Medicinal Chemistry - Volume 5, Issue 2, 2009

The synthesis of novel series of structurally related 4-pyrazolyl benzenesulfonamide derivatives is described. All the newly synthesized compounds were examined for their anti-inflammatory activity using cotton pellet induced granuloma and carrageenan induced rat paw edema bioassays. In addition the inhibitory activities of cyclooxygenase-1 and cyclooxygenase-2 (COX-1 and COX-2), ulcerogenic effect and acute toxicity were determined. Furthermore, all the compounds were evaluated for their in vitro antimicrobial activity against Eischerichia coli, Staphylococcus aureus and Candida albicans. Docking poses for compounds 6b and 7b separately in the active site of the human COX-2 enzyme and DNA-gyrase B were also obtained. The results revealed that compounds 3c, 4b, 4c, 5c, 6b and 7b exhibited comparable or better anti-inflammatory activity compared to indomethacin and celecoxib with no or minimal ulcerogenic effect and high safety margin. Compounds 3b, 3c, 4b, 4c, 5a-c, 6a, 6b and 7a-c displayed appreciable antibacterial activity against both E. coli and S. aureus compared with ampicillin. Compounds 5a-c and 7a had antibacterial activity against E. coli similar to ampicillin whereas compounds 3b, 3c, 4b, 4c, 6a and 7b displayed considerable activity against the microorganism. Compounds 3a, 3c, 4c, 5a-c, 6b and 7a-c had appreciable activity against S. aureus. Overall, compounds 4c, 6b and 7b are the most distinctive derivatives in the present study because of their remarkable anti-inflammatory potency and significant antibacterial activity. Furthermore, compounds 6b and 7b exhibited good selective inhibitory activity against COX-2 enzyme. Therefore, such compounds would represent a suitable template for the design of anti-inflammatory antimicrobial candidates with reasonable COX-2 selectivity.

18F-Labelled fluoroazomycin arabinoside ([18F]FAZA) is a 2-nitroimidazole (azomycin) based PET tracer used extensively in cancer clinics to diagnose tumour hypoxia. The hypoxia-specific uptake and rapid blood clearance kinetics of FAZA contribute to good tumor-to-background ratios (T/B ratios) and high image contrast. However, FAZA, an α- configuration nucleoside, is not transported by cellular nucleoside transporters. It enters cells only via diffusion, therefore not achieving the high uptake and T/B ratios characteristic of actively transported radiopharmaceuticals. The present work describes the synthesis, physicochemical properties and preliminary assessment of the radiosensitization properties of two novel azomycin nucleosides, 1-β-D-(2-deoxy-2-fluoroarabinofuranosyl)-2-nitroimidazole (β-2-FAZA) and 1-β-D-(3- deoxy-3-fluorolyxofuranosyl)-2-nitroimidazole (β-3-FAZL) (fluorination yields 60% and 55%, respectively). The tosylated precursors required to synthesize the corresponding F-18 labeled radiopharmaceuticals are also reported. The partition coefficients (P) for β-2-FAZA (1.0) and β-3-FAZL (0.95) were marginally lower than reported for FAZA (1.1). The radiosensitization properties of both these compounds are similar to that of FAZA, with sensitizer enhancement ratios (SER) of ∼1.8 for HCT-116 cells.

Cheminformatics approaches are currently not employed in any of the spices to study the medicinal properties traditionally attributed to them. The aim of this study is to find the most efficacious molecule which do not have toxic effects but at the same time have desired pharmacokinetic profile. In the present study of the class ‘diphenylheptanoids’ from turmeric, cheminformatics methods were employed to predict properties such as physicochemical properties, Absorption, Distribution, Metabolism, Toxicity (mutagenicity, rodent carcinogenicity and human hepatotoxicity). These studies confirmed that curcumin and its derivatives cause dose-dependent hepatotoxicity. The results of these studies indicate that, in contrast to curcumin, few other compounds in turmeric such as compounds (8) and (9) [refer text], exhibit better activities and are drugable and do not have any side-effects.

Ethanolic extracts of 30 Thai medicinal plants, traditionally used as alternative treatments in diabetes, were evaluated for antioxidative activity by the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method. They were evaluated in vitro for oxidative stress by thiobarbituric acid-reactive substance (TBARS) assay in pooled plasma of diabetic patients compared to without treatment of the extracts (control). The extracts were also assayed for protein glycation. The results showed that five plants had strong antioxidant activity: Phyllanthus emblica Linn. (PE), Terminalia chebula Retz. (TC), Morinda citrifolia Linn. (MC), Kaempferia parviflora Wall. (KP) and Houttuynia cordata Thunb.(HC), respectively. Thirty plant extracts were good correlation between total antioxidant activity and antiradical activity by TBARS as well as by glycation (r = 0.856, p<0.01 and r = 0.810, p<0.01). PE had stronger antioxidative activity as well as inhibition of TBARS and glycation than the other plants. The investigation showed that total polyphenol and tannin content of PE and the flavonoid content of HC were the highest. The results imply that these plants are potential sources of natural antioxidants which have free radical scavenging activity and might be used for reducing oxidative stress in diabetes.

The use of nanostructured TiO2 as mixed phase photocatalyst in the synthesis of 2H-pyrano/2H-thiopyrano [2,3-b]quinoline-2-carboxylic acid (2a/2b) is described. The binding modes of 2a/2b with ds DNA fragments d(CGCGAATTCGCG) were predicted by molecular docking studies. The lowest energy was found in the compound 2b with a binding energy of -7.44 Kcal/mol and inhibition constant of 5.39 x e-6. The interaction study with CT DNA was carried out by absorption spectra, (Kb constant obtained for 2a is 3.5x106 and for 2b it is 2.9x105), viscosity and thermal denaturation methods. The in vitro antioxidant activities were evaluated. Finally, the results showed that the intercalated 2a/2b compounds are strong antioxidants and they protect oxidative DNA damage from harmful free radicals.

It has been proposed a novel method for obtaining of 1,2,3,4-tetrahydroisoquinoline-7-carboxylic acid as Argmimetic within the framework of search for novel fibrinogen receptor antagonists. New αIIbβ3 antagonists were prepared on a base of 1,2,3,4-tetrahydroisoquinoline-7-carboxylic acid. Their high antiaggregatory activities in a human platelet rich plasma and ability to block FITC-Fg binding to αIIbβ3 on washed human platelets were estimated.

The effect exerted by two γ-endorphin derivatives (DTγE and DEγE) was investigated on morphine-induced inhibition on the electrically induced contractions of guinea pig ileum in vitro. Morphine (1x10-8-5x10-8-1x10-7 M) dose dependently and significantly reduced the E.C. of guinea pig ileum, IC50=.5x10-8 M (Confidence limits: 3.7x10-8- 9.1x10-8). DTγE and DEγE per se (1x10-6-5x10-6-1x10-5 M) did not modify significantly the E.C. of guinea pig ileum. Furthermore, DTγE or DEγE injection 10-30-60 min before morphine, did not affect the inhibitory effect of morphine on the E.C. of guinea pig ileum. By contrast, ilea from guinea-pigs treated for 4 days with DTγE or DEγE (1 mg/Kg/i.p.) were less sensitive to the inhibitory effect of morphine, IC50=8.3x10-7 M (Confidence limits: 1.4x10-6-3.5x10-7) for DTγE and IC50=7.7x10-7 M (Confidence limits: 2.7x10-6-8.7x10-7) for DEγE . The effect exerted by two β-endorphin fragments (DTγE and DEγE) was investigated on the acute opiate withdrawal induced by μ, k and δ receptor agonists in vitro. After a exposure in vitro for 4 min to morphine (less selective μ agonist), DAGO (highly selective μ agonist), U50-488H (highly selective k agonist) and β-endorphin (selective μ-δ agonist), a strong contracture of isolated guinea pig ileum was observed after the addition of naloxone. This effect was also observed when isolated rabbit jejunum was pretreated with deltorphin (highly selective δ agonist). DTγE or DEγE injection before or after treatment with morphine, DAGO, U50-488H, β-endorphin or deltorphin was able of both preventing and reversing the naloxone-induced contracture after exposure to the opioid agonists in a concentration- dependent fashion. Our results indicate that both DTγE or DEγE are able to reduce significantly opiate withdrawal in vitro, suggesting an important functional interaction beween β-endorphin fragments and opioid withdrawal at both μ, k and δ receptor level. Our results indicate that chronic treatment of guinea pigs with DTγE or DEγE induces a significant reduction of the inhibitory effect of morphine on the E.C. of guinea-pig ileum thus confirming an important functional interaction between γ- endorphin derivatives and opioid system.

Diagnostic agents enabling characterization of multidrug resistance (MDR) in tumors can aid in the selection of chemotherapy regimens. We report here synthesis and evaluation of radiopharmaceuticals based on the second-generation MDR-reversing drug MS-209. 5-[3-{4-(2-Phenyl-2-(4'-[125I]iodo-phenyl)acetyl)piperazin-1-yl}-2-hydroxypropoxy]quinoline (17) was prepared from the 4'-tributylstannyl precursor (16) in >95% radiochemical yield. (16) was synthesized in a six-step process with the overall yield of 25%. In vitro studies were conducted in MES-SA (drug-sensitive) and MESSA/ Dx5 (MDR) human uterine sarcoma cell lines. In vivo studies were performed in athymic mice bearing MES-SA and MES-SA/Dx5 xenografts. The uptake of (17) is higher in MES-SA than MES-SA/Dx5 cells. The uptake and efflux of (17) depend on temperature and concentration, and indicate active transport mechanism(s). Incubation of drug sensitive MES-SA cells with verapamil or (15), a nonradioactive analog of (17), alters the cellular retention of radioactivity only marginally. However, MESSA/ Dx5 cells retain ∼12% more of (17) when incubated with 10 μM verapamil. The addition of (15) or high concentrations of (17) also increase the uptake of (17) in MES-SA/Dx5 up to 200%, depending on the concentration and temperature. The dependence of (17) uptake on the MDR status is also evident in the ex vivo binding studies. In vivo tests in mice xenografted simultaneously with both tumor cell lines indicate distinct pharmacokinetics for each tumor. The absorption half-life in MES-SA/Dx5 xenograft is ∼10x shorter and the mean residence time ∼50% shorter compared to MES-SA xenograft in the same mouse. Radioiodinated derivatives of MS-209 appear to be good indicators of multidrug resistance. For supplement material, please see the online version of the article.

The most widely used molecules in cancer chemotherapy are Vinca-alkaloids and Taxoids, numerous chemists attempted the synthesis of analogs which bind to their well-known tubulin pharmacological site. Unfortunately, tumors develop resistance to these compounds; therefore the definition of anchoring points and potential binding sites for new drugs on tubulin is of major interest. Caulerpenyne (Cyn), the major secondary metabolite synthesized by the green marine alga Caulerpa taxifolia could be one of these drugs, since it inhibits the assembly of tubulin and MTP (Barbier et al., 2001). We observed that the tubulin-Cyn complex is poorly reversed. Cyn did not bind to sulfhydryl groups and the measure of the extent of binding is 1.6 ± 0.2 suggesting two potential binding sites. Then, we demonstrated by competition measurements that Cyn did not interact to colchicine, Taxol&reg and Vinca-alkaloid binding domain. Finally, mass spectrometric analysis of proteolytic cleavage of tubulin-Cyn complex demonstrated that Cyn did not bind covalently to tubulin and evidenced two good candidate regions for Cyn binding, one on α-tubulin and the other on β-tubulin.

Microparticles of chitosan (CHT) containing alendronate sodium (AL) were prepared in four drug:polymer ratios (1:1, 1:2, 1:4, 1:6) using the spray drying technique. The efficiency of the method was evaluated by determining production yield (about 70 %) and microencapsulation efficiency, which was almost 100 % in the case of all four of the formulations studied. Particles had a mean size of between 3.6 and 4.6 μm, and a near-spherical shape. The formulations with the highest content of AL (drug:polymer ratio 1:1 and 1:2) showed an asymmetrical distribution of particles, which were larger in size, and had a higher proportion of irregular particles than the other formulations. FT-IR analysis revealed an ionic interaction between AL and CHT. Differential scanning calorimetry and thermogravimetric analysis confirmed the microencapsulation of AL and the increased thermal stability of encapsulated AL. The dissolution profiles of AL from CHT microspheres, at pH values of 1.2 and 6.8, showed a delayed release of AL from microspheres, and the dissolution rate was dependent on the pH and the drug:polymer ratio. It can be concluded that spray drying is a suitable technique for preparing AL-loaded CHT microspheres, and that the drug:polymer ratio can be used to control the rate of AL release from microspheres.

Potent inhibitors of MenA (1,4-dihydroxy-2-naphtoate prenyltrasferase) in Mycobacterium tuberculosis are identified, and are also effective in inhibiting growth of Mycobacterium tuberculosis at low concentrations. The MenA inhibitors possess common chemical structural features of (alkylamino)oalkoxyphenyl)(phenyl)methanones. Significantly, the MenA inhibitors can be synthesized in a few steps with high overall yields. The representative MenA inhibitors are highly effective in killing nonreplicating Mycobacterium tuberculosis that is evaluated by using the Wayne low oxygen model. In addition, a series of drug resistant Mycobacterium spp. are sensitive to the MenA inhibitors. The results are expected to be of significance in terms of discovering new lead compounds that can be developed into new drugs to combat unmet diseases caused by Mycobacterium tuberculosis.