Dipeptide Derivatives Research Articles

Rare dipeptide and urea derivatives from roots of Moringa oleifera as potential anti-inflammatory and antinociceptive agents

In the course of our studies on the isolation of bioactive compounds from the roots of Moringa oleifera, a traditional herb in southeast Asia, rare aurantiamide acetate 4 and 1,3-dibenzyl urea 5 have been isolated and characterized. And also, this is the first report of isolation from this genus. Isolated compound inhibited the production of TNF-α and IL-2; further compound 5 showed significant analgesic activities in a dose dependant manner. These findings may help in understanding the mechanism of action of this traditional plant leading to control of activated mast cells on inflammatory conditions like arthritis, for which the crude extract has been used.

Amino Acid Derivatives, VI [1]: Synthesis, Antiviral, and Antimicrobial Evaluation of α-Amino Acid Esters Bearing a 1,2,3-Triazolo[4,5-d]pyrimidinedione Side Chain

A series of peptide and dipeptide derivatives conjugated with a 1,2,3-triazolo[4,5-d]pyrimidinedione residue were synthesized. The new compounds were evaluated in vitro for cytotoxicity against HAV-27 and HSV-1 and showed moderate activity. The prepared compounds were tested for antimicrobial activity against four different bacterial species, and they displayed different degrees of antibacterial activities or inhibitory actions.

Rapid generation of an anthrax immunotherapeutic from goats using a novel non-toxic muramyl dipeptide adjuvant

BackgroundThere is a clear need for vaccines and therapeutics for potential biological weapons of mass destruction and emerging diseases. Anthrax, caused by the bacterium Bacillus anthracis, has been used as both a biological warfare agent and bioterrorist weapon previously. Although antibiotic therapy is effective in the early stages of anthrax infection, it does not have any effect once exposed individuals become symptomatic due to B. anthracis exotoxin accumulation. The bipartite exotoxins are the major contributing factors to the morbidity and mortality observed in acute anthrax infections.MethodsUsing recombinant B. anthracis protective antigen (PA83), covalently coupled to a novel non-toxic muramyl dipeptide (NT-MDP) derivative we hyper-immunized goats three times over the course of 14 weeks. Goats were plasmapheresed and the IgG fraction (not affinity purified) and F(ab')2 derivatives were characterized in vitro and in vivo for protection against lethal toxin mediated intoxication.ResultsAnti-PA83 IgG conferred 100% protection at 7.5 μg in a cell toxin neutralization assay. Mice exposed to 5 LD50 of Bacillus anthracis Ames spores by intranares inoculation demonstrated 60% survival 14 d post-infection when administered a single bolus dose (32 mg/kg body weight) of anti-PA83 IgG at 24 h post spore challenge. Anti-PA83 F(ab')2 fragments retained similar neutralization and protection levels both in vitro and in vivo.ConclusionThe protection afforded by these GMP-grade caprine immunotherapeutics post-exposure in the pilot murine model suggests they could be used effectively to treat post-exposure, symptomatic human anthrax patients following a bioterrorism event. These results also indicate that recombinant PA83 coupled to NT-MDP is a potent inducer of neutralizing antibodies and suggest it would be a promising vaccine candidate for anthrax. The ease of production, ease of covalent attachment, and immunostimulatory activity of the NT-MDP indicate it would be a superior adjuvant to alum or other traditional adjuvants in vaccine formulations.

Synthesis, structural characterization and anticarcinogenic activity of a new Gly–Gly dipeptide derivative: Methyl 2-(2-(5-fluoro-2,4-dioxo-3,4-dihydropyrimidin-1(2 H)-yl)acetamido)acetate

A new anticarcinogenic Gly–Gly dipeptide derivative, methyl 2-(2-(5-fluoro-2,4-dioxo-3,4-dihydropyrimidin-1(2 H)-yl)acetamido) acetate, has been synthesized and identified by means of elemental analysis, IR, 1H NMR, 13C NMR, DSC–TGA and X-ray diffraction. It crystallizes in space group P−1 with a = 4.873(4), b = 9.118(7), c = 12.564(10) Å, α = 97.048(15)°, β = 96.159(16)°, γ = 104.987(15)°, Z = 2, V = 533.6(7) Å 3, C 9H 10FN 3O 5, M r = 259.2, D c = 1.613 g/cm 3, μ = 0.143 mm −1, F(0 0 0) = 268, R = 0.0626 and wR = 0.1284. In solid state, two adjacent molecules of the title compound are tied to form analogous antiparallel β-sheet arrangement typical of the Gly–Gly dipeptide sequence. The biological test shows that the title compound has certain anticarcinogenic activity, and the cyclic voltammetry test shows the title compound interacts with DNA more strongly than 5-fluorouracil does.

Force‐Field Development and Molecular Dynamics Simulations of Ferrocene–Peptide Conjugates as a Scaffold for Hydrogenase Mimics

The increasing importance of hydrogenase enzymes in the new energy research field has led us to examine the structure and dynamics of potential hydrogenase mimics, based on a ferrocene-peptide scaffold, using molecular dynamics (MD) simulations. To enable this MD study, a molecular mechanics force field for ferrocene-bearing peptides was developed and implemented in the CHARMM simulation package, thus extending the usefulness of the package into peptide-bioorganometallic chemistry. Using the automated frequency-matching method (AFMM), optimized intramolecular force-field parameters were generated through quantum chemical reference normal modes. The partial charges for ferrocene were derived by fitting point charges to quantum-chemically computed electrostatic potentials. The force field was tested against experimental X-ray crystal structures of dipeptide derivatives of ferrocene-1,1'-dicarboxylic acid. The calculations reproduce accurately the molecular geometries, including the characteristic C2-symmetrical intramolecular hydrogen-bonding pattern, that were stable over 0.1 micros MD simulations. The crystal packing properties of ferrocene-1-(D)alanine-(D)proline-1'-(D)alanine-(D)proline were also accurately reproduced. The lattice parameters of this crystal were conserved during a 0.1 micros MD simulation and match the experimental values almost exactly. Simulations of the peptides in dichloromethane are also in good agreement with experimental NMR and circular dichroism (CD) data in solution. The developed force field was used to perform MD simulations on novel, as yet unsynthesized peptide fragments that surround the active site of [Ni-Fe] hydrogenase. The results of this simulation lead us to propose an improved design for synthetic peptide-based hydrogenase models. The presented MD simulation results of metallocenes thereby provide a convincing validation of our proposal to use ferrocene-peptides as minimal enzyme mimics.

Coordination abilities of difunctional, diaminophosphonic acid and its dipeptides towards Cu(II) ions

Phenylenedi(aminomethylphosphonic) acid ( L9) and its peptides with L-Ala and β-Ala residues were synthesized and their ability to bind Cu(II) ions in aqueous solution was studied. L9 forms complexes with metal to ligand ratios of 1:1 and 1:2 which are typical for aminophosphonic acids coordination mode 1x or 2 x { NH 2 , PO 3 2 - } . In the case of their dipeptide derivatives ( L10– L12), only one peptidyl chain is involved in the binding of metal ion with stoichiometry 1:1 and coordination pattern similar to that found in the simple phosphonic dipeptides. The influence of metal ion chelation on the properties of uncoordinated group in the same ligand molecule was found.

New glycosidic derivatives of histidine-containing dipeptides with antioxidant properties and resistant to carnosinase activity

Synthesis, antioxidant properties and resistance to carnosinase hydrolysis of histidine-containing dipeptides are reported in this study. Carnosine (β-alanyl- l-histidine), homocarnosine (γ-aminobutyryl- l-histidine) and anserine (β-alanyl-3-methyl- l-histidine) were covalently derivatized with β-cyclodextrin to form different OH- or NH-bound conjugates. Mass spectroscopic and 1H NMR data were used to determine the structure and the purity of the various β-cyclodextrin derivatives. The inhibitory effect towards oxidation of human LDL induced by Cu 2+ ions, was estimated by measuring malondialdehyde formation as a function of increasing concentrations of these newly synthesized compounds (the β-cyclodextrin-anserine conjugated in 3 had the highest antioxidant effect). All derivatives had higher antioxidant effects than those of the corresponding free histidine-containing dipeptides. Resistance to rat brain carnosinase hydrolysis of the most active derivatives indicated that these compounds are good candidates for further studies in more complex cellular and animal models. Their possible applications for remedies in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, are discussed.

2-Alkyl-2-carboxy-azetidines as scaffolds for the induction of γ-turns

To investigate the ability of 2-alkyl-2-carboxy-azetidines (Azx) to induce reverse turns when incorporated into peptides, RCO-Azx- l-Ala-NHMe dipeptide derivatives were selected as simplified tetrapeptide models, in which the azetidine residue is incorporated at the i + 1 position. Molecular modelling, 1H NMR and FTIR studies showed the high tendency of the model tetrapeptides to adopt γ-turn conformations, indicating that these azetidine-containing amino acids could serve as general γ-turn promoters.

Synthesis and antioxidant activity of new homocarnosine β-cyclodextrin conjugates

Several in vitro and in vivo studies have suggested that carnosine (β-alanil- l-histidine) and homocarnosine (β-aminobutyril- l-histidine) can act as scavengers of reactive oxygen species. β-Cyclodextrin was functionalized with homocarnosine, obtaining the following new bioconjugate isomers: 6 A-[(4-{[(1 S)-1-carboxy-2-(1 H-imidazol-4-yl)ethyl]amino}-4-oxobutyl)amino]-6 A-deoxy-β-cyclodextrin and (2 A S,3 A R)-3A-[(4-{[(1 S)-1-carboxy-2-(1 H-imidazol-4-yl)ethyl]amino}-4-oxobutyl)amino]-3 A-deoxy-β-cyclodextrin. Pulse radiolysis investigations show that the β-cyclodextrin homocarnosine bioconjugates are scavengers of OH radicals because of the formation of stable imidazole-centered radicals and the scavenger ability of glucose molecules of the macrocycle. The ability of these new β-cyclodextrin derivatives to inhibit the copper(II) driven LDL oxidation was determined in comparison with that displayed by the analogous carnosine derivatives. Both the β-cyclodextrin carnosine isomers show a higher protective effect than that of free dipeptide and homocarnosine derivatives, bringing into light the role of the β-CD cavity. The ability of these new β-cyclodextrin derivatives to inhibit the copper(II) driven LDL oxidation was determined in comparison with that displayed by the analogous carnosine derivatives. Both the β-cyclodextrin carnosine isomers show a higher protective effect than that of free dipeptide and homocarnosine derivatives, bringing into light the role of the β-CD cavity.

Antibacterial Activity of Dipeptide Constructs of Acetylsalicylic Acid and Nicotinic Acid

Two dipeptide drugs are synthesized utilizing an acetylsalicylic acid or nicotinic acid molecule for the framework. A D-alanine-D-alanine dipeptide moiety is attached to the carbonyl carbon of acetylsalicylic acid (I) and nicotinic acid (II). Dipeptide derivatives (I) and (II) showed significant reduction of Escherichia coli (E. coli) bacterial growth and colony-forming units. A mixture of (I) and (II) induced growth inhibition of 8%, 17.5%, 28%, and 42.5% at concentrations of 100, 200, 300, and 400 μg/mL, respectively. Ampicillin demonstrated much less growth inhibition of this penicillin-resistant E. coli bacteria. Derivatives (I) and (II) showed significant reduction of colony-forming units at concentrations higher than 200 μg/mL, whereas ampicillin showed no significant affect on colony-forming units. Both (I) and (II) produced no violations of the Rule of 5, indicating favorable characteristics for bioavailability. Molecular properties were determined and showed (I) to have a Log Kow of −0.22 with aqueous solubility of 683.8 mg/L, whereas (II) had a Log Kow of −1.00 and aqueous solubility of 6859 mg/L. A mixture of the parent compounds acetyl salicylic acid and nicotinic acid demonstrated some antibacterial activity.

New insights into the metal ion–peptide hydroxamate interactions: Metal complexes of primary hydroxamic acid derivatives of common dipeptides in aqueous solution

Complex formation of primary dipeptide hydroxamic acids, L-Ala-L-AlaNHOH and L-Ala-L-SerNHOH, as well as the corresponding Z-protected ones, Z-L-Ala-L-AlaNHOH and Z-L-Ala-L-SerNHOH (Z = benzyloxycarbonyl), with iron(III), aluminium(III), nickel(II), copper(II) and zinc(II) was studied in aqueous solution by pH-potentiometric and spectroscopic (UV–Vis, EPR, CD, 1H NMR) methods. The exclusive formation of [O,O] chelated hydroxamate complexes was found with iron(III) and aluminium(III) with all the ligands. Formation of linkage isomers with the involvement of either [O,O] hydroxamate or [NH 2,CO] chelates was detected both in the zinc(II)-L-Ala-L-AlaNHOH and -L-Ala-L-SerNHOH systems. Upon increasing the pH, none of these chelating sets are capable of preventing the hydrolysis of the metal ion. The formation of stable complexes was found in the nickel(II) and copper(II) systems above pH ∼ 6 with a [NH 2, N amide, N hydrox.] binding mode after deprotonation and coordination of the peptide amide and the hydroxamate group. With an excess of copper(II), the formation of trinuclear [Cu 3H x L 2] x+4 type ( x = −4 to −6) complexes as the major species was also detected. Blocking the terminal amino group in the Z-protected ligands results in a dramatic decrease of the nickel(II) and zinc(II) binding strengths, and insoluble complexes with copper(II). No indication was found for the role of the hydroxyl group of the serine moiety in metal ion binding.

Preparation and characterization of d 6 tungsten compounds with amino acid derivatized diimine ligands and preparation of dipeptide derivatives using peptide coupling agents

Attempts to prepare dipeptide compounds from organometallic N-substituted amino acids are reported. Condensation of pyridine-2-carboxaldehyde, α-amino acids (H- l-Ala-OH or H- l-Asp-OH) and W(CO) 4(pip) 2 leads to formation of W(CO) 4(pyca-Et) ( 1) (pyca refers to the α-diimine fragment, C 5H 4NCH N) following decarboxylation of one or two equivalents of CO 2. This decarboxylation does not occur for β-alanine or GABA (γ-aminobutyric acid). Coupling of [Hpip][W(CO) 4(pyca-β-Ala-O)] ( 2) or [Hpip][W(CO) 4(pyca-GABA-O)] ( 3) to amino acid esters, H- l-Ala-OEt, or H- l-Val-OMe, using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) procedure produced four new dipeptide compounds, 4– 7. The reactions proceed in good yield and compounds were characterized spectroscopically. The dipeptide complex, W(CO) 4(pyca-Ala-Ala-OMe) ( 8), was prepared by reaction of W(CO) 4(pip) 2 with H- l-Ala- l-Ala-OMe and pyridine-2-carboxaldehyde. In addition the molecular structure of W(CO) 4(pyca-β-Ala-Val-OMe) ( 5) is reported.

Synthesis of novel vasodilatory active nicotinate esters with amino acid function

A variety of N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]amino acid esters 6a– h were synthesized through the reaction of 2-bromonicotinates 4 with a number of primary amino acid ester hydrochlorides 5 in refluxing tetrahydrofuran in the presence of triethylamine as dehydrohalogenating agent. Similarly, reaction of 4 with N-glycylglycine ethyl ester hydrochloride 7 ‘as a representative example of dipeptide derivative’ afforded smoothly the corresponding N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]- N′-glycylglycine ethyl ester analogues 8. However, reaction of 4 with 5 in refluxing pyridine yielded the unexpected 2-aminonicotinate esters 9. Vasodilation activity screening for the synthesized nicotinate esters was investigated in vitro on the contractile response of vascular thoracic aorta smooth muscle from Wistar rats, where all the tested compounds exhibit considerable vasodilatory properties. In addition, few prepared compounds especially, 6b, 6h and 9b reveal remarkable vasodilation potency (IC 50).

Old Molecules for New Receptors: Trp(Nps) Dipeptide Derivatives as Vanilloid TRPV1 Channel Blockers

The transient receptor potential vanilloid member 1 (TRPV1), an integrator of multiple pain-producing stimuli, is regarded nowadays as an important biological target for the discovery of novel analgesics. Here, we describe the first experimental evidence for the behavior of an old family of analgesic dipeptides, namely Xaa-Trp(Nps) and Trp(Nps)-Xaa (Xaa=Lys, Arg) derivatives, as potent TRPV1 channel blockers. We also report the synthesis and biological investigation of a series of new conformationally restricted Trp(Nps)-dipeptide derivatives with improved TRPV1/NMDA selectivity. Compound 15 b, which incorporates an N-terminal 2S-azetidine-derived Arg residue, was the most selective compound in this series. Collectively, a new family of TRPV1 channel blockers emerged from our results, although further modifications are required to fine-tune the potency/selectivity/toxicity balance.

Bortezomib Inhibits PKR-Like Endoplasmic Reticulum (ER) Kinase and Induces Apoptosis via ER Stress in Human Pancreatic Cancer Cells

Bortezomib (Velcade, formerly known as PS-341) is a boronic acid dipeptide derivative that is a selective and potent inhibitor of the proteasome. We hypothesized that proteasome inhibition would lead to an accumulation of misfolded proteins in the cell resulting in endoplasmic reticulum (ER) stress. The ability of bortezomib to induce ER stress and the unfolded protein response was investigated in a human pancreatic cancer cell line, L3.6pl. Bortezomib increased expression of ER stress markers, CHOP and BiP, but inhibited PKR-like ER kinase and subsequent phosphorylation of eukaryotic initiation factor 2alpha (eif2alpha), both of which are key events in translational suppression. These effects resulted in an accumulation of ubiquitylated proteins leading to protein aggregation and proteotoxicity. Peptide inhibitor or small interfering RNA targeting ER-resident caspase-4 blocked DNA fragmentation, establishing a central role for caspase-4 in bortezomib-induced cell death. The translation inhibitor cycloheximide abrogated bortezomib-induced protein aggregation, caspase-4 processing, and all other characteristics of apoptosis. Because malignant cells have higher protein synthesis rates than normal cells, they may be more prone to protein aggregation and proteotoxicity and possess increased sensitivity to bortezomib-induced apoptosis. Taken together, the results show that bortezomib induces a unique type of ER stress compared with other ER stress agents characterized by an absence of eif2alpha phosphorylation, ubiquitylated protein accumulation, and proteotoxicity.

The Photochemistry of N‐p‐Toluenesulfonyl Peptides: The Peptide Bond as an Electron Donor

The scope of photobiological processes that involve absorbers within a protein matrix may be limited by the vulnerability of the peptide group to attack by highly reactive redox centers consequent upon electronic excitation. We have explored the nature of this vulnerability by undertaking comprehensive product analyses of aqueous photolysates of 12 N-p-toluenesulfonyl peptides with systematically selected structures. The results indicate that degradation includes a major pathway that is initiated by intramolecular electron transfer in which the peptide bond serves as electron donor, and the data support the likelihood of a relay process in dipeptide derivatives.

Carnosine and Homocarnosine, the Forgotten, Enigmatic Peptides of the Brain

Carnosine (beta-alanyl-histidine) and homocarnosine (gamma-aminobutyryl-histidine) are major constituents of excitable tissues, brain and skeletal muscles, but their physiological functions are yet unknown. Using primary cell culture systems, synthesis and uptake of carnosine exclusively by glial cells could be demonstrated. Uptake of carnosine was found to be mediated by a high affinity, energy-dependent dipeptide transport system, subsequently identified as the peptide transporter PepT2. With the synthesis of beta-Ala-Lys-Nepsilon-AMCA as a fluorescent reporter molecule, accumulation of this dipeptide derivative could be monitored under viable conditions not only in astroglia cells but also in folliculostellate cells of the anterior pituitary and in gonadal resident macrophages. This reporter dipeptide provided a most valuable tool to identify an intrapituitary communication system by tracing folliculostellate cells in acute slice preparation. Moreover, this substance could also be used to prepare pituitary cell cultures enriched with or depleted of folliculostellate cells that are needed for further studies.

Amino-Acid and Dipeptide Derivatives of 2-(6-ethyl-4-oxo-3-(4-phenyl-4H-1,2,4-triazol-3-yl)-4H-chromen-7-yloxy)acetic Acid

Chromones modified by triazole, amino acids, and dipeptides were prepared by condensation of the N-hydroxysuccinimide ester of 2-(6-ethyl-4-oxo-3-(4-phenyl-4H-1,2,4-triazol-3-yl)-4H-chromen-7-yloxy)acetic acid with salts of amino acids or dipeptides. The dipeptide derivatives were also synthesized by extending the chain of amino acids.

Dipeptides as Effective Prodrugs of the Unnatural Amino Acid (+)-2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic Acid (LY354740), a Selective Group II Metabotropic Glutamate Receptor Agonist

(+)-2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (1), also known as LY354740, is a highly potent and selective agonist for group II metabotropic glutamate receptors (mGlu receptors 2 and 3) tested in clinical trials. It has been shown to block anxiety in the fear-potentiated startle model. Its relatively low bioavailability in different animal species drove the need for an effective prodrug form that would produce a therapeutic response at lower doses for the treatment of anxiety disorders. We have investigated the increase of intestinal absorption of this compound by targeting the human peptide transporter hPepT1 for active transport of di- and tripeptides derived from 1. We have found that oral administration of an N dipeptide derivative of 1 (12a) in rats shows up to an 8-fold increase in drug absorption and a 300-fold increase in potency in the fear-potentiated startle model in rats when compared with the parent drug 1.

New triorganotin (IV) derivatives of dipeptides as models for metal–protein interactions: Synthesis, structural characterization and biological studies

New non-electrolytic triorganotin(IV) derivatives of dipeptides with general formulae R3Sn(HL), where R=Ph and HL=monoanion of glycylisoleucine (H2L-1), valylvaline (H2L-2), alanylvaline (H2L-3), leucylalanine (H2L-4), leucylleucine (H2L-5); R=n-Bu and HL=monoanion of glycylisoleucine (H2L-1) and leucylalanine (H2L-4); and R=Me and HL=monoanion of leucylalanine (H2L-4) have been synthesized and characterized on the basis of infrared, multinuclear 1H, 13C and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that all the ligands in R3Sn(HL) act as monoanionic bidentates coordinating through the COO− and NH2 groups. The 119Sn Mössbauer studies, together with the NMR data, indicate that, for these polymeric derivatives, the polyhedron around tin in R3Sn(HL) is a trigonal-bipyramid with the three organic groups in the equatorial positions, while the axial positions are occupied by a carboxylic oxygen and the amino nitrogen atom from the adjacent molecule. The anti-inflammatory and cardiovascular activities and toxicity of all these compounds have been determined. Four of the complexes have also been screened against some of the chosen bacterial and fungal strains. The Ph3Sn(IV) compounds exhibit better anti-inflammatory and cardiovascular activities in comparison to the Me3Sn(IV) and n-Bu3Sn(IV) analogues. n-Bu3Sn(Gly-Ile) and Ph3Sn(Ala-Val) exhibit good antibacterial activity against all the chosen strains.