3-Arylpropionylhydroxamic acid derivatives as Helicobacter pylori urease inhibitors: Synthesis,molecular docking and biological evaluation

Helicobacter pylori urease is involved in several physiologic responses such as stomach and duodenal ulcers, adenocarcinomas and stomach lymphomas. Thus, inhibition of urease is taken for a good chance to treat H. pylori-caused infections, we have therefore focused our efforts on seeking novel urease inhibitors. Here, a series of arylpropionylhydroxamic acids were synthesized and evaluated for urease inhibition. Out of these compounds, 3-(2-benzyloxy-5-chlorophenyl)-3-hydroxypropionylhydroxamic acid (d24) was the most active inhibitor with IC₅₀ of 0.15 ± 0.05 μM, showing a mixed inhibition with both competitive and uncompetitive aspects. Non-linear fitting of kinetic data gives kinetics parameters of 0.13 and 0.12 μg·mL⁻¹ for K_i and K_i′, respectively. The plasma protein binding assays suggested that d24 exhibited moderate binding to human and rabbit plasma proteins.     

Syntheses of 4,6-dihydroxypyrimidine diones,their urease inhibition,in vitro,in silico,and kinetic studies

A library of 4,6-dihydroxypyrimidine diones (1–35) were synthesized and evaluated for their urease inhibitory activity. Structure-activity relationships, and mechanism of inhibition were also studied. All compounds were found to be active with IC₅₀ values between 22.6 ± 1.14–117.4 ± 0.73 µM, in comparison to standard, thiourea (IC₅₀ = 21.2 ± 1.3 µM). Kinetics studies on the most active compounds 2–7, 16, 17, 28, and 33 were performed to investigate their modes of inhibition, and dissociation constants K_i. Compounds 2, 3, 7, 16, 28, and 33 were found to be mixed-type of inhibitors with K_i values in the range of 7.91 ± 0.024–13.03 ± 0.013 µM, whereas, compounds 4–6, and 17 were found to be non-competitive inhibitors with K_i values in the range of 9.28 ± 0.019–13.05 ± 0.023 µM. In silico study was also performed, and a good correlation was observed between experimental and docking studies. This study is continuation of our previously reported urease inhibitory activity of pyrimidine diones, representing potential leads for further research as possible treatment of diseases caused by ureolytic bacteria.     

Hybrid benzothiazole analogs as antiurease agent: Synthesis and molecular docking studies

Benzothiazole analogs (1–20) have been synthesized, characterized by EI-MS and ¹H NMR, and evaluated for urease inhibition activity. All compounds showed excellent urease inhibitory potential varying from 1.4 ± 0.10 to 34.43 ± 2.10 μM when compared with standard thiourea (IC₅₀ 19.46 ± 1.20 μM). Among the series seventeen (17) analogs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, and 18 showed outstanding urease inhibitory potential. Analogs 15 and 19 also showed good urease inhibition activity. When we compare the activity of N-phenylthiourea 20 with all substituted phenyl derivatives (1–18) we found that compound 15 showed less activity than compound 20 having 3-methoxy substituent. The binding interactions of these active analogs were confirmed through molecular docking.     

Solution-phase microwave assisted parallel synthesis,biological evaluation and in silico docking studies of N,N′-disubstituted thioureas derived from 3-chlorobenzoic acid

A facile and robust microwave-assisted solution phase parallel synthesis protocol was exercised for the development of a 38-member library of N,N′-disubstituted thiourea analogues (1–38) by using an identical set of conditions. The reaction time for synthesis of N,N′-disubstituted thiourea analogues was drastically reduced from a reported duration of 8–12 h for conventional methods to only 1.5–2.0 min. All the derivatives (1–38) were characterized by physico-analytical techniques such as elemental analysis in combination with FT-IR, ¹H, ¹³C NMR and by single crystal XRD analysis have also been performed. These compounds were screened for their in vitro urease inhibition activities. Majority of compounds exhibited potent urease inhibition activities, however, the most significant activity was found for 16, with an IC₅₀ value of 1.23 ± 0.1 μM. Furthermore, the synthesized compounds were screened for their cytotoxic potential against lungs cancer cell lines. Cell culture studies demonstrated significant toxicity of the compounds on the cell lines, and the levels of toxicity were altered in the presence of various side groups. The molecular docking studies of the most potent inhibitors were performed to identify the probable binding modes in the active site of the urease enzymes. These compounds have a great potential and significance for further investigations.     

New coumarin derivatives: Design,synthesis and use as inhibitors of hMAO

A series new 2H-chromene-3-carboxamides (4a–4i) and S-2H-chromene-3-carbothioates (5j–5t) were synthesized and evaluated as monoamine oxidase A and B inhibitors. Among them, compound 5k (IC₅₀ = 0.21 μM, IC_{50 iproniazid} = 7.65 μM) showed the most activity and higher MAO-B selectivity (189.2-fold vs 1-fold) with respect to the MAO-A isoform. The need to clarify at a 3D level some important molecular aspects of discussed SAR, we undertaked a number of docking simulations to better assess. The steric effect was analyzed interms of both posing and scoring by investigating the nature of the binding interactions. The docking results of active compound 5k with hMAO-B complex indicated that conserved residue ILE 199 was important for ligand binding via Sigma–Pi interaction.     

Synthesis and antiproliferative evaluations of certain 2-phenylvinylquinoline (2-styrylquinoline) and 2-furanylvinylquinoline derivatives

The present study describes the synthesis of 2-phenylvinylquinoline (styrylquinoline) and 2-furanylvinylquinoline derivatives and evaluation for their antiproliferative activities. (E)-2-Styrylquinolin-8-ol (14a) was inactive against a 3-cell line panel consisting of MCF-7 (Breast), NCI-H460 (Lung), and SF-268 (CNS). Replacement of the phenyl ring with 5-nitrofuran-2-yl group significantly enhanced antiproliferative activity in which (E)-2-(2-(5-nitrofuran-2-yl)vinyl)quinolin-8-ol (14i) and its 4-substituted derivatives 15–19 exhibited strong inhibitory effects against the growth of all three cancer cells. These compounds were further evaluated for their IC₅₀ against the growth of MCF-7, LNCaP, and PC3. Results indicated that a hydrogen bond donating oxime derivative 19a was more active than its hydrogen bond accepting methyloxime derivative 19b. For the inhibition of LNCaP, the potency decreased in an order 14i > 19a > 19b > 15 > 18 > 16. Compound 14i is the most active with an IC₅₀ value of 0.35 and 0.14 μM, respectively, against the growth of LNCaP and PC3 cancer cells. Therefore, compound 14i was evaluated by flow cytometric analysis for its effects on cell cycle distributions. Results indicated that 14i effectively induced cell cycle arrest at S phase for both cell lines, which consequently trigger late apoptosis for both LNCaP and PC3 cells.     

Tyrosinase inhibitory effects of 1,3-diphenylpropanes from Broussonetia kazinoki

Six 1,3-diphenylpropanes exhibiting inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase were isolated from the methanol (95%) extract of Broussonetia kazinoki. These compounds, 1–6, were identified as kazinol C (1), D (2), F (3), broussonin C (4), kazinol S (5) and kazinol T (6). The latter two species (5 and 6) emerged to be new 1,3-diphenylpropanes which we fully spectroscopically characterized. The IC₅₀ values of compounds (1, 3–5) for monophenolase inhibition were determined to range between 0.43 and 17.9 μM. Compounds 1 and 3–5 also inhibited diphenolase significantly with IC₅₀ values of 22.8, 1.7, 0.57, and 26.9 μM, respectively. All four active tyrosinase inhibitors (1, 3–5) were competitive inhibitors. Interestigly they all mainfested simple reversible slow-binding inhibition against diphenolase. The most potent inhibitor, compound 4 diplayed the following kinetic parameters k₃ = 0.0993 μM^?1 min^?1, k₄ = 0.0048 min^-1, and K_i^app = 0.0485 μM.     

Synthesis,biological evaluation and molecular docking of N-phenyl thiosemicarbazones as urease inhibitors

Urease is an important enzyme which breaks urea into ammonia and carbon dioxide during metabolic processes. However, an elevated activity of urease causes various complications of clinical importance. The inhibition of urease activity with small molecules as inhibitors is an effective strategy for therapeutic intervention. Herein, we have synthesized a series of 19 benzofurane linked N-phenyl semithiocarbazones (3a–3s). All the compounds were screened for enzyme inhibitor activity against Jack bean urease. The synthesized N-phenyl thiosemicarbazones had varying activity levels with IC₅₀ values between 0.077 ± 0.001 and 24.04 ± 0.14 μM compared to standard inhibitor, thiourea (IC₅₀ = 21 ± 0.11 μM). The activities of these compounds may be due to their close resemblance of thiourea. A docking study with Jack bean urease (PDB ID: 4H9M) revealed possible binding modes of N-phenyl thiosemicarbazones.     

Design and synthesis of 2-substituted benzoxazoles as novel PTP1B inhibitors

A series of benzoxazole compounds containing oxamic acid were synthesized and screened for the PTP1B inhibition. Compound 31d showed best biochemical potency (K_i) of 6.7 μM. Structure–activity relationship were explained with the help of molecular modeling approach.     

Synthesis,biological evaluation and molecular docking study of N-arylbenzo[d]oxazol-2-amines as potential α-glucosidase inhibitors

A novel series of N-arylbenzo[d]oxazol-2-amines (4a–4m) were synthesized and evaluated for their α-glucosidase inhibitory activity. Compounds 4f–4i, 4k and 4m displayed potent inhibitory activity against α-glucosidase with IC₅₀ values in the range of 32.49 ± 0.17–120.24 ± 0.51 μM as compared to the standard drug acarbose. Among all tested compounds, compound 4g having 4-phenoxy substitution at the phenyl ring was found to be the most active inhibitor of α-glucosidase with an IC₅₀ value of 32.49 ± 0.17 μM. Analysis of the kinetics of enzyme inhibition indicated that compound 4g is a noncompetitive inhibitor of α-glucosidase with a K_i value of 31.33 μM. Binding interaction of compound 4g with α-glucosidase was explored by molecular docking simulation.     

Design and synthesis of biphenyl derivatives as mushroom tyrosinase inhibitors

Two new series of biphenyls, analogs of aglycone of natural product fortuneanoside E, were prepared using Suzuki–Miyaura cross-coupling and selective magnesium iodide demethylation/debenzylation, and their mushroom tyrosinase inhibitory activity was evaluated. Most of the 4-hydroxy-3,5-dimethoxyphenyl biphenyl compounds (series II, 20–36) were in general more active than 3,4,5-trimethoxyphenyl biphenyl compounds (series I, 1–19). Structure–activity relationships study showed that monosaccharide substituents, such as glucose, were not necessary and the presence of 4-hydroxy-3,5-dimethoxyphenyl moiety was crucial for inhibitory activity. Among the compounds synthesised, compound 21 (IC₅₀ = 0.02 mM) was found to be the most active one, which exhibited an activity that was 7 times higher than that of fortuneanoside E (IC₅₀ = 0.14 mM) and 10 times higher than that of arbutin (IC₅₀ = 0.21 mM), known as potent tyrosinase inhibitors. The inhibition kinetics analyzed by Lineweaver–Burk plots revealed that compound 21 was a competitive inhibitor (K_i = 0.015 mM).     

Novel indolizine derivatives with unprecedented inhibitory activity on human farnesyltransferase

The rational structural modification of new substituted indolizin-3-yl(phenyl)methanones 1a–i, 2a–i and 3a–i has greatly improved human farnesyltransferase inhibition. The para-bromophenyl analog 2f bearing an ester unit on the indolizine ring demonstrates the highest inhibition potential, with IC₅₀ value of 1.3 ± 0.2 μM. The amidic series 1a–i proves to be the most promising for future modulations, particularly at the triple bond level.     

Structural characteristics of thiosemicarbazones as inhibitors of melanogenesis

A series of thiosemicarbazones 2(e–s) have been synthesized and studied their structure–activity relationship as melanogenesis inhibitor. Among them, (Z)-2-(naphthalen-1-ylmethylene)hydrazinecarbothioamide (2q, >100% inhibition at 10 μM, IC₅₀ = 1.1 μM, C log P = 3.039) showed the strongest inhibitory activity. Regarding their structure–activity relationship, the hydrophobic substituents regardless the position on phenyl ring of benzaldehyde thiosemicarbazones enhance the inhibitory activity. Furthermore, the aromatic group of benzaldehydethiosemicarbazones can be replaced with sterically bulky cyclohexyl. Thus, hydrophobicity of the aryl or alkyl group on hydrazine of thiosemicarbazones is determinant factor for their inhibitory activity in melanogenesis rather than planarity.     

NAD-based inhibitors with anticancer potential

Three classes of novel inhibitors of inosine monophosphate dehydrogenase have been prepared and their anti-proliferative properties were evaluated against several cancer cell lines.(1) Mycophenolic adenine dinucleotide analogues (8–13) containing a substituent at the C2 of adenine ring were found to be potent inhibitors of IMPDH (K_i’s in range of 0.6–82 nM) and sub-μM inhibitors of leukemic K562 cell proliferation. (2) Mycophenolic adenosine (d and l) esters (20 and 21) showed a potent inhibition of IMPDH2 (K_i = 102 and K_i = 231 nM, respectively) and inhibition of K562 cell growth (IC₅₀ = 0.5 and IC₅₀ = 1.6 μM). These compounds serve both as inhibitors of the enzyme and as a depot form of mycophenolic acid. The corresponding amide analogue 22, also a potent inhibitor of IMPDH (K_i = 84 nM), did not inhibit cancer cell proliferation. (3) Mycophenolic-(l)- and (d)-valine adenine di-amide derivatives 25 (K_i = 9 nM) and 28 (K_i = 3 nM) were found to be very potent enzymatically, but did not inhibit proliferation of cancer cells.     

1,3,4-Oxadiazole-2(3H)-thione and its analogues: A new class of non-competitive nucleotide pyrophosphatases/phosphodiesterases 1 inhibitors

A series of 1,3,4-oxadiazole-2 (3H)-thiones and 1,3,4-thiadiazole-2 (3H)-thiones were synthesized and evaluated for their inhibitory activities against the two nucleotide pyrophosphatase phosphodiesterase 1 enzymes. Dixon, as well as Lineweaver–Burk plots, and their secondary replots have indicated that the inhibition was of pure non-competitive type, against both snake venom and pure human recombinant enzymes as the V_max values decreases without affecting the K_m values. 5-[4-(t-Butyldimethylsilyloxy)-phenyl]-1,3,4-thiadiazole-2 (3H)-thione (17) and [4-(t-butyldimethylsilyloxy)-phenyl]-1,3,4-oxadiazole-2 (3H)-thione (1) were found to be the most active compounds with IC₅₀ values 66.47 and 368 μM, respectively. The K_i values were 100 μM and 360 μM against the snake venom and human recombinant NPP1 enzyme, respectively. Most active compounds were found to be non-toxic in neutrophil viability assay.     

Probes for narcotic receptor mediated phenomena. 47.1 Novel C4a- and N-substituted-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ols

A series of N-methyl rac-cis-4a-aralkyl- and alkyl-substituted-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ols have been prepared (2a–l) using a simple previously designed synthetic route, in order to find a ligand that would interact with both μ- and δ-opioid receptors. A C4a-phenethyl derivative 2a, was found to have modest receptor affinity both at μ- (K_i = 60 nM) and δ-opioid receptors (K_i = 64 nM). The N-methyl substituent of 2a and that of other ligands in the series was then modified to obtain compounds with different N-substituents that might provide higher affinity at both receptors. A number of compounds differently substituted at C4a and N were synthesized and evaluated. Binding studies and functional assays revealed a moderately selective δ-antagonist (2l), selective μ–δ antagonists (3d, 3g), and a μ–κ antagonist (3f).     

4-Functionalized 1,3-diarylpyrazoles bearing 6-aminosulfonylbenzothiazole moiety as potent inhibitors of carbonic anhydrase isoforms hCA I,II, IX and XII

A series of 24 novel heterocyclic compounds—functionalized at position 4 with aldehyde (5a–5f), carboxylic acid (6a–6f), nitrile (7a–7f) and oxime (8a–8f) functional groups—bearing 6-aminosulfonybenzothiazole moiety at position 1 of pyrazole has been synthesized and investigated for the inhibition of four isoforms of the α-class carbonic anhydrases (CAs, EC 4.2.1.1), comprising hCAs I and II (cytosolic, ubiquitous isozymes) and hCAs IX and XII (transmembrane, tumor associated isozymes). Against the human isozyme hCA I, compounds 6a–6f showed medium-weak inhibitory potential with K_i values in the range of 157–690 nM with 6a showing better potential than the standard drug acetazolamide (AZA). Against hCA II, all the compounds showed excellent to moderate inhibition with K_i values of compounds 5a, 5d, 5f, 6a–6f, 8d and 8f lower than 12 nM (K_i of AZA). Against hCA IX, all the compounds showed moderate inhibition with the exception of 6e which showed nearly 9 fold a better profile compared to AZA, whereas against hCA XII, four compounds 6e, 7a, 7b and 7d showed K_i in the same order as that of AZA. Carboxylic acid 6e was found to be an excellent inhibitor of both hCA IX and XII, with K_i values of 2.8 nM and 5.5 nM, respectively.     

Synthesis,biological evaluation and molecular docking studies of benzyloxyacetohydroxamic acids as LpxC inhibitors

The inhibition of the UDP-3-O-[(R)-3-hydroxymyristoyl]-N-acetylglucosamine deacetylase (LpxC) represents a promising strategy to combat infections caused by multidrug-resistant Gram-negative bacteria. In order to elucidate the functional groups being important for the inhibition of LpxC, the structure of our previously reported hydroxamic acid 4 should be systematically varied. Therefore, a series of benzyloxyacetohydroxamic acids was prepared, of which the diphenylacetylene derivatives 28 (K_i = 95 nM) and 21 (K_i = 66 nM) were the most potent inhibitors of Escherichia coli LpxC. These compounds could be synthesized in a stereoselective manner employing a Sharpless asymmetric dihydroxylation and a Sonogashira coupling in the key steps. The obtained structure–activity relationships could be rationalized by molecular docking studies.     

Exploring the 2- and 5-positions of the pyrazolo[4,3-d]pyrimidin-7-amino scaffold to target human A1 and A2A adenosine receptors

A new series of 7-aminopyrazolo[4,3-d]pyrimidine derivatives (1–31) were synthesized to evaluate some structural modifications at the 2- and 5-positions aimed at shifting affinity towards the human (h) A_2A adenosine receptor (AR) or both hA_2A and hA₁ ARs. The most active compounds were those featured by a 2-furyl or 5-methylfuran-2-yl moiety at position 5, combined with a benzyl or a substituted-benzyl group at position 2. Several of these derivatives (22–31) displayed nanomolar affinity for the hA_2A AR (K_i = 3.62–57 nM) and slightly lower for the hA₁ ARs, thus showing different degrees (3–22 fold) of hA_2A versus hA₁ selectivity. In particular, the 2-(2-methoxybenzyl)-5-(5-methylfuran-2-yl) derivative 25 possessed the highest hA_2A and hA₁ AR affinities (K_i = 3.62 nM and 18 nM, respectively) and behaved as potent antagonist at both these receptors (cAMP assays). Its 2-(2-hydroxybenzyl) analog 26 also showed a high affinity for the hA_2A AR (K_i = 5.26 nM) and was 22-fold selective versus the hA₁ subtype. Molecular docking investigations performed at the hA_2A AR crystal structure and at a homology model of the hA₁ AR allowed us to represent the hypothetical binding mode of our derivatives and to rationalize the observed SARs.     

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.