Synthesis, hydrolysis studies and phamacodynamic profiles of amide prodrugs of dexibuprofen with amino acids

The present investigation deals with the synthesis of novel prodrugs of dexibuprofen with amino acids with an aim to achieve potent anti-inflammatory activity and less gastrointestinal toxicity. Structures of synthesized compounds were confirmed by spectral and elemental analyses. In vitro hydrolytic studies in simulated intestinal fluid, 80% plasma and rat faecal matter showed satisfactory release of dexibuprofen due to enzymatic cleavage. The synthesized prodrugs were evaluated for anti-inflammatory activity, analgesia, ulcerogenicity and histopathology. The anti-inflammatory activity of dexibuprofen was 43.3% whereas an improved value of 73.4, 77.3, 72.8 and 64.5% was observed for the synthesized prodrugs. The percentage analgesia of the prodrugs increased, whereas a decrease in the mean ulcer index values than dexibuprofen was observed. The histopathological studies revealed less ulceration in the gastric region when treated with prodrugs. Thus, the prodrugs were proved to be better in action as compared with the parent drug.     

Tyrosine and glycine derivatives as potential prodrugs: design,synthesis, and pharmacological evaluation of amide derivatives of mefenamic acid

This study deals with the synthesis, pharmacological activity, and kinetic studies of mefenamic acid (MA) prodrugs of tyrosine and glycine. The synthesis involved a series of protection and deprotection reactions. The hydrolysis of these prodrugs in the intestine was confirmed by hydrolysis kinetics studies in simulated gastric fluid, simulated intestinal fluid, and 80% plasma. The prodrugs were also evaluated for analgesic, anti-inflammatory, and ulcerogenic activities. The glycine prodrug showed maximum analgesic activity of 86%, and both tyrosine and glycine prodrugs showed better anti-inflammatory activity of 74% and 81%, respectively, when compared to the 40% of MA. Further, the prodrugs showed fewer gastric ulcers compared to MA; tyrosine and glycine prodrugs had an average ulcer index of 9.1 and 4.5, respectively, while an average ulcer index of 24.2 was observed with MA. These findings suggest that both prodrugs are better in action as compared to MA, and are advantageous in having fewer gastrointestinal side effects.     

Synthesis,characterization and pharmacological evaluation of certain enzymatically cleavable NSAIDs amide prodrugs

The presence of free carboxylic acid group in majority of non-steroidal anti-inflammatory drug (NSAIDs) is responsible from GI irritation. Coupling of the appropriate NSAIDs (diclofenac, naproxen, dexibuprofen and meclofenamic acid) 1–4, respectively with the appropriate amino acid ester 5 using dicyclohexylcarbodiimide afforded prodrugs 6–13. The structures of the prodrugs were verified based on spectral data. Chemical hydrolysis studies performed in three different non enzymatic buffer solutions at pH 1.2, 5.5 and 7.4, as well as in 80% human plasma and 10% rat liver homogenate using HPLC indicate no conversion of prodrugs to their respective NSAID in the studied buffers, while they underwent a reasonable plasma and rat liver homogenate hydrolysis. Furthermore, ulcerogenicity of prodrugs 9 and 12 were studied and results revealed no gastro-ulcerogenic effects.     

N,N'-Dialkylaminoalkylcarbonyl (DAAC) prodrugs and aminoalkylcarbonyl (AAC) prodrugs of 4-hydroxyacetanilide and naltrexone with improved skin permeation properties

N,N′-Dialkylaminoalkylcarbonyl (DAAC) and aminoalkylcarbonyl (AAC) prodrugs of phenolic drugs acetaminophen (APAP) and naltrexone (NTX) are reported. The effects of incorporation of a basic amine group into the promoiety of an acyl prodrug of a phenolic drug on its skin permeation properties are also presented. DAAC-APAP prodrugs were synthesized via a three-step procedure starting with haloalkylcarbonyl esters which were reacted with five different amines: dimethylamine, diethylamine, dipropylamine, morpholine, and piperidine. The spacing between the amino group and the carbonyl group of the acyl group was 1-3 CH₂. After the hydrolysis of the ester, the carboxylic acid product was subsequently coupled with the parent drug via a dicyclohexyl carbodiimide (DCC) mediated coupling to yield the DAAC-APAP-HCl prodrugs in excellent yields. The AAC prodrugs were synthesized using commercially available Boc-protected amino acids using DCC or EDCI as coupling agents. The yields of the prodrugs synthesized using these two different methods have been compared. Half-lives (t_1/2) of a few members of the DAAC and AAC series were measured in buffer (pH 6.0, 20 mM). The members evaluated in hydrolysis experiments exhibit a t_1/2 range of 15-113 min. Among AAC-APAP prodrugs, the isopropyl group in valinate-APAP-HCl exerted a steric effect that increased the t_1/2 value for this prodrug compared to alaninate-APAP-HCl or prolinate-APAP-HCl. The 2-morpholinylacetate-APAP prodrug was able to achieve twice the flux of APAP in in vitro diffusion cell experiments through hairless mouse skin.     

Synthesis,pH-dependent,and plasma stability of meropenem prodrugs for potential use against drug-resistant tuberculosis

Meropenem, a broad-spectrum parenteral β-lactam antibiotic, in combination with clavulanate has recently shown efficacy in patients with extensively drug-resistant tuberculosis. As a result of meropenem’s short half-life and lack of oral bioavailability, the development of an oral therapy is warranted for TB treatment in underserved countries where chronic parenteral therapy is impractical. To improve the oral absorption of meropenem, several alkyloxycarbonyloxyalkyl ester prodrugs with increased lipophilicity were synthesized and their stability in physiological aqueous solutions and guinea pig as well as human plasma was evaluated. The stability of prodrugs in aqueous solution at pH 6.0 and 7.4 was significantly dependent on the ester promoiety with the major degradation product identified as the parent compound meropenem. However, in simulated gastrointestinal fluid (pH 1.2) the major degradation product identified was ring-opened meropenem with the promoiety still intact, suggesting the gastrointestinal environment may reduce the absorption of meropenem prodrugs in vivo unless administered as an enteric-coated formulation. Additionally, the stability of the most aqueous stable prodrugs in guinea pig or human plasma was short, implying a rapid release of parent meropenem.     

Arachidonoyl amino acids and arachidonoyl peptides: Synthesis and properties

N-Arachidonoyl (AA) derivatives of amino acids (glycine, phenylalanine, proline, valine, γ-aminobutyric acid (GABA), dihydroxyphenylalanine, tyrosine, tryptophan, and alanine) and peptides (Semax, MEHFPGP, and PGP) were synthesized in order to study the biological properties of acylamino acids. The mass spectra of all the compounds at atmospheric pressure electrospray ionization display the most intense peaks of protonated molecular ions; the detection limits for these compounds are 10 fmol per sample. AA-Gly showed the highest inhibitory activity toward fatty acid amide hydrolase from rat brain (IC₅₀ 6.5 μM) among all the acylamino acids studied. AA-Phe, AA-Tyr, and AA-GABA exhibited a weak but detectable inhibitory effect (IC₅₀ 55, 60, and 50 μM, respectively). The acylated amino acids themselves, except for AA-Glu, were stable to the hydrolysis by this enzyme. All the arachidonoylamino acids inhibited cabbage phospholipase D to various degrees; AA-GABA and AA-Phe proved to be the most active (IC₅₀ 20 and 27 μM, respectively). Attempts to detect the biosynthesis of AA-Tyr in homogenates of rat liver and nerve tissue in vitro were unsuccessful; however, AA-dopamine and AA-Phe, the products of its metabolism, were found. The highest contents of these metabolites were detected in liver homogenate and in the brain homogenate, respectively. Acylamino acids exert no cytotoxic effect toward the glioma C6 cells. It was shown that N-acylation of Semax with arachidonic acid results in enhancement of its hydrolytic stability and increases its affinity for the sites of specific binding in rat cerebellum membranes.     

Synthesis and hydrolysis of a phenylalanyl adenylate pentacoordinated phosphorane

Amino acid-nucleotide conjugates have important biological functions and therapeutic applications. For example, aminoacyl adenylates are key intermediates in aminoacyl tRNA synthetase reactions. They may also be involved in the prebiotic synthesis of polypeptides. Finally, various amino acid carbomethoxy aryl phosphoramidates of nucleotide prodrugs may be activated through a mechanism involving a pentacoordinated phosphorane intermediates. In order to understand better the chemistry of these compounds, a phenylalanyl adenylate pentacoodinated phosphorane has been synthesized in 72% yield and its decomposition in aqueous solution studied. Hydrolysis gave 2('),3(')-O-isopropylidene adenosine 5(')-monophosphate, 2('),3(')-O-isopropylidene adenosine, and phenylalanine. The results provide model chemistry for the enzymatic degradation mechanism of antiviral aryl amino acid phosphodiester amidates in cells, which leads to their activation.     

Synthesis, biological evaluation and kinetic studies of glyceride prodrugs of diclofenac

The prodrugs (glyceride derivatives) 3a and 3b of diclofenac were prepared by reacting 1, 2, 3-trihydroxy propane-1,3-dipalmitate/stearate with the acid chloride of diclofenac as potential prodrugs to reduce the gastrointestinal toxicity associated with them. These prodrugs were evaluated for their ulcerogenicity, anti-inflammatory and analgesic activity. It was found that the prodrugs were significantly less irritating to the gastric mucosa as indicated by severity index of 0.86, 0.78 compared to 1.6 of diclofenac. The prodrugs 3a and 3b showed better anti-inflammatory and analgesic activity than the parent drugs. The hydrolysis of prodrugs 3a and 3b were studied at pH 3, 4, 5 and 7.4. The HPLC analysis showed that the prodrugs were resistant to hydrolysis at pH 3, 4 and 5 indicating that they did not hydrolyze in acidic environment, whereas at pH 7.4 the prodrugs readily released the parent drug in significant quantities. The plasma levels of diclofenac were also analyzed by HPLC in rats after single oral dose of the prodrugs. The results indicated that the parent drugs were readily released. The concentration of diclofenac during the study was found higher in animals treated with prodrugs 3a and 3b compared with animals treated with diclofenac. The concentration of diclofenac was found to be 38.59, 33.6 and 30.36 microg/ml in animals treated with prodrugs 3a, 3b and diclofenac respectively. In conclusion, all these studies indicated that the glyceride prodrugs of diclofenac might be considered as potential biolabile prodrugs of diclofenac.     

Synthesis of azide and amide analogs of platelet-activating factor and related derivatives

2-Azido-2-deoxy-1-O-hexadecyl-sn-glycero-3-phosphorylcholine was prepared in good yield from D-mannitol via 3-O-hexadecyl-2-O-methanesulfonyl-1-O-triphenylmethyl-sn-glycerol. Nucleophilic displacement of the 2-methanesulfonate function by benzoate or azide ion proceeded with inversion of configuration (Sn2) without racemization. Hydrogenation of the azidophospholipid gave 2-amino-2-deoxy-1-O-hexadecyl-sn-glycero-3-phosphorylcholine which is a versatile intermediate for the preparation of amide analogs of platelet-activating factor and related derivatives. The synthesis of 2-deoxy-2-fluoro-1-O-hexadecyl-sn-glycero-3-phosphorylcholine was also described.     

Synthesis of dihydroquinopimaric acid conjugates with amino acids

Synthesis of dihydroquinopimaric acid amides and their 2β-succinyl and 2β-phthalyl derivatives containing residues of amino acids was carried out for the first time. Antiviral properties of the compounds synthesized were investigated.     

Design,Synthesis, and Biological Evaluation of Dexibuprofen Derivatives as Novel Anti-Inflammatory,Antioxidant and Molecular Docking Studies

Prodrugs of dexibuprofen having ester moieties instead of free carboxylic acid which involves in gastrointestinal side effects have been synthesized. Dexibuprofen acid was condensed with different alcohols/phenols to afford the ester prodrugs. All of the synthesized prodrugs were characterized by their physical attributes, elemental analysis, FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. The in vitro anti-inflammatory studies was done by chemiluminescence technique reflect prodrugs have been more potent, owing to the different chemical structures. Lipoxygenase enzyme inhibition assay was also assess and found compound DR7 with IC₅₀=19.8 μM), DR9 (IC₅₀=24.8 μM) and DR3 (IC₅₀=47.2 μM) as compared with Dexibuprofen (IC₅₀=156.6 μM). It was also evaluated for docking studies revealed that DR7 has found to be more potent anti-inflammatory against 5-LOX (3 V99) as well as analgesic against COX-II (5KIR) enzyme. Anti-oxidant activities were also performed, DR3 (86.9 %), DR5 (83.5 %), DR7 (93.9 %) and DR9 (87.4 %) were found to be more anti-oxidant as compared to (2S)-2-[4-(2-methylpropyl)phenyl]propanoic acid (52.7 %).     

Synthesis of glycosyl amino acids by light-induced coupling of photoreactive amino acids with glycosylamines and 1-C-aminomethyl glycosides

The glycosylamines of O-acetyl-protected GlcNAc and chitobiose, as well as two partially unprotected 1-C-aminomethyl glucosides, were photochemically coupled with orthogonally protected N-aspartyl-5-bromo-7-nitroindoline derivatives. The reactions proceeded under neutral conditions by irradiation with near-UV light. The glycosyl asparagines with N- or C-glycosyl linkages were afforded in 60-85% yield on a 10-70 mg scale. Moreover, the ability of a highly photoreactive N-glutamyl-4-methoxy-7-nitroindoline derivative to acylate amino saccharides was tested. Upon irradiation in the presence of a dimeric 1-C-aminomethyl glycoside, or a glycosylamine, the corresponding glycosyl glutamines were obtained in 50% and 30% yield, respectively. Preparations of the photoreactive aspartates and the 1-C-aminomethyl glycosides are also described.     

Synthesis and structure activity relationships of glycine amide derivatives as novel Vascular Adhesion Protein-1 inhibitors

Vascular Adhesion Protein-1 (VAP-1) is a promising therapeutic target for the treatment of several inflammatory-related diseases including diabetic microvascular complication. We identified glycine amide derivative 3 as a novel structure with moderate VAP-1 inhibitory activity. Structure-activity relationship studies of glycine amide derivatives revealed that the tertiary amide moiety is important for stability in rat blood and that the position of substituents on the left phenyl ring plays an important role in VAP-1 inhibitory activity. We also found that low TPSA values and weak basicity are both important for high PAMPA values for glycine amide derivatives. These findings led to the identification of a series of orally active compounds with enhanced VAP-1 inhibitory activity. Of these compounds, 4g exhibited the most potent ex vivo efficacy, with plasma VAP-1 inhibitory activity of 60% after oral administration at 1 mg/kg.     

Effect of hydroxypropyl beta cyclodextrin complexation on aqueous solubility,stability, and corneal permeation of acyl ester prodrugs of ganciclovir

The purpose of the study was to investigate the effect of hydroxypropyl beta cyclodextrin (HPβCD) on aqueous solubility, stability, and in vitro corneal permeation of acyl ester prodrugs of ganciclovir (GCV). Aqueous solubility and stability of acyl ester prodrugs of Ganciclovir (GCV) were evaluated in pH 7.4 isotonic phosphate buffer solution (IPBS) in the presence and absence of HPβCD. Butyryl cholinesterase-mediated enzymatic hydrolysis of the GCV prodrugs was studied using various percentage w/v HPβCD. In vitro corneal permeation of GCV and its prodrugs (with and without 5% HPβCD) across isolated rabbit cornea was studied using side-by-side diffusion cells. HPβCD-prodrug complexation was of the A_L type with values for complexation constants ranging between 12 and 108 M⁻¹. Considerable improvement in chemical and enzymatic stability of the GCV prodrugs was observed in the presence of HPβCD. The stabilizing effect of HPβCD was found to depend on the degree of complexation and the degradation rate of prodrug within the complex. Five percent w/v HPβCD was found to enhance the corneal permeation of only the most lipophilic prodrug GCV dibutyrate (2.5-fold compared with 0% HPβCD). All other prodrugs showed little or no difference in transport in the presence of 5% w/v HPβCD. Agitation in the donor chamber largely influenced the transport kinetics of GCV dibutyrate across cornea. Results indicate the presence of an unstirred aqueous diffusion layer at the corneal surface that restricts the transport of the highly lipophilic GCV dibutyrate prodrug. HPβCD improves corneal permeation by solubilizing the hydrophobic prodrug and delivering it across the mucin layer at the corneal surface.     

Anticancer and DNA binding studies of potential amino acids based quinazolinone analogs: Synthesis,SAR and molecular docking

A novel series of amino acids conjugated quinazolinone-Schiff’s bases were synthesized and screened for their in vitro anticancer activity and validated by molecular docking and DNA binding studies. In the present investigations, compounds 32, 33, 34, 41, 42 and 43 showed most potent anticancer activity against tested cancer cell lines and DNA binding study using methyl green comparing to doxorubicin and ethidium bromide as a positive control respectively. The structure-activity relationship (SAR) revealed that the tryptophan and phenylalanine derived electron donating groups (OH and OCH₃) favored DNA binding studies and anticancer activity whereas; electron withdrawing groups (Cl, NO₂, and F) showed least anticancer activity. The molecular docking study, binding interactions of the most active compounds 33, 34, 42 and 43 stacked with A–T rich regions of the DNA minor groove by surface binding interactions were confirmed.     

Synthesis of peptides from amino acids and ATP with lysine-rich proteinoid

Summary Lysine-rich proteinoids in aqueous solution catalyze the formation of peptides from free amino acids and ATP. This catalytic activity is not found in acidic proteinoids, even though the latter contain some basic amino acid. The pH optimum for the synthesis is about 11, but is appreciable below 8 and above 13. Temperature data indicate an optimum at 20°C or above, with little increase in rate to 60°C. Pyrophosphate can be used instead of ATP, with lesser yields resulting. The ATP-aided syntheses of peptides in aqueous solution occur with several types of proteinous amino acid.Proofs should be sent to S.W. Fox, Institute for Molecular and Cellular Evolution, University of Miami, 521 Anastasia Avenue, Coral Gables, FL 33134     

Synthesis, mechanistic studies, and anti-proliferative activity of glutathione/glutathione S-transferase-activated nitric oxide prodrugs

Nitric oxide (NO) prodrugs such as O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K) are a growing class of promising NO-based therapeutics. Nitric oxide release from the anti-cancer lead compound, JS-K, is proposed to occur through a nucleophilic aromatic substitution by glutathione (GSH) catalyzed by glutathione S-transferase (GST) to form a diazeniumdiolate anion that spontaneously releases NO. In this study, a number of structural analogues of JS-K were synthesized and their chemical and biological properties were compared with those of JS-K. The homopiperazine analogue of JS-K showed anti-cancer activity that is comparable with that of JS-K but with a diminished reactivity towards both GSH and GSH/GST; both the aforementioned compounds displayed no cytotoxic activity towards normal renal epithelial cell line at concentrations where they significantly diminished the proliferation of a panel of renal cancer cell lines. These properties may prove advantageous in the further development of this class of nitric oxide prodrugs as cancer therapeutic agents.