In vitro and in silico biological studies of novel thiazolo[3,2-a]pyrimidine-6-carboxylate derivatives

In the present study, we report the synthesis, characterization of new series of thiazolo[3,2-a]pyrimidine-6-carboxylate derivatives 3a–f and 4a–f. The newly synthesized compounds were screened for in vitro antimicrobial and antiviral activities. The probable mode of action of these active compounds was determined through in silico docking study by docking the receptor methionyl-tRNA synthetase and human inosine-5′-monophosphate dehydrogenase (IMPDH) for antibacterial and antiviral activities, respectively. Among the compounds, 4c exhibited excellent in vitro antimicrobial activity against all tested strains with binding and docking energies ?35.6 and ?12.4 kcal/mol, respectively. The antiviral studies were carried out for the selected compounds in which 4a exhibited 73.69 and 54.42 % of inhibition of buffalopox and camelpox viruses, respectively. Furthermore, compound 4a showed minimum docking and binding energy along with the maximum hydrogen/hydrophobic interaction with IMPDH. The study contributes towards identification and screening of potential antimicrobial and antiviral agent’s against the pathogens.     

2-Phenylimidazo[1,2-a]pyridine-3-carboxylic Acid Derivatives: Synthesis and Antiinflammatory Activity

A series of 2-phenylimidazo[1,2-a]pyridine-3-carboxylic esters, acids, and amides were synthesized and pharmacologically tested in order to evaluate their antiinflammatory and analgesic activity and their ulcerogenic action on the gastro-intestinal tract. The most active member of this series of compounds was found to be 6-methyl-2-phenylimidazo[1,2-a]pyridine-3-carboxylic acid ( 5c ).     

Synthesis and in-vitro anti-hepatitis B virus activity of ethyl 6-bromo-8-hydroxyimidazo[1,2-a]pyridine-3-carboxylates

A series of ethyl 6‐bromo‐8‐hydroxyimidazo[1,2‐a]pyridine‐3‐carboxylate derivatives were synthesized and evaluated for their anti‐hepatitis B virus (HBV) activity and cytotoxicity in HepG2.2.15 cells. Nearly half of the tested compounds were proved to be highly effective in inhibiting the replication of HBV DNA with IC₅₀ values ranging from 1.3 to 9.1 µM. Among them, 10o and 10s were identified as the most promising compounds.     

Synthesis, characterization, and urease inhibition of 5-substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-diones

Abstract  

5-Substituted-8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione and its anilines, amino pyridines and hydrazides derivatives were prepared in a good to excellent yields. In the first step 8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione (1) was prepared by reacting 4-methyl-2-aminopyridine, with diethylmalonate. Compounds substituted pyrido[1,2-a]pyrimidine-2,4(3H)-diones (PPMDO) (2)–(17) were prepared by condensing 8-methyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione in the presence of triethylorthoformte (TEF) and dimethylformamide (DMF), with respective amino components viz. 2-aminoacetophenone, 3-aminoacetophenone, 4-aminoacetophenone, 2,4,6-trimethylaniline, 2-fluoroaniline, 3-fluoroaniline, 4-fluoroaniline, 2-aminothiophenol, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-5-nitropyridine, Benzoic hydrazide, 4-nitrobenzoic hydrazide, 4-bromobenzoic hydrazide, 4-chlorobenzoic hydrazide and 4-hydroxybenzoic hydrazide, respectively. The chemical structures of all the compounds were elucidated by IR, ¹H-NMR, ¹³C-NMR and elemental analysis data. The synthesized compounds were screened for their in vitro urease inhibition activity, by the phenol hypochlorite method. These compounds were found to exhibit either no or low to moderate or significant activity. The compounds (9) and (14) showed comparatively much higher activity. However, the compound (9) was found to be the most active one.     

In vitro enzymatic evaluation of some pyrazolo[1,5-a]pyrimidine derivatives: Design,synthesis, antioxidant,anti-diabetic,anti-Alzheimer,and anti-arthritic activities with molecular modeling simulation

The strategy of utilizing nitrogen compounds in various biological applications has recently emerged as a powerful approach to exploring novel classes of therapeutics to face the challenge of diseases. A series of pyrazolo[1,5-a]pyrimidine-based compounds 3a–l and 5a–f were prepared by the direct cyclo-condensation reaction of 5-amino-1H-pyrazoles 1a, b with 2-(arylidene)malononitriles and 3-(dimethylamino)-1-aryl-prop-2-en-1-ones, respectively. The structures of the new pyrazolo[1,5-a]pyrimidine compounds were confirmed via spectroscopic techniques. The in vitro biological activities of all pyrazolo[1,5-a]pyrimidines 3a–l and 5a–f were evaluated by assaying total antioxidant capacity, iron-reducing power, the scavenging activity against 1-diphenyl-2-picryl-hydrazyl (DPPH) and 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, anti-diabetic, anti-Alzheimer, and anti-arthritic biological activities. All compounds displayed good to potent bioactivity, and three compounds 3g, 3h , and 3l displayed the most active derivatives. Among these derivatives, compound 3l exhibited the highest antioxidant (total antioxidant capacity [TAC] = 83.09 mg gallic acid/g; iron-reducing power [IRP] = 47.93 µg/ml) and free radicals scavenging activities with (DPPH = 18.77 µg/ml; ABTS = 40.44%) compared with ascorbic acid (DPPH = 4.28 µg/ml; ABTS = 38.84%). Furthermore, compound 3l demonstrated the strongest inhibition of α-amylase with a percent inhibition of 72.91 ± 0.14 compared to acarbose = 67.92 ± 0.09%. Similarly, it displayed acetylcholinesterase inhibition of 62.80 ± 0.06%. However, compound 3i showed a significantly higher inhibition percentage for protein denaturation and proteinase at 20.66 ± 0.00 and 26.42 ± 0.06%, respectively. Additionally, some in silico ADMET properties were predicted and studied. Finally, molecular docking simulation was performed inside the active site of α-amylase and acetylcholinesterase to study their interactions.     

Derivatives of condensed thienopyrimidines: Synthesis and anticonvulsant and tranquilizer activity of hydrochlorides of pyrano[4′,3′:4,5]thieno[3,2-e]imidazo[1,2-a]pyrimidines

New methods for the synthesis of 4-substituted 6,7-dihydro-7,7-dimethyl-5-oxo-9H-pyrano-[4′,3′: 4,5]-thieno[3,2-e]imidazo[1,2-a]pyrimidines and their hydrochlorides are developed. The anticonvulsant and tranquilizer properties of newly synthesized compounds have been studied. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 11, pp. 22–24, November, 2007.     

Synthesis and cytotoxic activity of imidazo[1,2-a]-1,3,5-triazine analogues of 6-mercaptopurine

A series of 2-substituted imidazo[1,2-a]-1,3,5-triazines with various aliphatic and aromatic amines has been prepared and characterized by IR,1H-NMR, and elemental analysis. The initial in-vitro cytotoxicity studies with five human cancer cell lines showed that all but one of the compounds are without cytotoxic activity. The one active compound, 2-(indolin-1-yl)-7,8-dihydroimidazo[1,2-a]-1,3,5-triazine-4(6H)-thione 12, was tested on 12 human cancer cell lines. Of these, two lines, RT-4 and MCF-7, were the most sensitive to the compound, with IC50 values of 6.98 microM and 8.43 microM, respectively. When compared with the reference anticancer drug 6-mercaptopurine, only the RT-4 urinary bladder and KYSE-70 oesophagus cancer cell lines were more sensitive to the new compound. The antimetabolite thioguanine was more cytotoxic than 12 for all common cell lines tested.     

In vitro and in silico evaluation of P‐glycoprotein inhibition through 99mTc‐methoxyisobutylisonitrile uptake

P‐glycoprotein (P‐gp) is a multidrug resistance (MDR) transporter with unknown structural details. This macromolecule is normally responsible for extruding xenobiotics from normal cells. Overexpression of P‐gp in tumor cells is a major obstacle in cancer chemotherapy. In this study, human 3D model of P‐gp was built by homology modeling based on mouse P‐gp crystallographic structure and stabilized through 1 ns molecular dynamics (MD) simulation. Stabilized human P‐gp structure was used for flexible docking of 80 drugs into the putative active site of P‐gp. Accordingly, digoxin, itraconazole, risperidone, ketoconazole, prazosin, verapamil, cyclosporine A, and ranitidine were selected for further in vitro assay. Subsequently, cell‐based P‐gp inhibition assay was performed on Caco‐2 cells while ^99mTc‐methoxyisobutylisonitrile (MIBI) was used as a P‐gp efflux substrate for calculating IC50 values. Results of the ^99mTc‐MIBI uptake in drug‐treated Caco‐2 cells were in agreement with the previously reported activities. This study for the first time described the relation between molecular dynamics and flexible docking with cellular experiments using ^99mTc‐MIBI radiotracer for evaluation of potencies of P‐gp inhibitors. Finally, results showed that our radiotracer–cell‐based assay is an accurate and fast screening tool for detecting P‐gp inhibitors and non‐inhibitors in drug development process.     

Ameliorative effects of curcumin towards cyclosporine-induced genotoxic potential: an in vitro and in silico study

Several studies documented the ameliorative effects of curcumin which plays a pivotal role in radical scavenging activities. It also participates in various cellular pathways and interacts with multiple targets. In the present study, we investigated the ameliorative effect of curcumin upon chromosomal genotoxicity induced by cyclosporine, an immunosuppressant, using in vitro approaches. A plausible mechanism of how curcumin mitigates the genotoxic implications of cyclosporine was ascertained using in silico tools. We observed that the curcumin reduces the genotoxic consequences made by cyclosporine upon cell cycle checkpoints and associated chromosomal/DNA manifestations. In addition, we presented the mechanistic details of curcumin interaction with various biomacromolecule types using docking experiments which showed that the possible radical scavenging activities can only be emerged by inducing the expression of antioxidant enzymes, supported by available experimental evidences. We anticipate that the induction of antioxidant enzymes by curcumin would activate Nrf2-Keap1 pathway as the plausible mechanism to exert anti-inflammatory response as demonstrated in renal epithelial cells.     

Quinoxaline chemistry. Part 16. 4-substituted anilino and 4-substituted phenoxymethyl pyrrolo[1,2-a]quinoxalines and N-[4-(pyrrolo[1,2-a]quinoxalin-4-yl)amino and hydroxymethyl]benzoyl glutamates. Synthesis and evaluation of in vitro biological activity

Twenty eight pyrrolo[1,2-a]quinoxalines bearing at position 4 various substituents related to the moieties present in classical and non classical antifolic agents were prepared and evaluated in vitro for antiproliferative activity. In an in vitro screening performed at NCI, several compounds emerged as potent antiproliferative agents at concentrations ranging between 10 and 100 microM. Interestingly, some of these compounds proved active also against bovine and murine DHFR (Farmaco 53 (1998) 480). More recently, a compound of classical antifolate type has been reported to be a potent inhibitor of hDHFR in vitro (Farmaco 58 (2003) 51). We then synthesized new derivatives that, in our hands, were endowed with in vitro antiproliferative activities as low as 3.4 microM against a panel of cell lines derived from hematological and solid tumours. In addition, a complete screening of cytotoxicity, antiretroviral HIV-1 and antimicrobial activity has been carried out.     

Benzodiazepine receptor ligands. Synthesis and in vitro binding activity of some 6-substituted-3-aryl-1,2,4-triazolo[3,4-a]phthalazines

Some 3-aryl-6-hydroxymethyl-1,2,4-triazolo[3,4-a]phthalazines (VI a,b) and 3-aryl-6-(2-hydroxyethyl)-1,2,4-triazolo[3,4-a]phthalazines (XVIII) have been synthesized. From (VI b) some 3-aryl-6-(alkylamino)methyl- and 3-aryl-6-(alkoxy)methyl-1,2,4-triazolo[3,4-a]phthalazines have been prepared and evaluated in vitro for their ability to inhibit selective 3H-diazepam (3H-DZ) binding to benzodiazepine-receptors (BZRs) from homogenates of synaptosomes from rat brains. Several compounds have been shown to displace 3H-DZ from BZRs with Ki (nM) values ranging from 2.2 to 88, comparable to those of the reference drugs including Diazepam.     

Synthesis and Evaluation of 3-Fluoro-2-piperazinyl-5,8,13-trihydro-5-oxoquino[1,2-a][3,1]benzoxazine-6-carboxylic Acids as Potential Antibacterial Agents

3-Fluoro-2-piperazinyl-5,8,13-trihydro-5-oxoquino[1,2-a][3,1]-benzoxazine-6-carboxylic acids were designed and synthesized as potential DNA gyrase inhibitors and antibacterial agents. The design rationale rests on the proposition made by Ohta and Koga that in order for N₁-aryl substituted quinolones to posses antibacterial activity the N₁-aryl ring should be oriented out of the plane of the quinolone ring. α-[Bis(methylthio)methylene]-2,4,5-trifluoro-β-oxobenzenepropanoic acid tert-butyl ester ( 6 ) obtained by the treatment of 2,4,5-trifluoro-β-oxobenzenepropanoic acid tert-butyl ester ( 5 ) with carbon disulfide and methyl iodide in the presence of cesium carbonate was used as a key intermediate, yielding tert-butyl 2,3-difluoro-5,8,13-trihydro-5-oxoquino[1,2-a][3,1]benzoxazine-6-carboxylate ( 8 ) upon treatment with 2-aminobenzyl alcohol. The coupling of 8 with piperazines followed by the hydrolysis of the ester under acidic conditions afforded the desired product ( 3 ). Contrary to expectation, both compounds ( 3a,b ) were, however, devoid of antibacterial activity, suggesting that for N₁-aryl substituted quinolones to exhibit antimicrobial activity important structural feature(s) other than the conformational requirement of the N₁-aryl ring with respect to the quinolone nucleus should also be satisfied.     

Cardiovascular effects of the new cardiotonic agent 1,2-dihydro-6-methyl-2-oxo-5-(imidazo[1,2-a]pyridin-6-yl)-3-pyridine carbonitrile hydrochloride monohydrate. 2nd communication: studies in dogs

The cardiovascular effects of 1,2-dihydro-6-methyl-2-oxo-5-(imidazo[1,2-a]pyridin-6-yl)-3-pyridine carbonitrile hydrochloride monohydrate (E-1020), a new nonglycoside, noncatechol cardiotonic agent, were investigated in dogs. In anesthetized dogs, E-1020 (10-100 micrograms/kg i.v.) dose-relatedly increased cardiac contractility (LV dP/dtmax), enhanced cardiac index and decreased systemic vascular resistance accompanying relatively small reduction in mean aortic pressure and a mild increase in heart rate. Coronary and femoral arterial blood flow were increased by either systemic intravenous or topical administration of E-1020. The degree of increase in myocardial oxygen consumption was only slight (10% at 30 micrograms/kg i.v.). The inotropic effect of E-1020 was not markedly affected by pretreatment with beta-adrenoceptor blockade, reserpine or other cardiotonic agents such as dobutamine or ouabain. In two experimental heart failure models induced by an excessive dose of propranolol or by coronary occlusion following volume-loading, E-1020 (30 micrograms/kg i.v.) rapidly reversed the cardiac depression. In chronically instrumented conscious dogs, E-1020 (30-100 micrograms/kg i.v. or 0.3-10 mg/kg p.o.) produced dose-dependent increases in LV dP/dtmax with minor increases in heart rate. E-1020 did not exacerbate arrhythmias of several experimental models in anesthetized dogs even at high dose of 100 micrograms/kg i.v. These results indicate that E-1020 is an intravenously and orally effective cardiotonic agent with vasodilating property, and that it may be beneficial in the treatment of acute and chronic congestive heart failure.     

In silico and in vitro studies of two non‐imidazole multiple targeting agents at histamine H3 receptors and cholinesterase enzymes

Recently, multi‐target directed ligands have been of research interest for multifactorial disorders such as Alzheimer's disease (AD). Since H₃ receptors (H₃Rs) and cholinesterases are involved in pathophysiology of AD, identification of dual‐acting compounds capable of improving cholinergic neurotransmission is of importance in AD pharmacotherapy. In the present study, H₃R antagonistic activity combined with anticholinesterase properties of two previously computationally identified lead compounds, that is, compound 3 (6‐chloro‐N‐methyl‐N‐[3‐(4‐methylpiperazin‐1‐yl)propyl]‐1H‐indole‐2‐carboxamide) and compound 4 (7‐chloro‐N‐[(1‐methylpiperidin‐3‐yl)methyl]‐1,2,3,4‐tetrahydroisoquinoline‐2‐carboxamide), was tested. Moreover, molecular docking and binding free energy calculations were conducted for binding mode and affinity prediction of studied ligands toward cholinesterases. Biological evaluations revealed inhibitory activity of ligands in nanomolar (compound 3 : H₃R EC₅₀ = 0.73 nM; compound 4 : H₃R EC₅₀ = 31 nM) and micromolar values (compound 3 : AChE IC₅₀ = 9.09 µM, BuChE IC₅₀ = 21.10 µM; compound 4 : AChE IC₅₀ = 8.40 µM, BuChE IC₅₀ = 4.93 µM) for H₃R antagonism and cholinesterase inhibition, respectively. Binding free energies yielded good consistency with cholinesterase inhibitory profiles. The results of this study can be used for lead optimization where dual inhibitory activity on H₃R and cholinesterases is needed. Such ligands can exert their biological activity in a synergistic manner resulting in higher potency and efficacy.     

Identification of 1, 4‐Dihydrothieno[3′, 2′:5, 6]thiopyrano[4, 3‐c]pyrazole Derivatives as Human 5‐Lipo‐oxygenase Inhibitors

A series of novel 1,4‐dihydrothieno[3′,2′:5,6]thiopyrano[4,3‐c]‐pyrazole‐3‐carboxamide derivatives were synthesized and evaluated for their inhibitory activity to human 5‐lipo‐oxygenase (5‐LOX). Compound 7c was found to exhibit significant inhibition to human 5‐LOX with IC₅₀ value of 5.7 ± 0.9 μm . Compound 7c was further studied using molecular docking in order to delineate its structure–activity relationship and to gain insight into the design of effective 5‐LOX inhibitors.     

7-[3-氨甲基-4-(脲亚氨基)吡咯烷-1-基]喹诺酮衍生物的合成与抗菌作用研究

目的 寻找新的喹诺酮类抗菌药.方法 设计合成7-位具有较强亲水性取代基的7个氟喹诺酮衍生物,测定其体外抗菌活性.结果 化合物10对金葡菌(包括MRSA)和表葡菌(包括MRSE)的活性(MIC:0.06～4μg/mL)与左氧氟沙星和吉米沙星基本相当.化合物11对肺炎链球菌08-2的活性(MIC:0.25μg/mL)分别是左氧氟沙星和吉米沙星的128倍和32倍,化合物12对肺炎克雷伯菌09-22和09-23的活性(MIC:1μg/mL)分别是左氧氟沙星和吉米沙星的16倍和4倍,但目标物对革兰阴性菌的活性普遍弱于对照药.结论 7-位取代基的水溶性并非决定喹诺酮抗菌活性的主要因素.