Synthesis of novel 2-phenyl-3-[2-(substituted amino) ethylamino] quinazolin-4(3H)-ones as a new class of H1-antihistaminic agents

A series of novel 2-phenyl-3-[2-(substituted amino) ethylamino] quinazolin-4(3H)-ones was synthesized by the nucleophilic substitution of 3-(2-bromo ethylamino)-2-phenyl quinazolin-4(3H)-one with various amines. The starting material, 3-(2-bromo ethylamino)-2-phenyl quinazolin-4(3H)-one, was synthesized from anthranilic acid by a multistep synthesis. All the title compounds were tested for their in vivo H₁-antihistaminic activity on conscious guinea pigs at the dose level of 10 mg/kg using chlorpheniramine as the standard drug. The results of the biologic activity revealed that all the test compounds protected the animals from histamine-induced bronchospasm significantly. Compound 2-phenyl-3-[2-(piperazinyl) ethylamino] quinazolin-4(3H)-one (S3) emerged as the most active compound of the series (73.67 % protection) when compared to the standard chlorpheniramine (70.09 % protection). Interestingly, compound S3 shows negligible sedation (8.21 %) compared to chlorpheniramine maleate (29.58 %). Therefore, compound S3 can serve as the lead molecule for further development into a new class of H₁-antihistaminic agents.     

Design and synthesis of novel 3-(4-chlorophenyl)-2-(3-substituted propyl thio) quinazolin-4-(3H)-ones as a new class of H1-antihistaminic agents

A series of novel 3-(4-chlorophenyl)-2-(3-substituted propyl) quinazolin-4-(3H)-ones have been synthesized and tested for their in vivo H1-antihistaminic activity on conscious guinea pigs. All the test compounds have protected the animals from histamine induced bronchospasm significantly. Compound 3-(4-chlorophenyl)-2-(3-(4-methylpiperazin-1-yl) propylthio) quinazolin-4(3H)-one (PC5) emerged as the most active compound (77.53% protection) of the series when compared to the reference standard chlorpheniramine maleate (70.09% protection). Compound PC5 shows negligible sedation (6.16%) compared to chlorpheniramine maleate (29.58%). Therefore, compound PC5 can serve as the lead molecule for further development into a new class of H1-antihistaminic agents.     

Efficient synthesis, anticonvulsant and muscle relaxant activities of new 2-((5-amino-1,3,4-thiadiazol-2-yl)methyl)-6-phenyl-4,5-dihydropyridazin-3(2H)-one derivatives

A series of 2-(2-(3-(4-chlorophenyl)-6-oxo-5,6-dihydropyridazin-1(4H)yl)acetyl)hydrazine carbothioamide and 2-((5-amino-1,3,4-thiadiazol-2-yl)methyl)-6-(4-chlorophenyl)-4,5-dihydropyridazin-3(2H)-one derivatives were synthesized, characterized, and evaluated for anticonvulsant activity and muscle relaxant activity. The synthesized compounds 5d (82.75 %) and 5e (85.44 %) showed promising anticonvulsant activity by protection against tonic hind limb extensor phase in maximal electroshock model (MES) at (50 mg/kg) compared to standard drug phenytoin and also compounds 5d (82.75 %), and 5e (85.44 %) showed significant anticonvulsant activity by protection against pentylenetetrazole-induced generalized convulsions in pentylenetetrazole model (PTZ) at (100 mg/kg) compared to standard drug diazepam. On the other hand, compound 5e showed significant muscle relaxant activity (84.57 %) by rotarod and traction test model comparing with diazepam as a standard drug.     

Novel 4(3H)-quinazolinone analogs: synthesis and anticonvulsant activity

A new series of quinazoline analogs was designed, synthesized, and evaluated for their anticonvulsant activity. Compounds 6, 12, 21, 36, 37, and 38 showed 70–100 % protection against PTZ-induced seizures acting as GABA_A receptor agonists. Compound N-(3,4,5,6-tetrachloro-phthalimido)-2-[(3-phenyl-4-oxo-6-methyl-3H-quinazolin-2-yl)-thio]acetamide (12) representing the moderate active compounds and 2-[6-iodo-4-oxo-2-(thiophen-2-yl)-quinazolin-3(4H)-yl]-isoindoline-1,3-dione (38) representing the remarkably active compounds in this stud, showed ED₅₀ values of 457 and 251 mg/kg; TD₅₀ values of 562 and 447 mg/kg; PI values of 1.22 and 1.78, LD₅₀ values of 1,288 and 1,380 mg/kg, and TI values of 2.82 and 5.50, respectively. Compound 38 proved to be almost twofold more active than the standard drug sodium valproate.     

Synthesis and H1-antihistaminic activity of some novel 1-substituted-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones

A series of novel 1-substituted-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones were synthesized by the cyclization of 2-hydrazino-3-(3-methylphenyl) quinazolin-4(3H)-one with various one carbon donors. The starting material 2-hydrazino-3-(3-methylphenyl)quinazolin-4(3H)-one, was synthesized from 3-methylaniline by a novel innovative route. When tested for their in vivo H(1)-antihistaminic activity on conscious guinea pigs, all the test compounds protected the animals from histamine induced bronchospasm significantly, whereas the compound 1-methyl-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-one II was found to be equipotent (percent protection 70.0%) with the reference standard chlorpheniramine maleate (percent protection 71%). Compound II show negligible sedation (7%) when compared to chlorpheniramine maleate (25%). Hence it could serve as prototype molecule for further development as a new class of H(1)-antihistamines.     

Dimeric 2-(2-chlorophenyl)-quinazolin-4-ones as potential antimicrobial agents

3-(Aryl)-2-(2-chlorophenyl)-6-{2-[2-(2-chlorophenyl)-4-oxo(3-hydroquinazolin-3yl)]ethyl}-3-hydroquinazolin-4-ones had been selected as target bio-active molecules. Several quinazoline derivatives were prepared by using anthranilic acid, acid chloride, 2-amino-ethanol, and different amines. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger, and Aspergillus clavatus. The compounds 5e, 5g, and 5h are shown to have excellent activity, while 5c, 5d, 5i, 5k, 5l are shown to have very good activity against several strains of bacteria. The structures of the synthesized compounds were firmly established by well-defined spectral analysis techniques like IR, ¹H-NMR, ¹³C-NMR, and Mass spectra.     

Design, synthesis, anti-inflammatory, analgesic screening, and molecular docking of some novel 2-pyridyl (3H)-quinazolin-4-one derivatives

A novel series of 6-bromo-2-(4-pyridyl)-quinazolin-4(3H)-ones were synthesized by reacting 5-bromo anthranilic acid with isonictinoly chloride in the presence of acetic anhydride, which were further reacted with p-amino acetophenone to obtain 3-(4-acetylphenyl)-6-bromo-2-(pyridin-4-yl)quinazolin-4(3H)-one (3). Compound 3 underwent further reactions with different aldehydes to afford chalcone derivatives 4–10, which in turn underwent various cyclization reactions to afford cyclized products 15–18. 2-aminothiazole derivatives 12 obtained by reaction of 3 with bromine then with thiourea. Compound 14 obtained by treatment of 11 with KSCN followed by cyclization. Some of the synthesized compounds 4, 5, 12, 14, 15 and 18 were screened for both analgesic and anti-inflammatory activities. All tested compounds showed good analgesic and anti-inflammatory activity in comparison to the reference standard indomethacin. Compounds 4 and 5 showed the highest anti-inflammatory activity, while compounds 14 and 15 showed the highest analgesic activity among all the tested compounds.     

Synthesis and biological evaluation of 1-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives

A new series of eleven novel 1-(3-chloro-2-oxo-4-phenylazetidin-1yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives were synthesized by cyclocondensation of various Schiff bases of phenothiazine with chloroacetyl chloride in the presence of triethylamine. Various Schiff bases of phenothiazine were synthesized by condensation of 4-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl semicarbazide with various aryl aldehydes. The synthesized compounds were characterized by IR, MASS and ¹H NMR spectral data and evaluated for in vitro antimicrobial, antitubercular, antioxidant and anticancer activities by disc diffusion method, MIC method, REMA, DPPH, FRAP and MTT assay method, respectively. All synthesized compounds showed moderate-to-significant anti-bacterial and anti-fungal activity and compound 4d, 4g, 4h and 4k showed good antioxidant activity with EC₅₀ value of 55, 57, 56 and 47 μg/ml tested by DPPH method. The compounds 4j at a concentration of 10 μg/ml showed inhibition against the growth of Mycobacterium tuberculosis and 4f showed significant activity against human cervical cancer cell line with IC₅₀ values of 18.26 μM.     

Synthesis and anticonvulsant activity of novel quinazolin-4(3H)-one derived pyrazole analogs

Eighteen novel 6,8-(dibromo/unsubstituted)-2-(methyl/phenyl)-3-(4-(5-(substitutedphenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-carbonyl)phenyl)-quinazolin-4(3H)-ones 4a–4r were designed and synthesized in good yield. Antiepileptic screening of the title compounds was performed using MES and scPTZ seizures tests while the neurotoxicity was determined by rotorod test. In the preliminary screening, compounds 4d, 4e, 4p, 4q, and 4r were found active in MES model, while 4a, 4d, 4f, 4m, and 4p showed significant antiepileptic activity in scPTZ model. Further, all these eight compounds were administered to rats and compounds 4e, 4p, and 4q showed better activity than Phenytoin in oral route. Among these compounds 4p revealed protection in MES after i.p. administration at a dose of 30 mg/kg (0.5 h) and 100 mg/kg (4 h). The compound 4p also provided protection in the scPTZ at a dose of 100 mg/kg (0.5 h) and 300 mg/kg (4 h).     

Synthesis and pharmacological investigation of novel 1-alkyl-4-(4-substituted aryl/heteroaryl)-1,2,4-triazolo [4,3- a] quinazolin-5 (4H)-ones as a new class of H1-antihistaminic agents

A series of novel 1-alkyl-4-(4-substituted aryl/heteroaryl)- 1,2,4-triazolo [4,3-a] quinazolin-5(4H)-ones were synthesized by the cyclization of 2-hydrazino-3-(4-subst. aryl/heteroaryl) quinazolin-4(3H)-one with various carbon donors. The starting material, 2-hydrazino-3-(4-subst. aryl/heteroaryl) quinazolin-4(3H)-one, was synthesized from 4-subst. arylamine/ heteroarylamine by a novel innovative route. When tested for their in vivo Hi-antihistaminic activity on conscious guinea pigs, all the test compounds protected the animals from histamine induced bronchospasm significantly, whereby the compound 1-methyl-4-(2-py-ridyl)-1,2,4-triazolo[4,3-a] quinazolin-5(4H)-one (II) was found to be more potent (percent protection 71.43 %) when compared to the reference standard, chlorpheniramine maleate (percent protection 71 %). Compound II showed negligible sedation (8 %) when compared to chlorpheniramine maleate (25 %). Hence it could serve as prototype molecule for further development as a new class of H1-antihistamines.     

7-chloro-3-(substituted benzylidene/phenyl ethylidene amino)-2-phenylquinazolin-4(3H)-ones: synthesis, antimicrobial and antitubercular evaluation

In this study, a series of 7-chloro-3-(substituted benzylidene/phenyl ethylidene amino)-2-phenyl quinazolin-4(3H)-ones (1–10) were prepared and evaluated for antitubercular activity against Mycobacterium tuberculosis (MTB). The antitubercular screening results indicated that 7-chloro-3-(4-(dimethylamino)benzylidene amino)-2-phenylquinazolin-4(3H)-one (10) was the most potent one (MIC?=?0.78?×?10^?3?μM) and exhibited activity equivalent to the standard compound isoniazid (MIC?=?0.80?×?10^?3?μM). Further, the synthesized compounds were tested for their antibacterial activity against Gram positive and Gram negative bacteria. The comparison of antibacterial and antimycobacterial results indicated that different structural requirements are necessary for a compound to be effective against bacterial and mycobacterial targets.     

Anti-HIV-1 screening of (2E)-3-(2-chloro-6-methyl/methoxyquinolin-3-yl)-1-(aryl)prop-2-en-1-ones

Biological studies of two series of 38 quinolinyl chalcones (4a–s and 5a–s) were investigated for their in vitro anti-HIV-1 and cytotoxic activities. Out of 38 compounds, seventeen compounds were observed as good anti-HIV-1 agents with EC₅₀ values less than 20 μM. Compounds 4a, 4l, 4o, 5e, 5h, 5l, 5o, and 5r displayed potent anti-HIV-1 activity with EC₅₀ values less than 5 μM. Among these, compound 5h emerged as the best anti-HIV-1 agent (EC₅₀ = 1.1 μM). Compounds 4d, 4n, 4q, 4r, 4s, 5n, and 5r showed no toxicity in human lymphocytes. Bioassay results show that the type(s) and position(s) of the substituents seem to be critical for their cytotoxic and anti-HIV-1 activities. These results could be useful in the invention of new anti-HIV agents through structural modification.     

Design, synthesis and biological evaluation of some novel benzylidene-2-(4-phenylthiazol-2-yl) hydrazines as potential anti-inflammatory agents

A series of substituted benzylidene-2-(4-phenylthiazol-2-yl) hydrazines (2a–q) have been synthesized, characterized and evaluated for their anti-inflammatory activity by carrageenin-induced hind paw edema (acute inflammation) and cotton pellet granuloma (chronic inflammation) methods in rats. In carrageenin-induced hind paw edema method, compounds 2a, 2b, 2c, 2d, 2h, 2k and 2p at a dose of 20 mg kg^?1 body weight, p.o. showed excellent inhibitions (51.80–86.74 %) in between 1 and 4 h. Similarly, in cotton pellet granuloma method, compounds 2a, 2b, 2c, 2d, 2h, 2k and 2p at a dose of 20 mg kg^?1 body weight, p.o. inhibited the granuloma formation (71.71–90.19 % inhibition) which was comparable to that of standard drug, ibuprofen (90.36 % inhibition of paw volume at 3 h and 94.02 % inhibition of granuloma formation). Structure activity relationship studies showed excellent activity of the compounds containing electron withdrawing group (fluoro, chloro, bromo or nitro) in phenyl ring at C2 and/or C4 position of thiazole ring.     

Synthesis and cytotoxicity of novel 4-(4-(substituted)-1H-1,2,3-triazol-1-yl)-N-phenethylbenzenesulfonamides

A new series of 4-(4-(substituted)-1H-1,2,3-triazol-1-yl)-N-phenethylbenzenesulfonamide derivatives 5 were synthesized through the Click approach and evaluated for their cytotoxic activity against four cancer cell lines (HuCCA-1, HepG2, A549, and MOLT-3). Most of the synthesized triazoles 5 displayed cytotoxicity against MOLT-3 cell line, except for analogs 5a–c and 5e. Significantly, 4-phenyltriazoles (5a and 5n), 4-(naphthalen-2-yloxy)methyltriazole 5d, as well as 4-((2-oxo-2H-chromen-7-yl)oxy)methyltriazole 5l showed higher cytotoxic activity against HepG2 cells than the reference drug, etoposide. Interestingly, the 4-phenyltriazole 5a was the most potent and promising compound with IC₅₀ value of 9.07 μM against HepG2 cell line. The analog 5a also exerted the highest cytotoxic activity against HuCCA-1 cells. This finding provides the novel lead molecules for further development.     

Design, synthesis, molecular docking, and biological evaluation of N-methyl-3-nitro-4-(nitromethyl)-4H-chromen-2-amine derivatives as potential anti-cancer agents

A series of N-methyl-3-nitro-4-(nitromethyl)-4H-chromen-2-amine derivatives 8 were synthesized from 2-((E)-2-nitrovinyl)phenol 7 and ((E)-N-methyl)-1-(methylthio)-2-nitroethenamine 5. The cytotoxic activity of these molecules was tested against two cancer cell lines namely HeLa (cervical cancer) and HEp-2 (epidermoid laryngeal carcinoma). Among them, two molecules (4H-chromenes 8h and 8i) displayed potent anti-proliferative activity with IC₅₀ values of 115.04 and 18.96 μM for HeLa and 86.94 and 25.08 μM for Hep-2 cell lines, respectively. Morphological evaluation of the cell lines revealed that both 8h and 8i induce the apoptotic process. Molecular docking studies of all the 4H-chromenes 8 with anti-apoptotic Bcl-2, Bcl-w, and Bcl-xL proteins revealed that the 4H-chromenes 8h and 8i have good docking score and thus corroborated in vitro studies. Furthermore, evaluation of Lipinski and ADMET properties revealed their drug-like pharmacokinetic profiles. Thus, 4H-chromenes 8h and 8i exhibit promising anti-cancer properties and can be used as lead compounds for further development.     

Microwave-assisted synthesis,molecular docking and antimicrobial activity of novel 2-(3-aryl,1-phenyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-4-yl)-8<Emphasis Type="Italic">H</Emphasis>-pyrano[2,3-f]chromen-4-ones

An efficient synthetic protocol of microwave-assisted synthesis of some novel 2-(3-aryl,1-phenyl-1H-pyrazol-4-yl)-8H-pyrano[2,3-f]chromen-4-ones 6a–j in excellent yields starting from 3-(3-aryl,1-phenyl-1H-pyrazol-4-yl)-1-(5-hydroxy-2H-chromen-6-yl)-propenones 5a–j was described. This approach offers the advantages of short reaction time (3–5 min), mild reaction conditions, high yields (80–88 %) and convenient operation. All the synthesized compounds were tested in vitro for their antimicrobial activity. The compounds 5h (Ar = 3-ethoxyphenyl), 6c (Ar = 4-chlorophenyl), 6e (Ar = 4-hydroxyphenyl) and 6i (Ar = 3,4-methoxyphenyl) were found to be potent against tested bacterial strains, and compounds 5g (Ar = 4-ethoxyphenyl), 6c (Ar = 4-chlorophenyl) and 6i (Ar = 3,4-methoxyphenyl) were found to be potent against tested fungal strains. The final compounds were subjected to molecular docking studies for the inhibition of enzyme DNA gyrase. The in silico molecular docking results are matching with the in vitro antimicrobial studies, and they may be considered as good inhibitor of DNA gyrase.     

Synthesis, in vitro antimicrobial, antiproliferative, and QSAR studies of N-(substituted phenyl)-2/4-(1H-indol-3-ylazo)-benzamides

In this study, N-(substituted phenyl)-2/4-(1H-indol-3-ylazo)-benzamides (1–26) were synthesized and screened for their in vitro antibacterial (Gram positive; S. aureus, B. subtilis and Gram negative; E. coli) and antifungal (C. albicans and A. niger) activities. The antimicrobial activity results indicated that compound, 4-(1H-indol-3-ylazo)-N-(4-nitro-phenyl)-benzamide (12, pMIC_am = 1.61) was the most potent. In general, it was found that the synthesized compounds were bacteriostatic/fungistatic in action except fungicidal for A. niger. The synthesized compounds were also evaluated for their antiproliferative activity against human colon cancer (HCT116), murine leukemia (P388), and breast cancer (MCF7) cell lines. The antiproliferative study results demonstrated 4-(1H-indol-3-ylazo)-N-p-tolyl-benzamide (2, IC₅₀ = 0.0003 μM/mL) and 4-(1H-indol-3-ylazo)-N-p-tolyl-benzamide (21, 0.0003 μM/mL) as lead compounds for the development of novel antiproliferative agents. The QSAR studies indicated the importance of topological parameters, Kier’s alpha second-order shape indice (κα₂) and Wiener index (W) in describing the antimicrobial activity of the synthesized compounds.     

Synthesis and pharmacological evaluation of novel 4-isopropylthiazole-4-phenyl-1,2,4-triazole derivatives as potential antimicrobial and antitubercular agents

A series of novel 4-isopropylthiazol-4-phenyl-1,2,4-triazol derivatives, N′-(substituted benzylidene)-2-(5-(4-isopropylthiazol-2-yl)-4-phenyl-4H-1,2,4-triazol-3-ylthio)acetohydrazides 4a–e, 4-isopropylthiazol-2-yl-4′-phenyl-4′H-1′, 2′,4′-triazol-3′-ylthio (substituted methyl benzylidene) acetohydrazides 5a–f, 3-(4-isopropylthiazol-2-yl)-4-phenyl-5-(5-substituted-1,3,4-oxadiazol-2-ylthio)-4H-1,2,4-triazole derivatives 6a–f and N-acetyl-5′-(4-isopropylthiazol-2-yl)-4′-phenyl-4′H-1,2,4-triazol-3′-ylthio) acetohydrazide 7 were synthesized and characterized by spectroscopy, elemental, and mass spectral analysis. These compounds were evaluated for their preliminary in vitro antibacterial, antifungal, and antitubercular activity against Mycobacterium tuberculosis (M. tuberculosis) H37Rv strain by broth dilution assay method. All the compounds exhibited moderate to significant antibacterial and antifungal activities. Results of the antitubercular screening against Mycobacterium tuberculosis H37Rv showed that compounds 4c and 6c exhibited good antitubercular activity when compared with first line drug isoniazid.     

Synthesis and pharmacological investigation of novel 2-substituted-3-carboxamido-4H-pyrimidobenzothiazole derivatives as a new class of H1-antihistaminic agent

With the aim of developing potential H₁-antihistaminic agents, a series of novel 2-substituted-3-carboxamido-4-oxo-4H-pyrimido[2,1-b][1,3]benzothiazole (8a–g) and 2-substituted-3-carboxamido-8-chloro-4-oxo-4H-pyrimido[2,1-b][1,3]benzothiazole (9a–g) were synthesized and evaluated in vitro for H₁-antihistaminic activity on guinea pig ileum preparation. IC₅₀ values of the compounds were found to be in the micromolar range. Chlorpheniramine maleate was used as a standard drug. The active derivatives (8d–8g and 9d–9g) were found to have IC₅₀ values comparable to reference standard chlorpheniramine maleate. The sedative potential of both series (8a–g and 9a–g) is less than the reference drug. Hence, it could serve as prototype molecules for further development as a new class of H₁-antihistaminic agents.