Rational design and synthesis of potent and long-lasting glutamic acid-based dipeptidyl peptidase IV inhibitors

A series of (2S)-cyanopyrrolidines with glutamic acid derivatives at the P2 site have been prepared and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-IV). The structure–activity relationships (SAR) led to the discovery of potent 3-substituted glutamic acid analogues, providing enhanced chemical stability and excellent selectivity over the closely related enzymes, DPP8, DPP-II and FAP. Compound 13f exhibited the ability to both significantly decrease the glucose excursion and inhibit plasma DPP-IV activity.     

Synthesis and the 5-HT6 receptor antagonistic effect of 3-arylsulfonylamino-5,6-dihydro-6-substituted pyrazolo[3,4]pyridinones for neuropathic pain treatment

A novel series of 3-arylsulfonylamino-5,6-dihydro-6-substituted-1H-pyrazolo[3,4-c]pyridine-7-ones was designed and synthesized as 5-HT₆ ligands. Among the derivatives synthesized, the lead compound, 12b, having piperidine functionality at the 6-position and (1-naphthyl)sulfonamino at the 3-position of the core structure showed the most potent 5-HT₆ inhibitory activity in vitro, good stability without CYP liability, and good neuropathic pain alleviation activity in a rat animal model.     

Synthesis and biological evaluation of some nitrogen containing steroidal heterocycles

epi-Androsterone 1 was converted into its hydrazone derivative through the reaction with hydrazine hydrate 80%. Hydrazonoandrostane derivative 2b reacted with hydrazonoyl halides in the presence of K₂CO₃ forming the corresponding hydrazopyridazinoandrostane derivatives 6a–d. The 3β-acetyl-17-hydrazonoandrostane derivative 2b reacted with a halogen reagent, benzoyl chloride, to form the non-cyclic 16-benzoylated hydrazone 9.On the other hand, compound 2b produced the corresponding pyridazinoandrostane derivatives 11 and 12 via its reaction with phenacyl bromide and chloroacetone respectively. Reaction of the hydrazono derivative 2b with benzaldehyde in the presence of acetic acid drops led to the formation of the benzylidenehydrazonoandrostane derivative 13. The product 14, phosphinom-ethylenehydrazonoandrostane was obtained by the reaction of the derivative 13 with trisdimethylaminophosphine in the presence of dry benzene. The reaction of compound 2b with phenyl isothiocyanate followed by boiling in chloroacetic acid or thioglycolic acid produced the pyrazoloandrostane derivatives 17 and 18 respectively. The biological activity of compounds 6a, 6d, 11, 12, and 15 was evaluated as inhibitor of growth in a human liver carcinoma cell line and doxorubicine was used for comparison. Compounds 15 and 12 showed a higher potency than the other tested compounds.     

Synthesis of novel morpholine conjugated benzophenone analogues and evaluation of antagonistic role against neoplastic development

A series of novel 4-benzyl-morpholine-2-carboxylic acid N′-[2-(4-benzoyl-phenoxy)-acetyl]-hydrazide derivatives 8a-j has been synthesized from (4-hydroxy-aryl)-aryl methanones through a multi-step reaction sequence and then evaluated for anti-proliferative activity in vitro against various types of neoplastic cells of mouse and human such as DLA, EAC, MCF-7 and A549 cells. From the cytotoxic studies and structural activity relationship of compounds 8a-j, it is clear that methyl group on the B ring of benzophenone is essential for antiproliferative activity and bromo at ortho position (compound 8b) and methyl at para position (compound 8f) on A ring of benzophenone are significant for extensive anti-mitogenic activity. Investigation on clonogenesis and Fluorescence-activated cell sorting suggests that compounds 8b and 8f have the potency to exhibit the prolonged activity with cell cycle arrest on G2/M phase against cancer progression. Further, the compounds 8b and 8f inhibit murine ascites lymphoma through caspase activated DNase mediated apoptosis.     

Synthesis,biological evaluation and molecular modeling of novel selective COX-2 inhibitors: sulfide,sulfoxide, and sulfone derivatives of 1,5-diarylpyrrol-3-substituted scaffold

A novel series of 1,5-diarylpyrrol-3-sulfur derivatives (10–12) was synthesized and characterized by NMR and mass spectroscopy and x-ray diffraction. The biological activity of these compounds was evaluated in in vitro and in vivo tests to assess their COX-2 inhibitory activity along with anti-inflammatory and antinociceptive effect.Results showed that the bioisosteric transformation of previously reported alkoxyethyl ethers (9a-c) into the corresponding alkyl thioethers (10a-c) still leads to selective and active compounds being the COX-2 inhibitory activity for most of them in the low nanomolar range. The oxidation products of 10a,b were also investigated and both couple of sulfoxides (11a,b) and sulfones (12a,b) showed an appreciable COX-2 inhibitory activity. Molecular modeling studies were performed to investigate the binding mode of the representative compounds 10b, 11b, and 12b into COX-2 enzyme and to explore the potential site of metabolism of 10a and 10b due to the different in vivo efficacy. Among the developed compounds, compound 10b showed a significant in vivo anti-inflammatory and antinociceptive activity paving the way to develop novel anti-inflammatory drugs.     

Design and synthesis of thiourea derivatives with sulfur-containing heterocyclic scaffolds as potential tyrosinase inhibitors

Tyrosinase is a key enzyme during the production of melanins in plants and animals. A class of novel N-aryl-N′-substituted phenylthiourea derivatives (3a–i, 6a–k) were designed, synthesized and their inhibitory effects on the diphenolase activity of mushroom tyrosinase were evaluated. The results showed some 4,5,6,7-tetrahydro-2-[[(phenylamino)thioxomethyl]amino]-benzo[b]thiophene-3-carboxylic acid derivatives (3a–i) exhibited moderate inhibitory potency on diphenolase activity of tyrosinase. When the scaffold of 4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid was replaced with 2-(1,3,4-thiadiazol-2-yl)thio acetic acid, the inhibitory activity of compounds (6a–k) against tyrosinase was improved obviously; especially, the inhibitory activity of compound 6h (IC₅₀ = 6.13 μM) is significantly higher than kojic acid (IC₅₀ = 33.3 μM). Moreover, the analysis on inhibition mechanism revealed that compound 6h might plays the role as a noncompetitive inhibitor.     

Semisynthesis,cytotoxicity, antimalarial evaluation and structure-activity relationship of two series of triterpene derivatives

In this report, we describe the semisynthesis of two series of ursolic and betulinic acid derivatives through designed by modifications at the C-3 and C-28 positions and demonstrate their antimalarial activity against chloroquine-resistant P. falciparum (W2 strain). Structural modifications at C-3 were more advantageous to antimalarial activity than simultaneous modifications at C-3 and C-28 positions. The ester derivative, 3β-butanoyl betulinic acid (7b), was the most active compound (IC₅₀?=?3.4?µM) and it did not exhibit cytotoxicity against VERO nor HepG2 cells (CC₅₀?>?400?µM), showing selectivity towards parasites (selectivity index?>?117.47). In combination with artemisinin, compound 7b showed an additive effect (CI?=?1.14). While docking analysis showed a possible interaction of 7b with the Plasmodium protease PfSUB1, with an optimum binding affinity of ?7.02?kcal/mol, the rather low inhibition displayed on a Bacillus licheniformis subtilisin A protease activity assay (IC₅₀?=?93?µM) and the observed accumulation of ring forms together with a delay of appearance of trophozoites in vitro suggests that the main target of 3β-butanoyl betulinic acid on Plasmodium may be related to other molecules and processes pertaining to the ring stage. Therefore, compound 7b is the most promising compound for further studies on antimalarial chemotherapy. The results obtained in this study provide suitable information about scaffolds to develop novel antimalarials from natural sources.     

Synthesis and biological evaluation of pyrano[4,3-b][1]benzopyranone derivatives as monoamine oxidase and cholinesterase inhibitors

A series of eighteen pyrano[4,3-b][1]benzopyranone derivatives (1a-9b) were synthesized, and structure-activity relationships of their monoamine oxidase (MAO) A and B, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibitory activities were evaluated. Most of the synthesized compounds exhibited weak inhibitory activity toward MAO-A, whereas compounds 2a, 2b, 4a, 4b, 5a, 5b, 6a, 6b, 8a and 8b showed potent inhibitory activities toward MAO-B. Intriguingly, compounds 5a, 5b, and 8a showed inhibitory activities comparable to pargylin, used as a positive control for MAO-B. Substitution of butoxy at the C3 position or of chlorine at the C8 position of pyrano[4,3-b][1]benzopyranone increased the inhibitory activity of the compound toward MAO-B. The results of a molecular docking study supported this structural effect. Most of the compounds exhibited no or slight inhibitory activity toward AChE and BChE, with exo type compounds bearing a butoxy group, such as compounds 2b, 5b and 8b, showing weak but distinct inhibitory activities toward BChE. This report is the first to identify pyrano[4,3-b][1]benzopyranone derivatives as potent and selective MAO-B inhibitors. 3-Butoxy-8-chloro-pyrano[4,3-b][1]benzopyranone (5b) may be useful as a lead compound for the development of MAO-B inhibitors.     

Synthesis,characterization and in vitro,in vivo,in silico biological evaluations of substituted benzimidazole derivatives

A series of substituted benzimidazole derivatives were synthesized by reacting O-phenylenediamine with various aromatic aldehydes or glycolic acid using various inexpensive reagents in aqueous media. Synthesized compounds were characterized and elucidated by IR, ¹H NMR, ESI-MS spectra. Resultant compounds were screened for in vitro antimicrobial, cytotoxic, antioxidant, lipid peroxidation and cholinesterase inhibitory activities, in vivo analgesic and anti-inflammatory, and in silico anti-acetylcholinesterase and anti-butyrylcholinesterase activities. Among the synthesized compounds, compound 3b showed most promising central analgesic effect (46.15%) compared to morphine (48.08%), whereas compounds 6, 3c and 3a showed significant peripheral analgesic activity at two different dose levels (25 mg/kg and 50 mg/kg). Compounds 3b and 3a at the dose of 100 mg/kg showed significant anti-inflammatory effects from the first hour and onward, whereas compounds 6 and 3b showed moderate cytotoxic activities. In addition, compound 3a showed significant antioxidant activity having IC₅₀ value of 16.73 µg/ml compared to 14.44 µg/ml for the standard BHT. Compound 6, 3a and 3b exhibited mild to moderate cholinesterase inhibitory activity. In silico studies revealed that compound 3a and 3b might be suitable for cholinesterase inhibitory activity. A comprehensive computational and experimental data suggested compounds 3b and 3a as the best possible candidates for pharmacological activity. All the experimental data were statistically significant (p < 0.01 level).     

Identification of novel uracil derivatives incorporating benzoic acid moieties as highly potent Dipeptidyl Peptidase-IV inhibitors

Dipeptidyl Peptidase-IV (DPP-4) is a validated therapeutic target for type 2 diabetes. Aiming to interact with both residues Try629 and Lys554 in S₂′ site, a series of novel uracil derivatives 1a–l and 2a–i incorporating benzoic acid moieties at the N₃ position were designed and evaluated for their DPP-4 inhibitory activity. Structure-activity relationships (SAR) study led to the identification of the optimal compound 2b as a potent and selective DPP-4 inhibitor (IC₅₀?=?1.7?nM). Docking study revealed the additional salt bridge formed between the carboxylic acid and primary amine of Lys554 has a key role in the enhancement of the activity. Furthermore, compound 2b exhibited no cytotoxicity in human hepatocyte LO2 cells up to 50?μM. Subsequent in vivo evaluations revealed that the ester of 2b robustly improves the glucose tolerance in normal mice. The overall results have shown that compound 2b has the potential to a safe and efficacious treatment for T2DM.     

Design,synthesis, in vivo,and in silico evaluation of new coumarin-1,2,4-oxadiazole hybrids as anticonvulsant agents

A novel series of coumarin-1,2,4-oxadiazole hybrids were designed, synthesized, and evaluated as anticonvulsant agents. The title compounds were easily synthesized from reaction of appropriate coumarins and 3-aryl-5-(chloromethyl)-1,2,4-oxadiazole derivatives. In vivo anticonvulsant activity of the synthesized compounds were determined using pentylenetetrazole (PTZ)- and maximal electroshock (MES)-induced seizures confirming that they were more effective against MES test than PTZ test. It should be noted that compounds 3b, 3c, and 3e showed the best activity in MES model which possessed drug-like properties with no neurotoxicity. Anticonvulsant activity of the most potent compound 3b was remarkably reduced after treatment with flumazenil which confirmed the participation of a benzodiazepine mechanism in the anticonvulsant activity. Also, docking study of compound 3b in the BZD-binding site of GABA_A receptor confirmed possible binding of 3b to the BZD receptors.     

Structural development of 1H-pyrazolo-[3,4-b]pyridine-4-carboxylic acid derivatives as human peroxisome proliferator-activated receptor alpha (PPARα)-selective agonists

We previously reported that 1H-pyrazolo-[3,4-b]pyridine-4-carboxylic acid derivative 6 is an agonist of human peroxisome proliferator-activated receptor alpha (hPPARα). Here, we prepared a series of 1H-pyrazolo-[3,4-b]pyridine-4-carboxylic acid derivatives in order to examine the structure-activity relationships (SAR). SAR studies clearly indicated that the steric bulkiness of the substituent on 1H-pyrazolo-[3,4-b]pyridine ring, the position of the distal hydrophobic tail part, and the distance between the distal hydrophobic tail part and the acidic head part are critical for hPPARα agonistic activity. These SAR results are somewhat different from those reported for fibrate-class hPPARα agonists. A representative compound (10f) was as effective as fenofibrate in reducing the elevated plasma triglyceride levels in a high-fructose-fed rat model.     

Synthesis and in vitro evaluation of 12-(substituted aminomethyl) berberrubine derivatives as anti-diabetics

By introducing various amino methyl groups into 12-position of berberrubine, a series of 12-(substituted aminomethyl) berberrubine derivatives were synthesized and evaluated for their anti-diabetic activity against type 2 diabetes mellitus. The results indicated that most of the prepared compounds exhibited moderate to good anti-diabetic activity, which were comparable to or even better than the berberine, the positive control rosiglitazone and insulin. Especially, compound 3b with an N-methyl piperazine-4-methyl group at C-12, exerted the most powerful anti-diabetic activity.     

Discovery and structure–activity relationships of a novel series of benzopyran-based KATP openers for urge urinary incontinence

A novel series of benzopyran derivatives were synthesized and evaluated as K_ATP channel openers. Structure–activity relationships were investigated around 4-position of the benzopyran nucleus. Optimization of 4-substituent with some heterocyclic rings led to compound 13b bearing a benzo[d]isoxazol-3-one moiety as a potent and selective K_ATP channel opener in vitro. In two anesthetized rat models of myogenic bladder overactivity, compound 13b was found to inhibit spontaneous bladder contractions.     

Design,synthesis, anti-schistosomal activity and molecular docking of novel 8-hydroxyquinoline-5-sufonyl 1,4-diazepine derivatives

Schistosomiasis remains one of the most prevalent parasitic infections and has significant public health consequences. Praziquantel (PZQ) is the only drug currently administrated to treat this disease. However, praziquantel-resistant parasites have been identified in endemic areas and can be generated in the laboratory. Therefore, it is essential to find new therapeutics. Herein we report a series of novel 8-hydroxyquinoline-5-sufonyl 1,4-diazepine derivatives, which were synthesized, characterized and tested as anti-schistosomal agents in vitro. Among all tested compounds, compounds 4a, 5b, and 7b at different tested concentrations (50, 100, and 200 μg/mL) showed the highest schistosomicidal activity. Among those 3 compounds, compound 7b was the most potent anti-schistosomal one. Moreover, all tested compound, at 50 μg/mL concentration, significantly reduced oviposition of adult worms in vitro. Furthermore, both compound 4a and 7b, as well as compound 6a, completely diminished egg deposition. To clarify the possible mechanism by which novel 8-hydroxyquinoline-5-sufonyl 1,4-diazepine derivatives act as anti-schistosomal agents, molecular docking of all new compounds was carried out using Molsoft ICM pro 3.5-0a to investigate the binding affinity and binding mode to thioredoxin glutathione reductase enzyme (TGR), a potential drug target for anti-schistosomal agents. The docking results revealed moderate to high affinity of the new compounds towards TGR. Compound 7b scored the highest binding energy (−101.13 kcal/mol) against TGR crystal structure forming eight hydrogen bonds with the amino acid residues at the binding site of the receptor. This result indicates that compound 7b could exert its effect through inhibition of TGR, which is a vital enzyme for schistosome survival.     

Discovery of novel benzene 1,3-dicarboxylic acid inhibitors of bacterial MurD and MurE ligases by structure-based virtual screening approach

The peptidoglycan biosynthetic pathway provides an array of potential targets for antibacterial drug design, attractive especially with respect to selective toxicity. Within this pathway, the members of the Mur ligase family are considered as promising emerging targets for novel antibacterial drug design. Based on the available MurD crystal structures co-crystallised with N-sulfonyl glutamic acid inhibitors, a virtual screening campaign was performed, combining three-dimensional structure-based pharmacophores and molecular docking calculations. A novel class of glutamic acid surrogates—benzene 1,3-dicarboxylic acid derivatives—were identified and compounds 14 and 16 found to possess dual MurD and MurE inhibitory activity.     

Discovery of 2,6-disubstituted pyrazine derivatives as inhibitors of CK2 and PIM kinases

The design and synthesis of a novel series of 2,6-disubstituted pyrazine derivatives as CK2 kinase inhibitors is described. Structure-guided optimization of a 5-substituted-3-thiophene carboxylic acid screening hit (3a) led to the development of a lead compound (12b), which shows inhibition in both enzymatic and cellular assays. Subsequent design and hybridization efforts also led to the unexpected identification of analogs with potent PIM kinase activity (14f).     

Synthesis and biological evaluation of hesperetin derivatives as agents inducing apoptosis

A flavanone, hesperetin, has been known to exert antitumor activity by inducing apoptosis. To find hesperetin derivatives showing better antitumor activity, 12 derivatives were designed and synthesized. Their antitumor activities were measured using a long-term survival clonogenic assay. Among the compounds, K-5b, hesperetin-7-butyrate, showed the half-maximal cell growth inhibitory concentration three times as low as that of hesperetin. To compare the cytotoxicity of hesperetin and K-5b, the HCT116 human colon cancer cell line was treated with various concentrations of each compound. K-5b decreased the cell viability to a larger extent than hesperetin and triggered apoptosis more efficiently than hesperetin in an apoptosis detection assay using fluorescein isothiocyanate-labeled annexin V. Immunoblotting analysis showed that K-5b promoted caspase-mediated apoptosis more efficiently than hesperetin. Because hesperetin has been reported to induce apoptosis through the activation of the c-Jun N-terminal kinase (JNK) pathway, we tested whether K-5b activates JNKs. K-5b stimulated JNK1 and JNK2 more efficiently than hesperetin as shown by western blot analysis. In conclusion, hesperetin derivatives exerting better antitumor activity than hesperetin by inducing apoptosis were found.     

Novel salicylamide derivatives as potent multifunctional agents for the treatment of Alzheimer's disease: Design,synthesis and biological evaluation

A series of salicylamide derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer’s disease. In vitro assays demonstrated that most of the derivatives were selective AChE inhibitors. They showed good inhibitory activities of self- and Cu²⁺-induced Aβ_1–42 aggregation, and significant antioxidant activities. Among them, compound 15b exhibited good inhibitory activity toward RatAChE and EeAChE with IC₅₀ value of 10.4 μM and 15.2 μM, respectively. Moreover, 15b displayed high antioxidant activity (2.46 Trolox equivalents), good self- and Cu²⁺-induced Aβ_1–42 aggregation inhibitory potency (42.5% and 31.4% at 25.0 μM, respectively) and moderate disaggregation ability to self- and Cu²⁺-induced Aβ_1–42 aggregation fibrils (23.4% and 27.0% at 25 μM, respectively). Furthermore, 15b also showed biometal chelating abilities, anti-neuroinflammatory ability and BBB permeability. These multifunctional properties indicated compound 15b was worthy of being chosen for further pharmacokinetics, toxicity and behavioral researches to test its potential for AD treatment.     

Design,synthesis, anti-inflammatory activity and molecular docking of potential novel antipyrine and pyrazolone analogs as cyclooxygenase enzyme (COX) inhibitors

As a part of a directed program for development of new active agents, novel heterocyclic derivatives with antipyrine and pyrazolone moieties -incorporated in- have been designed and synthesized. Starting with 4-arylidene-3-methyl-1-phenyl-5-pyrazolone derivative 2a,b novel Mannich bases derivatives have been synthesized and biologically evaluated for their anti-inflammatory activity. Furthermore, the activity of such compounds has been tested interestingly as COX-1 and COX-2 inhibitors. Structure elucidation of the synthesized compounds was attained by the use of elemental analysis, IR, ¹H NMR, ¹³C NMR, and Mass spectrometry techniques. Compounds 3b, 3d and 4b represent the high % inhibition values for both COX-1 and COX-2. On the other hand, compound 8 showed little selectivity against COX-2 while compound 10 showed good selectivity against COX-1 only. Structure activity relationship has been discussed and the results were confirmed by molecular docking calculations.