Design,Synthesis, and Evaluation of 3‐Aryl‐4‐pyrrolyl‐maleimides as Glycogen Synthase Kinase‐3β Inhibitors

A series of 3‐aryl‐4‐pyrrolyl‐maleimides were designed, synthesized, and evaluated for their glycogen synthase kinase‐3β (GSK‐3β) inhibitory activity. Most compounds exhibited potent activity against GSK‐3β. Among them, compounds 11a , 11c , 11h , 11i , and 11j significantly reduced Aβ‐induced Tau hyperphosphorylation, showing the inhibition of GSK‐3β at the cellular level. Structure–activity relationships were discussed based on the experimental data obtained.     

Synthesis and Evaluation of 3‐(furo[2,3‐b]pyridin‐3‐yl)‐4‐(1H‐indol‐3‐yl)‐maleimides as Novel GSK‐3β Inhibitors and Anti‐Ischemic Agents

A series of novel 3‐(furo[2,3‐b]pyridin‐3‐yl)‐4‐(1H‐indol‐3‐yl)‐maleimides were designed, synthesized, and biologically evaluated for their GSK‐3β inhibitory activities. Most compounds showed favorable inhibitory activities against GSK‐3β protein. Among them, compounds 5n , 5o , and 5p significantly reduced GSK‐3β substrate tau phosphorylation at Ser396 in primary neurons, indicating inhibition of cellular GSK‐3β activity. In the in vitro neuronal injury models, compounds 5n , 5o , and 5p prevented neuronal death against glutamate, oxygen–glucose deprivation, and nutrient serum deprivation which are closely associated with cerebral ischemic stroke. In the in vivo cerebral ischemia animal model, compound 5o reduced infarct size by 10% and improved the neurological deficit. The results may provide new insights into the development of novel GSK‐3β inhibitors with potential neuroprotective activity against brain ischemic stroke.     

The Synthesis and Evaluation of C7‐Substituted α‐Tetralone Derivatives as Inhibitors of Monoamine Oxidase

Based on a previous report that α‐tetralone (3,4‐dihydro‐2H‐naphthalen‐1‐one) is a promising scaffold for the design of highly potent inhibitors of the enzyme, monoamine oxidase, the present study investigates the monoamine oxidase inhibitory properties of a synthetic series of fifteen C7‐substituted α‐tetralone derivatives. Arylalkyloxy substitution on C7 of the α‐tetralone moiety yielded compounds with high inhibition potencies toward the human monoamine oxidase‐B isoform with all compounds possessing IC₅₀ values in the submicromolar range (0.00089–0.047 μm ). The C7‐substituted α‐tetralones also were highly potent monoamine oxidase‐A inhibitors with thirteen (of fifteen) compounds possessing IC₅₀ values in the submicromolar range (0.010–0.741 μm ). The α‐tetralones were, however, in each instance selective for monoamine oxidase‐B over the monoamine oxidase‐A isoform. Dialyses of enzyme–inhibitor mixtures show that, while a representative inhibitor acts as a reversible monoamine oxidase‐A inhibitor, inhibition of monoamine oxidase‐B is not readily reversed by dialysis. Using a molecular modeling approach, possible binding orientations and interactions of selected α‐tetralones with the active sites of the monoamine oxidases are also proposed. This study suggests that C7‐substituted α‐tetralones are promising monoamine oxidase inhibitors and may represent lead compounds for the development of therapies for Parkinson's disease and depression.     

Protective effects of β‐sheet breaker α/β‐hybrid peptide against amyloid β‐induced neuronal apoptosis in vitro

Alzheimer's disease is most common neurodegenerative disorder and is characterized by increased production of soluble amyloid‐β oligomers, the main toxic species predominantly formed from aggregation of monomeric amyloid‐β (Aβ). Increased production of Aβ invokes a cascade of oxidative damages to neurons and eventually leads to neuronal death. This study was aimed to investigate the neuroprotective effects of a β‐sheet breaker α/β‐hybrid peptide (BSBHp) and the underlying mechanisms against Aβ₄₀‐induced neurotoxicity in human neuroblastoma SH‐SY5Y cells. Cells were pretreated with the peptide Aβ₄₀ to induce neurotoxicity. Assays for cell viability, cell membrane damage, cellular apoptosis, generation of reactive oxygen species (ROS), intracellular free Ca²⁺, and key apoptotic protein levels were performed in vitro. Our results showed that pretreatment with BSBHp significantly attenuates Aβ₄₀‐induced toxicity by retaining cell viability, suppressing generation of ROS, Ca²⁺ levels, and effectively protects neuronal apoptosis by suppressing pro‐apoptotic protein Bax and up‐regulating antiapoptotic protein Bcl‐2. These results suggest that α/β‐hybrid peptide has neuroprotective effects against Aβ₄₀‐induced oxidative stress, which might be a potential therapeutic agent for treating or preventing neurodegenerative diseases.     

Design,Synthesis and Biological Evaluation of Peptidyl Epoxyketone Proteasome Inhibitors Composed of β‐amino Acids

A series of novel di‐ and tripeptidyl epoxyketone derivatives composed of β‐amino acids were designed, synthesized and evaluated for their proteasome inhibitory activities and anti‐proliferation activities against two multiple myeloma cell lines RPMI 8226 and NCI‐H929 and normal cells (peripheral blood mononucleated cells). Among these tested compounds, tripeptidyl analogues showed much more potent activities than dipeptides, and four tripeptidyl compounds exhibited proteasome inhibitory activities with IC₅₀ values ranging from 0.97 ± 0.05 to 1.85 ± 0.11 μm . In addition, all the four compounds showed anti‐proliferation activities with IC₅₀ values at low micromolar levels against two multiple myeloma cell lines and weak activities against normal cells. Furthermore, Western blot analysis was performed to verify the proteasome inhibition induced by compounds 21d and 21e . All the experimental results validated that the β‐amino acid building block has the potential for the development of proteasome inhibitors.     

Novel Piperine Derivatives with Antidiabetic Effect as PPAR‐γ Agonists

Piperine is an alkaloid responsible for the pungency of black pepper. In this study, piperine isolated from Piper nigrum L. was hydrolyzed under basic condition to obtain piperic acid and was used as precursor to carry out the synthesis of twenty piperine derivatives containing benzothiazole moiety. All the benzothiazole derivatives were evaluated for their antidiabetic potential by OGT test followed by assessment of active derivatives on STZ‐induced diabetic model. It was observed that nine of twenty novel piperine analogues ( 5b, 6a‐h) , showed significantly higher antidiabetic activity in comparison with rosiglitazone (standard). Furthermore, these active derivatives were evaluated for their action as PPAR‐γ agonists demonstrating their mechanism of action. The effects on body weight, lipid peroxidation, and hepatotoxicity after administration with active derivatives were also studied to further establish these derivatives as lead molecules for treatment of diabetes with lesser side‐effects.     

Synthesis,crystal structure and molecular conformation of Nα‐Boc‐l‐leucyl‐(Z)‐β‐(3‐pyridyl)‐α,β‐ dehydroalanyl‐l‐leucine methyl ester*

Abstract: A protected tridehydropeptide containing (Z)‐β‐(3‐pyridyl)‐α,β‐dehydroalanine (Δ^Z3Pal) residue, Boc‐Leu‐Δ^Z3Pal‐Leu‐OMe ( 1 ), was synthesized via Erlenmeyer azlactone method. X‐ray crystallographic analysis revealed that the peptide 1 adopts an extended conformation, which is similar to that of a Δ^ZPhe analog, Boc‐Leu‐Δ^ZPhe‐Leu‐OMe ( 2 ).     

The Proteolytic Stability and Cytotoxicity Studies of l‐Aspartic Acid and l‐Diaminopropionic Acid derived β‐Peptides and a Mixed α/β‐Peptide

The use of peptides as drugs in pharmaceutical applications is hindered by their susceptibility to proteolysis and therefore low bioavailability. β‐Peptides that contain an additional methylene group in the backbone, are gaining recognition from a pharmaceutical stand point as they are considerably more resilient to proteolysis and metabolism. Recently, we reported two new classes of β ‐peptides, β ³‐ and β²‐peptides derived from l ‐aspartic acid and l ‐diaminopropionic acid, respectively. Here, we report the proteolytic stability of these β‐peptidic compounds and a mixed α /β‐peptide against three enzymes (pronase, trypsin and elastase), as well as, human serum. The stability of these peptides was compared to an α‐peptide. Peptides containing β‐linkages were resistant to all conditions. The mixed α /β‐peptide, however, exhibited proteolysis in the presence of trypsin and pronase but not elastase. The rate of degradation of the mixed α /β‐peptide was slower than that would be expected for an α‐peptide. In addition, these β‐peptides were not toxic to HeLa and COS‐1 cell lines as observed by MTT cytotoxicity assay. These results expand the scope of mixed α /β‐peptides containing β‐amino acids or small β‐peptide fragments as therapeutic peptides.     

Estrogen and ERα enhanced β‐catenin degradation and suppressed its downstream target genes to block the metastatic function of HA22T hepatocellular carcinoma cells via modulating GSK‐3β and β‐TrCP expression

In our previous experiments, we found β‐catenin was highly expressed in the tumor area with high invasive ability and poor prognosis. In this study, we have examined the mechanism by which ERα regulates β‐catenin expression as well as the metastasis ability of hepatocellular cancer HA22T cells. To identify whether the anticancer effect of estrogen and ERα is mediated through suppression of β‐catenin expression, we co‐transfected pCMV‐β‐catenin and ERα into HA22T cells, and determined the cell motility by wound healing, invasion, and migration assays. Results showed that estrogen and/or ERα inhibited β‐catenin gene expression and repressed HA22T cell motility demonstrated that similar data was observed in cells expressing the ERα stable clone. Moreover, we examined the protein‐protein interaction between ERα and β‐catenin by immunostain, co‐immunoprecipitation, and Western blotting. E2 enhanced the binding of ERα with β‐catenin and then triggered β‐catenin to bind with E3 ligase (βTrCP) to promote β‐catenin degradation. Finally by employing systematic ChIP studies, we showed ERα can interact directly with the β‐catenin promoter region following E2 treatment. All our results reveal that estrogen and ERα blocked metastatic function of HA22T cells by modulating GSK3β and βTrCP expression and further enhanced β‐catenin degradation and suppressed its downstream target genes. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 519–529, 2017.     

Synthesis and Evaluation of Benzophenone O‐Glycosides as α‐Glucosidase Inhibitors

The first total synthesis of benzophenone O‐glycosides (iriflophenone 2‐O‐α‐L ‐rhamnopyranoside: 1 and aquilarisinin: 2 ) isolated from the leaves of Aquilaria sinensis and related new derivatives ( 3 – 12 ) was accomplished through suitable protecting group manipulations and glycosylation starting from commercially available L ‐rhamnose, D ‐glucose, D ‐galactose, D ‐mannose, D ‐xylose, and 1,3,5‐trihydroxybenzene. All synthesized benzophenone O‐glycosides were evaluated for their inhibitory activities against α‐glucosidase. Of these, benzophenone O‐glycosides 4 and 10 exhibited the most potent inhibitory activity in vitro against α‐glucosidase with IC₅₀ values of 168.7 ± 13.9 and 210.1 ± 23.9 µM, respectively, when compared with that of the positive control acarbose with an IC₅₀ value of 569.3 ± 49.7 µM.     

Blocking UV‐Induced eIF2α Phosphorylation with Small Molecule Inhibitors of GCN2

The eIF2α kinase general control non‐depressible 2 integrates translation initiation rates to amino acid availability. General control non‐depressible 2 also regulates translation initiation during synaptic plasticity and GCN2^?/? mice show improved memory compared with wild‐type mice with a reduced threshold for triggering late long‐term potentiation. This property suggests that inhibiting general control non‐depressible 2 function might represent a therapeutic avenue for improving memory. We screened for general control non‐depressible 2 inhibitors using a small library of known kinase inhibitors and ATP‐analogs and identified three compounds – indirubin‐3′‐monoxime, SP600125 and a SyK inhibitor with activity against general control non‐depressible 2. All three compounds inhibit the ability of general control non‐depressible 2 to phosphorylate eIF2αin vitro as well as in vivo following UV‐treatment of mouse embryonic fibroblasts. Using computer‐assisted modeling, we modeled the binding of the inhibitors in the ATP‐binding site of general control non‐depressible 2. This work provides the molecular basis for undertaking structure–activity relationships of these compounds in order to develop specific inhibitors of general control non‐depressible 2.     

Synthesis of 1,4‐Anthracene‐9,10‐dione Derivatives and Their Regulation of Nitric Oxide,IL‐1β and TNF‐α in Activated RAW264.7 Cells

Mitoxantrone is an anthracenedione antineoplastic and immunosuppressive agent approved for multiple sclerosis treatment. Novel mono‐ and disubstituted anthraquinone derivatives, analogues of mitoxantrone, were synthesized through the addition of lipophilic amino alcohols and evaluated for their effect on IL‐1β, TNF‐α and nitric oxide production by LPS/IFN‐γ‐stimulated RAW264.7 cells. The disubstituted 1,4‐anthracene‐9,10‐dione 10 showed significant inhibition of nitric oxide, TNF‐α and IL‐1β production at the concentration of 5 μg/mL, with a much lower cytotoxicity than mitoxantrone. The monosubstituted 3 , 4 , 11, 12 and 13 also displayed a moderate to good inhibitory capacity on IL‐1β production. However, the methylated compounds 11, 12 and 13 failed to inhibit the TNF‐α production, and compound 13 was the only one to decrease the production of nitric oxide. None of these derivatives was toxic at the tested concentrations. Compounds 10 and 13 had better inhibitory capacity of the inflammatory mediators analyzed, with reliable viability of the cells.