Drug Design, Synthesis and Biological Evaluation of Heterocyclic Molecules as Anti-Inflammatory Agents

Non-steroidal anti-inflammatory drugs (NSAIDs) are generally utilized for numerous inflammatory ailments. The long-term utilization of NSAIDs prompts adverse reactions such as gastrointestinal ulceration, renal dysfunction and hepatotoxicity; however, selective COX-2 inhibitors prevent these adverse events. Various scientific approaches have been employed to identify safer COX-2 inhibitors, as in any case, a large portion of particular COX-2 inhibitors have been retracted from the market because of severe cardiovascular events. This study aimed to develop and synthesize a novel series of indomethacin analogues with potential anti-inflammatory properties and fewer side effects, wherein carboxylic acid moiety was substituted using DCC/DMAP coupling. This study incorporates the docking of various indomethacin analogues to detect the binding interactions with COX-2 protein (PDB ID: 3NT1). MD simulation was performed to measure the stability and flexibility of ligand–protein interactions at the atomic level, for which the top-scoring ligand–protein complex was selected. These compounds were evaluated in vitro for COX enzymes inhibition. Likewise, selected compounds were screened in vivo for anti-inflammatory potential using the carrageenan-induced rat paw oedema method and their ulcerogenic potential. The acute toxicity of compounds was also predicted using in silico tools. Most of the compounds exhibited the potent inhibition of both COX enzymes; however, 3e and 3c showed the most potent COX-2 inhibition having IC50 0.34 µM and 1.39 µM, respectively. These compounds also demonstrated potent anti-inflammatory potential without ulcerogenic liability. The biological evaluation revealed that the compound substituted with 4-nitrophenyl was most active.

A Simple Small Molecule with Synergistic Passive and Active Dual-Targeting Effects for Imaging-Guided Photothermal Cancer Therapy

Photothermal therapy allows spatiotemporal control of the treatment effect only at the site of the disease and provides promising opportunities for imaging-guided precision therapy. However, the development of photothermal transduction agents (PTAs) for tumor-specific accumulation and precision imaging, avoiding toxicity to the surrounding healthy tissue, is still challenging. Herein, a cyclooxygenase-2-specific small-organic-molecule-based PTA (Cy7-TCF-IMC) is developed, which can self-assemble into nanosaucers having unique photothermal and photoacoustic properties. Specifically, the self-assembling nature of Cy7-TCF-IMC affords preferential accumulation in tumors arising from synergistic passive enhanced permeability and retention effects and active targeting for precision theranostics. Antitumor therapy results show that these Cy7-TCF-IMC nanosaucers are highly photoacoustic imaging-guided PTAs for tumor ablation. These findings suggest the self-assembled Cy7-TCF-IMC nanosaucer represents a new paradigm as a single-component supramolecular medicine that can synergistically optimize passive and active targeting, thereby improving the therapeutic index of cancer and future clinical outcomes.

Design, Synthesis, In Silico and In Vitro Studies for New Nitric Oxide-Releasing Indomethacin Derivatives with 1,3,4-oxadiazole-2-thiol Scaffold

Starting from indomethacin (IND), one of the most prescribed non-steroidal anti-inflammatory drugs (NSAIDs), new nitric oxide-releasing indomethacin derivatives with 1,3,4-oxadiazole-2-thiol scaffold (NO-IND-OXDs, 8a-p) have been developed as a safer and more efficient multitarget therapeutic strategy. The successful synthesis of designed compounds (intermediaries and finals) was proved by complete spectroscopic analyses. In order to study the in silico interaction of NO-IND-OXDs with cyclooxygenase isoenzymes, a molecular docking study, using AutoDock 4.2.6 software, was performed. Moreover, their biological characterization, based on in vitro assays, in terms of thermal denaturation of serum proteins, antioxidant effects and the NO releasing capacity, was also performed. Based on docking results, 8k, 8l and 8m proved to be the best interaction for the COX-2 (cyclooxygense-2) target site, with an improved docking score compared with celecoxib. Referring to the thermal denaturation of serum proteins and antioxidant effects, all the tested compounds were more active than IND and aspirin, used as references. In addition, the compounds 8c, 8h, 8i, 8m, 8n and 8o showed increased capacity to release NO, which means they are safer in terms of gastrointestinal side effects.

Solid state properties and drug release behavior of co-amorphous indomethacin-arginine tablets coated with Kollicoat® Protect

A promising approach to improve the solubility of poorly water-soluble drugs and to overcome the stability issues related to the plain amorphous form of the drugs, is the formulation of drugs as co-amorphous systems. Although polymer coatings have been proven very useful with regard to tablet stability and modifying drug release, there is little known on coating co-amorphous formulations. Hence, the aim of the present study was to investigate whether polymer coating of co-amorphous formulations is possible without inducing recrystallization. Tablets containing either a physical mixture of crystalline indomethacin and arginine or co-amorphous indomethacin-arginine were coated with a water soluble polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat® Protect) and stored at 23°C/0% RH and 23°C/75% RH. The solid state properties of the coated tablets were analyzed by XRPD and FTIR and the drug release behavior was tested for up to 4h in phosphate buffer pH 4.5. The results showed that the co-amorphous formulation did not recrystallize during the coating process or during storage at both storage conditions for up to three months, which confirmed the high physical stability of this co-amorphous system. Furthermore, the applied coating could partially inhibit recrystallization of indomethacin during drug release testing, as coated tablets reached a higher level of supersaturation compared to the respective uncoated formulations and showed a lower decrease of the dissolved indomethacin concentration upon precipitation. Thus, the applied coating enhanced the AUC of the dissolution curve of the co-amorphous tablets by about 30%. In conclusion, coatings might improve the bioavailability of co-amorphous formulations.

Bifunctional conjugates with potent inhibitory activity towards cyclooxygenase and histone deacetylase

We herein disclose a series of compounds with potent inhibitory activities towards histone deacetylases (HDAC) and cyclooxygenases (COX). These compounds potently inhibited the growth of cancer cell lines consistent with their anti-COX and anti-HDAC activities. While compound 2b showed comparable level of COX-2 selectivity as celecoxib, compound 11b outperformed indomethacin in terms of selectivity towards COX-2 relative to COX-1. An important observation with our lead compounds (2b, 8, 11b, and 17b) is their enhanced cytotoxicity towards androgen dependent prostate cancer cell line (LNCaP) relative to androgen independent prostate cancer cell line (DU-145). Interestingly, compounds 2b and 17b arrested the cell cycle progression of LNCaP in the S-phase, while compound 8 showed a G0/G1 arrest, similar to SAHA. Relative to SAHA, these compounds displayed tumor-selective cytotoxicity as they have low anti-proliferative activity towards healthy cells (VERO); an attribute that makes them attractive candidates for drug development.

EFFECT OF INDOMETHACIN AND ITS COMPLEXES ON REPRODUCTIVE PERFORMANCE AND OXIDATIVE STRESS IN TESTIS AND STOMACH OF MALE ALBINO RATS WITH REFERENCE TO THEIR CHEMICAL CHARACTERIZATIONS

Four new complexes of Hg (II), Pb (II), Sn (II) and Bi (III) with indomethacin drug ligand (IMC) were synthesized and characterized by using infrared, electronic, 1H-NMR spectral, thermogravimetric and conductivity measurements. The IMC was found to act as bidentate chelating agent. IMC complexes coordinate through the oxygen of the carboxyl group. The molar ratio chelation is 1:2 (M2+:IMC) with general formula [M (IMC) 2], nH2O for Hg (II), Pb(II) and Sn(II), but 1:3 for Bi(III) ions. Antibacterial screening of these heavy metal complexes against Escherichia coli (Gram-ve), Bacillus subtilis (Gram +ve) and anti-fungi (Asperagillus oryzae, Asperagillus niger, Asperagillus Flavus) were investigated. In the present study, we found evidence suggesting that Bi+3/IMC possesses the capacity to protect the stomach, sperm, testes, cellular ATP, cellular NAD, INSL3, PGD2, PGE2 and antioxidant enzymes from deleterious actions of IMC.

[Synthesis of colon-specific prodrug of indomethacin and its inhibitory effect on liver metastasis from colon cancer]

OBJECTIVE

To develop a colon-specific prodrug of Indomethacin microbially triggered, carry out in vitro/in vivo evaluation of drug release, and appraise its inhibitory effect on liver metastasis from colon cancer.

METHODS

Indomethacin prodrugs were synthesized and characterized by FTIR and NMR, and dissolution test simulating gastrointestinal tract was employed to screen the colon-specific prodrug. Then, the pharmacokinetic profile of portal vein and peripheral blood in Sprague-Dawley rats was studied. Lastly, the inhibitory effect on liver metastasis from colon cancer in nude mice was observed.

RESULTS

The chemical structure characterized by FTIR and NMR demonstrated that six kinds of indomethacin-block-amylose with different drug loading (IDM-AM-1-6) were synthesized, among which IDM-AM-3 was degraded 1.3%, 9.3% and 95.3%, respectively, in simulated gastric fluid for 4 h, small intestine for 6 h, and colon for 36 h. The pharmacokinetic test of IDM-AM-3 showed that absorption was delayed significantly (P < 0.01), peak time [(11.35 + or - 2.45) h], elimination half-life [(16.74 + or - 4.04) h] and mean residence time [(22.27 + or - 0.52) h] were significantly prolonged (P < 0.01), as well as peak serum concentrations [(9.69 + or - 2.40) mg/L] and AUC(0-t) [(236.7 + or - 13.1) mg x L(-1) x h] were decreased markedly (P < 0.01) as compared with those of IDM regarding to portal vein. Additionally, its AUC(0-t) in peripheral blood was remarkably lower than that in Portal vein (P < 0.01). The tumor suppression observation showed that it could remarkably reduce the number of liver metastases in contrast to IDM (P < 0.05).

CONCLUSION

Colon-specific IDM-AM-3 possesses advantage of sustained release in portal vein providing some experimental basis for colon-specific delivery system applied to sustained release in the portal vein.

Lipid-core nanocapsules restrained the indomethacin ethyl ester hydrolysis in the gastrointestinal lumen and wall acting as mucoadhesive reservoirs

The aim of this work was to investigate if the indomethacin ethyl ester (IndOEt) released from lipid-core nanocapsules (NC) is converted into indomethacin (IndOH) in the intestine lumen, intestine wall or after the particles reach the blood stream. NC-IndOEt had monomodal size distribution (242 nm; PDI 0.2) and zeta potential of -11 mV. The everted rat gut sac model showed IndOEt passage of 0.16 micromol m(-2) through the serosal fluid (30 min). From 15 to 120 min, the IndOEt concentrations in the tissue increased from 6.13 to 27.47 micromol m(-2). No IndOH was formed ex vivo. A fluorescent-NC formulation was used to determine the copolymer bioadhesion (0.012 micromol m(-2)). After NC-IndOEt oral administration to rats, IndOEt and IndOH were detected in the gastrointestinal tract (contents and tissues). In the tissues, the IndOEt concentrations decreased from 459 to 5 microg g(-1) after scrapping, demonstrating the NC mucoadhesion. In plasma (peripheric and portal vein), in spleen and liver, exclusively IndOH was detected. In conclusion, after oral dosing of NC-IndOEt, IndOEt is converted into IndOH in the intestinal lumen and wall before reaching the blood stream. The complexity of a living system was not predicted by the ex vivo gut sac model.

Indomethacin-saccharin cocrystal: design, synthesis and preliminary pharmaceutical characterization

PURPOSE

To design and prepare cocrystals of indomethacin using crystal engineering approaches, with the ultimate objective of improving the physical properties of indomethacin, especially solubility and dissolution rate.

MATERIALS AND METHODS

Various cocrystal formers, including saccharin, were used in endeavours to obtain indomethacin cocrystals by slow evaporation from a series of solvents. The melting point of crystalline phases was determined. The potential cocrystalline phase was characterized by DSC, IR, Raman and PXRD techniques. The indomethacin-saccharin cocrystal (hereafter IND-SAC cocrystal) structure was determined from single crystal X-ray diffraction data. Pharmaceutically relevant properties such as the dissolution rate and dynamic vapour sorption (DVS) of the IND-SAC cocrystal were evaluated. Solid state and liquid-assisted (solvent-drop) cogrinding methods were also applied to indomethacin and saccharin.

RESULTS

The IND-SAC cocrystals were obtained from ethyl acetate. Physical characterization showed that the IND-SAC cocrystal is unique vis-à-vis thermal, spectroscopic and X-ray diffraction properties. The cocrystals were obtained in a 1:1 ratio with a carboxylic acid and imide dimer synthons. The dissolution rate of IND-SAC cocrystal system was considerably faster than that of the stable indomethacin gamma-form. DVS studies indicated that the cocrystals gained less than 0.05% in weight at 98%RH. IND-SAC cocrystal was also obtained by solid state and liquid-assisted cogrinding methods.

CONCLUSIONS

The IND-SAC cocrystal was formed with a unique and interesting carboxylic acid and imide dimer synthons interconnected by weak N-Hcdots, three dots, centeredO hydrogen bonds. The cocrystals were non-hygroscopic and were associated with a significantly faster dissolution rate than indomethacin (gamma-form).

A new entry to the synthesis of 2,3-disubstituted indoles

[reaction: see text] The Stille coupling of N-acyl-2-iodoanilines with the 1-(tributylstannyl)-1-substituted allenes affected the successive one-step formation of the 2-methyl-3-substituted indoles. Alternatively, the other type of 2-alkyl-3-substituted indoles could be synthesized in a one-pot operation, which consists of the Stille coupling reaction with the 1-(tributylstannyl)-1,3-disubstituted allenes, followed by TBAF treatment. This procedure could be applied to the synthesis of indomethacin.

Synthesis and stability of two indomethacin prodrugs

The purpose of this study was to synthesize and study the in vitro enzymatic and non-enzymatic hydrolysis of indomethacin-TEG ester and amide prodrugs. It was found that the ester conjugate 10 was comparatively stable between pH 3 and 6 (half-life>90h), with a half-life equal to 5.2h in 80% buffered plasma. In contrast, the amide conjugate 12 appeared to be stable over the entire pH range studied with the only observed degradation being cleavage of the indolic N-4-chlorobenzoyl moiety.

Modulation of MRP-1-mediated multidrug resistance by indomethacin analogues

Multidrug resistance (MDR) is a major limiting factor in the development and application of drug candidates. MDR caused by MRP-1 is known to be modulated by the nonsteroidal antiinflammatory drug indomethacin. We have synthesized and biologically evaluated a library of indomethacin analogues. The indomethacin-derived compound library was synthesized employing the Fischer-indole synthesis as the key transformation and making use of a "resin-capture-release" strategy. Sixty representative members of the library were evaluated in a cell biological cytotoxicity assay employing the MRP-1 expressing human glioblastoma cell line T98G as a model system. Nine of the 60 tested derivatives increased the doxorubicin-mediated cytotoxicity at a comparable or higher level than indomethacin itself. Analysis of these derivatives revealed an interesting structure-function relationship. Most remarkably, two substances increased the toxicity, when doxorubicin was used at clinically relevant low concentrations, at a higher degree than indomethacin.

Preparation, characterization, and tableting of a solid dispersion of indomethacin with crospovidone

A significant problem with solid dispersion (SD) systems is the difficulty in preparing dosage forms. This difficulty can be overcome using crospovidone (CrosPVP) as a carrier. A powder SD of indomethacin (IM) with CrosPVP was prepared using mechanical mixing followed by heating to temperatures below the melting point. IM and CrosPVP interacted to produce IM in an amorphous state when its concentration was <40%. The solubility of IM was improved about fourfold compared to IM crystal. The SD had good fluidity, and tablets were prepared by direct compression. Tablets with small weight variation and acceptable hardness were obtained using only 1% of magnesium stearate as excipient. The dissolution of IM from tablets was similar to that of SD powder because CrosPVP, a disintegration agent, caused the tablets to break up rapidly.

Solid dispersion particles of amorphous indomethacin with fine porous silica particles by using spray-drying method

The solid dispersion particles of indomethacin (IMC) were prepared with different types of silica, non-porous (Aerosil 200) or porous silica (Sylysia 350) by using spray-drying method. Powder X-ray diffraction analysis showed that IMC in solid dispersion particles is in amorphous state irrespective of the type of silica formulated. In DSC analysis, the melting peak of IMC in solid dispersion particles with Sylysia 350 shifted to lower temperature than that in solid dispersion particles with Aerosil 200 although the peak of each solid dispersion particles was much smaller than that of original IMC crystals. Dissolution property of IMC was remarkably improved by formulating the silica particles to the solid dispersion particles. In comparing the effect of the type of the silica particles, the dissolution rate of solid dispersion particles with Sylysia 350 was faster than that with Aerosil 200. The formulation amount of IMC did not affect on the amorphous state of IMC in the resultant solid dispersion particles in powder X-ray diffraction patterns. However, the area of the melting peak of IMC in the solid dispersion particles increased and an exothermic peak owing to recrystallization was observed with increasing the IMC content in the DSC patterns. The dissolution rate of IMC from the solid dispersion particles with Sylysia 350 was faster than that of Aerosil 200 irrespective of IMC content. In stability test, amorphous IMC in the solid dispersion particles with each silica particles did not crystallize under storing at severe storage conditions (40 degrees C, 75% RH) for 2 months, while amorphous IMC without silica easily crystallized under same conditions.

Tabletting of Solid Dispersion Particles Consisting of Indomethacin and Porous Silica Particles

We attempted to make the rapidly dissolving tablet (Tab) containing solid dispersion particles (SD) with indomethacin (IMC) and porous silica (Sylysia350) as carrier prepared by using spray-drying technique. Rapidly dissolving tablet was formulated with mannitol as a diluent and low substituted hydroxypropylcellulose (L-HPC) or partly pre-gelatinized starch (PCS) as a disintegrant. The percent dissolved from Tab (SD) was higher than that of tablet containing physical mixture (PM) at 20 min. Nearly 100% of drug in Tab (SD) was dissolved within 60 min, while the drug dissolution of Tab (PM) was not completed at the same time period. In addition, the tensile strength of Tab (SD) was much higher than that of Tab (PM). Adding L-HPC in Tab (SD) (Tab (SD-L-HPC)), the percent dissolved from Tab (SD-L-HPC) at 5 min became much higher than that from Tab (SD). The dissolution profile of IMC from Tab (SD-L-HPC) was almost the same irrespective of the compression pressure, while the tensile strength of tablet increased with increasing the compression pressure. In comparing the compaction property of these tablets by observing the ratio of residual die wall pressure (RDP) to maximum die wall pressure (MDP) (RDP/MDP), it was found that addition of L-HPC in the tablet formulation improved compactibility. In case that PCS was formulated as disintegrant, Tab (SD-PCS), similar improvement in the dissolution profile and tensile strength was observed, though the dissolution rate of IMC from Tab (SD-PCS) was slightly lower than that from Tab (SD-L-HPC) irrespective of the compression pressure.

Mg,Al layered double hydroxides with intercalated indomethacin: Synthesis, characterization, and pharmacological study

Magnesium aluminium layered double hydroxides (LDH) with a molar Mg/Al ratio of 2.0 have been prepared with intercalated indomethacin following two routes: reconstruction from a previously calcined Mg(2)Al-CO(3) LDH, and coprecipitation from the corresponding chlorides. The solids have been characterized by powder X-ray diffraction, FTIR, and (13)C CP/MAS NMR spectroscopies and thermal stability (differential thermal analysis and thermogravimetric analysis). Intercalation of the drug is attained by both routes; however, while coprecipitation leads to a single layered structure, contamination with another layered MgAl-CO(3) phase occurs by the reconstruction method. The amount of drug intercalated, as well as the height of the gallery, are larger by the coprecipitation than by the reconstruction one. The data obtained support a somewhat tilted, upwards orientation of the drug molecules forming an interdigited bilayer, in the case of the sample prepared by coprecipitation, with the carboxylate groups pointing towards the hydroxyl layers. However, in the case of the sample prepared by reconstruction, the molecules are forming a tilted, upwards monolayer. The solids prepared are stable up to 250 degrees C. Pharmacological studies in vivo show that intercalation of the drug in the LDH reduces the ulcerating damage of the drug.

Alkaline Hydrolysis as a Tool to Determine the Association form of Indomethacin in Nanocapsules Prepared with Poly(ε-Caprolactone)

To determine the association form of indomethacin in nanocapsules prepared with poly(eta-caprolactone) as polymer and a triglyceride as oil, two methods were studied. The indomethacin ethyl ester was prepared as control, which showed a higher affinity for the oil than the indomethacin. Two differently loaded nanocapsule formulations were prepared. For both formulations, a burst effect was detected using ethanol as release medium. Light scattering (PCS) and NMR analyses suggested the ethanol diffuses through the nanocapsule polymeric wall promoting the total release of indomethacin and its ester. The results showed the inability of this approach to determine the association form of indomethacin. On the other hand, the alkaline hydrolysis of indomethacin and its ester, followed by their disappearance (HPLC), were evaluated. The nanocapsule suspensions containing indomethacin or its ester were treated with 50 mM NaOH. The total disappearance of indomethacin associated with nanocapsules was determined after 2 min, whereas the ester associated with colloids was consumed during 24 h. The constant particle sizes (264 and 259 nm) during the hydrolysis reactions showed that neither the nanocapsules were dissolved nor the polymer sorbed water during the contact with NaOH aqueous solution. The ester rate hydrolysis was determined by its diffusion from the nanocapsules to the interface particle/water. Finally, the indomethacin association model considers the burst release of drug after the addition of NaOH by the formation of its carboxylate, followed by its hydrolysis in aqueous solution promoted by the excess of NaOH. The adsorption was the mechanism of indomethacin association with nanocapsules.

Microcrystallization of indomethacin using a pH-shift method

This study developed a microcrystallization process for indomethacin, a nonsteroidal anti-inflammatory drug (NSAID), using a pH-shift method in aqueous solution. The physicochemical properties of the microcrystals produced were similar to those of the standard crystalline powder in X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR) analyses, except for a lower XRD peak height and a slightly lower melting temperature (Tm) (1.5 degrees C). Phase contrast microscopy and scanning electron microscopy (SEM) showed that the indomethacin microcrystals were plate-like with a uniform size distribution (mean diameter =10.4+/-0.4 microm). In the initial phase, the dissolution rate of the indomethacin microcrystals was about 2.2 times higher than that of the standard crystalline powder. The biological activity of the indomethacin microcrystals was about 20% higher than that of the standard crystalline powder in their ability to inhibit the proliferation of colon cancer cells (HT-29).

Prediction of apparent equilibrium solubility of indomethacin compounded with silica by 13C solid state NMR

The apparent equilibrium solubility (AES) of indomethacin increased by co-grinding with silica. Change in the long- and short range disorder of indomethacin by co-grinding was examined by X-ray powder diffraction and 13C solid state NMR, respectively, to elucidate the increased AES. Since the increase in AES was particularly marked after complete disappearance of X-ray diffraction peaks, we attributed the enhanced AES primarily to the short range disorder on the molecular basis. This was confirmed by a high correlation between the standardized full width at half maximum (SFWHM) of the specific peaks observed by 13C solid state NMR and log (AES). The correlation enables the prediction of AES as well.

Ultrasound-compacted and spray-congealed indomethacin/polyethyleneglycol systems

The product obtained by ultrasound (US)-assisted compaction was compared with a solid dispersion for systems containing polyethyleneglycols (PEGs) of different molecular weights and indomethacin (IMC), at the weight ratio 9:1, obtained by traditional melting and followed by a new US-assisted spray-congealing technique. US-discharge during compaction affects crystallinity of both IMC and PEG: pure IMC changes to an amorphous form and, when in mixture with PEG, partially dissolves in the excipient: this causes an increase of the dissolution rate of the drug. Differential scanning calorimetry (DSC) thermograms do not reveal any endothermic peak associated with the melting of the drug, while X-ray diffractograms show a loss of crystallinity of both IMC and PEG in the US-compacted granules. The extent of a back-crystallisation, which reduces the dissolution rate, as a function of the ageing of the material, depends on the type of the selected PEG. When a molten IMC/PEG mixture was transformed into microspheres by an US-assisted spray-congealing technique, the behaviour at dissolution almost recalls that of US-compacted granulates and some differences are briefly discussed.

Profiling indomethacin impurities using high-performance liquid chromatography and nuclear magnetic resonance

The anti-inflammatory drug indomethacin was investigated regarding new related impurities. Therefore, related substances 2-9 were prepared by independent synthesis and physicochemically characterized. To determine indomethacin and its related substances, a new HPLC-UV method was developed and validated. Indomethacin and its impurities were eluted on a C(18) column with a mobile phase consisting of methanol and an aqueous solution of 0.2% phosphoric acid at a flow rate of 1.5 ml/min and were quantified by UV detection at 320 nm. Overall, the HPLC-UV method was simple and reliable for the detection of eight impurities in indomethacin. In addition to the HPLC-UV method, 1H nuclear magnetic resonance (NMR) was used to investigate indomethacin regarding impurities. For that purpose, related substances 2-9 were systematically added to indomethacin and investigated. The NMR method was found to be very useful for the identification of impurities in bulk substance without prior separation. Both HPLC-UV and NMR were used to analyze 38 batches of indomethacin available on the European market. The outcome was that 42% of the batches did not meet the compendial requirements although they met the specifications of current compendial methods. Some batches contained the previously undescribed impurity 8, while other batches contained by-products from two distinct synthetic routes. The methods presented herein are important contributions to the ongoing efforts to reduce impurities and therefore the risk of adverse side-effects in drugs that are no longer under patent protection.

Thiazole analogues of the NSAID indomethacin as selective COX-2 inhibitors

The carboxyl group of the NSAID indomethacin was replaced with a variety of substituted thiazoles to obtain a series of potent, selective inhibitors of COX-2. Additional substitutions were made at the 1-position and 5-position of the indole of indomethacin.

Synthesis of indomethacin analogues for evaluation as modulators of MRP activity

Synthesis of a range of indomethacin analogues, required for investigation in combination toxicity assays, bearing both N-benzyl and N-benzoyl groups, is described.

Kinetic study of the indomethacin synthesis and thermal decomposition reactions

The kinetics of indomethacin synthesis (achieved through a new method) was studied at 80 degrees C. The reaction proceeds in four steps. In the first step, by the condensation of levulinic acid with p-chlorobenzoyl-p-methoxy-phenyl-hydrazine in homogeneous acidic catalysis an intermediate is formed. In the second step, by the isomerisation of this intermediate a hydrazo compound is formed. In the third step, the isomerisation is followed by the o-benzydinic transposition of the reaction product mentioned above. In the fourth step, indomethacin is formed through a cyclization reaction. The rate constant of the indomethacin synthesis reaction was determined assuming that the cyclization reaction constitutes the rate-determining step. Spectrophotometric methods were used both in order to investigate the kinetics of the synthesis reaction and to verify the proposed mechanism. Then, a thermogravimetric study was performed on the purpose of finding out the temperature range in which indomethacin is stable. From the thermogravimetric curve kinetic parameters have been derived, using different calculation techniques.

Ester and amide derivatives of the nonsteroidal antiinflammatory drug, indomethacin, as selective cyclooxygenase-2 inhibitors

Recent studies from our laboratory have shown that derivatization of the carboxylate moiety in substrate analogue inhibitors, such as 5,8,11,14-eicosatetraynoic acid, and in nonsteroidal antiinflammatory drugs (NSAIDs), such as indomethacin and meclofenamic acid, results in the generation of potent and selective cyclooxygenase-2 (COX-2) inhibitors (Kalgutkar et al. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 925-930). This paper summarizes details of the structure-activity studies involved in the transformation of the arylacetic acid NSAID, indomethacin, into a COX-2-selective inhibitor. Many of the structurally diverse indomethacin esters and amides inhibited purified human COX-2 with ICo5 values in the low-nanomolar range but did not inhibit ovine COX-1 activity at concentrations as high as 66 microM. Primary and secondary amide analogues of indomethacin were more potent as COX-2 inhibitors than the corresponding tertiary amides. Replacement of the 4-chlorobenzoyl group in indomethacin esters or amides with the 4-bromobenzyl functionality or hydrogen afforded inactive compounds. Likewise, exchanging the 2-methyl group on the indole ring in the ester and amide series with a hydrogen also generated inactive compounds. Inhibition kinetics revealed that indomethacin amides behave as slow, tight-binding inhibitors of COX-2 and that selectivity is a function of the time-dependent step. Conversion of indomethacin into ester and amide derivatives provides a facile strategy for generating highly selective COX-2 inhibitors and eliminating the gastrointestinal side effects of the parent compound.

The control over the new obtaining procedeum of indomethacin

The synthesis of the indomethacin (1H-indole-3-acetic acid, 1(4-chlorobenzoyl)-5-methoxy-2-methyl) was achieved through a new method, which reduces some stages from the previous methods. Both the structure of the finished product and the structures of the intermediaries were investigated by chromatographic methods (TLC, chromatography on column, GC-MSD) and spectroscopic methods (UV, IR, 1H-NMR, 13C-NMR). The chromatographic and spectroscopic studies proved that these had a special analytical value and they serve to control synthesis and to identify the compounds in all the stages of the process.

Prodrugs. Part 3. 2-Formylphenyl esters of indomethacin, ketoprofen and ibuprofen and 6-substituted 2-formyl and 2-acylphenyl esters of aspirin

The synthesis and study of a novel series of potential prodrugs of indomethacin, ketoprofen, ibuprofen and aspirin are reported. 2-Formylphenyl esters of the NSAIDs, together with two 6-substituted 2-formyl and two 2-acylphenyl aspirins and 4-formylphenyl indomethacin, have been prepared. A study of their alkaline and neutral hydrolysis shows that these compounds, with the exception of 2-acetylphenyl aspirin, act as true prodrugs of the NSAIDs, giving the NSAID and acylphenol. The rates of hydrolysis and activation parameters indicate that the 2-acylphenyl esters employ an intramolecular catalytic route. The 2-formylphenyl esters were more potent as anti-inflammatory agents than the parent compounds in the carragheenan-induced paw oedema test.

Synthesis and use of iodinated nonsteroidal antiinflammatory drug analogs as crystallographic probes of the prostaglandin H2 synthase cyclooxygenase active site

The cyclooxygenase activity of the membrane protein prostaglandin H2 synthase isoform 1 (PGHS-1) is the target of the nonsteroidal antiinflammatory drugs (NSAIDs). The X-ray crystal structures of PGHS-1 in complex with the NSAIDs flurbiprofen and bromoaspirin have been determined previously [Picot, D., et al. (1994) Nature 367, 243-249; Loll, P. J., et al. (1995) Nat. Struct. Biol. 2, 637-643]. We report here the preparation and characterization of novel potent iodinated analogs of the NSAIDs indomethacin and suprofen, as well as the refined X-ray crystal structures of their complexes with PGHS-1. The PGHS-iodosuprofen complex structure has been refined at 3.5 A to an R-value of 0.189 and shows the suprofen analog to share a common mode of binding with flurbiprofen. The PGHS-iodoindomethacin complex structure has been refined at 4.5 A to an R-value of 0.254. The low resolution of the iodoindomethacin complex structure precludes detailed modeling of drug-enzyme interactions, but the electron-dense iodine atom of the inhibitor has been unambiguously located, allowing for the placement and approximate orientation of the inhibitor in the enzyme's active site. We have modeled two equally likely binding modes for iodoindomethacin, corresponding to the two principal conformers of the inhibitor. Like flurbiprofen, iodosuprofen and iodoindomethacin bind at the end of the long channel which leads into the enzyme active site. Binding at this site presumably blocks access of substrate to Tyr-385, a residue essential for catalysis. No evidence is seen for significant protein conformational differences between the iodoindomethacin and iodosuprofen of flurbiprofen complex structures.

Inactivation of prostaglandin endoperoxide synthase by acylating derivatives of indomethacin

Derivatives of the potent antiinflammatory agent and cyclooxygenase inhibitor indomethacin were synthesized in which the carboxylic acid moiety was converted into reactive acylating agents. Indomethacin imidazole (indomethacin-IM) and indomethacin N-hydroxysuccinimide (indomethacin-NHS) inactivated both the cyclooxygenase and peroxidase activities when incubated with the apo form of purified prostaglandin endoperoxide synthase (PGH synthase) at a stoichiometry of 1:1. Treatment of the inactivated enzyme with hydroxylamine at neutral pH led to recovery of all peroxidase and about 50% of the cyclooxygenase activity. Hydroxylamine did not regenerate the cyclooxygenase activity of indomethacin-inactivated protein. Reconstitution of the apoprotein with heme protected against inactivation by indomethacin-NHS. Visible spectroscopy established that indomethacin-NHS-inactivated apoenzyme had a reduced capacity to bind heme. Indomethacin-NHS also substantially protected the apoenzyme from cleavage at the trypsin-sensitive Arg277 site. Incubation of [2-14C]indomethacin-NHS with PGH synthase led to incorporation of radioactivity into the protein, but no adduct was detected by reversed-phase HPLC, suggesting it was unstable to the chromatographic conditions. Incubation of indomethacin-NHS with apoprotein followed by HPLC analysis led to the formation of greater amounts of the hydrolysis product indomethacin than did similar treatment of holoprotein. The results suggest that indomethacin-IM and indomethacin-NHS covalently and selectively label PGH synthase near the heme binding site, leading to loss of both catalytic activities of the enzyme.

Design, synthesis and antiinflammatory activity of a new indomethacin ester. 2-[N-[3-(3-(piperidinomethyl)phenoxy)propyl]carbamoylmethylthio]ethyl 1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole-3-acetate

A novel indomethacin ester prodrug, 2-[N-[3-(3-(piperidinomethyl)phenoxy)propyl]carbamoylmethylthio ]ethyl 1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetate (1) was prepared from a new histamine H2-receptor antagonist, N-[3-(3-(piperidinomethyl)phenoxy)propyl]-2-(2-hydroxyethylthio )acetamide (2) and indomethacin (3). The compound 1 was shown to be essentially similar to 3 in its antiinflammatory action and to almost completely inhibit carrageenin-induced hind-paw edema in the rat at a very high dose of 230 mg/kg (280 mumol/kg), which is comparable to that of 100 mg/kg (280 mumol/kg) of 3, without producing gastric lesions. On a molar basis, the acute gastric lesioning properties of 1 were near one-hundred times less than those of 3, resulting in over a twenty-fold improvement in the ratio of antiedema activity to ulcerogenicity. The effect of the co-administration of histamine H2-receptor antagonists on antiedema activity and ulcerogenicity caused by 3 is also discussed.

Acyloxyamines as prodrugs of anti-inflammatory carboxylic acids for improved delivery through skin

An N,N-dialkylhydroxylamine derivative of indomethacin has been synthesized. It has been shown to improve the delivery of indomethacin through mouse skin (compared to indomethacin itself) by a factor of two, to be more effective than indomethacin in inhibiting thermal inflammation (two to three times) in animal models, but to be only as effective as indomethacin in inhibiting UV-B radiation erythema in human volunteers.

Glycerides as prodrugs. 3. Synthesis and antiinflammatory activity of [1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetyl]glycerides (indomethacin glycerides)

Mono-, bis-, and tris[1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetyl]glycerides and 1,3-dialkanoyl-2-[1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetyl]glycerides were synthesized and evaluated for antiinflammatory activity in the rat paw carrageenin edema assay. Three of the most active compounds (4, 18a, and 18e) were tested in the rat adjuvant arthritis model and found to be essentially equivalent in activity to indomethacin. On a molar basis, the acute gastric irritating properties of 18a and 18e were seven to eight times less than indomethacin, resulting in a 2.5- to 3-fold improvement in the ratio of antiedema activity to ulcerogenicity.

Polymorphism of indomethacin. Part I. Preparation of polymorphic forms of indomethacin

Technologically useful methods of preparing defined polymorphic forms of indomethacin (especially gemma-form) have been described. The influence of various crystallization parameters on the formation of individual form of indomethacin have been discussed.