Medicinal Chemistry - Volume 13, Issue 5, 2017

Background: Non-steroidal anti-inflammatory drugs are the oldest and most widely used medicines. However, their untoward effects, especially gastrointestinal toxicity, remain the main obstacle to their application. Because of their mechanism of action, cycloxygenase (COX) inhibition, in combination with the weekly acidic character of most of them, major protective mechanisms of the gastrointestinal system are suppressed and deregulated. Objective: In this review, several compounds designed to retain anti-inflammatory activity, but devoid of gastrointestinal side effects, are presented. Thus, gastro-protective drugs, selective COX-2 inhibitors, nitric monoxide- and hydrogen sulphide-releasing agents, prodrugs, lipoxygenase (LOX) inhibitors and dual COX/LOX inhibitors are presented. Their mechanism of action, as well as their advantages and disadvantages are discussed. Conclusion: Efforts, aiming to the development of safe non-steroidal anti-inflammatory agents, are evolving, however there are still several problems concerning gastro-protection to be efficiently solved, thus, design of effective and safe agents for the treatment of inflammatory conditions still remains a major challenge.

Background: Cholesterol cholelithiasis is a multifactorial hepatobiliary disease. Methods: Interactions between genetic and environmental factors play a critical role in biliary cholesterol homeostasis and its imbalance enhances cholelithogenesis. Results: In patients developing symptoms or complications of gallstone disease, laparoscopic cholecystectomy is recommended for treatment of gallstones. In a subgroup of patients with small, radiolucent pure cholesterol gallstones, the hydrophilic bile acid, ursodeoxycholic acid (UDCA) is still considered the only pharmacological therapy able to induce oral litholysis. Identifying novel and effective pharmacological therapies is being investigated. Conclusions: We propose that the specific intestinal Niemann-Pick C1-like 1 protein inhibitor ezetimibe is a potential agent for preventing gallstone formation by reducing bioavailability of intestine- derived cholesterol to the liver for biliary secretion and desaturating bile through the inhibition of intestinal absorption of cholesterol.

Background: Naphthyridine scaffold is an important pharmacophore in compounds which have shown various biological activities like antiviral, antimicrobial, anticancer, antiinflammatory and analgesic. This scaffold is also reported to exhibit activity against HIV, HCMV, HSV, HPV and HCV. Antiviral activity displayed by many naphthyridine analogs is in nM range. Only few review articles are available in literature which describe about various biological activities of naphthyridines, but there is no comprehensive compilation particularly for antiviral activities. Objectives: The objective of this review is to compile the literature on anti-viral activities of naphthyridine analogs. Methods: SciFinder, Google Scholar and PubMed database were searched with keyword “naphthyridine” and the references obtained were further sorted using keywords “antihiv”, “antiviral” and “virus”, separately. References obtained were considered to review the antiviral literature of naphthyridines. Results: Literature search using SciFinder database with different keywords gave several references. Only references of antiviral activities of naphthyridine compounds were reviewed. References to in-silico studies alone or on formulation development or on patents were excluded. Conclusion: This review will be helpful for future researches to design and synthesize naphthyridine analogs with improved antiviral activities.

Background: Tuberculosis (TB) is the second leading cause of mortality worldwide being a highly contagious and insidious illness caused by Mycobacterium tuberculosis, Mtb. Additionally, the emergence of multidrug-resistant and extensively drug-resistant strains of Mtb, together with significant levels of co-infection with HIV and TB (HIV/TB) make the search for new antitubercular drugs urgent and challenging. Methods: This work was based on the hypothesis that an active compound could be obtained if substituents present in some other active compounds were attached on a core of an important structure, in this case the indole scaffold, thus generating a hybrid compound. A QSAR-oriented design based on classification and regression models along with the estimation of physicochemical and biological properties have also been used to assist in the selection of compounds. Chosen compounds were synthesized using various synthetic procedures and evaluated against M. tuberculosis H37Rv strain. Results: Selected compounds possess substituents at positions C5, C2 and N1 of the indole ring. The substituents involve p-halophenyl, pyridyl, benzyloxy and benzylamine groups. Four compounds were synthesised using suitable synthetic procedures to attain the desired substitution at the indole core. From these, three compounds are new and have been fully characterized, and tested in vitro against the H37Rv ATCC27294T Mtb strain, using isoniazid as a control. One of them, compound 2, with the pyridyl group at N1, has an experimental log (1/MIC) very close to 5 and can be considered as being (weakly) active. In fact, it is more active than 64% of all indole molecules in our data sets of experimental results from literature. The most active indole in this data sets has log (1/MIC)=5.93 with only 6 compounds with log (1/MIC) above 5.5. Conclusion: Despite the lower activity found for the tested compounds, when compared to other reported indole-derivatives, these structures, which rely on a hybrid design concept, may constitute interesting scaffolds to prepare a new family of TB inhibitors with improved activity.

Background: Many 2-substituted quinolines and especially 2-arylvinyl derivatives isolated from plants or prepared by synthesis have been designed from ethnopharmacological studies. Objective: In order to explore new aspects of the structure-antituberculosis activity relationship, a series of styrylquinoline derivatives was prepared. Method: A series of styrylquinoline derivatives was prepared from quinaldic acid and a variety of arylbenzaldehydes under eco-friendly conditions via Knoevenagel reaction and trifluoroacetic acid (TFA) as catalyst. Results: The products were obtained in short reaction times and good yields and were evaluated for growth inhibitory activity towards Mycobacterium tuberculosis H37Rv (Mtb) through the National Institute of Allergy and Infectious Diseases (NIAID, USA). Conclusion: Three compounds had activity under aerobic conditions.

Background: All of the clinical drugs for herpesvirus infections exhibit high toxicity and suffer from significant drug-resistantance. There is a great need for the development of new, effective, and safe anti-herpesvirus agents with different mechanisms of action. Methods: A series of novel 5-(benzylthio)-1H-1,2,3-triazole-4-carboxamides were efficiently synthesized and EC50 values against human cytomegalovirus (HCMV), varicella-zoster virus (VZV) and herpes simplex virus (HSV) were evaluated in vitro. Results: Some compounds possess antiviral activity. Compound 7f exhibits promising inhibitory activity against both HCMV and VZV. Our results also indicate that these derivatives are independent of the viral thymidine kinase (TK) for activation, which is indispensable for current drugs. Conclusion: 4,5-Bissubstiuted triazoles are active against herpesviruses and the nature and the position of substituents in the benzene ring remarkably affect their activity, such as bromo, cyano and cyanovynil substituents. Future studies should be undertaken to investigate the mechanism of action of these compounds.

Background: Multidrug resistance (MDR) is a major challenge in the treatment of infectious diseases. The MDR in urinary tract infection causing bacteria, such as Escherichia coli, has made treatment of UTI very difficult. Objective: The aims of the current study were to synthesize a library of harmaline derivatives, and to evaluate their activity against various strains of multi-drug resistance (MDR) E. coli. Method: Harmaline derivatives were synthesized by the reaction of harmaline (1) with various acid halides and anhydrides. These compounds were subjected to susceptibility determination by in vitro MTT assay. The changes in morphology of the bacterial cells after the treatment with harmaline (1) and its new derivatives 2 and 3 were studied through scanning electron, atomic force and fluorescence microscopy. Effect of harmaline and its derivatives on the production of Reactive Oxygen Species (ROS) in MDR E. coli was assessed through lucigenin chemiluminescence assays. Results: The selected compounds assisted the fluorescently labeled dye DiBAC4(3) to bind to the lipid rich intra-cellular entities, and thus produced a sharp green fluorescence by easily penetrating into the compound-induced depolarized membrane of MDR E. coli. These compounds have also triggered a significant generation of ROS from bacterial cells as compared to the conventional antibiotics. The current study demonstrated that harmaline (1), and its derivatives 2 and 3 were identified as anti-MDR agents against MDR strains of E. coli. Antibacterial effect of compounds 1-3 on MDR E. coli is possibly due to membrane depolarization due to ROS-induced damage to the bacterial cell membrane. Conclusion: Harmaline and its derivatives were identified as anti-MDR agents against various highly resistant and Pakistani MDR clinical isolates of E. coli. These compounds may serve as the leads for further studies towards the development of treatment against the infections caused by MDR E. coli.

Background: The voltage-dependent anion channels (VDAC) play an essential role in the cross talk between mitochondria and the rest of the cell. Their implication in cell life and cell death has been studied extensively in recent years. In this work we studied the impact of mitochondrial membrane (VDACs) on cell survival and response to X-ionizing radiation (IR) of human lymphoblastoid K562 cells. Methods: The inhibition of VDACs was achieved by 4,4`-diisothiocyanostilbene-2,2`-disulfonic acid (DIDS) inhibitor and in vitro experiments including clonogenity assay, UV-visible spectrophotometry, comet assay and FACS analysis were implemented. Results: Inhibition of VDAC led to augmentation of IR-induced apoptosis and ROS production. Additionally, DIDS affected repair of IR-induced DNA strand breaks and was in line with both induction of apoptosis and caspase activity. The IR-induced NO production was potently reduced by inhibition of VDAC. Conclusion: Our results suggest that VDAC control cellular response to ionizing radiation through modulation of the ROS- and NO-dependent signaling pathways. Inhibition of VDAC with DIDS induced apoptosis in irradiated K562 lymphoblastoid cells points at DIDS, as a promising agent to enhance the effectiveness of radiotherapy.

Background: Cyclooxygenase (COX-2) inhibitors have been developed to provide better anti-inflammatory and analgesic efficacy than those of traditional NSAIDs. Several compounds having selective COX-2 inhibitors such as SC-558, Celecoxib, Rofecoxib, Valdecoxib and Etoricoxib are marketed as new generation NSAIDs and block the production of prostaglandins (PGs) in inflammatory cells. New anti-inflammatory agents with improved potency and safety profile are still needed. Objective: As a part of our continuation research work towards new anti-inflammatory agents, the synthesis of N-substituted aryl/heteroaryl-pyrazole-1yl benzene sulfonamide (Celecoxib) derivatives, their anti-inflammatory activity in both methods in vitro and in vivo and molecular docking study on COX-2 enzyme will be discussed in this study. Methods: A series of N-substituted (aryl/heteroarylpyrazol-1-yl)benzenesulfonamide (Celecoxib) derivatives was synthesized and characterized them using IR, NMR (1H and 13C), mass and elemental analyses. Anti-inflammatory activity of the title compounds was evaluated by in vitro initially using albumin denaturation and membrane stabilization methods, enzymatic activity against COX-2 enzyme using colorimetric assay and then in vivo by carrageenan induced paw oedema and cotton pellet induced granuloma methods. The docking study was performed, to find the binding mode of the title compounds with the binding site of the COX-2 enzyme. Results: The biological activity screening data disclosed that some of the compounds 5b, 5e, 5f and 5i exhibited potent anti-inflammatory activity in both methods, in vitro and in vivo. The enzymatic assay on COX-2 enzyme demonstrated that few compounds potently inhibit COX-2 enzyme activity with IC50 of <0.89 μM. Unexpectedly, compound 5e (IC50, 0.62±0.17 μM) showed more potent COX-2 inhibited activity than that of parent drug, celecoxib (IC50, 0.62±0.25 μM) and the standard, flufenamic acid (IC50, 0.71±0.12 μM). Conclusion: The bio-screening data, in vitro and in vivo anti-inflammatory activity and COX-2 enzymatic assay revealed that few N-substituteed aryl/heteroaryl-pyrazol-1-yl) benzene sulfonamides showed potent activity and compound 5e showed more potent COX-2 inhibit activity than that of parent drug, celecoxib and the standard, flufenamic acid. Moreover, all the newly synthesized title products were bonded well with good binding energies in the sight of COX-2 enzyme. Therefore, the described study might provide sustained information to the development of new series of derivatives with potent drug like activity.

Background: Centaurea virgata Lam. is a species widely used in the traditional medicine in Turkey for the treatment of diabetes, allergy and gastric ulcers. The rationale of its use in the therapy has not been studied previously, therefore the present work aimed at the chemicalpharmacologicalevaluation of the plant. Objective: The xanthine oxidase (XO) inhibitory activity of the MeOH extract and its subextracts (n-hexane, CHCl3 and remaining MeOH-H2O) prepared from C. virgata was investigated in vitro. Moderate activity was exerted in case of the CHCl3 extract (98.9 ± 15.8 μg/mL), therefore constituents of this extract were analysed. Method: Different purification steps, such as VLC, CPC, PLC and crystallization were used for the isolation, and ESIMS, NMR, LC-MS and authentic standards were applied for identification of the compounds. XO inhibitory and DPPH assays were used for evaluation of the bioactivities. Results: Sesquiterpenes [8α-hydroxysonchucarpolide, 8α-(3,4-dihydroxy-2-methylenebutanoyloxy)- dehydromelitensine, and cnicin], flavones (apigenin, hispidulin, salvigenin, eupatorin, 3’-methyleupatorin), and the flavonol isokaempferide were isolated from the active extract. The XO-inhibitory activity of these compounds was analyzed using allopurinol as a positive control (IC50 7.49 ± 0.29 μM). It was found that sesquiterpenes and flavonoids, containing 7- OMe group, are inactive. Conclusion: 7-Hydroxyflavones (apigenin and hispidulin) exerted significant XO inhibitory effect with IC50 values of 0.99 ± 0.33 μM and 4.88 ± 1.21 μM, respectively. Therefore, these compounds are responsible for the XO-inhibitory effect of the extract. The free radical scavenging activity of the isolated flavonoids was determined by DPPH assay, and it was stated that none of the compounds have substantial antioxidant activity, therefore the reduced generation of reactive oxygen species may be the consequence only of XO inhibition.