Recent Advances in the Synthesis of Ibuprofen and Naproxen

Herein, we review the recent progress in the synthesis of representative nonsteroidal anti-inflammatory drugs (NSAIDs), ibuprofen and naproxen. Although these drugs were discovered over 50 years ago, novel practical and asymmetric approaches are still being developed for their synthesis. In addition, this endeavor has enabled access to more potent and selective derivatives from the key frameworks of ibuprofen and naproxen. The development of a synthetic route to ibuprofen and naproxen over the last 10 years is summarized, including developing methodologies, finding novel synthetic routes, and applying continuous-flow chemistry.

Biocatalytic Approach for Direct Esterification of Ibuprofen with Sorbitol in Biphasic Media

Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) introduced in the 1960s and widely used as an analgesic, anti-inflammatory, and antipyretic. In its acid form, the solubility of 21 mg/L greatly limits its bioavailability. Since the bioavailability of a drug product plays a critical role in the design of oral administration dosage, this study investigated the enzymatic esterification of ibuprofen as a strategy for hydrophilization. This work proposes an enzymatic strategy for the covalent attack of highly hydrophilic molecules using acidic functions of commercially available bioactive compounds. The poorly water-soluble drug ibuprofen was esterified in a hexane/water biphasic system by direct esterification with sorbitol using the cheap biocatalyst porcine pancreas lipase (PPL), which demonstrated itself to be a suitable enzyme for the effective production of the IBU-sorbitol ester. This work reports the optimization of the esterification reaction.

From Combinations to Single-Molecule Polypharmacology-Cromolyn-Ibuprofen Conjugates for Alzheimer's Disease

Despite Alzheimer's disease (AD) incidence being projected to increase worldwide, the drugs currently on the market can only mitigate symptoms. Considering the failures of the classical paradigm "one target-one drug-one disease" in delivering effective medications for AD, polypharmacology appears to be a most viable therapeutic strategy. Polypharmacology can involve combinations of multiple drugs and/or single chemical entities modulating multiple targets. Taking inspiration from an ongoing clinical trial, this work aims to convert a promising cromolyn-ibuprofen drug combination into single-molecule "codrugs." Such codrugs should be able to similarly modulate neuroinflammatory and amyloid pathways, while showing peculiar pros and cons. By exploiting a linking strategy, we designed and synthesized a small set of cromolyn-ibuprofen conjugates (4-6). Preliminary plasma stability and neurotoxicity assays allowed us to select diamide 5 and ethanolamide 6 as promising compounds for further studies. We investigated their immunomodulatory profile in immortalized microglia cells, in vitro anti-aggregating activity towards Aβ42-amyloid self-aggregation, and their cellular neuroprotective effect against Aβ42-induced neurotoxicity. The fact that 6 effectively reduced Aβ-induced neuronal death, prompted its investigation into an in vivo model. Notably, 6 was demonstrated to significantly increase the longevity of Aβ42-expressing Drosophila and to improve fly locomotor performance.

Dexibuprofen amide derivatives as potential anticancer agents: synthesis, in silico docking, bioevaluation, and molecular dynamic simulation

BACKGROUND

The amide derivatives of nonsteroidal anti-inflammatory drugs have been reported to possess antitumor activity. The present work describes the synthesis of dexibuprofen amide analogues (4a-j) as potential anticancer agents.

METHODS

The title amides (4a-j) were obtained by simple nucleophilic substitution reaction of dexibuprofen acid chloride with substituted amines in good yield and chemical structures were confirmed by FTIR, 1H NMR, 13C NMR and mass spectral data.

RESULTS

The brine shrimp lethality assay results showed that all of the synthesized compounds are non-toxic to shrimp larvae. The inhibitory effects on tumor growth were evaluated and it was observed that N-(2,5-dichlorophenyl)-2-(4-isobutylphenyl) propionamide (4e) and N-(2-chlorophenyl)-2-(4-isobutylphenyl) propionamide (4g) exhibited excellent antitumor activity compared to all other derivatives. The compound 4e bearing 2,5-dichloro substituted phenyl ring and 4g possesses 2-chloro substituted phenyl ring exhibited 100% inhibition of the tumor growth. The anticancer activity was evaluated against breast carcinoma cell line (MCF-7) and it was observed that derivative 4e exhibited excellent growth inhibition of cancer cells with IC50 value of 0.01±0.002 µm, which is better than the standard drugs. The docking studies against breast cancer type 1 susceptibility protein BRCA1 (PDBID 3K0H) exhibited good binding affinities, which are in good agreement with the wet lab results. The compounds 4e and 4g showed the binding energy values of -6.39 and -6.34 Kcal/mol, respectively. The molecular dynamic (MD) simulation was also carried out to evaluate the residual flexibility of the best docking complexes of compounds 4e and 4g. The MD simulation analysis assured that the 4e formed a more stable complex with the target protein than the 4g. The synthesized amide derivatives exhibited were devoid of gastrointestinal side effects and no cytotoxic effects against human normal epithelial breast cell line (MCF-12A) were found.

CONCLUSION

Based upon our wet lab and dry lab findings we propose that dexibuprofen analogue 4e may serve as a lead structure for the design of more potent anticancer drugs.

Conformational study of the electronic interactions and nitric oxide release potential of new S‑nitrosothiols esters derivatives of ibuprofen, naproxen and phenyl acids substituted (SNO-ESTERS): Synthesis, infrared spectroscopy analysis and theoretical calculations

The conformational study on the new S‑nitrosothiols esters (SNO-ESTERS): para-substituted (X = H, OMe, Cl and NO₂) S‑nitrosothiol derivatives 2‑methyl‑2‑(sulfanyl)propyl phenylacetates (R1), 2‑(4‑isobutylphenyl)propanoate (ibuprofen, R2), and 2‑(4‑isobutylphenyl)propanoate of 2‑methyl‑2‑(nitrososulfanyl)propyl (naproxen, R3) was performed using infrared spectroscopy (IR) in solvents with increasing polarity (CCl₄, CH₃Cl, and CH₃CN), and theoretical calculations, to determine the preferential conformer and the potential of these compounds to release nitric oxide (NO). S‑Nitrosothiols were synthesized by esterification reactions, using chlorides of the corresponding carboxylic acids, with good yields (~60%). IR results showed that these compounds presented only one conformation, and the experimental data were supported by the theoretical results obtained by density functional theory (DFT) calculations using the 6311+G (2df, 2p) basis set. The calculations revealed that all S‑nitrosothiols presented one preferential anticlinal (ac) geometric conformation, which agrees with the data obtained experimentally in CCl₄. These conformers are stabilized by intramolecular hydrogen bonds. Examination of the geometry with regard to the RSNO group revealed that these compounds are preferentially in the trans (anti) conformation. The calculation of the orbital interactions using the Natural Bond Orbital (NBO) method showed that the n_O(NO) → σ_(SN)^∗ hyper-conjugative interaction increases the SN bond length. The strong n_S → π_(NO)^∗ interaction and electronic delocalization induces a partial π character to the SN bond. The weak σ_SN bond indicates strong delocalization of the electron pair in O (NO) by the n_O(NO) → σ_(SN)^∗ interaction, thereby increasing the capacity of NO release from SNO-ESTERS.

Synthesis and antinociceptive evaluation of bioisosteres and hybrids of naproxen, ibuprofen and paracetamol

The aim of this work was to design, synthesize and characterize the potential anti-nociceptive and anti-inflammatory activities of a new series of bioisosteres and hybrids from known non-steroidal anti-inflammatory drugs (NSAIDs). The compounds 4-(acetylamino)phenyl (2S)-2-(6-methoxy-2-naphthyl)propanoate (GUF-1) and 4-(acetylamino)phenyl 2-(R,S)-(4-isobutylphenyl)propanoate (GUF-2) were synthesized as hybrids (also known as heterodimers); whereas those named 2-(R,S)-(4-isobutylphenyl)-N-1H-tetrazol-5-ylpropanamide (GUF-3), (2S)-2-(6-methoxy-2-naphthyl)-N-1H-tetrazol-5-ylpropanamide (GUF-4), [2-(R,S)-N-hydroxy-2-[4-(2-methylpropyl)phenyl]propanamide] (GUF-5), and (2S)-N-hydroxy-2-(6-methoxy-2-naphthyl)propanamide (GUF-6) were synthesized as bioisosteres of the NSAIDs paracetamol, ibuprofen, and naproxen, respectively. All these compounds were characterized by spectroscopic and spectrometric analysis. Antinociceptive activity of GUF-1 to GUF-6 was evaluated using the formalin test in rats. Pharmacological responses of GUF-1, GUF-2 (hybrids), and GUF-5 (bioisostere) demonstrated significant antinociceptive effects; thus these compounds were assayed in an inflammation test like carrageenan-induced paw oedema in rats. Complete molecular docking of cyclooxygenase and the GUF-1 and GUF-2 hybrids showed high docking scores, compared to the reference drugs. Our data demonstrate that compounds GUF-1, GUF-2, and GUF-5 possesses antinociceptive and antiinflammatory activities resembling and improving those known for the traditional NSAIDs, paracetamol, naproxen and ibuprofen.

New derivatives of aryl-propionic acid. Synthesis and biological evaluation

AIM

To design new derivatives of aryl-propionic acid with potential antibacterial and antioxidant activity.

MATERIAL AND METHODS

New hydrazone of ibuprofen (2-(4-isobutylphenyl)propionic acid) have been synthesized by reaction of ethyl ester of ibuprofen with hydrazine hydrate and then condensation of corresponding hydrazide with various aromatic aldehydes.

RESULTS

The synthesized compounds were screened for their antibacterial activity against Gram positive (Staphylococcus aureus ATCC 25923, Sarcinalutea ATCC 9341, Bacillus cereus ATCC 14579, Bacillus subtilis) and Gram negative bacterial strains (Escherichia coli ATCC 25922). Some of them were found to have good antibacterial activity. The antioxidant activity of these compounds was also tested using the total antiox idant capacity test.

CONCLUSIONS

The chemical modulations performed on ibuprofen structure have a good influence on the biological activity of the synthesized compounds.

Nitrooxyethylation reverses the healing-suppressant effect of Ibuprofen

Nonsteroidal antiinflammatory drugs like ibuprofen impede tissue repair by virtue of retarding inflammation. The present study was undertaken to explore if linking of nitrooxyethyl ester to ibuprofen reverses its healing-depressant propensity. Nitrooxyethyl ester of ibuprofen (NOE-Ibu) was synthesized in our laboratory through a well-established synthetic pathway. NOE-Ibu was screened for its influence on collagenation, wound contraction and epithelialization phases of healing, and scar size of healed wound in three wound models, namely, incision, dead space, and excision wounds. Besides, its influence on the oxidative stress (levels of GSH and TBARS) was also determined in 10-day-old granulation tissue. NOE-Ibu was further screened for its antiinflammatory activity in rat paw edema model. NOE-Ibu promoted collagenation (increase in breaking strength, granulation weight, and collagen content), wound contraction and epithelialization phases of healing. NOE-Ibu also showed a significant antioxidant effect in 10-day-old granulation tissue as compared to ibuprofen. Results vindicate that the esterification of ibuprofen with nitrooxyethyl group reverses the healing-suppressant effect of ibuprofen. The compound also showed equipotent antiinflammatory activity as ibuprofen.

Synthesis and biological activities of novel dexibuprofen tetraacetylriboflavin conjugates

A series of novel dexibuprofen derivatives covalently linked via alkylene spacers of variable length to tetraacetylated riboflavin have been developed. The target compounds became accessible by reaction of the chloromethyl ester of dexibuprofen with tetraacetylriboflavin (compound 7) or by synthesis of the appropriate N3-(omega-iodoalkyl)-2',3',4',5'-Tetraacetylriboflavin followed by treatment with dexibuprofen (derivatives 8-11), respectively. Biological screening revealed that the target compounds exhibit antiproliferative effects on MCF-7 breast cancer and HT-29 colon carcinoma cells with IC50 values in the range of 8-15 microM. Enzymatic studies on human platelets indicated significant COX-1 inhibitory activities of the target compounds.

Pharmacological activity and hydrolysis behavior of novel ibuprofen glucopyranoside conjugates

Novel ester prodrugs (II, III and IV) of ibuprofen (I) were synthesized using alpha-methyl, ethyl and propyl glucopyranoside as promoieties and tested for their anti-inflammatory, analgesic and ulcerogenic activities. Study of their chemical hydrolysis in aqueous buffer (pH 3.0-10.0) showed that these compounds acted as true prodrugs of ibuprofen, giving the ibuprofen and alkyl glucopyranoside. Additionally, all the derivatives studied did cleave rapidly inside the biological system and on oral administration did elicit a pharmacological profile quite similar to that of ibuprofen, but, unlike this drug, they displayed reduced gastric ulceration. In conclusion, these alkyl glucopyranoside esters have promising properties as prodrugs for oral delivery of ibuprofen.

Design and study of some novel ibuprofen derivatives with potential nootropic and neuroprotective properties

Six novel ibuprofen derivatives and related structures, incorporating a proline moiety and designed for neurodegenerative disorders, are studied. They possess anti-inflammatory properties and three of them inhibited lipoxygenase. One compound was found to inhibit cyclooxygenase (COX)-2 production in spleenocytes from arthritic rats. The HS-containing compounds are potent antioxidants and one of them protected against glutathione loss after cerebral ischemia/reperfusion. They demonstrated lipid-lowering ability and seem to acquire low gastrointestinal toxicity. Acetylcholinesterase inhibitory activity, found in two of these compounds, may be an asset to their actions.

Synthesis and study of controlled release of ibuprofen from the new acrylic type polymers

New acrylic type polymeric systems having degradable ester bonds linked to ibuprofen were synthesized and evaluated as materials for drug delivery. Methacryloyloxy(2-hydroxy)propyl-4-isobutyl-alpha-methylphenyl acetate (MOPE), a new methacrylic derivative of ibuprofen in which the drug is separated from the methacrylic backbone by an oxy(2-hydroxy)propylene spacer arm and hydrolytically labile ester bond, was synthesized from reaction of glycidyl methacrylate with ibuprofen. The resulting drug containing monomer was copolymerized with methacrylamide, 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidone or n-butyl methacrylate by free radical polymerization method in N,N-di-methylformamide (DMF) solution, utilizing azobisisobutyronitrile as initiator at the temperature range 65-70 degrees C. The obtained polymers were characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. Gel permeation chromatography (GPC) was used for determination of average molecular weights of drug-polymer conjugates and showed that the polydispersity indices of the polymers are in the range of 1.9-2.3. Drug release studies were performed by hydrolysis in buffered solutions (pH 1 and 8) at 37 degrees C. Detection of hydrolysis by UV spectroscopy at selected interval showed that the drug can be released by selective hydrolysis of the ester bond at the side of drug moiety. The release profiles indicated that the hydrolytic behavior of polymeric prodrugs is strongly based on the hydrophilicity of polymer and the pH of the hydrolysis solution. The hydrophilic polymers containing ibuprofen were hydrolyzed in buffer solutions rather than the hydrophobic polymers.

Preparative method ofR-(−)-ibuprofen by diastereomer crystallization

The economic and effective method for preparation of R-(-)-ibuprofen by diastereomer crystallization was developed. R-(-)-ibuprofen was resolved from racemic ibuprofen by forming R-(-)-ibuprofen-R-(+)-alpha-methylbenzylamine diastereomeric salt with R-(+)-alpha(-methylbenzylamine and crystallization. The purity of R-(-)-ibuprofen-R-(+)-alpha-methylbenzylamine diastereomeric salt was tested and confirmed using HPLC and 1H-NMR method. The pure diastereomeric salt collected from repeated recrystallization was further fractionated by liquid-liquid extraction to the pure enantiomer without racemization. R-(-)-ibuprofen was recovered producing overall yield of 2.4% with the purity more than 99.97%.

Synthesis, properties and microemulsion formulation of ibuprofen eugenol ester

Ibuprofen-eugenol ester (IEE), a highly lipophilic compound, was synthesized from ibuprofen in order to reduce the common side effects induced by this classic anti-inflammatory drug. IEE was isolated as an amorphous whitish solid with a melting point at 40.2 +/- 0.1 degrees C, whose structure was confirmed by IR, 1H NMR and MS spectra. The hydrolysis results showed that the ester was stable over a wide pH range from 1.1-9.96. However, it could be hydrolyzed easily by enzymes from rat plasma and rat liver homogenate. A pharmaceutically acceptable microemulsion system was presented and characterized in terms of stability, droplet size distribution (DSD) and their solubilization capacity for IEE. The solubility of IEE in the optimized microemulsion formulation was about 21,000 times higher than that in water. The AUC of ibuprofen from the prodrug showed a remarkable increase compared to oral ibuprofen suspension. These results suggest that synthesizing the ibuprofen prodrug was justified and the presented microemulsion system might be a promising oral dosage form for poorly water-soluble drugs.

Dynamic kinetic resolution: alternative approach in optimizing S-ibuprofen production

A lipase catalysed enantioselective hydrolysis process under in situ racemization of the remaining (R)-ibuprofen ester substrate with sodium hydroxide as the catalyst was developed for the production of S-ibuprofen from (R,S)-ibuprofen ester in isooctane. Detailed investigations on parameters study indicated that 0.5 M NaOH, addition of 20% (v/v) co-solvent (dimethyl sulphoxide), operating temperature of 45 degrees C, and 40 mmol/L substrate gave 86% conversion and 99.4% optical purity of S-ibuprofen in dynamic kinetic resolution. Meanwhile, in common enzymatic kinetic resolution process, only 42% conversion of the racemate and 93% enantiomeric excess of the product was obtained which are of lower values as compared to dynamic kinetic resolution. The S-ibuprofen produced during each process was evaluated and approximately 50% increment in concentration of S-acid product was produced when dynamic kinetic resolution was applied into the process.

Preparation of ibuprofen-loaded liquid suppository using eutectic mixture system with menthol

To prepare an ibuprofen-loaded liquid suppository using eutectic mixture with menthol, the effects of menthol and poloxamer 188 (P 188) on the aqueous solubility of ibuprofen were investigated. The physicochemical properties such as gelation temperature, gel strength and bioadhesive force of various formulations composed of ibuprofen, menthol and P 188 were investigated. Then, the pharmacokinetic study of ibuprofen delivered by the liquid suppositories composed of P 188 and menthol were then performed. In the absence of P 188, the solubility of ibuprofen increased until the ratio of menthol to ibuprofen increased from 0:10 to 4:6 followed by an abrupt decrease in solubility above the ratio of 4:6, indicating that four parts of ibuprofen formed eutectic mixture with six parts of menthol. In the presence of P 188, the solutions with the same ratio showed abrupt increase in the solubility of ibuprofen. Furthermore, the solution with ratio of 4:6 showed more than 2.5- and 6-fold increase in the solubility of ibuprofen compared with that without additives and that without menthol, respectively. The poloxamer gel with menthol/ibuprofen ratio of 1:9 and higher than 15% poloxamer 188 showed the maximum solubility of ibuprofen, 1.2mg/ml. Ibuprofen increased the gelation temperature and weakened the gel strength and bioadhesive force of liquid suppositories. However, menthol did the opposite due to forming the eutectic mixture with ibuprofen. The ibuprofen-loaded liquid suppository [P 188/menthol/ibuprofen (15/0.25/2.5%)] with the maximum ibuprofen solubility of 1.2mg/ml was administered easily to the anus and to remain at the administered site without leakage after the dose. Furthermore, it gave significantly higher initial plasma concentrations, Cmax and AUC of ibuprofen than did solid suppository, indicating that the drug from poloxamer gel could be more absorbed than that from solid one in rats. Thus, the liquid suppository system with P 188 and menthol, a more convenient and effective rectal dosage form for ibuprofen will be expected to enhance the rectal bioavailability of ibuprofen.

Melt solidification technique: incorporation of higher wax content in ibuprofen beads

The purpose of this study was to achieve incorporation of a higher amount of wax during the preparation of ibuprofen beads by a melt solidification technique for better integrity and prolonged drug release by using a combination of waxes. A mixture of cetyl alcohol (CA) and palmitic acid (PA) was used to improve the matrix integrity and drug release. The effect of variables such as CA, PA, and speed of agitation were studied using 3(3) factorial design. Yield, crushing strength, and drug release were analyzed using response surface methodology. The in vitro dissolution test did not show any significant improvement in the drug release. Scanning electron microscopy (SEM) showed that beads were spherical with a smooth surface, but after dissolution became rough and porous. Differential scanning calorimetry (DSC) studies showed that different solidification and erosion properties of waxes are responsible for the inability of waxes to retard drug release even at higher concentration.

Synthesis of precursor of anti-inflammatory agents by using highly reactive zinc

Highly reactive zinc metal was prepared by electrolysis of a N,N-dimethylformamide (DMF) solution containing naphthalene and a supporting electrolyte in a one-compartment cell fitted with a platinum cathode and a zinc anode. This highly reactive electrogenerated zinc (EGZn/Naph) was used for transformation of ethyl 2-bromoacrylate into the corresponding organozinc compound, which can not be achieved by the use of usual zinc metals. Reaction of the organozinc compounds thus prepared with various aryl halides in the presence of 5 mol% of palladium catalyst gave the corresponding cross-coupling products in high yields. These cross-coupling reactions were successfully applied to a synthesis of the precursor of anti-inflammatory agents such as ibuprofen, naproxen, cicloprofen and suprofen.

[Synthesis of (+/-) ibuprofen sugar derivatives]

AIM

(+/-) Ibuprofen sugar derivatives were prepared in order to decrease side-effects and increase bioavailability of (+/-) ibuprofen.

METHODS

The synthesis of derivatives were performed using 1,2:3, 4-di-O-isopropylidene-beta-D-galactopyranose, 1,3,4,5-tetra-O-acetyl-2-deoxy-2-amino-beta-D-gluctopyranose, 3,4 6-tri-O-acetyl-2-deoxy-2-N-acetyl-beta-D-gluctosylamine and 2,3,6,2',3',4',6'-hepta-O-acetyl-beta-D-lactosylamine as glycosyl donors, respectively. Target products (4, 7, 12a, 12b, 13) were obtained after deprotection.

RESULTS

Five compounds (4, 7, 12a, 12b, 13) were synthesized as new compounds. The structures of all objective compounds were confirmed by 1HNMR, 13CNMR, HMQC, COSY, IR and MS.

CONCLUSION

It was found that 12a showed better anti-inflammatory activity than (+/-) ibuprofen.

Bifunctional constructs of aspirin and ibuprofen (non-steroidal anti-inflammatory drugs; NSAIDs) that express antibacterial and alkylation activities

Ibuprofen and aspirin are two common non-steroidal anti-inflammatory drugs (NSAIDs). Both NSAIDs have a carbonyl carbon [-C(O)-], which was utilized to attach a nitrogen mustard (N-mustard) ester group or a tripeptide group. The tripeptide consisted of a L-Gly-D-Ala-D-Ala sequence, where D-Ala-D-Ala is the reactive site for antibacterial activity and L-Gly serves as a linker to the NSAID carrier drug. The aspirin tripeptide and N-mustard show significant antibacterial activity at >or=5.0 x 10(-5) M against penicillin-susceptible or -resistant Escherichia coli. The partition coefficients (log Kow)log P of aspirin and ibuprofen tripeptide drugs were -1.05 and 2.23, respectively. The NSAIDs served as carrier drugs of the N-mustard group which expressed alkylation activity directed towards the nucleophilic primary amine of p -chloroaniline. Hydrolysis of the N-mustard agents yielded the parent structure of aspirin (or ibuprofen) and an N-mustard moiety, 2-[bis(2-chloroethyl)amino]ethanol. The (log Kow)log P for the N-mustard structures of aspirin and ibuprofen were 2.61 and 5.63, respectively. The (log Kow)log P value of 2-[bis(2-chloroethyl)amino]ethanol was 0.56. Fluorescamine was utilized to determine unreacted p -chloroaniline at known time intervals, which permitted calculation of rate constants and rate equations. The aspirin N-mustard agent expressed strong antibacterial activity against a penicillin-resistant bacteria and first-order alkylation kinetics. The ibuprofen N-mustard and 2-[bis(2-chloroethyl)amino]ethanol followed second-order alkylation kinetics. All N-mustard and tripeptide compounds showed zero violations of the Rule of 5. Values of TPSA (molecular polar surface area), C log P and molecular dipoles were calculated.

Comparison of dissolution profiles of Ibuprofen pellets

In this work we use both model dependent and independent techniques to assess the difference between dissolution profiles in which ibuprofen, in the form of uncoated pellets, is used as a model drug. The choice of a proper regression function, the relevance of the estimated parameters and the influence of the choice of dissolution points in the assessment of differences is discussed. The results obtained via mean dissolution times (MDT) and fit-factors (f(1) and f(2)) are also discussed and a non-quantitative method based on profiles correlation with graphical representation (concentration vs. concentration and rate vs. rate) presented. The tested methods discriminate similarly between curves, although not in all cases, but those based on modeling, MDT and fit-factors have shown to be less informative than the correlation approach.

Fast dispersible ibuprofen tablets

Fast dispersible tablets disintegrate either rapidly in water, to form a stabilized suspension, or disperse instantaneously in the mouth to be swallowed without the aid of water. A direct compression method was used to prepare these two types of tablets containing coated ibuprofen as a high dosed model drug. The properties of the water dispersible tablet, such as porosity, hardness, disintegration time and increase in viscosity after dispersion, were investigated. The selected tablet formulation, containing 26% galactomannan and 5% crospovidone, disintegrates before the galactomannan starts to swell. These tablets disperse in water within 40 s and show a crushing strength of 95 N. To develop an orodispersible tablet, a rotatable central composite design was applied to predict the effects of the quantitative factors mannitol and crospovidone as well as compression force on the characteristics of the tablet. Special emphasis was paid to the development of a wetting test, replacing the normal disintegration method. An optimum tablet formulation, containing 34% mannitol and 13% crospovidone, provides a short wetting time of 17 s and a sufficient crushing strength of 40 N. In conclusion, fast dispersible tablets with acceptable hardness and desirable taste could be prepared within the optimum region.

Synthesis and characterization of water-soluble hydroxybutenyl cyclomaltooligosaccharides (cyclodextrins)

We have examined the synthesis of hydroxybutenyl cyclomaltooligosaccharides (cyclodextrins) and the ability of these cyclodextrin ethers to form guest-host complexes with guest molecules. The hydroxybutenyl cyclodextrin ethers were prepared by a base-catalyzed reaction of 3,4-epoxy-1-butene with the parent cyclodextrins in an aqueous medium. Reaction byproducts were removed by nanofiltration before the hydroxybutenyl cyclodextrins were isolated by co-evaporation of water-EtOH. Hydroxybutenyl cyclodextrins containing no unsubstituted parent cyclodextrin typically have a degree of substitution of 2-4 and a molar substitution of 4-7. These hydroxybutenyl cyclodextrins are randomly substituted, amorphous solids. The hydroxybutenyl cyclodextrin ethers were found to be highly water soluble. Complexes of HBen-beta-CD with glibenclamide and ibuprofen were prepared and isolated. In both cases, the guest content of the complexes was large, and a significant increase in the solubility of the free drug was observed. Dissolution of the complexes in pH 1.4 water was very rapid, and significant increases in the solubility of the free drugs were observed. Significantly, after reaching equilibrium concentration, a decrease in the drug concentration over time was not observed.

A new class of ibuprofen derivatives with reduced gastrotoxicity

A new series of nonsteroidal antiinflammatory drugs (NSAIDs) obtained by linking ibuprofen to selected furoxan moieties and to related furazans were synthesized and tested for their antiinflammatory, antiaggregatory, and ulcerogenic properties. All the derivatives are endowed with antiinflammatory activity comparable to that of ibuprofen, but, unlike this drug, they display reduced acute gastrotoxicity. The masking of the ibuprofen-free carboxylic group seems to be principally at the basis of this reduced topical irritant action. The two furoxan derivatives 8 and 9 also trigger potent antiaggregatory effects, principally as a consequence of their NO-donor ability.

Synthesis and hydrolytic behaviour of glycerol-1,2-diibuprofenate-3-nitrate, a putative pro-drug of ibuprofen and glycerol-1-nitrate

Nitroxylated derivatives of non-steroidal anti-inflammatory drugs appear to offer protection against the gastrotoxicity normally associated with non-steroidal anti-inflammatory drugs, ostensibly via local production of nitric oxide. A diester of ibuprofen and glycerol-1-mononitrate has been prepared via the condensation of ibuprofen with 3-bromopropan-1,2-diol, followed by silver-(I)-nitrate-mediated nitroxylation. The release of ibuprofen from this diester has been studied in a simulated gastric fluid model with direct analysis by reverse-phase HPLC, using an acetonitrile-water (80%:20%) mobile phase containing trifluoroacetic acid (0.005%). n-Propyl ibuprofen was found to undergo pH-dependent hydrolysis, ranging from negligible hydrolysis at pH 5 to 52% hydrolysis at pH 3, over a 2-h period in this model. The ibuprofen-glycerol mononitrate diester was subjected to the most vigorous model hydrolytic conditions and was found to undergo 50 % hydrolysis during the study period. This study shows that pro-drugs of ibuprofen and glycerol mononitrate can be obtained, and can undergo degradation to the parent drugs under conditions simulating those likely to be encountered in the stomach.

Chiral recognition between a substituted cyclooctatetraene dianion and a half crown ether substituted with ibuprofen

(S)-Verbenol was substituted onto cyclooctatetraene (COT) via an ether linkage. In tetrahydrofuran (THF), Cs(+) or Na(+) counterions are tightly ion associated with the verbenoxy-COT dianion. A cosolvent, consisting of an ibuprofen unit connected to a half crown ether, was added to the verbenoxy-COT(2)(-),M(+)(2) solutions. The intimate interaction between the chiral cosolvent (ibuprofoxymethoxyethoxyethane) and the ion-associated counterion (either Na(+) or Cs(+)) forces a chiral recognition between the verbenoxy moiety and the ibuprofoxy moiety. When a molar excess of the cosolvent is present in the dianion THF solution, separation of the cosolvent associated with the verbenoxy-COT(2)(-),M(+)(2) complex from the uncomplexed cosolvent allows partial resolution of the enantiomers of ibuprofoxymethoxyethoxyethane.

Enantioselective synthesis of (S)-ibuprofen ester prodrug in cyclohexane by Candida rugosa lipase immobilized on Accurel MP1000

An enantioselective esterification process was developed for the synthesis of 2-N-morpholinoethyl (S)-ibuprofen ester prodrug from racemic ibuprofen by using Candida rugosa lipase immobilized on Accurel MP1000 in cyclohexane. Compared with the performance of Lipase MY, the immobilized lipase possesses a higher enzyme activity and thermal stability, but with a slightly suppressed enantioselectivity. A kinetic model was proposed and confirmed from experiments, for the simulation of time-course conversions of both enantiomers at various combinations of substrate concentrations in a batch reactor. Preliminary results of employing the proposed model and the immobilized lipase in a continuous packed-bed reactor were also reported and discussed.

Synthesis, chromatographic resolution and chiroptical properties of carboxyibuprofen stereoisomers: major metabolites of ibuprofen in man

The chromatographic resolution of the four stereoisomers of carboxy-ibuprofen, a major metabolite of ibuprofen in man, was achieved using a Chiralpak AD chiral stationary phase (CSP) (J.T. Baker, Milton, Keynes, UK). The elution order of the stereoisomers was determined to be 2'S,2R;2'R,2R;2'R,2S;2'S,2S by a combination of stereoselective synthesis of diastereoisomeric mixtures and analysis of the two diastereoisomers isolated from human urine following the administration of (S)-ibuprofen. The individual stereoisomers were isolated by semipreparative chiral phase chromatography and characterized by circular dichroism spectroscopy.

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 pharmacokinetic behaviour of ester derivatives of 4-isobutylphenyl-2-propionic acid (Ibuprofen) with end-hydroxylated poly(N-vinyl pyrrolidinone) and poly(N-acryloyl morpholine) oligomers

Four derivatives of 4-isobutylphenyl-2-propionic acid (Ibuprofen), in which the drug was bound by ester linkages to poly(ethylene glycols) (PEG 2000-I), monomethoxy poly(ethylene glycols) (PEG 1900-I), poly(N-vinyl pyrrolidinone) (PVP-I) and poly(N-acryloyl morpholine) (PACM-I), all having approximatively the same number average molecular weight (Mn congruent equal to 2000), were prepared and tested for their pharmacokinetic properties after oral administration. It was found that the two end-hydroxylated amphiphilic oligomers of polyvinylic structure, PACM and PVP, whose physico-chemical properties are comparable to those of PEGs especially as regards solvent affinity, have in principle a similar potential as promoieties for preparing oligomeric prodrugs.

Synthesis of the cholesteryl ester prodrugs cholesteryl ibuprofen and cholesteryl flufenamate and their formulation into phospholipid microemulsions

Phospholipid micoremulsions have been suggested as a drug-delivery system for hydrophobic compounds. In this study hydrophobicity was achieved by derivatizing with cholesterol. Cholesteryl ibuprofen (3) and cholesteryl flufenamate (4) were synthesized. 3 was isolated as an amorphous, white solid with a melting range of 114-120 degrees C. 4 was isolated as a crystalline, white solid with a melting range of 145-148 degrees C. The proposed structures of 3 and 4 were supported by IR, NMR, MS, and organic microanalysis. Phospholipid:cholesteryl ester microemulsions were prepared by the addition of a 1-propanol solution of the cholesteryl ester, other lipids, and phospholipid to a rapidly mixing KCl/KBr solution. The hydrophobic phase was modified by the addition of cholesteryl oleate or triolein to study the effect of the fluidity of the hydrophobic core on the formation of the microemulsions. The results indicated that a molar ratio of 75:25 and a total lipid concentration of 60 mg/mL consistently gave microemulsions with a mean size of 100-150 nm. In addition, the formation of eutectic mixtures of 3 and 4 with cholesteryl oleate were determined to be 16% (w/w) for 3 and 12% (w/w) for 4; melting points were 35.2 and 45.2 degrees C, respectively. The solubilities of 3 and 4 in triolein were determined to be 13.2% (w/w) and 11.5% (w/w), respectively. Other investigators have shown that if the core of a phospholipid:cholesteryl estermicroemulsion exists in a liquid state at physiologic temperature, the turnover of the cholesteryl esters from these microemulsions occurs at a faster rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Preparation of controlled-release microspheres of ibuprofen with acrylic polymers by a novel quasi-emulsion solvent diffusion method

A novel quasi-emulsion solvent diffusion method to prepare the controlled-release microspheres of ibuprofen with acrylic polymers has been developed. An ethanol solution of ibuprofen and acrylic resin was poured into aqueous medium with stirring. The finely dispersed ethanolic droplet-like coacervates formed in aqueous medium were gradually solidified and transformed into microspheres during agitation. The size of microspheres was determined by the concentrations of drug and polymer and the agitation speed of the system. The flowability, the packability, and the compressibility of the resultant microspheres were much improved compared with the raw crystals of the drug. The drug release rate from the microspheres could be controlled by the type and the concentration of polymer formulated. A unique principle of the present method and the resultant microspheres, having a matrix- or sponge-like texture, can provide characteristic advantages compared with a conventional reservoir-type device drug, like a microcapsule.

Synthesis and pharmacological evaluation of poly(oxyethylene) derivatives of 4-isobutylphenyl-2-propionic acid (ibuprofen)

The synthesis of three oligomeric derivatives of 4-isobutylphenyl-2-propionic acid (ibuprofen), namely, the monoester of tetraethylene glycol (I) and the diesters of poly(oxyethylene) samples having molecular weights of 1000 (+/- 50) and 2000 (+/- 150) (II and III), has been performed via the imidazolide method. The antiinflammatory activity of I-III, and of equivalent amounts of free drug, was determined in the carrageenan-induced rat paw edema assay at different times after oral administration and found to be considerably prolonged in the case of the three derivatives. The lowest molecular weight derivative (I) also had an enhanced initial activity with regard to 4-isobutylphenyl-2-propionic acid. These results were confirmed by measuring the plasma levels of 4-isobutylphenyl-2-propionic acid in rats at different times after oral administration.

GLC determination of ibuprofen [dl-2-(p-isobutylphenyl) propionic acid] enantiomers in biological specimens

To study the behavior of the d- and l-isomers of ibuprofen in humans, a method for the determination of the individual enantiomers in plasma and urine was required. A specific procedure was developed based on (a) benzene extraction of the acidified specimens, (b) TLC of the benzene extract residue, (c) formation of the l-alpha-methylbenzylamides of the materials eluted from the chromatograms, and (d) quantification of the resulting diastereoisomeric amides by GLC in conjunction with flame-ionization detection. When using a 1-ml aliquot of the specimen, the method is sensitive to 1 mug of each enantiomer/ml of plasma or urine. As compared to simple aqueous solutions, the average recoveries of the enantiomers from plasma and urine ranged from 94 to96%. Mass spectrometric analyses, in conjunction with GLC, confirmed the specificity of the method for the intact enantiomers. The procedure was applied successfully to drug absorption studies in humans. After oral administration of the racemic mixture, the predominant enantiomer in peripheral circulation and excreted in urine was of the d-configuration.