Design, Synthesis, and Physicochemical and Pharmacological Profiling of 7-Hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide Derivatives with Antiosteoarthritic Activity In Vivo.

The hallmark of joint diseases, such as osteoarthritis (OA), is pain, originating from both inflammatory and neuropathic components, and compounds able to modulate the signal transduction pathways of the cannabinoid type-2 receptor (CB2R) can represent a helpful option in the treatment of OA. In this perspective, a set of 18 cannabinoid type-2 receptor (CB2R) ligands was developed based on an unprecedented structure. With the aim of improving the physicochemical properties of previously reported 4-hydroxy-2-quinolone-3-carboxamides, a structural optimization program led to the discovery of isosteric 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide derivatives. These new compounds are endowed with high affinity for the CB2R and moderate to good selectivity over the cannabinoid type-1 receptor (CB1R), associated with good physicochemical characteristics. As to the functional activity at the CB2R, compounds able to act either as agonists or as inverse agonists/antagonists were discovered. Among them, compound 51 emerged as a potent CB2R agonist able to reduce pain in rats carrying OA induced by injection of monoiodoacetic acid (MIA).

Chemical constituents from Waltheria indica exert in vitro activity against Trypanosoma brucei and T. cruzi.

Six extracts from the roots and the aerial parts of Waltheria indica L. (Malvaceae) were screened for their in vitro antitrypanosomal activity towards Trypanosoma brucei brucei STIB 427 strain, T. brucei rhodesiense STIB 900 and Trypanosoma cruzi Tulahuen C4. The dichloromethane extract from the roots showed the highest activity against T. cruzi (IC50=0.74 µg/mL) as well as a good selectivity index (SI value of 35). Based on these results, this extract was fractionated and led to the isolation of three alkaloids (adouetin X (1), waltheriones A (2) and C (3)) and three pentacyclic triterpene derivatives (betulinic acid (4), 3ß-acetoxy-27-trans-caffeoyloxyolean-12-en-28-oic acid methyl ester (5) and 3ß-acetoxy-27-cis-caffeoyloxyolean-12-en-28-oic acid methyl ester (6)) identified by 1D and 2D NMR, UV, IR and MS analyses. Among these, waltherione C exhibited the highest and selective antitrypanosomal activity towards T. cruzi (IC50=1.93 µM) with low cytotoxicity (IC50=101.23 µM), resulting in a selectivity index value of 52. Waltherione C conforms to hit activity criteria with respect to T. cruzi as required by the WHO/TDR.

Nematicidal activities of 4-quinolone alkaloids isolated from the aerial part of Triumfetta grandidens against Meloidogyne incognita.

The methanol extract of the aerial part of Triumfetta grandidens (Tiliaceae) was highly active against Meloidogyne incognita, with second-stage juveniles (J2s) mortality of 100% at 500 µg/mL at 48 h post-exposure. Two 4-quinolone alkaloids, waltherione E (1), a new alkaloid, and waltherione A (2), were isolated and identified as nematicidal compounds through bioassay-guided fractionation and instrumental analysis. The nematicidal activities of the isolated compounds against M. incognita were evaluated on the basis of mortality and effect on egg hatching. Compounds 1 and 2 exhibited high mortalities against J2s of M. incognita, with EC50 values of 0.09 and 0.27 µg/mL at 48 h, respectively. Compounds 1 and 2 also exhibited a considerable inhibitory effect on egg hatching, which inhibited 91.9 and 87.4% of egg hatching, respectively, after 7 days of exposure at a concentration of 1.25 µg/mL. The biological activities of the two 4-quinolone alkaloids were comparable to those of abamectin. In addition, pot experiments using the crude extract of the aerial part of T. grandidens showed that it completely suppressed the formation of gall on roots of plants at a concentration of 1000 µg/mL. These results suggest that T. grandidens and its bioactive 4-quinolone alkaloids can be used as a potent botanical nematicide in organic agriculture.

[2-Methyl-3-phenylaminomethylquinolin-4-one as potential antidepressant with nootropic properties].

The new compound, 2-methyl-3-phenylaminomethylquinolin-4-on, belongs to V class of toxicity and exhibits antidepressant and antiamnesic properties. It is established that this compound reduces the duration of immobilization in the test of behavioral despair, prevents from the scopolamine induced amnesia, and exhibits antagonism with reserpine in mice. In a dose of 100 mg/kg, the synthesized compound influences the levels of cerebral catecholamines similarly to imipramine, but with a more pronounced decrease in the level of 5-hydroxytryptamine.

Synthesis and structure-activity relationship of 4-quinolone-3-carboxylic acid based inhibitors of glycogen synthase kinase-3ß.

The synthesis, GSK-3ß inhibitory activity, and anti-microbial activity of bicyclic and tricyclic derivatives of the 5,7-diamino-6-fluoro-4-quinolone-3-carboxylic acid scaffold were studied. Kinase selectivity profiling indicated that members of this class were potent and highly selective GSK-3 inhibitors.

4-quinolone derivatives: high-affinity ligands at the benzodiazepine site of brain GABA A receptors. synthesis, pharmacology, and pharmacophore modeling.

The 3-ethoxycarbonyl-4-quinolone compound 1 has previously been identified via a database search as an interesting lead compound for ligand binding at the benzodiazepine site of GABA(A) receptors (Kahnberg et al. J. Mol. Graphics Modelling 2004, 23, 253-261). Pharmacophore-guided optimization of this lead compound yielded a number of high-affinity ligands for the benzodiazepine site including compounds 20 and 23-25 displaying sub-nanomolar affinities. A few of the compounds have been tested on the alpha(1)beta(2)gamma(2S) and alpha(3)beta(2)gamma(2S) GABA(A) receptor subtypes, and two of the compounds (5 and 19) display selectivity for alpha(1)- versus alpha(3)-containing receptors by a factor of 22 and 27, respectively. This selectivity for alpha(1)beta(2)gamma(2S) is in the same range as that for the well-known alpha(1) subunit selective compound zolpidem.

Assessment of the antibacterial activity of galangin against 4-quinolone resistant strains of Staphylococcus aureus.

The flavonol galangin is present in numerous plants and is a major constituent of Helichrysum aureonitens, a perennial herb used by South African indigenes to treat infection. In the present study, the antibacterial activity of galangin was assessed against 17 strains of 4-quinolone resistant S. aureus using an agar dilution assay. It was determined that the flavonol had a minimum inhibitory concentration (MIC) of approximately 50 microg/ml against 16 of these strains, including those which exhibited 250- and 500-fold increases in norfloxacin resistance. The remaining one strain, which possessed an amino acid alteration in the GrlB subunit of topoisomerase IV, had increased susceptibility to galangin. Control strains of 4-quinolone sensitive S. aureus were also found to have MICs of 50 microg/ml. The topoisomerase IV enzyme may therefore be implicated in the antibacterial mechanism of action of galangin. Clearly however, there is no cross-resistance between galangin and the 4-quinolones, and the flavonol therefore warrants further investigation as an antibacterial agent.

In vivo action of novel alkyl methyl quinolone alkaloids against Helicobacter pylori.

Previously purified and isolated compounds of novel alkyl methyl quinolone alkaloids (AM quinolones) from Gosyuyu (Wu-Chu-Yu), a Chinese herbal medicine, have a strong and highly selective antibacterial activity against Helicobacter pylori in vitro. To clarify the antibacterial mechanism(s) of AM quinolones, we examined the effects of AM quinolones on respiration of H. pylori in vitro. One week after treatment with AM quinolones alone (2, 10 or 20 mg/kg/day, orally) or combinations of AM quinolones and omeprazole (30 mg/kg/day) for H. pylori (1 x 10(8) cfu)-infected Mongolian gerbils, we checked viable H. pylori and myeloperoxidase (MPO) activity in the gastric tissues. AM quinolones decreased the number of H. pylori and inhibited H. pylori respiration in a dose-dependent manner. AM quinolones decreased the number of viable H. pylori (AM quinolones alone: 46.0 +/- 22.6 x 10(4), 17.3 +/- 4.9 x 10(4) and 8.1 +/- 6.6 x 10(4) cfu/stomach, respectively; and combinations of AM quinolones and omeprazole: 8.0 +/- 5.6 x 10(4), 4.2 +/- 2.5 x 10(4) and 5.5 +/- 2.7 x 10(4) cfu/stomach) compared with the vehicle-treated group (control: 359.9 +/- 180.3 x 10(4) cfu/stomach). AM quinolones significantly decreased MPO activity of H. pylori-inoculated gastric tissues. These findings suggest that AM quinolones have a potent antibacterial effect against H. pylori through respiratory inhibition, and reduced bacterial growth in vivo. AM quinolones might be novel therapeutic agents for H. pylori eradication.

[Prospects for development of new antituberculous drugs].

Tuberculosis (TB) is a growing international health concern, since it is the leading infectious cause of death in the world today. Moreover, the resurgence of TB in industrialized countries and the worldwide increase in the prevalence of Mycobacterium avium complex (MAC) infections in immunocompromised hosts have prompted the quest for new antimycobacterial drugs. In particular, the appearance of multidrug-resistant (MDR) strains of M. tuberculosis, which exhibit in vitro resistance to at least two major antituberculous drug (usually INH and RFP) and cause intractable TB, has greatly contributed to the increased incidence of TB. Because of the global health problems of TB, the increasing rate of MDR-TB and the high rate of a co-infection with HIV, the development of potent new antituberculous drugs without cross-resistance with known antimycobacterial agents is urgently needed. In this article, I reviewed the following areas. First, I briefly reviewed some new findings (mainly reported after 2000) on the pharmacological status of rifamycin derivatives (rifabutin, rifapentine, and rifalazil), fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin, levofloxacin, gatifloxacin, sitafloxacin, moxifloxacin, and others), and new macrolides (clarithromycin, azithromycin, and roxithromycin). Second, I described other types of agents which are being developed as antimycobacterial drugs. Some of the agents discussed are already under preliminary clinical investigation, and others appear to be promising candidates for future development. In this review, the status of the development of new antimycobacterial, especially antituberculous agents including oxazolidinone (PNU-100480), 5'-nitroimidazole (CGI 17341), 2-pyridone (ABT-255), new riminophenazines, nitroimidazopyran (PA-824), new ketolides (ABT-773, telithromycin) and defensins (human neutrophil peptide-I), was examined. Third, the development of new antitubercular drugs was discussed according to the potential pharmacological target. New critical information on the whole genome of M. tuberculosis recently elucidated and increasing knowledge on various mycobacterial virulence genes will promote the progression in the identification of genes that code for new drug targets. Using such findings on mycobacterial genomes, drug development using quantitative structure-activity relationship may be possible in the near future. In this review, I described the screening of drugs that have an inhibitory activity against dTDP-rhamnose synthesis of M. tuberculosis, as a new drug target of the organism. In addition, I discussed the usefulness of antisense oligo DNAs specific to mycobacterial genes encoding certain metabolic enzymes or virulence factors that play roles in the bacterial escape from antimicrobial mechanisms of host macrophages. Fourth, I reviewed the drug vehicles which enable efficacious drug delivery to their target in vivo. The usefulness of poly (DL-lactide-co-glycolide) microsphere technology, which enables the encapsulated drugs to deliver the requested doses of them for prolonged time periods by a single shot without causing any toxicity and, moreover, enables the highly targeted delivery of the drugs to host macrophages, was discussed. Fifth, I described adjunctive immunotherapy for the management of patients with mycobacterial infections by giving certain immunomodulators in combination with antimycobacterial drugs. Adjuvant clinical trials using IL-2 or GM-CSF have been found to be efficacious to some extent in improving patients with tuberculosis or disseminated MAC infections. However, it seems that these immunopotentiating cytokines as well as IFN-gamma and IL-12 are not so promising for the therapeutic agents of mycobacterial infections because of the possible induction of immunosuppressive cytokines during adjuvant therapy and, in some cases, severe side-effect. Thus, the development of new classes of immuno-modulators other than cytokines, particularly those with no severe side-effect, is needed. This review dealt with ATP and its analogues which potentiate macrophage antimycobacterial activity via a purinergic P2X7 receptor. Finally, I described the roles of type II alveolar epithelial cells in the establishment of mycobacterial infections in the host lungs and the profiles of drug susceptibilities of M. tuberculosis and MAC organisms replicating within the type II pneumocytes. These findings are useful to precisely assess or predict the in vivo therapeutic activity of a given antimycobacterial drug from its in vitro activity. In this article, I have thoroughly reviewed the status of the development of new antimycobacterial drugs. There are a number of difficulties in the drug-design for the development of new drug formulations with increased potential for antimycobacterial effects, excellent pharmacokinetics, and tolerability. It should be emphasized that the most urgent goal of chemotherapy of tuberculosis and MAC infections, especially that associated with HIV infection, is to develop highly active, low-cost drugs which can be used not only in industrialized countries but also in developing countries, since the incidences of AIDS-associated intractable tuberculosis is rapidly increasing in the latter.

Gemifloxacin is efficacious against penicillin-resistant and quinolone-resistant pneumococci in experimental meningitis.

In experimental rabbit meningitis, gemifloxacin penetrated inflamed meninges well (22 to 33%) and produced excellent bactericidal activity (change in log(10) [Deltalog(10)] CFU/ml/h, -0.68 +/- 0.30 [mean and standard deviation]), even superior to that of the standard regimen of ceftriaxone plus vancomycin (-0.49 +/- 0.09 deltalog(10) CFU/ml/h), in the treatment of meningitis due to a penicillin-resistant pneumococcal strain (MIC, 4 mg/liter). Even against a penicillin- and quinolone-resistant strain, gemifloxacin showed good bactericidal activity (-0.48 +/- 0.16 deltalog(10) CFU/ml/h). The excellent antibacterial activity of gemifloxacin was also confirmed by time-kill assays over 8 h in vitro.

Comparative antibiotic resistance of diarrheal pathogens from Vietnam and Thailand, 1996-1999.

Antimicrobial resistance rates for shigella, campylobacter, nontyphoidal salmonella, and enterotoxigenic Escherichia coli were compared for Vietnam and Thailand from 1996 to 1999. Resistance to trimethoprim-sulfamethoxazole, ampicillin, chloramphenicol, and tetracycline was common. Quinolone resistance remains low in both countries, except among campylobacter and salmonella organisms in Thailand. Nalidixic acid resistance among salmonellae has more than doubled since 1995 (to 21%) in Thailand but is not yet documented in Vietnam. Resistance to quinolones correlated with resistance to azithromycin in both campylobacter and salmonella in Thailand. This report describes the first identification of this correlation and its epidemiologic importance among clinical isolates. These data illustrate the growing magnitude of antibiotic resistance and important differences between countries in Southeast Asia.

Cefepime is efficacious against penicillin- and quinolone-resistant pneumococci in experimental meningitis.

In experimental rabbit meningitis, cefepime given at a dose of 100 mg/kg was associated with concentrations in the cerebrospinal fluid of between 5.3 and 10 mg/L and a bactericidal activity of -0.61 +/- 0.24 Delta log(10) cfu/mL x h, similar to the standard regimen of ceftriaxone combined with vancomycin (-0.58 +/- 0.14 Delta log(10) cfu/mL x h) in the treatment of meningitis due to a penicillin- and quinolone-resistant pneumococcal mutant strain (MIC 4 mg/L). Compared with the penicillin-resistant parental strain, the penicillin- and quinolone-resistant mutant was killed more slowly by cefepime and ceftriaxone in time-killing assays in vitro over 8 h.

Efficacies of BMS 284756 against penicillin-sensitive, penicillin-resistant, and quinolone-resistant pneumococci in experimental meningitis.

BMS 284756 penetrated well into inflamed meninges (44% +/- 11%) and produced good bactericidal activity (-0.82 +/- 0.22 Delta log(10) CFU/ml. h) in the treatment of experimental meningitis in rabbits due to a penicillin-sensitive strain. BMS 284756 monotherapy had a greater potency than the standard regimen of ceftriaxone and vancomycin (-0.49 +/- 0.08 Delta log(10) CFU/ml. h) against a penicillin-resistant strain (MIC, 4 mg/liter). Even against a penicillin- and quinolone-resistant strain, BMS 284756 showed good bactericidal activity (-0.52 +/- 0.12 Delta log(10) CFU/ml. h). The antibacterial activity of BMS 284756 was confirmed by time-killing assays over 8 h in vitro.

Quinolone, everninomycin, glycylcycline, carbapenem, lipopeptide and cephem antibacterials in clinical development.

The development of antibacterials was a very successful endeavor in the pharmaceutical company repertoire through the late 1970s, when interest in investing in antibiotic research and development temporarily waned. More recently, there have been a number of failures in late stage development or post-launch of human antibiotics. The answer to the dilemma of less-than-desired success may be the introduction of novel classes of agents, as well as development of new agents in traditional classes. This review provides an overview of the various "miscellaneous" antibacterials in development, excluding glycopeptides, macrolides, ketolides, and oxazolidinones. Among the agents highlighted in this review are the clinical candidates of quinolones, everninomycins, carbapenems, lipopeptides, glycylcyclines, and cephems. In several cases, certain quinolone agents described in this review will have been approved for marketing before press time.

Inhibitors of bacterial topoisomerases: mechanisms of action and resistance and clinical aspects.

The quinolone class of inhibitors of bacterial type II topoisomerases has gained major clinical importance during the last years due to improvements in both pharmacokinetic and pharmacodynamic properties. These include favorable bioavailability allowing oral administration, good tolerability, high tissue concentrations as well as superior bactericidal activity against a broad spectrum of clinically relevant pathogens, like enterobacteria, Pseudomonas aeruginoso, Staphylococcus aureus, and Streptococcus pneumoniae. In addition, no enzymatic mechanism of drug inactivation exists in bacteria and no indications for transfer of clinically relevant resistance exist. Nevertheless, resistance is being increasingly reported, even for naturally highly susceptible species like Escherichia coli. The underlying mechanisms of resistance include alterations in both bacterial targets, DNA gyrase and topoisomerase IV, often combined with mutations affecting drug accumulation, e.g., by increased drug efflux, reduced drug influx, or both. Investigations aiming at understanding the molecular mechanisms of quinolone action and resistance in more detail should provide a basis for a rational design of more potent derivatives. In addition, a prudent use of these highly valuable "magic bullets" is necessary to preserve their potential for the future.

Alumina-supported synthesis of antibacterial quinolines using microwaves.

7-(5'-Alkyl-1',3',4'-thiadiazol/oxadiazol-2'-ylthio)-6 -fluoro-2,4-dimethylquinolines and 3-formyl-2-(2'-hydroxy- 1',4'-naphthoquinon-3'-yl)-4-methyl/6-methyl/7-quinolines have been synthesised by the reaction of 5-alkyl-1,3,4-thiadiazol/oxadiazol-2-thiols with 7-chloro-6-fluoro-2,4-dimethylquinoline and by the reaction of 2-hydroxy-1,4-naphthoquinone with 2-chloro-3-formyl-4-methyl/6-methyl/7-methyl/8-methylquinolines respectively on basic alumina using microwaves, the reaction time has been brought down from hours to seconds with improved yield as compared to conventional heating. The compounds were tested for their in vitro antibacterial activity. All compounds showed promising antibacterial activity. The best activity was observed by compounds 3a and 3f.