A Review on the Mechanism and Structure-activity Relationship of Resveratrol Heteroaryl Analogues

Resveratrol is one of the most interesting naturally-occurring nonflavonoid phenolic compounds with various biological activities, such as anticancer, neuroprotection, antibacterial, and anti-inflammatory. However, there is no clinical usage of resveratrol due to either its poor activity or poor pharmacokinetic properties. Heteroarenes-modified resveratrol is one pathway to improve its biological activities and bioavailability, and form more modification sites. In this review, we present the progress of heteroaryl analogues of resveratrol with promising biological activities in the latest five years, ranging from the synthesis to the structure-activity relationship and mechanism of actions. Finally, introducing heteroarenes into resveratrol is an effective strategy, which focuses on the selectivity of structure-activity relationship in vivo.

Discovery of Novel Coumarin-Schiff Base Hybrids as Potential Acetylcholinesterase Inhibitors: Design, Synthesis, Enzyme Inhibition, and Computational Studies

To discover anti-acetylcholinesterase agents for the treatment of Alzheimer's disease (AD), a series of novel Schiff base-coumarin hybrids was rationally designed, synthesized successfully, and structurally characterized using Fourier transform infrared (FTIR), Nuclear magnetic resonance (NMR), and High-Resolution Mass Spectrometry (HRMS) analyses. These hybrids were evaluated for their potential inhibitory effect on acetylcholinesterase (AChE). All of them exhibited excellent inhibitory activity against AChE. The IC₅₀ values ranged from 87.84 to 515.59 μg/mL; hybrids 13c and 13d with IC₅₀ values of 0.232 ± 0.011 and 0.190 ± 0.004 µM, respectively, showed the most potent activity as acetylcholinesterase inhibitors (AChEIs). The reference drug, Galantamine, yielded an IC₅₀ of 1.142 ± 0.027 µM. Reactivity descriptors, including chemical potential (μ), chemical hardness (η), electrophilicity (ω), condensed Fukui function, and dual descriptors are calculated at wB97XD/6-311++ G (d,p) to identify reactivity changes of the designed compounds. An in-depth investigation of the natural charge pattern of the studied compounds led to a deep understanding of the important interaction centers between these compounds and the biological receptors of AChE. The molecular electrostatic surface potential (MESP) of the most active site in these derivatives was determined using high-quality information and visualization. Molecular docking analysis was performed to predict binding sites and binding energies. The structure-activity-property relationship studies indicated that the proposed compounds exhibit good oral bioavailability properties. To explore the stability and dynamic behavior of the ligand-receptor complexes, molecular dynamics simulations (MDS) were performed for 100 ns on the two best docked derivatives, 13c and 13d, with the AChE (4EY7) receptor. A popular method for determining the free binding energies (MM/GBSA) is performed using snapshots taken from the systems' trajectories at 100 ns. These results revealed that the complex system of compound 13d acquired a relatively more stable conformation and exhibited better descriptors than the complex system of compound 13c and the Galantamine drug, suggesting its potential as an effective inhibiting drug. The binding free energy analysis revealed that the 13d-4EY7 complex exhibited greater stability with AChE receptors compared to other complexes.

Synthetic Access to Unsymmetric, Tridentate, Pyridyl-1,3,4-oxadiazole Complexants via Intramolecular Oxidative Annulation of Arylhydrazides with Heteroaryl Carbaldehydes

Over the last four decades, an ideal complexant for the chemoselective liquid-liquid separation of the minor actinides from the lanthanides contained within spent nuclear fuel has yet to be realized. As strategic performance objectives continue to evolve as a function of time, solubility in process-relevant diluents, fast complexation kinetics, as well as robustness to hydro- and radiolytic degradation remain at the forefront of this grand challenge. While the vast majority of soft-N-donors are symmetric in nature, this laboratory has focused on defining synthetic methods to afford unsymmetric complexants for further study to explore the impact subtle changes to the molecular topography of the complexant moiety have on performance, in addition to working toward the definition of structure-activity relationships. The development of an intramolecular iodine-mediated oxidative annulation of heteroaryl-aryl-hydrazones for the production of functionalized, tridentate, and unsymmetric 1,3,4-oxadiazole-based complexants is reported. Optimization of reaction conditions afforded numerous products in high isolated yield over two linear steps in one pot in one hour of reaction time. The cleanliness of the optimized conditions negated the need for the chromatographic purification of 32 of 44 examples attempted. Method development, optimization, substrate scope, application to related heteroarenes, and a scale-up reaction are described herein.

Coumarins and Gastrointestinal Cancer: A New Therapeutic Option?

Cancers of the gastrointestinal (GI) tract are often life-threatening malignancies, which can be a severe burden to the health care system. Globally, the mortality rate from gastrointestinal tumors has been increasing due to the lack of adequate diagnostic, prognostic, and therapeutic measures to combat these tumors. Coumarin is a natural product with remarkable antitumor activity, and it is widely found in various natural plant sources. Researchers have explored coumarin and its related derivatives to investigate their antitumor activity, and the potential molecular mechanisms involved. These mechanisms include hormone antagonists, alkylating agents, inhibitors of angiogenesis, inhibitors of topoisomerase, inducers of apoptosis, agents with antimitotic activity, telomerase inhibitors, inhibitors of human carbonic anhydrase, as well as other potential mechanisms. Consequently, drug design and discovery scientists and medicinal chemists have collaborated to identify new coumarin-related agents in order to produce more effective antitumor drugs against GI cancers. Herein, we summarize the therapeutic effects of coumarin and its derivatives against GI cancer.

Oxidant/Solvent-Controlled I2-Catalyzed Domino Annulation for Selective Synthesis of 2-Aroylbenzothiazoles and 2-Arylbenzothiazoles under Metal-Free Conditions

A simple and practical domino protocol for the selective synthesis of 2-aroylbenzothiazoles and 2-aryl benzothiazoles catalyzed by I₂ is developed under metal-free conditions. The reaction outcomes are exclusively controlled by the reaction oxidant/medium. With DMSO employed as both the solvent and the oxidant, an oxidation of aromatic methyl ketones takes precedence over the condensation with 2-aminobenzenethiols. On the other hand, when the reaction was carried out in PhNO₂ or in 1,4-dioxane containing PhNO₂, the condensation of aromatic methyl ketones with 2-aminobenzenethiols has priority to form imines which is followed by an oxidation of the methyl group from ketones to afford 2-arylbenzothiazoles as a sole product. The PhNO₂/I₂ co-catalytic system is proposed first time.

Uses of Cyclohexan-1,3-dione for the Synthesis of Thiazole, Pyrazole, Thiophene, Isoxazole and Pyran Derivatives with Antitumor Activities

Background:

A wide range of thiazole, pyrazole and pyran derivatives gained special attention due to pharmacological activities especially therapeutic activities. Many pharmacological drugs containing the thiazole and pyrazole nuclei are known in the market.

Methods:

The 2-arylidencyclohexan-1,3-dione 3a-c were the key starting compounds for many heterocyclic reactions to produce substituted heterocyclic derivatives.

Results:

Antiproliferative activities of the produced compounds against six cancer cell lines A549, HT-29, MKN-45, U87MG, SMMC-7721 and H460 were measured in which the compounds showed high inhibition. The most promising compounds were tested against tyrosine kinases (c-Kit, Flt-3, VEGFR-2, EGFR, and PDGFR). Structure-Activity Relationship (SAR) was rationalized by assessing the varying structural features of the molecules. In addition, the most active compounds were selected for Pim-1 inhibition.

Conclusion:

Thirty compounds were synthesized. Ten of them (3a, 3c, 5a, 5c, 7a, 10f, 11a, 13c, 16a and 16c) were the most active compounds for selected cancer cell lines. Compounds 3c, 5c, 7a, 10f, 13c and 16c showed high inhibition toward the tyrosine kinases while compounds 3c, 5c and 10f were the most potent to inhibit Pim-1.

Synthesis and Biological Evaluation of Novel 4,5,6,7-Tetrahydrobenzo[D]-Thiazol-2- Yl Derivatives Derived from Dimedone with Anti-Tumor, C-Met, Tyrosine Kinase and Pim-1 Inhibitions

BACKGROUND

Dimedone and thiazole moieties are privileged scaffolds (acting as primary pharmacophores) in many compounds that are useful to treat several diseases, mainly tropical infectious diseases. Thiazole derivatives are a very important class of compounds due to their wide range of pharmaceutical and therapeutic activities. On the other hand, dimedone is used to synthesize many therapeutically active compounds. Therefore, the combination of both moieties through a single molecule to produce heterocyclic compounds will produce excellent anticancer agents.

OBJECTIVE

The present work reports the synthesis of 47 new substances belonging to two classes of compounds: Dimedone and thiazoles, with the purpose of developing new drugs that present high specificity for tumor cells and low toxicity to the organism. To achieve this goal, our strategy was to synthesize a series of 4,5,6,7-tetrahydrobenzo[d]-thiazol-2-yl derivatives using the reaction of the 2-bromodimedone with cyanothioacetamide.

METHODS

The reaction of 2-bromodimedone with cyanothioacetamide gave the 4,5,6,7-tetrahydrobenzo[d]- thiazol-2-yl derivative 4. The reactivity of compound 4 towards some chemical reagents was observed to produce different heterocyclic derivatives.

RESULTS

A cytotoxic screening was performed to evaluate the performance of the new derivatives in six tumor cell lines. Thirteen compounds were shown to be promising toward the tumor cell lines which were further evaluated toward five tyrosine kinases.

CONCLUSION

The results of antitumor screening showed that many of the tested compounds were of high inhibition towards the tested cell lines. Compounds 6c, 8c, 11b, 11d, 13b, 14b, 15c, 15g, 21b, 21c, 20d and 21d were the most potent compounds toward c-Met kinase and PC-3 cell line. The most promising compounds 6c, 8c, 11b, 11d, 13b, 14b, 15c, 15g, 20c, 20d, 21b, 21c and 21d were further investigated against tyrosine kinase (c-Kit, Flt-3, VEGFR-2, EGFR, and PDGFR). Compounds 6c, 11b, 11d, 14b, 15c, and 20d were selected to examine their Pim-1 kinase inhibition activity the results revealed that compounds 11b, 11d and 15c had high activities.

Therapeutic significance of β-glucuronidase activity and its inhibitors: A review

The emergence of disease and dearth of effective pharmacological agents on most therapeutic fronts, constitutes a major threat to global public health and man's existence. Consequently, this has created an exigency in the search for new drugs with improved clinical utility or means of potentiating available ones. To this end, accumulating empirical evidence supports molecular target therapy as a plausible egress and, β-glucuronidase (βGLU) - a lysosomal acid hydrolase responsible for the catalytic deconjugation of β-d-glucuronides has emerged as a viable molecular target for several therapeutic applications. The enzyme's activity level in body fluids is also deemed a potential biomarker for the diagnosis of some pathological conditions. Moreover, due to its role in colon carcinogenesis and certain drug-induced dose-limiting toxicities, the development of potent inhibitors of βGLU in human intestinal microbiota has aroused increased attention over the years. Nevertheless, although our literature survey revealed both natural products and synthetic scaffolds as potential inhibitors of the enzyme, only few of these have found clinical utility, albeit with moderate to poor pharmacokinetic profile. Hence, in this review we present a compendium of exploits in the present millennium directed towards the inhibition of βGLU. The aim is to proffer a platform on which new scaffolds can be modelled for improved βGLU inhibitory potency and the development of new therapeutic agents in consequential.

Synthesis, Molecular Docking and β-Glucuronidase Inhibitory Potential of Indole Base Oxadiazole Derivatives

β-glucuronidase is a lysosomal glycosidase enzyme which catalyzes the extracellular matrix of cancer and normal cells and the glycosaminoglycans of the cell membrane, which is important for cancer cell proliferation, invasion, and metastasis. Liver cancer, colon carcinoma, and neoplasm bladder are triggered by the increase of the level of β-glucuronidase activity. The most valuable structures are indole and oxadiazole which has gain immense attention because of its pharmacological behavior and display many biological properties. Twenty-two (1⁻22) analogs of indole based oxadiazole were synthesized and screened for their inhibitory potential against β-glucuronidase. Majority of the compounds showed potent inhibitory potential with IC₅₀ values ranging between 0.9 ± 0.01 to 46.4 ± 0.9 µM, under positive control of standard drug d-saccharic acid 1,4 lactone (IC₅₀ = 48.1 ± 1.2 µM). Structural activity relationship (SAR) has been established for all synthesized compounds. To shed light on molecular interactions between the synthesized compounds and β-glucuronidase, 1, 4, and 6 compounds were docked into the active binding site of β-glucuronidase. The obtained results showed that this binding is thermodynamically favorable and β-glucuronidase inhibition of the selected compounds increases with the number of hydrogen bonding established in selected compound-β-glucuronidase complexes.

Synthesis, SAR elucidations and molecular docking study of newly designed isatin based oxadiazole analogs as potent inhibitors of thymidine phosphorylase

Thymidine phosphorylase is an enzyme involved in pyrimidine salvage pathway that is identical to platelet-derived endothelial cell growth factor (PD-ECGF) and gliostatin. It is enormously up regulated in a variety of solid tumors. Furthermore, surpassing of TP level protects tumor cells from apoptosis and helps cell survival. Thus TP is identified as a prime target for developing novel anticancer therapies. A new class of exceptionally potent isatin based oxadiazole (1-30) has been synthesized and evaluated for thymidine phosphorylase inhibitory potential. All analogs showed potent thymidine phosphorylase inhibition when compared with standard 7-Deazaxanthine, 7DX (IC₅₀ = 38.68 ± 1.12 µM). Molecular docking study was performed in order to determine the binding interaction of these newly synthesized compounds, which revealed that these synthesized compounds established stronger hydrogen bonding network with active site of residues as compare to the standard compound 7DX.

Novel hydrazide-hydrazone and amide substituted coumarin derivatives: Synthesis, cytotoxicity screening, microarray, radiolabeling and in vivo pharmacokinetic studies

The current work presents the synthesis and biological evaluation of new series of coumarin hydrazide-hydrazone derivatives that showed in vitro broad spectrum antitumor activities against resistant pancreatic carcinoma (Panc-1), hepatocellular carcinoma (HepG2) and leukemia (CCRF) cell lines using doxorubicin as reference standard. Bromocoumarin hydrazide-hydrazone derivative (BCHHD) 11b showed excellent anticancer activity against all tested cancer cell lines. Enzyme assays showed that BCHHD 11b induced apoptosis due to activation of caspases 3/7. Moreover, 11b inhibited GST and CYP3A4 in a dose dependent manner and the induced cell death could be attributed to metabolic inhibition. Moreover, 11b microarray analysis showed significant up- and down-regulation of many genes in the treated cells related to apoptosis, cell cycle, tumor growth and suppressor genes. All of the above presents BCHHD 11b as a potent anticancer agent able to overcome drug resistance. In addition, compound 11b was able to serve as a chemical carrier for ^99mTc and the in vivo biodistribution study of ^99mTc-11b complex revealed a remarkable targeting ability of ^99mTc into solid tumor showing that ^99mTc-11b might be used as a promising radiopharmaceutical imaging agent for cancer.

Synthesis: Small library of hybrid scaffolds of benzothiazole having hydrazone and evaluation of their β-glucuronidase activity

Due to the great biological importance of β-glucuronidase inhibitors, here in this study, we have synthesized a library of novel benzothiazole derivatives (1-30), characterized by different spectroscopic methods and evaluated for β-glucuronidase inhibitory potential. Among the series sixteen compounds i.e.1-6, 8, 9, 11, 14, 15, 20-23 and 26 showed outstanding inhibitory potential with IC₅₀ value ranging in between 16.50 ± 0.26 and 59.45 ± 1.12 when compared with standard d-Saccharic acid 1,4-lactone (48.4 ± 1.25 µM). Except compound 8 and 23 all active analogs showed better potential than the standard. Structure activity relationship has been established.

Synthesis, in vitro β-glucuronidase inhibitory activity and in silico studies of novel (E)-4-Aryl-2-(2-(pyren-1-ylmethylene)hydrazinyl)thiazoles

Current research is based on the synthesis of novel (E)-4-aryl-2-(2-(pyren-1-ylmethylene)hydrazinyl)thiazole derivatives (3-15) by adopting two steps route. First step was the condensation between the pyrene-1-carbaldehyde (1) with the thiosemicarbazide to afford pyrene-1-thiosemicarbazone intermediate (2). While in second step, cyclization between the intermediate (2) and phenacyl bromide derivatives or 2-bromo ethyl acetate was carried out. Synthetic derivatives were structurally characterized by spectroscopic techniques such as EI-MS, ¹H NMR and ¹³C NMR. Stereochemistry of the iminic double bond was confirmed by NOESY analysis. All pure compounds 2-15 were subjected for in vitro β-glucuronidase inhibitory activity. All molecules were exhibited excellent inhibition in the range of IC₅₀=3.10±0.10-40.10±0.90μM and found to be even more potent than the standard d-saccharic acid 1,4-lactone (IC₅₀=48.38±1.05μM). Molecular docking studies were carried out to verify the structure-activity relationship. A good correlation was perceived between the docking study and biological evaluation of active compounds.

Synthesis and in vitro acetylcholinesterase and butyrylcholinesterase inhibitory potential of hydrazide based Schiff bases

To discover multifunctional agents for the treatment of Alzheimer's disease, a series of hydrazide based Schiff bases were designed and synthesized based on multitarget-directed strategy. We have synthesized twenty-eight analogs of hydrazide based Schiff bases, characterized by various spectroscopic techniques and evaluated in vitro for acetylcholinesterase and butyrylcholinesterase inhibition. All compounds showed varied degree of acetylcholinesterase and butyrylcholinesterase inhibition when compared with standard Eserine. Among the series, compounds 10, 3 and 24 having IC50 values 4.12±0.01, 8.12±0.01 and 8.41±0.06μM respectively showed potent acetylcholinesterase inhibition when compared with Eserine (IC50=0.85±0.0001μM). Three compounds 13, 24 and 3 having IC50 values 6.51±0.01, 9.22±0.07 and 37.82±0.14μM respectively showed potent butyrylcholinesterase inhibition by comparing with eserine (IC50=0.04±0.0001μM). The remaining compounds also exhibited moderate to weak inhibitory potential. Structure activity relationship has been established. Through molecular docking studies the binding interaction was confirmed.

Synthesis of novel disulfide and sulfone hybrid scaffolds as potent β-glucuronidase inhibitor

Novel series of disulfide and sulfone hybrid analogs (1-20) were synthesized and characterized through EI-MS and (1)H NMR and evaluated for β-glucuronidase inhibitory potential. All synthesized analogs except 13 and 15 showed excellent β-glucuronidase inhibitory potential with IC50 value ranging in between 2.20-88.16μM as compared to standard d-saccharic acid 1,4 lactone (48.4±1.25μM). Analogs 19, 16, 4, 1, 17, 6, 10, 3, 18, 2, 11, 14 and 5 showed many fold potent activity against β-glucuronidase inhibitor. Structure activity relationship showed that substitution of electron withdrawing groups at ortho as well as para position on phenyl ring increase potency. Electron withdrawing groups at meta position on phenyl ring showed slightly low potency as compared to ortho and para position. The binding interactions were confirmed through molecular docking studies.

Synthesis and biological evaluation of novel N-arylidenequinoline-3-carbohydrazides as potent β-glucuronidase inhibitors

Thirty N-arylidenequinoline-3-carbohydrazides (1-30) have been synthesized and evaluated against β-glucuronidase inhibitory potential. Twenty four analogs showed outstanding β-glucuronidase activity having IC50 values ranging between 2.11±0.05 and 46.14±0.95 than standard d-saccharic acid 1,4 lactone (IC50=48.4±1.25μM). Six analogs showed good β-glucuronidase activity having IC50 values ranging between 49.38±0.90 and 80.10±1.80. Structure activity relationship and the interaction of the active compounds and enzyme active site with the help of docking studies were established. Our study identifies novel series of potent β-glucuronidase inhibitors for further investigation.