6 contains an ethoxy group at 2-position, which is responsible for accepting free radicals from DPPH. e synthesized compounds have stronger activities when compared with related compounds reported in the literature, which differ in substituents and functional groups. ese were due to the presence of proton and other groups, which were accepting radicals from DPPH.

In Silico Molecular Docking Analysis against E. coli DNA Gyrase B.
e DNA gyrase, an enzyme belonging to a member of bacterial topoisomerase, controls the topology of DNA during transcription, replication, and recombination by introducing transient breaks to both DNA strands. In this regard, bacterial DNA gyrase is essential for bacterial survival and, therefore, necessary to be exploited as an antibacterial drug target [29]. us, in this study, the molecular docking analysis of the synthesized compounds was conducted to investigate their binding pattern with DNA gyrase and compared them with ciprofloxacin used as a standard drug. e synthesized compounds (5-8 and 12) were found to have minimum binding energy ranging from −6.1 to −6.6 kcal/mol (Table 3), with is better achieved using compound 8 (−6.6 kcal/mol). e binding affinity, H-bond, and residual interaction of five compounds and ciprofloxacin are summarized in Table 3.
Compared to ciprofloxacin, the synthesized compounds (5, 6, and 12) showed similar residual interactions (Van der Waals interaction) with amino acid residues Ala-47 and hydrophobic interaction with amino acid residues Ile-78, and   e findings of the in silico molecular docking analysis match with the in vitro antibacterial activity of the synthesized compounds. Among the compounds synthesized, compounds 6 (−6.4 kcal/mol) and 8 (−6.6 kcal/mol) had better activity compared with the others. e synthesized compounds have minimum binding energy when compared with related compounds reported in [19], which differ in substituents and functional groups. ese were due to chlorine substituted at 7-position and the amide and nitrile functional groups. e 3-dimensional binding interaction of compounds 6, 8 and that of ciprofloxacin against E. coli gyrase B complex are illustrated in Figures 4-6.

In Silico Molecular Docking Analysis against Human
Topoisomerase IIβ. Topoisomerase II is an enzyme belonging to a human topoisomerase that cuts both strands of the DNA helix simultaneously to manage DNA tangles and supercoils [30]. Human DNA topoisomerase II is an important target in anticancer therapy. e human topoisomerase II is crucial to control the topology of DNA during replication, transcription, and recombination by introducing temporary breaks to both DNA strands. erefore, in this study, the molecular docking analysis of the synthesized compounds was conducted to investigate their binding pattern with DNA topoisomerase IIβ and compare them with a standard drug (vosaroxin), which is an anticancer drug. e synthesized compounds were found to have minimum binding energy ranging from −6.9 to −7.3 kcal/mol (Table 4), best results achieved with compound 8 (−7.3 kcal/ mol), 5 (−7.1 kcal/mol), and 6 (−7.1 kcal/mol). e binding affinity, H-bond, and residual interaction of five compounds and vosaroxin were summarized in Table 4.
Compared to vosaroxin, the synthesized compounds (5, 6, 7, and 12) showed similar residual interactions (Van der Waals interaction) with amino acid residues Tyr-684, compound 12 with Gln-542. Compounds 5-8 showed similar residual interactions (hydrophobic interactions) with amino acid residues Leu-705 and Pro-593, and compound 12 showed similar hydrophobic interactions with amino acid   residues Leu-705 and Ile-577. Compound 8 showed additional hydrogen-bonding interactions with amino acid residues Ser-591 and Leu-685, and compounds 6, 7, and 12 also showed additional hydrogen-bonding interactions with amino acid residues Leu-685. Compounds 5 and 6's docking results partially matched the vosaroxin interactions with amino acid residues. e docking result of compound 8 was found to be stronger than that vosaroxin. erefore, compounds 5, 6, and 8 might have the best anticancer agents among the synthesized compounds in this study. e 3-dimensional binding interaction of compounds 5, 6, 8, and vosaroxin against human topoisomerase IIβ is illustrated in Figures 7-10.
A drug-likeness prediction model introduced by Hu et al. involved molecular descriptors related to numbers of different atom types and decision trees for discriminating between potential drugs and nondrugs [31]. ADME describes the disposition and fate of pharmaceutical compounds within an organism, especially in the human body [32]. e primary cause of failure during the drug development phase is poor pharmacokinetics (PK) and toxicity rather than poor efficacy of the candidate compound. e prediction of compound toxicities is an important part of the drug design development process. ProTox-II incorporates molecular similarity, fragment propensities, most frequent features, and machine learning, based a total of 33 models for the prediction of various toxicity endpoints such as acute toxicity, hepatotoxicity, cytotoxicity, carcinogenicity, mutagenicity, immunotoxicity, adverse outcomes pathways, and toxicity targets [33].
e SwissADME predicted results showed that the synthesized compounds 5-8 and 12 satisfy Lipinski's rule of five with zero violations for their drug-like molecular nature (Table 5). According to Lipinski's rule of five, the molecular weight of the molecules should be less than 500, number of hydrogen bond acceptors less than ten, number of hydrogen bond donors less than five, and the lipophilicity (cLogP) values less than five [25]. e SwissADME predicted LogP values ranged from 1.85 to 2.37, assuring optimal lipophilicity of the synthesized compounds. e predicted TPSA value in (Å 2 ) for synthesized compounds ranged from 36.68 to 55.98, inferring very good absorption. It has been suggested that molecules with a TPSA of 140Å 2 and above would be poorly absorbed (<10 percent fractional absorption), while compounds with a TPSA less than 60Å 2 would be well absorbed (>90 percent) [34].
Pharmacokinetically, all synthesized compounds have high GI absorption, blood-brain barrier (BBB) permeability, and medium skin permeation value, and none of the synthesized compounds were predicted as P-glycoprotein substrate ( Table 6). Under normal physiological conditions, the substance entering the brain requires being lipid-soluble, less than 400 daltons, and not substrate of active efflux transporters (AET). In this study, all synthesized compounds can pass through blood-brain barrier. Besides, the interaction of therapeutic molecules with cytochromes P450 (CYP) isoforms as a substrate of these enzymes was proposed to screen a therapeutically active molecule. It is reported that the inhibition of CYP isoenzymes is certainly one  major cause of pharmacokinetics-related drug-drug interactions thereby leading to toxic or adverse effects due to the lower clearance and accumulation of the drug or its metabolites [35]. e synthesized compounds were none inhibitors of three enzymes, namely, CYP2C9, CYP2D6, and CYP3A4, and inhibitors of CYP1A2 and CYP2C19 except for compound 12 not inhibiting CYP2C19. All synthesized compounds were similar to vosaroxin in all enzymes, except for CYP2C19, which was not inhibited by compounds 5-8.
e organ toxicity (hepatotoxicity) and toxicological endpoints (carcinogenicity, immunotoxicity, mutagenicity, and cytotoxicity) of the synthesized compounds were predicted with the results presented in Table 7. e ProTox II predicted organ toxicity results revealed that all the synthesized compounds were inactive in hepatotoxicity, immunotoxicity, mutagenicity, and cytotoxicity. Compounds 5, 6, and 12 were also inactive in carcinogenicity, and compounds 7 and 8 have carcinogenic properties.    Almost all synthesized compounds are similar to vosaroxin in immunotoxicity, mutagenicity, cytotoxicity, and carcinogenicity properties, but none hepatotoxicity, whereas vosaroxin was hepatotoxic. LD 50 is the amount of substance given all at once, which causes the death of 50% (one-half ) of a group of tested animals. It is one way to measure the acute toxicity of materials. e order of toxicity of synthesized compounds toward human body 6 (LD 50 � 705) > 12 (LD 50 � 1100) > 7 and 8 (LD 50 � 2190) > 5 (LD 50 � 5000). e "Lethal Dose" of compound 5 was higher than other synthesized compounds, whereas compound 6 was the least. In this study, the "Lethal Dose" of compound 6 was closer to control (vosaroxin) than other synthesized compounds.

Conclusion
In conclusion, five novel chloroquinoline derivatives were synthesized and characterized. e antibacterial activities of the compounds synthesized were assessed against two Gram-negative and two Gram-positive bacteria, and most of them were found to have weak-to-moderate activities against the bacterial strains used for the screening. e inhibition zone displayed by compounds 6 and 8 against E. coli was significant compared with the others. ese compounds showed a better binding affinity with E. coli DNA gyrase in their in silico molecular docking analysis. is suggests compounds 6 and 8 as a candidate for further analysis as antibacterial agents. Compounds 5 and 6 displayed better antioxidant activity compared with ascorbic acid suggesting these compounds as a radical scavenger. Compound 8 showed a strong binding affinity against human topoisomerase IIβ compared with vosaroxin suggesting this compound as a lead compound for further study as an anticancer drug.

Conflicts of Interest
e authors declare that there are no conflicts of interest regarding the publication of this paper.