Synthesis and Biological Evaluation of Dithiobisacetamides as Novel Urease Inhibitors.

Thirty-eight disulfides containing N-arylacetamide were designed and synthesized in an effort to develop novel urease inhibitors. Biological evaluation revealed that some of the synthetic compounds exhibited strong inhibitory potency against both cell-free urease and urease in intact cell with low cytotoxicity to mammalian cells even at concentration up to 250 µM. Of note, 2,2'-dithiobis(N-(2-fluorophenyl)acetamide) (d7), 2,2'-dithiobis(N-(3,5-difluorophenyl)acetamide) (d24), and 2,2'-dithiobis(N-(3-fluorophenyl)acetamide) (d8) were here identified as the most active inhibitors with IC50 of 0.074, 0.44, and 0.81 µM, showing 32- to 355-fold higher potency than the positive control acetohydroxamic acid. These disulfides were confirmed to bind urease without covalent modification of the cysteine residue and to inhibit urease reversibly with a mixed inhibition mechanism. They also showed very good anti-Helicobacter pylori activities with d8 showing a comparable potency to the clinical used drug amoxicillin. The impressive in vitro biological profile indicated their immense potential as therapeutic agents to tackle H. pylori caused infections.

Synthesis and Structure-Activity Relationship Studies of N-monosubstituted Aroylthioureas as Urease Inhibitors.

BACKGROUND: Thiourea is a classical urease inhibitor which is usually used as a positive control, and many N,N'-disubstituted thioureas have been determined as urease inhibitors. However, due to steric hindrance, N,N'-disubstituted thiourea motif could not bind urease as thiourea. On the contrary, N-monosubstituted thiourea with a tiny thiourea motif could theoretically bind into the active pocket as thiourea. OBJECTIVE: A series of N-monosubstituted aroylthioureas were designed and synthesized for evaluation as urease inhibitors. METHODS: Urease inhibition was determined by the indophenol method and IC50 values were calculated using computerized linear regression analysis of quantal log dose-probit functions. The kinetic parameters were estimated via surface plasmon resonance (SPR) and by nonlinear regression analysis based on the mixed type inhibition model derived from Michaelis-Menten kinetics. RESULTS: Compounds b2, b11, and b19 reversibly inhibited urease with a mixed mechanism, and showed excellent potency against both cell-free urease and urease in the intact cell, with IC50 values being 90- to 450-fold and 5- to 50-fold lower than the positive control acetohydroxamic acid, respectively. The most potent compound b11 showed an IC50 value of 0.060 ± 0.004µM against cell-free urease, which bound to urea binding site with a very low KD value (0.420±0.003nM) and a very long residence time (6.7 min). Compound b11 was also demonstrated to have very low cytotoxicity to mammalian cells. CONCLUSION: The results revealed that N-monosubstituted aroylthioureas bound to the active site of urease as expected, and represent a new class of urease inhibitors for the development of potential therapeutics against infections caused by urease-containing pathogens.

Resolution and evaluation of 3-chlorophenyl-3-hydroxypropionylhydroxamic acid as antivirulence agent with excellent eradication efficacy in Helicobacter pylori infected mice.

The continuing emergence of drug-resistant Helicobacter pylori (HP) drives the ongoing need for the development of new and effective anti-HP drugs. Urease inhibitor has now gained strong interest as an alternative approach for HP infections. 3-Chlorophenyl-3-hydroxypropionylhydroxamic acid (CPH), a novel urease inhibitor identified in our group, shows impressive potency, which was optically separated for a further exploration. Here, we report in vitro/in vivo pharmacological evaluation of (±)-CPHs and the enantiomers. The raceme and the individual enantiomers significantly suppress gastritis at 32 mg/kg b.i.d dose with lower toxicity to mammalian cells (with CC50s ≥ 3.16 mM) and mice (LD50s ≥ 2338 mg/kg) than the clinically used agent acetohydroxamic acid. Furthermore, a significant increase of eradication of HP is observed for the combination of (±)-CPHs or the enantiomers with an antimicrobial. These studies revealed that CPH is a promising candidate for an alternative treatment of HP-dependent conditions by targeting virulence factor urease, and CPH may be used as a raceme.

Synthesis and evaluation of adenosine containing 3-arylfuran-2(5H)-ones as tyrosyl-tRNA synthetase inhibitors.

Tyrosyl-tRNA synthetase (TyrRS) is an aminoacyl-tRNA synthetase family protein that possesses an essential role in bacterial protein synthesis. The synthesis, structure-activity relationship, and evolution of a novel series of adenosine-containing 3-arylfuran-2(5H)-ones as TyrRS inhibitors are described. Advanced compound d3 from this series exhibited excellent affinity for TyrRS with IC50 of 0.61 ± 0.04 µM. Bacterial growth inhibition assays demonstrated that d3 showed submicromolar antibacterial potency against Escherichia coli and Pseudomonas aeruginosa, and compared to the marketed antibiotics ciprofloxacin.

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±0.05µM, showing a mixed inhibition with both competitive and uncompetitive aspects. Non-linear fitting of kinetic data gives kinetics parameters of 0.13 and 0.12µg·mL(-1) for Ki and Ki', respectively. The plasma protein binding assays suggested that d24 exhibited moderate binding to human and rabbit plasma proteins.

Adenosine analogs as inhibitors of tyrosyl-tRNA synthetase: Design, synthesis and antibacterial evaluation.

Herein we describe the synthesis and evaluation of a series of adenosine analogs for in vitro antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Out of these compounds, compound c6 has much stronger antibacterial potency against Pseudomonas aeruginosa than ciprofloxacin, and was determined to target tyrosyl-tRNA synthetase with IC50 of 0.8±0.07 µM. Structure-activity relationship analysis suggested that introduction of a fluorine atom at the 3'-position of benzene ring of the phenylacetyl moiety significantly increased affinities to the enzyme. In comparison with isopropylidene analogs, 2',3'-deprotected compounds displayed higher inhibitory activity. Molecular dockings provided an explanation for observations in biological assays.

Synthesis, molecular docking and evaluation of thiazolyl-pyrazoline derivatives as EGFR TK inhibitors and potential anticancer agents.

Fourty-two thiazolyl-pyrazoline derivatives were synthesized to screen for their EGFR kinase inhibitory activity. Compound 4-(4-chlorophenyl)-2-(3-(3,4-dimethylphenyl)-5-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)thiazole (11) displayed the most potent EGFR TK inhibitory activity with IC(50) of 0.06 µM, which was comparable to the positive control. Molecular docking results indicated that compound 11 was nicely bound to the EGFR kinase. Compound 11 also showed significant antiproliferative activity against MCF-7 with IC(50) of 0.07 µM, which would be a potential anticancer agent.

Synthesis, antiproliferative activity, and structure-activity relationships of 3-aryl-1H-quinolin-4-ones.

The antiproliferative activities of 36 3-aryl-1H-quinolin-4-ones were determined against two cancer cell lines (Hep G2 and KB) in vitro. The results indicate that most of these compounds show good cytotoxic activity against human cancer cell lines, but no cytotoxicity against a human normal cell line (L02). The positive control compounds genistein and 5-fluorouracil show no selectivity at inhibiting the growth of the above three cell lines. Generally, compounds that bear a halogen atom at the 8 position and a methoxy group at the 3' position exhibited remarkable cytotoxicity toward human cancer cell lines. Electron-withdrawing substituents at the 6 position decrease the antiproliferative activity significantly. We also put forward a pharmacophore model for 3-aryl-4-quinolinones binding with epidermal growth factor receptor protein tyrosine kinases (EGFR PTK). Out of the 36 synthetic compounds, 34 are reported for the first time.

Polyphenols based on isoflavones as inhibitors of Helicobacter pylori urease.

Twenty polyphenols were synthesized and evaluated for their effect on Helicobacter pylori urease. Among these compounds, 4-(p-hydroxyphenethyl)pyrogallol (15) (IC(50)=0.03 mM) and 7,8,4'-trihydroxyisoflavone (19) (IC(50)=0.14 mM) showed potent inhibitory activities, and inhibited Helicobacter pylori urease in a time-dependent manner. The structure-activity relationship of these polyphenols revealed: the two ortho hydroxyl groups were essential for inhibitory activity of polyphenol. When the C-ring of isoflavone was broken, the inhibitory activity markedly decreased. As for deoxybenzoin, the carboxyl group was clearly detrimental.

Synthesis and cytotoxic evaluation of novel 7-O-modified genistein derivatives.

Two series of genistein (=5,7-dihydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) derivatives with heterocycles were prepared, in which genistein and heterocyclic moieties were separated by C(2) and C(3) spacers. Among the 24 compounds we prepared, 22, i.e., 3a-3k and 4a-4k, were reported for the first time, while the preparation of 2a and 2b was reported in our recent paper. The cytotoxic activities of these compounds were evaluated against human chronic myeloid leukemia cells (K562) and a human nasopharyngeal epidermoid tumor cell line (KB). Compounds 4a, 4d, 4e, 4h, and 4i showed remarkable anticancer activities in vitro that are comparable with 5-fluorouracil, an canonical anticancer drug. Structure-effect relationships were also discussed based on the experimental data obtained.