Synthesis of 2,4-dihydroxyacetophenone derivatives as potent PDE-1 and -3 inhibitors: in vitro and in silico insights.

Aim: Synthesis of novel bis-Schiff bases having potent inhibitory activity against phosphodiesterase (PDE-1 and -3) enzymes, potentially offering therapeutic implications for various conditions. Methods: Bis-Schiff bases were synthesized by refluxing 2,4-dihydroxyacetophenone with hydrazine hydrate, followed by treatment of substituted aldehydes with the resulting hydrazone to obtain the product compounds. After structural confirmation, the compounds were screened for their in vitro PDE-1 and -3 inhibitory activities. Results: The prepared compounds exhibited noteworthy inhibitory efficacy against PDE-1 and -3 enzymes by comparing with suramin standard. To clarify the binding interactions between the drugs, PDE-1 and -3 active sites, molecular docking studies were carried out. Conclusion: The potent compounds discovered in this study may be good candidates for drug development.

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Discovery of acetophenone/piperazin-2-one hybrids as selective anti-TNBC cancer agents by causing DNA damage.

Twenty-five acetophenone/piperazin-2-one (APPA) hybrids were designed and synthesized based on key pharmacophores found in anti-breast cancer drugs Neratinib, Palbociclib, and Olaparib. Compound 1j exhibited good in vitro antiproliferative activity (IC50 = 6.50 µM) and high selectivity (SI = 9.2 vs HER2-positive breast cancer cells SKBr3; SI = 7.3 vs normal breast cells MCF-10A) against triple negative breast cancer (TNBC) cells MDA-MB-468. In addition, 1j could selectively cause DNA damage, inducing the accumulation of γH2AX and P53 in MDA-MB-468 cells. It also reduced the phosphorylation level of P38 and the expression of HSP70, which further prevented the repair of DNA damage and caused cells S/G2-arrest leading to MDA-MB-468 cells death.

Discovery of novel paeonol-based derivatives against skin inflammation in vitro and in vivo.

T-LAK-cell-originated protein kinase (TOPK), a novel member of the mitogen-activated protein kinase family, is considered an effective therapeutic target for skin inflammation. In this study, a series (A - D) of paeonol derivatives was designed and synthesised using a fragment growing approach, and their anti-inflammatory activities against lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 cells were tested. Among them, compound B12 yielded the best results (IC50 = 2.14 µM) with low toxicity (IC50 > 50 µM). Preliminary mechanistic studies indicated that this compound could inhibit the TOPK-p38/JNK signalling pathway and phosphorylate downstream related proteins. A murine psoriasis-like skin inflammation model was used to determine its therapeutic effect.

Imidazolylacetophenone oxime-based multifunctional neuroprotective agents: Discovery and structure-activity relationships.

Alzheimer's disease (AD) possesses a complex pathogenetic mechanism. Nowadays, multitarget agents are considered to have potential in effectively treating AD via triggering molecules in functionally complementary pathways at the same time. Here, based on the screening (∼1400 compounds) against neuroinflammation, an imidazolylacetophenone oxime ether (IOE) was discovered as a novel hit. In order to obtain SARs, a series of imidazolylacetophenone oxime derivatives were constructed, and their C=N bonds were confirmed as the Z configuration by single crystals. These derivatives exhibited potential multifunctional neuroprotective effects including anti-neuroinflammatory, antioxidative damage, metal-chelating, inhibition of acetylcholinesterase (AChE) properties. Among these derivatives, compound 12i displayed the most potent inhibitory activity against nitric oxide (NO) production with EC50 value of 0.57 µM 12i can dose-dependently suppress the expression of iNOS and COX-2 but not change the expression of HO-1 protein. Moreover, 12i exhibited evidently neuroprotective effects on H2O2-induced PC12 cells damage and ferroptosis without cytotoxicity at 10 µM, as well as selectively metal chelating properties via chelating Cu2+. In addition, 12i showed a mixed-type inhibitory effect on AChE in vitro. The structure-activity relationships (SARs) analysis indicated that dioxolane groups on benzene ring and rigid oxime ester can improve the activity. Parallel artificial membrane permeation assay (PAMPA) also verified that 12i can overcome the blood-brain barrier (BBB). Overall, this is the first report on imidazolylacetophenone oxime-based multifunctional neuroprotective effects, suggesting that this type of compounds might be novel multifunctional agents against AD.

Synthesis and Evaluation of Trypanocidal Activity of Chromane-Type Compounds and Acetophenones.

American trypanosomiasis (Chagas disease) caused by the Trypanosoma cruzi parasite, is a severe health problem in different regions of Latin America and is currently reported to be spreading to Europe, North America, Japan, and Australia, due to the migration of populations from South and Central America. At present, there is no vaccine available and chemotherapeutic options are reduced to nifurtimox and benznidazole. Therefore, the discovery of new molecules is urgently needed to initiate the drug development process. Some acetophenones and chalcones, as well as chromane-type substances, such as chromones and flavones, are natural products that have been studied as trypanocides, but the relationships between structure and activity are not yet fully understood. In this work, 26 compounds were synthesized to determine the effect of hydroxyl and isoprenyl substituents on trypanocide activity. One of the compounds showed interesting activity against a resistant strain of T. cruzi, with a half effective concentration of 18.3 µM ± 1.1 and an index of selectivity > 10.9.

2,2,2-trifluoro-1-(1,4,5,6-tetrahydropyridin-3-yl)ethanone derivative as efflux pump inhibitor in Mycobacterium tuberculosis.

Although the administration of combined therapy is efficient to tuberculosis (TB) treatment caused by susceptible Mycobacterium tuberculosis strains, to overcome the multidrug resistance is still a challenge. Some studies have reported evidence about tetrahydropyridines as a putative efflux pump inhibitor, including in mycobacteria, being a promising strategy against M. tuberculosis. Thus, we investigated the biological potential of 2,2,2-trifluoro-1-(1,4,5,6-tetrahydropyridin-3-yl)ethanone derivative (NUNL02) against two strains of M. tuberculosis. NUNL02 was able to increase the susceptibility of the multidrug resistant strain to the anti-TB drugs, resulting in synergism with rifampicin. Still, we assume that this compound plays a role in the efflux mechanism in M. tuberculosis, besides, to be able to kill the bacillus under the deprivation of essential nutrients. Thus, our findings highlight NUNL02 as a promising prototype to develop a new adjuvant for TB treatment, mainly as EPI.

Total Syntheses of (±)-Melicolones A and B.

The first total syntheses of (±)-melicolones A and B, which have a unique and densely functionalized framework derived from a rearranged prenylated acetophenone, were accomplished in 12.3% combined overall yield. The concise and divergent synthesis of these two natural products, which were isolated in racemic form, was achieved in a longest linear sequence requiring only 9 steps (11 total steps) and 8 isolated intermediates using commercially available starting materials. This approach, which might enable access to all tetracyclic melicolones, features the highly regioselective (16:1) and diastereoselective (15:1) dipolar cycloaddition of a carbonyl ylide generated by the unusual cyclization of a rhodium carbene with the carbonyl oxygen atom of an aliphatic aldehyde. This cycloaddition proceeds with dominant steric control to give a highly functionalized oxabicycloheptane core. Stereoselective enolate alkylation led to a prenylated intermediate that underwent an intramolecular aldol reaction to give the penultimate tricyclic intermediate. Tandem epoxidation of the pendant prenyl group followed by a regioselective, acid-catalyzed cyclization delivered (±)-melicolones A and B.

HDAC-Bax Multiple Ligands Enhance Bax-Dependent Apoptosis in HeLa Cells.

Inspired by the synergistic effect of BTSA1 (a Bax activator) and SAHA (a histone deacetylase (HDAC) inhibitor) in HeLa cell growth suppression, a series of novel HDAC-Bax multiple ligands were designed rationally. Compound 23, which possesses similar HDAC inhibitory activity relative to SAHA and Bax affinity comparable to BTSA1, exhibits a superior growth suppression against HeLa cells, and its antiproliferative activities are 15-fold and 3-fold higher than BTSA1 and SAHA, respectively. The better antiproliferative activity and lower cytotoxicity of compound 23 indicated that our HDAC-Bax multiple ligand design strategy achieved success. Further studies suggested that compound 23 could enhance Bax-dependent apoptosis by upregulating Bax, followed by inducing the conformational activation of Bax. To our knowledge, we first report HDAC-Bax multiple ligands and demonstrate a new paradigm for the treatment of solid tumors by enhancing Bax-dependent apoptosis.

Exploring efficacy of natural-derived acetylphenol scaffold inhibitors for α-glucosidase: Synthesis, in vitro and in vivo biochemical studies.

The discovery of novel α-glucosidase inhibitors and anti-diabetic candidates from natural or natural-derived products represents an attractive therapeutic option. Here, a collection of acetylphenol analogues derived from paeonol and acetophenone were synthesized and evaluated for their α-glucosidase inhibitory activity. Most of derivatives, such as 9a-9e, 9i, 9m-9n and 11d-1e, (IC50 = 0.57 ± 0.01 µM to 8.45 ± 0.57 µM), exhibited higher inhibitory activity than the parent natural products and were by far more potent than the antidiabetic drug acarbose (IC50 = 57.01 ± 0.03 µM). Among these, 9e and 11d showed the most potent activity in a non-competitive manner. The binding processes between the two most potent compounds and α-glucosidase were spontaneous. Hydrophobic interactions were the main forces for the formation and stabilization of the enzyme - acetylphenol scaffold inhibitor complex, and induced the topography image changes and aggregation of α-glucosidase. In addition, everted intestinal sleeves in vitro and the maltose loading test in vivo further demonstrated the α-glucosidase inhibition of the two compounds, and our findings proved that they have significant postprandial hypoglycemic effects.

N-Substituted pyrimidinethione and acetophenone derivatives as a new therapeutic approach in diabetes.

In this study, compounds with 4-hydroxybutyl, 4-phenyl, 5-carboxylate, and pyrimidine moieties were determined as α-glycosidase inhibitors. N-Substituted pyrimidinethione and acetophenone derivatives (A1-A5, B1-B11, and C1-C11) were good inhibitors of the α-glycosidase enzyme, with Ki values in the range of 104.27 ± 15.75 to 1,004.25 ± 100.43 nM. Among them, compound B7 was recorded as the best inhibitor, with a Ki of 104.27 ± 15.75 nM against α-glycosidase. In silico studies were carried out to clarify the binding affinity and interaction mode of the compounds with the best inhibition score against α-glycosidase from Saccharomyces cerevisiae. Compounds B7 (S) and B11 (R) exhibited a good binding affinity with docking scores of -8.608 and 8.582 kcal/mol, respectively. The docking results also showed that the 4-hydroxybutyl and pyrimidinethione moieties play a key role in S. cerevisiae and human α-glycosidase inhibition.

Rottlerin: Structure Modifications and KCNQ1/KCNE1 Ion Channel Activity.

The slow delayed rectifier potassium current (IKs ) is formed by the KCNQ1 (Kv 7.1) channel, an ion channel of four α-subunits that modulates KCNE1 ß-subunits. IKs is central to the repolarization of the cardiac action potential. Loss of function mutation reducing ventricular cardiac IKs cause the long-QT syndrome (LQTS), a disorder that predisposes patients to arrhythmia and sudden death. Current therapy for LQTS is inadequate. Rottlerin, a natural product of the kamala tree, activates IKs and has the potential to provide a new strategy for rational drug therapy. In this study, we show that simple modifications such as penta-acetylation or penta-methylation of rottlerin blunts activation activity. Total synthesis was used to prepare side-chain-modified derivatives that slowed down KCNQ1/KCNE1 channel deactivation to different degrees. A binding hypothesis of rottlerin is provided that opens the way to improved IKs activators as novel therapeutics for the treatment of LQTS.

Novel paeonol derivatives: Design, synthesis and anti-inflammatory activity in vitro and in vivo.

Paeonol has been proved to have potential anti-inflammatory activity, but its clinical application is not extensive due to the poor anti-inflammatory activity (14.74% inhibitory activity at 20 µM). In order to discover novel lead compound with high anti-inflammatory activity, series of paeonol derivatives were designed and synthesized, their anti-inflammatory activities were screened in vitro and in vivo. Structure-activity relationships (SARs) have been fully concluded, and finally (E)-N-(4-(2-acetyl-5-methoxyphenoxy)phenyl)-3-(3,4,5-trimet-hoxyphenyl)acrylamide (compound 11a) was found to be the best active compound with low toxicity, which showed 96.32% inhibitory activity at 20 µM and IC50 value of 6.96 µM against LPS-induced over expression of nitric oxide (NO) in RAW 264.7 macrophages. Preliminary mechanism studies indicated that it could inhibit the expression of TLR4, resulting in inhibiting of NF-κB and MAPK pathways. Further studies have shown that compound 11a has obvious therapeutic effect against the adjuvant-induced rat arthritis model.

Paeonol Derivatives and Pharmacological Activities: A Review of Recent Progress.

Paeonol, 2-hydroxy-4-methoxy acetophenone, is one of the main active ingredients of traditional Chinese medicine such as Cynanchum paniculatum, Paeonia suffruticosa Andr and Paeonia lactiflora Pall. Modern medical research has shown that paeonol has a wide range of pharmacological activities. In recent years, a large number of studies have been carried out on the structure modification of paeonol and the mechanism of action of paeonol derivatives has been studied. Some paeonol derivatives exhibit good pharmacological activities in terms of antibacterial, anti-inflammatory, antipyretic analgesic, antioxidant and other pharmacological effects. Herein, the research progress on paeonol derivatives and their pharmacological activities were systematically reviewed.

Prenylated Acetophloroglucinol Dimers from Acronychia trifoliolata: Structure Elucidation and Total Synthesis.

The isolation of 12 secondary metabolites, including seven new acetophenone monomers, from the 50% CH3OH/CH2Cl2 extract (N089419-L/6) of Acronychia trifoliolata was reported previously. In the present work, three new prenylated acetophenone dimers (1-3) and five known dimers (4-8) were isolated, and their structures were elucidated by using various NMR spectroscopic techniques and HRMS. Among the new dimers, an unprecedented 4-isobutyl-3-isopropyltetrahydro-2H-pyran ring was observed in the structure of 1. This study is the first to report the formation of a 2H-pyran ring between two prenylated acetophloroglucinols. Only four related dimers have been reported before, and they were formylated phloroglucinol dimers from the family Eucalypteae. Compounds 2 and 3 are acrovestone-like dimers, and the structure of 3 was confirmed by total synthesis. The evaluation of the antiproliferative activity of isolated and synthesized acrovestone-like dimers indicated that a double bond in the prenyl-like moiety as found in the more active compounds might be important for mediating activity, while the pendant isobutyl group seems to be less important.

Benzonate derivatives of acetophenone as potent α-glucosidase inhibitors: synthesis, structure-activity relationship and mechanism.

In this article, 23 compounds (6 and 7a-7v) were prepared and evaluated for their in vitro α-glucosidase inhibitory activity. The compounds 7d, 7f, 7i, 7n, 7o, 7r, 7s, 7u, and 7v displayed the α-glucosidase inhibition activity with IC50 values ranging from 1.68 to 7.88 µM. Among all tested compounds, 7u was found to be the most efficient, being 32-fold more active than the standard drug acarbose, which significantly attenuated postprandial blood glucose in mice. In addition, the compound 7u also induced the fluorescence quenching and conformational changes of enzyme, by forming α-glucosidase-7u complex in a mixed inhibition type. The thermodynamic constants recognised the interaction between 7u and α-glucosidase and was an enthalpy-driven spontaneous exothermic reaction. The synchronous fluorescence and CD spectra also indicate that the compound 7u changed the enzyme conformation. The findings identify the binding interactions between new ligands and α-glucosidase and reveal the compound 7u as a potent α-glucosidase inhibitor.

The Mosaic of Rottlerin: The Sequel.

Rottlerin (1) is a potent protein kinase C δ inhibitor that possesses a wide range of biological activities. However, the potential of this molecule to be developed as a drug has been restricted by its limited availability. We report herein a gram scale quantity synthesis of rottlerin in a five-step synthetic route that can be completed within 2 days. The methodology was extended by the reaction of the key aminochromene intermediate (15) with various electron-rich arenes, forming novel unsymmetrical methylene-bridged compounds. The X-ray crystal structure revealed the boomerang shape of this kind of molecule for the first time. The direct transformation of rottlerin (1) into the natural product, isorottlerin (35), was observed for the first time, and we named this transformation the "isorottlerin change". In addition, the antibacterial activities of rottlerin (1) and new rottlerin analogues 32-34 were examined against Staphylococcus aureus. The compounds showed MIC values as low as 2.0 µM, which were comparable to the clinically used antibiotic gentamicin.

Apoptosis induced by synthetic compounds containing a 3,4,5-trimethoxyphenyl fragment against lymphoid immature neoplasms.

T-cell acute lymphoblastic leukemia is an aggressive hematological malignancy originating from the malignant transformation of progenitor T cells at different stages of development. The treatment causes severe adverse effects and is associated with relapses and high morbidity and mortality rates. The present study aimed to evaluate the cytotoxic activity of 28 new compounds containing 3,4,5-trimethoxyphenyl analogues on hematological neoplastic cells lines. Cytotoxicity screening by the MTT method revealed that compound 1d was the most promising. Cell viability of neoplastic cells decreased in a concentration- and time-dependent manner, with compound 1d not causing hemolysis or reducing peripheral blood mononuclear cells viability, suggesting a selective cytotoxicity. We also suggested that compound 1d induced apoptotic-like cell death with mitochondrial involvement in Jurkat cells.

Microwave-Assisted Synthesis of Mono- and Disubstituted 4-Hydroxyacetophenone Derivatives via Mannich Reaction: Synthesis, XRD and HS-Analysis.

An efficient microwave-assisted one-step synthetic route toward Mannich bases is developed from 4-hydroxyacetophenone and different secondary amines in quantitative yields, via a regioselective substitution reaction. The reaction takes a short time and is non-catalyzed and reproducible on a gram scale. The environmentally benign methodology provides a novel alternative, to the conventional methodologies, for the synthesis of mono- and disubstituted Mannich bases of 4-hydroxyacetophenone. All compounds were well-characterized by FT-IR, ¹H NMR, 13C NMR, and mass spectrometry. The structures of 1-{4-hydroxy-3-[(morpholin-4-yl)methyl]phenyl}ethan-1-one (2a) and 1-{4-hydroxy-3-[(pyrrolidin-1-yl)methyl]phenyl}ethan-1-one (3a) were determined by single crystal X-ray crystallography. Compound 2a and 3a crystallize in monoclinic, P21/n, and orthorhombic, Pbca, respectively. The most characteristic features of the molecular structure of 2a is that the morpholine fragment adopts a chair conformation with strong intramolecular hydrogen bonding. Compound 3a exhibits intermolecular hydrogen bonding, too. Furthermore, the computed Hirshfeld surface analysis confirms H-bonds and π⁻π stack interactions obtained by XRD packing analyses.

Synthesis and Evaluation of the in vitro Antimicrobial Activity of Triazoles, Morpholines and Thiosemicarbazones.

BACKGROUND: Microbial infections is a global public health problem. The aim of this work was to synthesize and evaluate the antimicrobial activity of novel triazoles, morpholines and thiosemicarbazones. METHODS: Compounds were synthesized using 2,4-Dihydroxyacetophenone and 4-hydroxybenzaldehyde as starting materials. The antimicrobial activity of these compounds against bacteria and yeast was evaluated by the broth microdilution method. RESULTS: The proposed route for synthesis gave high to moderate yields, moreover these compounds were successfully characterized by 1H NMR, 13C NMR and LC-MS. Antimicrobial testing indicated that the thiosemicarbazone and morphine derivatives had the best antimicrobial activity against the microorganisms tested with minimum inhibitory concentrations (MIC) between 0.29 and 5.30 µM. Thiosemicarbazone derivative (12) was able to inhibit the growth of C. tropicalis, with minimum fungicidal concentration (MFC) of 0.55 µM. In addition, this compound was active against E. coli, S. aureus and S. epidermidis, with MIC values ranging from 0.29 to 1.11 µM. Moreover, the morpholine derivative (15) had an MIC value of 0.83 µM against C. albicans and E. coli. CONCLUSION: We have efficiently synthesized a series of eleven novel triazoles, thiosemicarbazones and morpholine derivatives using 2,4-Dihydroxyacetophenone and 4-hydroxybenzaldehyde as starting materials. Thiosemicarbazone derivative (12) showed promising antifungal and antibacterial activity and these findings suggest that this compound can be used as scaffolds to design new antimicrobial drugs.

Hits-to-Lead Optimization of the Natural Compound 2,4,6-Trihydroxy-3-geranyl-acetophenone (tHGA) as a Potent LOX Inhibitor: Synthesis, Structure-Activity Relationship (SAR) Study, and Computational Assignment.

A new series of 2,4,6-trihydroxy-3-geranyl-acetophenone (tHGA) analogues were synthesized and evaluated for their lipoxygenase (LOX) inhibitory activity. Prenylated analogues 4a⁻g (half maximal inhibitory concentration (IC50) values ranging from 35 µ M to 95 µ M) did not exhibit better inhibitory activity than tHGA (3a) (IC50 value: 23.6 µ M) due to the reduction in hydrophobic interaction when the alkyl chain length was reduced. One geranylated analogue, 3d, with an IC50 value of 15.3 µ M, exhibited better LOX inhibitory activity when compared to tHGA (3a), which was in agreement with our previous findings. Kinetics study showed that the most active analogue (3e) and tHGA (3a) acted as competitive inhibitors. The combination of in silico approaches of molecular docking and molecular dynamic simulation revealed that the lipophilic nature of these analogues further enhanced the LOX inhibitory activity. Based on absorption, distribution, metabolism, excretion, and toxicity (ADMET) and toxicity prediction by komputer assisted technology (TOPKAT) analyses, all geranylated analogues (3a⁻g) showed no hepatotoxicity effect and were biodegradable, which indicated that they could be potentially safe drugs for treating inflammation.