Innovational combination of hetero-bifunctional N-PEG quinoline scaffolds derivatives with improved anticancer activity against breast and colon cancer cell lines and P-glycoprotein, cytochrome p450 enzyme activity prediction

Polyethylene glycol (PEG) is a polymer that is widely used as a carrier for drug delivery systems (DDS). A library of N-PEGylated quinoline derivatives of PEG molecular weight 200 was prepared rapidly after the activation of PEGs using maleic anhydride. Quinoline with a polymer backbone is essential as new material. PEG is a water-soluble nonionic polymer approved by food and drug organizations for medicine applications. Because of its nontoxic grapheme, it is widely utilized in numerous biochemical, cosmetic, pharmaceutical, and industrialized applications. The modern SwissADME is a web tool that stretches free admittance to a pool of hasty, yet solid, clarifying models for physicochemical properties, pharmacokinetics, and therapeutic science. The present facile synthetic strategy can be a practical approach for incorporating polymeric carriers conjugated with drug moieties, either in the backbone of the polymer or as a terminal and pendant group on the polymer chains.

by coupling PEG 200(n) with 2-formyl, 3-chloro, 6-amino quinoline via maleic anhydride as an activator was presented herein. Antimicrobial activities of the quinoline-PEG polymer and quinoline were tested against gram-positive and gramnegative bacteria. The results indicated that the new polymers had potential as potent antimicrobial agents. Since these polymers were comparatively stable at high temperatures, they can be used for medical and biomaterial applications with prior thermal sterilization. SwissADME permits the review of absorption, distribution, metabolism, and excretion (ADME) restrictions of medication aspirants and small molecules and provides statistics that authorize the early hazard calculation in drug enhancement progression. Exceptionally, SwissADME affords a point to estimate Lipinski's rule of five [17] for medication semblance of oral bioavailability. The present facile synthetic strategy can be a practical approach for incorporating the polymeric carriers conjugated with drug moieties, either in the backbone of the polymer or as a terminal and pendant group on the polymer chains.
PEG is the covalent link of nonpoisonous, hydrophilic polyethylene glycol (PEG) to dynamic pharmaceutical constituents [18]. The technology established from revolutionary work was conducted in the 1950s and 1960s on the coupling of polymers to protein. The amendment of a biopharmaceutical with polyethylene glycol increases its hydrodynamic area and reduces its immunogenicity and antigenicity. Other achievements included braked renal evacuation, enhanced stability in the direction of proteolysis, and increased solubility of the biopharmaceutical in aqueous solution [19]. The synthesis of macromolecules with different functional groups in 2 ends is a promising field of research. A lot of useful materials can be designed from the macromolecules. However, due to the difficulty of separation of the reacted mixture, significant achievements have not yet been made. Pozzo et al. reported that some monofunctional derivatives of PEG could be prepared and separated using excess PEG, but the molecular weight of the monosubstituted PEGs was no more than 1000. It was evident that the higher the molecular weight of the starting PEG, the more difficult it was for the isolation of monosubstituted PEG from the reacted mixture. This is because there was no sharp difference between monosubstituted, disubstituted, and raw PEGs in the chemical and physical properties [20][21][22].Heterocyclic mixes have increased gigantic significance as a result of their low reverberation vitality and solid hydrogen-bonding capacities [23]. A recent investigation reported the fruitful synthesis of new heterocyclic-like ester and amide under water as a solvent and the surface of silica-coated CoFe 2 O 4 magnetic nanoparticles for the synthesis of 3-pyrrolin-2-ones [24], as well as for the preparation of 2-amino-4,6-diarylnicotinonitrile under microwave irradiation [25].

Result and discussion
An extension of PEG-supported chemistry was linked in the arena of functionalized polymers as reagent supports. Prepared was novel PEG N-terminal quinoline substituted derivatives and it was shown that, when related to a heterogeneous commercially-existing counterpart, they held promising reaction kinetics equal to the Staudinger and Mitsunobu etherification reactions. They were evaluated for their in vitro anticancer, antibacterial, and antifungal activities. The present study expanded on those preliminary investigations to explore the synergistic effects of such pharmacophores.
The PEGylation chemistry successfully demonstrated at the amino group was situated at C-7 of the quinoline hybrids. To couple a PEG to a quinoline molecule, it is first necessary to activate the polymer by converting the hydroxyl terminus to some functional group proficient reacting with the functional group situated on quinoline molecule. Herein, it was opted to activate the PEG by turning it to its acid derivative and coupling it with an amino group of quinoline molecules. This PEGylation methodology involved the conjugation of quinoline onto hetero-bifunctional PEG derivatives that had -OH on one terminus and -COOH on the other for covalent attachment of the amino group. The free carboxyl group of compounds was used for conjugation through an amine connection. It was determined that this conjugation proceeded through the formation of amide linkage between the PEG chain and quinoline under mild reaction conditions.
In its most common form, PEG is a linear or branched polyether terminated with hydroxyl groups and has the general structure as shown below: HO-(CH 2 CH 2 O) n -CH 2 CH 2 -OH. PEG is synthesized by anionic ring-opening polymerization of ethylene oxide initiated by the nucleophilic attack of a hydroxide ring.
PEG 200(n) (5 mL, 0.028 moles, 200 g/mole) was dissolved in 20 mL of dry CH 2 Cl 2 . Added to this solution was tetrahydrofuran (THF) containing maleic anhydride (0.056 mol, 0.54 mg) and pyridine (0.056 mol, 0.46 mL). After stirring overnight at room temperature, the reaction was completed, as indicated by thin-layer chromatography (TLC) (methanol:ethyl acetate, 7:3) (no anhydride left and the detection of a single polar PEG compound). The monoacid derivative of the poly (ethylene glycol) 200(n) was used without purification. The most useful for polypeptide modification is monoacid PEG, which has the general structure: HO-(CH 2 CH 2 O) n -CH 2 CH 2 -O-COOH. Now, for this monoacid derivative of PEG coupled to a 6-amino-2-chloroquinoline-3-carbonitrile (3a), it was necessary to activate the PEG by maleic anhydride. In the present study, the solution synthesis of a novel family of PEGylating reagent was presented, which contained a free -COOHterminus. Conditions were developed for the coupling of this novel PEGylating reagents to the -NH 2 function of model quinoline to illustrate their general utility. Together, this study demonstrated that these PEGylating reagents were well-suited for conjugation peptide and protein containers, either free -COOH or -NH 2 functions. These reagents might have wide utility in therapeutic expansion, as branched PEGylation has been observed to deliver more effective protection of proteins from proteolysis by protecting the protein surface approaching the macromolecules.
The monoacid derivative of hydroxycarboxy PEG (HO-PEG 200 COOH) (28.0mmol) was activated with a 1:2molar equivalent of 6-amino-2-chloroquinolin-3-carbonitrile (2a) (46.0mmol) and N, N dicyclocarbidiimide (46.0mmol) dissolved in dichloromethane. The solution was stirred for 24 h at room temperature. A syrupy resin was obtained and dried under a vacuum. The syrupy resin was dissolved in 15 mL of acetone. A white precipitate of dicyclohexylurea (DCU) appeared and was discarded, and the filtrate was collected. The final filtrate was evaporated to afford the product. TLC (methanol:ethyl acetate, 7:3) was performed to check the existence ofDCU, which exposed a negative outcome that was confirmed by the infrared spectroscopy (IR) spectra. A negative dye test indicated complete amino group capping.
The resin was dehydrated in a vacuum for IR, 1 HNMR, 13 CNMR, and mass spectral analysis. At this point, the adhesive did not stick to the glass wall anymore. The IR spectrum of the resin showed the characteristic absorption band of the PEG ether backbone (1120 cm -1 ) and absorption bands (1760 and 1685 cm -1 )for the ester and amide bond, respectively (C=O) ( Table 2).

Experimental
All of the recorded melting points were taken in open capillary tubes and were uncorrected. The IR spectra were recorded with a FTIR PerkinElmer Rx-I instrument (PerkinElmer, Inc., Waltham, MA, USA) using Nujol. 1 HNMR spectra were recorded on 400 MHz Bruker AC-300 F instrument (Bruker BioSpin Corp., Billerica, MA, USA) using tetramethylsilane as the internal standard and deuterated chloroform as the solvent, and the mass spectra were recorded on a VG.70 S instrument at SAIF Chandigarh. The TLC technique was used to check the purity of the compound using silica gel G.

In vitro anticancer assays
A library of 24 compounds was tested using the Alamar blue (AB) assay (in the case of leukemia cells) for their antiproliferative activity in vitro against 2 cancer cell lines: SW620, MD468, and MD468-2 were all colon cancer cell lines obtained from the American Tissue Culture Collection (ATCC, Manassas, VA, USA). MD468 is a mismatched repairdeficient cell line, and MD468-2 has a p53 mutation. The results of the cytotoxic activity in vitro were expressed as an ID 50 (nM/mL), i.e. the concentration of the compound that inhibited the proliferation of 50% of the tumor cells when compared to the untreated control cells. Camptothecin (10 nM), Paclitaxel (10 nM), Doxorubicin (250 nM), and Oxaliplatin (2000 nM) were applied as referential cytotoxic agents (positive test controls). A value of less than 10 nM/mL was considered as an antiproliferative activity criterion for synthetic compounds. The results of the cytotoxicity studies are summarized in Table 3.

3.1.2.Antiproliferative activity
All 24 compounds were tested via AB assay (in the case of leukemia cells) for their antiproliferative activity in vitro against 2 cancer cell lines: SW620, MD468, and MD468-2 were all colon cancer cell lines obtained from the ATCC. MD468 is a mismatched repair-deficient cell line, and MD468-2 has a p53 mutation. The results of the cytotoxic activity in vitro were expressed as an ID 50 (nM/mL), as stated above. Camptothecin (10nM), Paclitaxel (10 nM), Doxorubicin (250 nM), and Oxaliplatin (2000 nM) were applied as referential cytotoxic agents (positive test controls). A value of less than 10 nM/mL was considered as an antiproliferative activity criterion for synthetic compounds. The results of the cytotoxicity studies are summarized in Table 3.
In general, compounds 3a-4i did not display any anticancer activity, whereas compounds 4a-4i exhibited potent antiproliferative activity against theSW620, MD468, and MD468-2 colon cancer cell lines. This implied that after PEGylation, the anticancer activity enormously increased in multiples of 469-to 11896-fold. PEGylated 1-H-pyrazol (3 and 4b) and quinolin-6-amine (4h) exhibited the highest activity against the SW620, MD468, and MD468-2 colon cancer  when the IC 50 values of all of the compounds were compared with those of standard drugs like Camptothecin (IC 50 :10 nM) and Paclitaxel (IC 50 : 10 nM). Doxorubicin (IC 50 : 250 nM) and Oxaliplatin (IC 50 : 2000 nM) were also suited as reference cytotoxic agents. A comparative investigation of the IC 50 concentrations of compounds 4a-4i with those of Doxorubicin (IC 50 : 250nM) and Oxaliplatin (IC 50 : 2000nM) was conducted. The anticancer activity displayed at an IC 50 concentration ranging from 7.8 nM/mL to 49.8 nM/mL indicated that all of the synthesized compounds exhibited incredibly higher potency than those of Doxorubicin (IC 50 : 250 nM) and Oxaliplatin (IC 50 : 2000 nM). The results summarized in Table 3 suggested that the potency of each compound as an anticancer agent was irrespective of its substituents and showed high selectivity and more specificity towards the binding targeted sites. Compound 4h proved to be a highly-potent candidate against the SW620, MD468, and MD468-2 colon cancer cell lines than the existing armory of anticancer drugs attributable to the ring annulations with fused pyrazole nucleus.

Assay principle
In this assay, the viability of chemically-treated cells were measured by a dye, Resazurin or Alamar blue (AB). AB, a nonfluorescent pointer dye, changed to bright red-fluorescent resorufin through the reduction reactions of metabolically active cells. The quantity of fluorescence produced was directly proportional to the number of living cells.
Cells: For the initial screen of A549, the lung cancer cells were used. Positive hits were then used to screen 7 other cell lines used in the NIH assays.
Protocol: Standard AB assay protocol for cell viability assay was used. Confluently-grown cells were trypsinzed, and around 10,000 cells were seeded in each well of a 96-well plate. The next day, the medium was replaced with medium containing the appropriate concentration of the drug. The maximum concentration of each drug was 400µg/mL, and a one-quarter dilution was used for each drug. The cells were treated for 48 h and 2µL of AB was added to each well and incubated for 2 h. Fluorescence intensity was read with a plate reader. From the graph, the IC 50 value was calculated. SW620, MD468, and MD468-2 were all colon cancer cell lines obtained from the ATCC. MD468 is a mismatched repairdeficient cell line, and MD468-2 has a p53 mutation. The effects of all of the new compounds on colon cancer cell lines SW620, MD468, and MD468-2, were observed and the results are depicted in Figures 1and 2. The growth inhibition percentages were compared with those of standard drugs Camptothecin, Paclitaxel, Doxorubicin, and Oxaliplatin (Table  3, Figures 1 and 2). For the rows, alcohol was added to generate killed cells.

In vitro antibacterial and antifungal activity
All of the newly synthesized compounds were screenedin vitrofor their antimicrobial activity and antifungal activity against a variety of bacterial and fungal strains, such as Staphylococcus Aureus (gram +ve), Escherichia Coli (gram -ve), Pseudomonas Aeruginosa (Gram -ve), and Candida Albicans using the disc diffusion method. The nutrient agar broth was prepared by aseptic inoculation with 0.5 mL of 24-h-old subcultures of S. Aureus, E. Coli, and C. Albicans in separate flasks at 40-50 °C and mixing well by gentle shaking. About 25 mL of the contents of the flask were poured and evenly spread in a Petri dish (13 cm in diameter) and allowed to set for 2h. Each test compound (20 mg) was dissolved in 2 mL of dimethyl sulfoxide (DMSO), which was used as a sample solution. A concentrated (100 µg/mL) solution was prepared using the dilution method. The sample size for all of the compounds was fixed as 10 µL.
The plates were incubated at 37 °C for 24 h, the control was similarly maintained with 1 mL of DMSO, and the zones of inhibition of the bacterial growth were measured in mm using a zone reader.

In vitro antibacterial and antifungal activity
The newly synthesized compounds (3a-3i and 4a-4i) were tested for theirin vitro antimicrobial activity against clinical isolates of gram-positive bacteria S.Aureus, gram-negative bacteria E.coli and P. Aeruginosa, and the fungus C. Albicans. For all of the compounds, along with the standards for the bacteria, doxycycline, ampicillin, and fungi, fluconazole was used at a concentration of 100 µg/mL in DMSO as the solvent control and nutrient agar was used as the culture method [26][27][28][29]. After 24h of incubation at 37 °C, the zones of inhibition were measured in mm.
All of the synthesized compounds exhibited good to moderate activity against all of the microbes. No zone of inhibition was observed against the strains of P. Aeruginosa with compounds 3c, 3h, and 4c, while all of the compounds displayed significant activity against the strains of C. Albicans, E. Coli, and S. Aureus.  The toxicity increased with the increase in the concentration of the test solution containing new compounds, suggesting a maximum tolerated dose. Some compounds did not meet the conventional bacteriostatic standards at lower concentration levels. The variance in the efficiency of compounds in contradiction ofdiverse organisms depends on either the impenetrability of the cell microorganisms or dispersion in the ribosomes of microbial cells. The results obtained after screening the synthesized compounds against various microorganisms are shown in Table 4.

SwissADME pharmacokinetics, physicochemical, and medicinal properties study [30]
The functioning highlights of these molecules were entered into the SwissADME site (http://swissadme.ch) using the ChemAxon's Marvin JS structure drawing instrument (Budapest, Hungary). Assistant highlights of the pharmacophore sway included bioavailability, transport properties, sympathy to proteins,reactivity, poisonous quality, and metabolic steadiness. Unique to SwissADME is the bioavailability radar [31], which gives a graphical assessment of the prescription resemblance parameters of an orally-accessible bioactive drug. The drug impression chart is exhibited as a hexagon ( Figure  3) with every one of the vertices dialogs to a restriction that symbolizes a bioavailable drug.
The pink location inside the hexagon speaks to the perfect range for each property (lipophilicity: XLOGP3 somewhere in the array of −0.7 and +5.0, size: extremity: topological polar surface area (TPSA) somewhere in the field of 20 and 130 Å2, MW somewhere in the scope of 150 g/mol and 500g/mol, solubility: log S not higher than 6, adaptability: close to 9 rotatable bonds, and saturation: some portion of carbons in the sp3 hybridization at any rate 0.25). The recommended run for the compound as bioavailable medication is portrayed in Table 5.

Drug-likeness
The drug resemblance properties of the fused compound are indicated by the red mutilated hexagon inside of the pink shade ( Figure 3). SwissADME, likewise, has computational channels that incorporate Ghose [32], Egan [33], Veber [34], and Muegee [35], created by top pharmaceutical organizations and cheminfomaticians to assess the drug resemblance of molecules. The values maintain in Table 6 indicated the violation of the prescribed range for the molecule to act as a drug.

PAINS, break, and leadlikeness screening
Pan-assay interference compound (PAINS) screening, which regularly gives bogus positive chemical properties, brings about high-throughput screens. PAINS will in general respond vaguely with various biological targets as opposed to explicitly influencing one foreseen objective. The SwissADME evaluation did not post any PAINS alert (Table 7). In additional to the verdict model, Brenk [36] measured combinations that were smaller and less hydrophobic, and not those described by Lipinski's standard of 5 to augment open doors for lead streamlining. Leadlikeness tests have been projected to provide primes with extraordinary kinship in high-throughput screens that consider the recognition and control of new exchanges ahead of the pack headway stage ( Table 7). All of the synthesized compounds (3a-3i) drifted the break alert and leadlikeness criteria.

P-glycoprotein and CYP enzyme activity prediction
SwissADME, furthermore, permits the valuation for a compound to be a substrate of p-glycoprotein (P-gp) or inhibitor of the cytochrome p450 isoenzymes (CYP isoenzymes). P-gp is largely spread and linked in the intestinal epithelium where    it drives xenobiotics [37]. The generations return Yes or No if the particle under assessment has a higher probability to be a substrate or nonsubstrate of P-gp or inhibitor or noninhibitor of a given CYP. The screening results were classified in Table 8.

Human intestinal absorption and blood-brain barrier prediction
Suitable for P-gp and CYP protein vitality is human intestinal absorption (HIA) and blood-brain barrier (BBB) infiltration. SwissADME BOILEDegg (Figure 4) grants the appraisal of HIA as a component of the circumstance of the molecules in the WLOGP-versus-TPSA referential. The white segment of the BOILEDegg is for a high chance of reflexive adjustment by the gastrointestinal tract, and the yellow region (yolk) is for a high prospect of cerebrum entrance, and it can be seen that some of the blended particles (3b,3e,3f, and 3i) are under the white segment. With this, the focuses are concealed in blue at whatever point was foreseen as adequately effluxed by P-gp (PGP+), shown by 3h and in red, anticipated as a nonsubstrate of P-gp (PGP−) by 3a, 3b, 3c, 3d, and 3g. HIA and the BBB are responsible for the water solvency and lipophilicity of the medication. There are 2 topological ways to deal with the predicted water solvency contained in the SwissADME. The first was an implementation  of the estimated solubility (ESOL) [38] model, and the resulting one was improved by Ali et al. [39]. Silicos-IT made SwissADME third pointer for molar solvency. Every single foreseen quality is the decimal logarithm of the molar solvency in water (log S) portrayed in Table 9. Agreement Log p is the normal estimation of all Log P assessed with different lipophilicity criteria (Table 10).

Structure-activity relationship
Depending upon the structural features, the newly synthesized molecules (4a-4i) could be divided into 3 discrete segments, as the diversely substituted central core quinoline ring A PEGylation center, ring B, and substitution at C-2/C-3 ( Figure 5). The exceptionally high anticancer activity of PEGylated quinoline derivatives is suggestive of the fact that the enhanced efficacy of molecules maybe because of the high mobility of the end terminal of the tethered PEG molecules, and due to the presence of inter-repulsive forces exerted between the hydrated PEG chains. There is a strong possibility of single PEG molecule conjugation with the approaching protein.
The data evident in Table 3 led to another noteworthy deduction, that the molecules with unsaturated centers at C-3 position exhibited good to moderate anticancer activity against the cancer cell lines. In contrast, the quinoline scaffold that amalgamated with the fused pyrazole and pyrimidine ring structures showed excellent anticancer activity against the SW620, MD468, and MD468-2 colon cancer cell lines. However, the imine derivatives of the PEGylated quinoline did  not display significant activity. These annotations proposed that C-2 and C-3 played a vital role in the structure-activity relationship of compounds 4a-4i. Compounds 4a and 4i were found to be most potent amongst the synthesized compounds against the microbial strains of E. Coli. The rest of these compounds showed moderate to potent activities against S. Aureus. All of the compounds screened against S. Aureus showed moderate to potent activities, confirming the fact that the substituted quinoline, with an adjacent ring C like the cyano group and pyrazole, played a vital role in enhancing the efficacy of the compounds, thus modulating the antibacterial activity.
All of the compounds screened as antifungals showed moderate to potent activities. The synthesized PEGylated quinoline was found to possess moderate antifungal activity against C. Albicans.

Synthesis of 6-amino-2-chloroquinoline-3-carbaldehyde (2):
Dissolve sodium sulfide (2 g) in water (5-6 mL) was added to NaHCO 3 (0.7 g) in small portions and stirred. When the added NaHCO 3 had dissolved, methanol (5-6 mL) was added and the reaction mixture was cooled to below 20 °C. Filtering off of the precipitated sodium carbonate was performed with pump. The precipitate was then washed with a small amount of methanol. The filtrate was then used for further reactions.
Next, 2-chloro-6-nitro-3-formilquinoline (0.75 g) was dissolved in hot methanol (6 mL), added to the above solution containing sodium hydrogen sulfide, and shaken. The reaction mixture refluxed for 2 h. The reaction mixture was then allowed to cool and was then placed into ice water (20-40 mL)

Synthesis of hydroxy carboxy polyethylene glycol (HO-PEG200COOH)
Polyethylene glycol (5 mL, 0.028 mol, 200 g/mol) was dissolved in 20 mL of dry CH 2 Cl 2 . To this solution was added THF containing maleic anhydride (0.056 mol, 0.54 mg) and pyridine (0.056 mol, 0.46 mL). After stirring overnight at room temperature, the reaction was completed, as indicated by TLC (methanol:ethyl acetate, 7:3) (no anhydride was left and there was the detection of a single polar PEG compound). The monoacid derivative of (polyethylene glycol) 200 was used without purification.

Synthesis of resin via N-terminal of PEGylated-6-amino-2-chloroquinoline-3-carbonitrile (4a) like syrupy material
The monoacid derivative of hydroxy carboxy polyethylene glycol (HO-PEG 200 COOH) (0.028 mol) was activated with a 1:2 molar equivalent of 6-amino-2-chloroquinoline-3-carbonitrile (3a) (0.046 mol) and N, N-dicyclocarbidiimide (0.046 mol) was dissolved in dichloromethane. The solution was stirred over night at room temperature. This reaction mixture appeared like a resin when dried under a vacuum. This syrupy resin was dissolved in 15 mL of acetone. Later the white precipitate of DCU that appeared was discarded and the filtrate was collected. The final filtrate was evaporated to afford compound 4a. TLC in (methanol:ethyl acetate 7:3) was performed to check for the presence of DCU. It showed a negative result. The IR spectra confirmed this negative result. A negative dye test indicated complete amino group capping.
The resin was dried in a vacuum for IR, H 1 NMR, C 13 NMR, and mass spectral analysis. At this stage, the resin did not stick to the glass wall anymore. The IR spectrum of the resin showed the characteristic absorption band of the PEG ether backbone (1120 cm -1 ) and absorption bands at 1760 and 1685 cm -1 for the ester and amid bond, respectively (C=O).