Acridone alkaloids from Glycosmis chlorosperma as DYRK1A inhibitors

Synthesis, Structural Modification, and Bioactivity Evaluation of Substituted Acridones as Potent Microtubule Affinity-Regulating Kinase 4 Inhibitors

Acridones present numerous pharmacological activities, including inhibition of microtubule affinity-regulating kinase 4 (MARK4) kinase activity. To investigate structure-activity relationships and develop potent MARK4 inhibitors, derivatives of 2-methylacridone were synthesized and tested for their activity against MARK4 kinase. Selective substitutions at the nitrogen atom were accomplished by treating 2-methylacridone with alkyl halides in the presence of K2CO3. In addition, amidation of acridone acetic acid 11 with piperazine or tryptophan methyl ester followed by derivatization with various amines gave a series of new acridone derivatives. Among the tested compounds, six were identified as possessing high inhibitory activity against MARK4. The molecular modeling studies showed that the derivatives bearing piperazine or tryptophan bind well to the ATP-binding site of MARK4. The antiproliferative activity of six active compounds was evaluated against HeLa and U87MG cancer cells. Tryptophan derivatives 23a, 23b, and 23c showed significant cytotoxicity against both cell lines with EC50 values ranging from 2.13 to 4.22 μM, while derivatives bearing piperazine were found to be not cytotoxic. Additionally, compound 23a decreased the proliferation of human MDA-MB-435 and U251 cancer cells in the low micromolar range; however, it also affects the non-cancerous HGF cells. Due to their high binding affinity against MARK4, the synthesized compounds could be potential agents to target MARK4 against cancer and tauopathies.

Structurally diverse sulphur-containing amides from Glycosmis craibii with their potential antiproliferative activities

Fourteen new sulphur-containing amides, glycocramides A-N (1-14), as well as nine known analogues (15-23) were isolated and characterized from Glycosmis craibii Tanaka. The chemical structures of new sulphur-containing amides 1-14 were ambiguously elucidated by extensive spectroscopic methods, while the known compounds 15-23 were identified by the comparison of their experimental spectral data with those described data in the literatures. The antiproliferative effects of all isolated sulphur-containing amides were evaluated in vitro. As a result, part of sulphur-containing amides showed remarkable inhibitory effects against MGC-803 cell line with IC₅₀ values ranging from 13.12 ± 0.10 to 20.03 ± 0.13 μM. These research results suggest that the sulphur-containing amides are potentially to be developed as a new natural anti-tumor drugs.

Isolation and Characterization of One New Natural Compound with Other Potential Bioactive Secondary Metabolites from Glycosmis cyanocarpa (Blume) Spreng. (Family: Rutaceae)

Glycosmis cyanocarpa (Blume) Spreng is a plant in the Rutaceae family and a species in the Glycosmis genus that has received little attention. Therefore, this research aimed to report the chemical and biological analysis of Glycosmis cyanocarpa (Blume) Spreng. The chemical analysis involved the isolation and characterization of secondary metabolites through an extensive chromatographic study, and the structures of these metabolites were elucidated on the basis of a detailed analysis of NMR and HRESIMS spectroscopic data and by comparison with those of related compounds reported in the literature. Different partitions of the crude ethyl acetate (EtOAc) extract were evaluated for antioxidant, cytotoxic, and thrombolytic potentials. In chemical analysis, one new phenyl acetate derivative, namely 3,7,11,15-tetramethylhexadec-2-en-1-yl 2-phenylacetate (1), along with four known compounds N-methyl-3-(methylthio)-N-(2-phenylacetyl) acrylamide (2), penangin (3), β-Caryophyllene oxide (4), and acyclic diterpene-phytol (5) were isolated for the first time from the stem and leaf of the plant. The ethyl acetate fraction showed significant free radical scavenging activity with an IC₅₀ value of 11.536 µg/mL compared to standard ascorbic acid (4.816 µg/mL). In the thrombolytic assay, the dichloromethane fraction showed the maximum thrombolytic activity of 16.42% but was still insignificant compared to the standard streptokinase (65.98%). Finally, in a brine shrimp lethality bioassay, the LC₅₀ values of dichloromethane, ethyl acetate, and aqueous fractions were found to be 0.687 µg/mL, 0.805 µg/mL, and 0.982 µg/mL which are significant compared to the standard vincristine sulfate of 0.272 µg/mL.

Severinia buxifolia-isolated acridones inhibit lung cancer invasion and decrease HIFα protein synthesis involving 5'UTR-mediated translation inhibition

BACKGROUND

Lung cancer is one of the most common cancers worldwide and is by far the leading cause of cancer death attributed to its rapid metastasis and poor prognosis. Given that hypoxia-inducible factors (HIFs) are associated with cancer metastasis, discovering agents to inhibit HIF-mediated invasive cancer is highly desired.

PURPOSE

This study aimed to investigate the natural acridone compounds isolated from Severinia buxifolia for the potential to delay hypoxia-induced lung cancer invasiveness by HIF inhibition.

METHODS

Using a hypoxia-responsive element (HRE) luciferase reporter, cell migration and invasion assays, real-time PCR, Western blot, and DNA recombinant clones, compound effect on HIF activity, cancer metastasis, HIF-1α mRNA transcription, HIFs protein stability, and HIF-1α translation were observed under hypoxia conditions.

RESULTS

Atalaphyllidine (Sbs-A) and atalaphyllinine (Sbs-B) were found to show the most potent effects on HIF transcriptional activity and HIF-1α protein expression in NSCLC cell line A549, although Sbs-A and Sbs-B might not attribute decreasing HIF-1α mRNA expression to potent inhibition of HIF activity. HIF-1α protein stability was not affected by Sbs-A; also, prolyl hydroxylase and proteasome inhibitors could not reverse the inhibitory effect from compounds. Furthermore, 3 - 10 μM low concentrations of Sbs-A inhibited HIF target gene expression, gelatin zymography activity, and A549 cancer invasion. Ultimately, Sbs-A inhibited HIF-1α 5'UTR-mediated translation independent of oxygen concentration, underlying the mechanism of compounds inhibiting HIF-1α protein expression.

CONCLUSION

Our study proposed Severinia buxifolia-isolated acridone compounds inhibited 5'-mRNA HIFA-mediated translation and provided evidence supporting the ability of acridone compounds in targeting HIFα for delayed lung cancer metastasis.

Phenolic furanochromene hydrazone derivatives: Synthesis, antioxidant activity, ferroptosis inhibition, DNA cleavage and DNA molecular docking studies

Twenty-four phenolic furanochromene hydrazone derivatives were designed and synthesized in order to evaluate structure-activity relationships in a series of antioxidant-related assays. The derivatives have varying substitution patterns on the phenol ring, with some compounds having one, two or three hydroxy groups, and others containing one hydroxy group in combination with methoxy, methyl, bromo, iodo and/or nitro groups. Antioxidant activity was determined using the DPPH free radical scavenging and CUPRAC assays. Compounds containing ortho-dihydroxy and para-dihydroxy patterns had the highest free radical scavenging activity, with IC50 values ranging from 5.0 to 28 μM. Similarly, derivatives with ortho-dihydroxy and para-dihydroxy patterns, together with a 4-hydroxy-3,5‑dimethoxy pattern, displayed strong copper (II) ion reducing capacity, using Trolox as a standard. Trolox equivalent antioxidant capacity (TEAC) coefficients for these derivatives ranged from 1.75 to 3.97. As further evidence of antioxidant potential, greater than half of the derivatives reversed erastin-induced ferroptosis in HaCaT cells. In addition, twenty-three of the derivatives were effective at cleaving supercoiled plasmid DNA in the presence of copper (II) ions at 1 mM, with the 3,4‑dihydroxy derivative showing cleavage to both the linear and open circular forms at 3.9 uM. The interaction of the phenolic furanochromene derivatives with DNA was confirmed by molecular docking studies, which revealed that all the derivatives bind favorably in the minor groove of DNA.

A comprehensive review on acridone based derivatives as future anti-cancer agents and their structure activity relationships

The development of drug resistance and severe side-effects has reduced the clinical efficacy of the existing anti-cancer drugs available in the market. Thus, there is always a constant need to develop newer anti-cancer drugs with minimal adverse effects. Researchers all over the world have been focusing on various alternative strategies to discover novel, potent, and target specific molecules for cancer therapy. In this direction, several heterocyclic compounds are being explored but amongst them one promising heterocycle is acridone which has attracted the attention of medicinal chemists and gained huge biological importance as acridones are found to act on different therapeutically proven molecular targets, overcome ABC transporters mediated drug resistance and DNA intercalation in cancer cells. Some of these acridone derivatives have reached clinical studies as these heterocycles have shown huge potential in cancer therapeutics and imaging. Here, the authors have attempted to compile and make some recommendations of acridone based derivatives concerning their cancer biological targets and in vitro-cytotoxicity based on drug design and novelty to increase their therapeutic potential. This review also provides some important insights on the design, receptor targeting and future directions for the development of acridones as possible clinically effective anti-cancer agents.

Synthesis and Anticancer Properties of New 3-Methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones

Quinolinones have been known for a long time as broad-spectrum synthetic antibiotics. More recently, the anticancer potential of this group of compounds has been investigated. Following this direction, we obtained a small library of 3-methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones with various substituents at positions 1, 2, 6, and 7 of the quinolinone ring system. The cytotoxic activity of the synthesized analogs was tested in the MTT assay on two cancer cell lines in order to determine the structure–activity relationship. All compounds produced high cytotoxic effects in MCF-7, and even higher in HL-60 cells. 2-Ethyl-3-methylidene-1-phenylsulfonyl-2,3-dihydroquinolin-4(1H)-one, which was over 5-fold more cytotoxic for HL-60 than for normal HUVEC cells, was selected for further tests. This analog was shown to inhibit proliferation and induce DNA damage and apoptosis in HL-60 cells.

Preparation and characterization of Gum Arabic Schiff's bases based on 9-aminoacridine with in vitro evaluation of their antimicrobial and antitumor potentiality

The conjugation between drug and biopolymers through an easily hydrolysable bond such as ester linkage, disulfide linkage, or imine-bond have been extensively employed to control the drug release pattern and improve its bioavailability. This work described the conjugation of 9-aminoacridine (9-AA) to Gum Arabic (GA) via Schiff's base, as a pH-responsive bond. First, GA was oxidized to Arabic Gum dialdehyde (AGDA), then a different amount of 9-AA (10, 25, and 50 mg 9-AA) was coupled to defined amount of AGDA, the coupling was confirmed by elemental analysis and different spectroscopic tools. In addition, the physical features of Schiff's base conjugates including surface morphology, thermal stability, and crystalline structure were examined. The thermogravimetric analysis revealed that the incorporation of 9-AA slightly improved the thermal stability. The coupling of 9-AA to AGDA dramatically enhanced its in vitro antimicrobial and antitumor activities. All conjugates exhibited broad-spectrum activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, and Candida albicans. Moreover, AGA 25 and AGA 50 demonstrated promising capability to suppress the proliferation of human colon cancer cell line (Caco-2), with IC₅₀ 190.10 and 180.80 μg/mL respectively.

Aristolactam BIII, a naturally derived DYRK1A inhibitor, rescues Down syndrome-related phenotypes

BACKGROUND

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a significant pathogenic factor in Down syndrome (DS), wherein DYRK1A is overexpressed by 1.5-fold because of trisomy of human chromosome 21. Thus, DYRK1A inhibition is considered a therapeutic strategy to modify the disease.

PURPOSE

This study aims to identify a novel DYRK1A inhibitor and validate its therapeutic potential in DS-related pathological conditions.

STUDY DESIGN

In order to identify a novel DYRK1A inhibitor, we carried out two-step screening: a structure-based virtual screening of > 300,000 chemical library (first step) and cell-based nuclear factor of activated T-cells (NFAT)-response element (RE) promoter assay (second step). Primary hits were evaluated for their DYRK1A inhibitory activity using in vitro kinase assay and Tau phosphorylation in mammalian cells. Confirmed hit was further evaluated in pathological conditions including DYRK1A-overexpressing fibroblasts, flies, and mice.

RESULTS

We identified aristolactam BIII, a natural product derived from herbal plants, as a novel DYRK1A inhibitor. It potently inhibited the kinase activity of DYRK1A in vitro (IC₅₀ = 9.67 nM) and effectively suppressed DYRK1A-mediated hyperphosphorylation of Tau in mammalian cells. Aristolactam BIII rescued the proliferative defects of DYRK1A transgenic (TG) mouse-derived fibroblasts and neurological and phenotypic defects of DS-like Drosophila models. Oral administration of aristolactam BIII acutely suppressed Tau hyperphosphorylation in the brain of DYRK1A TG mice. In the open field test, aristolactam BIII significantly ameliorated the exploratory behavioral deficit of DYRK1A TG mice.

CONCLUSION

Our work revealed that aristolactam BIII as a novel DYRK1A inhibitor rescues DS phenotypes in cells and in vivo and suggested its therapeutic potential for the treatment of DYRK1A-related diseases.

Studies Directed towards the Synthesis of the Acridone Family of Natural Products: Total Synthesis of Acronycines and Atalaphyllidines

A modular and flexible three-step synthetic strategy has been developed for the synthesis of acridone natural products of biological significance. The tetracyclic core of acridone derivatives has been achieved efficiently in high yield from commercially available anthranilic acid and phenol derivatives via condensation reaction, followed by regioselective annulation. Acridone alkaloids acronycine and noracronycine are synthesized in improved overall yields in fewer steps than the previously reported approaches. The method has further been used for the synthesis of atalaphyllidine and 5-hydroxynoracronycine in excellent yields for the first time. Moreover, the synthetic utility of the present strategy has been showcased by the synthesis of oxa and thia analogues of acronycine alkaloid.

Access to acridones by tandem copper(I)-catalyzed electrophilic amination/Ag(I)-mediated oxidative annulation of anthranils with arylboronic acids

An efficient and practical approach for the synthesis of medicinally important acridones was developed from anthranils and commercially available arylboronic acids by a tandem copper(I)-catalyzed electrophilic amination/Ag(I)-mediated oxidative annulation strategy. This new and straightforward protocol displayed a broad substrate scope (25 examples) and high functional group tolerance. What's more, a possible mechanistic proposal was also presented.

Traditional uses, phytochemistry, pharmacology, toxicology and formulation aspects of Glycosmis species: A systematic review

The present article is a systematic and constructive review of the traditional medicinal uses, chemistry, pharmacology, toxicology, and formulation aspects of Glycosmis species. The genus Glycosmis comprise 51 accepted species broadly distributed in Australia, China, India, and South-East Asia. Traditionally, Glycosmis species are used in folk medicines to treat cancer, anaemia, rheumatism, fever, cough, liver-related problems, skin ailments, intestinal worm infections, wounds, and facial inflammation. This review aims to provide readers with the latest information highlighting chemical constituents isolated from the Glycosmis species, plant parts utilized for their isolation and their pharmacological activities. So far, 307 chemical constituents have been isolated and characterized from different species of the genus Glycosmis; among these constituents, alkaloids, flavonoids, terpenoids, phenolics, and sulphur-containing amides are the major bioactive compounds. Modern pharmacological studies have shown that the crude extracts and compounds isolated from this genus exhibit a broad spectrum of biological activities like anticancer, antimicrobial, anti-inflammatory, antipyretic, antidiabetic, antioxidant, larvicidal, insecticidal, hepatoprotective, wound healing, antiviral, antidiarrheal, and anxiolytic. The carbazole and acridone alkaloids from this genus have shown potential anticancer activity in various in vitro and in vivo studies. Rare scaffolds like dimeric carbazoles, dimeric acridone alkaloids, flavanocoumarins and sulphur-containing amides from this genus need further exploration for their potential bioactivity. This article also briefs about the toxicological screening and discusses various polyherbal and nano formulation aspects of Glycosmis species. Most of the pharmacological studies reported from this genus were carried out in vitro. An in-depth in vivo and toxicology evaluation of the crude extracts and isolated specialized compounds is required to explore the full therapeutic potential of this genus.

Development of Cdc2-like Kinase 2 Inhibitors: Achievements and Future Directions

Cdc2-like kinases (CLKs; CLK1-4) are associated with various neurodegenerative disorders, metabolic regulation, and viral infection and have been recognized as potential drug targets. Human CLK2 has received increasing attention as a regulator that phosphorylates serine- and arginine-rich (SR) proteins and subsequently modulates the alternative splicing of precursor mRNA (pre-mRNA), which is an attractive target for degenerative disease and cancer. Numerous CLK2 inhibitors have been identified, with several molecules currently in clinical development. The first CLK2 inhibitor Lorecivivint (compound 1) has recently entered phase 3 clinical trials. However, highly selective CLK2 inhibitors are rarely reported. This Perspective summarizes the biological roles and therapeutic potential of CLK2 along with progress on the development of CLK2 inhibitors and discusses the achievements and future prospects of CLK2 inhibitors for therapeutic applications.

Indole alkaloids from the leaves of Ravenia spectabilis engl. with activity against pancreatic cancer cell line

Two previously undescribed indole alkaloids, 3-prenyl-5(3-keto-but-1-enyl) indole and 3-prenyl-indole-5-carbaldehyde, the structurally-related 3,5-diprenyl indole and four known alkaloids were isolated from the leaves of Ravenia spectabilis Engl. Structures were elucidated based on nuclear magnetic resonance (1D and 2D NMR) spectroscopic and mass spectrometric analysis. The previously undescribed compounds isolated were subsequently screened against the HeLa (human cervical cancer), MIA PaCa-2 (human pancreatic adenocarcinoma) and A549 (lung cancer) cell lines. Among the isolated compounds, 3,5-diprenyl indole was the most cytotoxic across all three cell lines (MIA PaCa-2 IC₅₀ = 9.5 ± 2.2 μM). Molecular modelling studies suggested DNA intercalation as the mode of action of these compounds.

Plant Extracts and their Secondary Metabolites as Modulators of Kinases

Natural Products (NP), specifically from medicinal plants or herbs, have been extensively utilized to analyze the fundamental mechanisms of ultimate natural sciences as well as therapeutics. Isolation of secondary metabolites from these sources and their respective biological properties, along with their lower toxicities and cost-effectiveness, make them a significant research focus for drug discovery. In recent times, there has been a considerable focus on isolating new chemical entities from natural flora to meet the immense demand for kinase modulators, and also to overcome major unmet medical challenges in relation to signal transduction pathways. The signal transduction systems are amongst the foremost pathways involved in the maintenance of life and protein kinases play an imperative part in these signaling pathways. It is important to find a kinase inhibitor, as it can be used not only to study cell biology but can also be used as a drug candidate for cancer and metabolic disorders. A number of plant extracts and their isolated secondary metabolites such as flavonoids, phenolics, terpenoids, and alkaloids have exhibited activities against various kinases. In the current review, we have presented a brief overview of some important classes of plant secondary metabolites as kinase modulators. Moreover, a number of phytocompounds with kinase inhibition potential, isolated from different plant species, are also discussed.

Synthesis of novel cytotoxic tetracyclic acridone derivatives and study of their molecular docking, ADMET, QSAR, bioactivity and protein binding properties

Acridone based synthetic and natural products with inherent anticancer activity advancing the research and generating a large number of structurally diversified compounds. In this sequence we have designed, synthesized a series of tetracyclic acridones with amide framework viz., 3-(alkyloyl/ aryloyl/ heteroaryloyl/ heteroaryl)-2,3-dihydropyrazino[3,2,1-de]acridin-7(1H)-ones and screened for their in vitro anti-cancer activity. The in vitro study revealed that compounds with cyclopropyl-acetyl, benzoyl, p-hydroxybenzoyl, p-(trifluoromethyl)benzoyl, p-fluorobenzoyl, m-fluorobenzoyl, picolinoyl, 6-methylpicolinoyl and 3-nicotinoyl groups are active against HT29, MDAMB231 and HEK293T cancer cell lines. The molecular docking studies performed for them against 4N5Y, HT29 and 2VWD revealed the potential ligand-protein binding interactions among the neutral aminoacid of the enzymes and carbonyl groups of the title compounds with a binding energy ranging from - 8.1394 to - 6.9915 kcal/mol. In addition, the BSA protein binding assay performed for them has confirmed their interaction with target proteins through strong binding to BSA macromolecule. The additional studies like ADMET, QSAR, bioactivity scores, drug properties and toxicity risks ascertained them as newer drug candidates. This study had added a new collection of piperazino fused acridone derivatives to the existing array of other nitrogen heterocyclic fused acridone derivatives as anticancer agents.

A new indole alkaloid from the stems of Glycosmis puberula var. craibii

A phytochemical investigation on the stems of Glycosmis puberula var. craibii led to the isolation of a new indole alkaloid (named glycosmiscrol A, 1), together with four known compounds (2-5). The new structure was elucidated by detailed analysis of comprehensive spectroscopic methods. All isolated compounds were evaluated for their antiproliferative activities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Compounds 1-5 showed significant antiproliferative effects with IC₅₀ values ranging from 0.16 to 8.58 µM.

Syntheses of 12H-benzo[a]xanthen-12-ones and benzo[a]acridin-12(7H)-ones through Au(i)-catalyzed Michael addition/6-endo-trig cyclization/aromatization cascade annulation

A multifaceted gold(i)-catalyzed aromaticity-driven double 6-endo cascade cyclization strategy to synthesize both 12H-benzo[a]xanthen-12-ones and benzo[a]acridin-12(7H)-ones, whose core motifs xanthone and acridone both exist as important scaffolds in an immense number of bioactive compounds, was developed. The scopes of this strategy were examined by using a batch of synthetic 1,3-diphenylprop-2-yn-1-one substrates. To probe the mechanism of this cyclization a control experiment for synthesizing intermediates was performed. Thus, a putative mechanism was determined according to this experiment and previous studies.

Probing the Inhibition of Microtubule Affinity Regulating Kinase 4 by N-Substituted Acridones

Microtubule affinity regulating kinase 4 (MARK4) becomes a unique anti-cancer drug target as its overexpression is responsible for different types of cancers. In quest of novel, effective MARK4 inhibitors, some acridone derivatives were synthesized, characterized and evaluated for inhibitory activity against human MARK4. Among all the synthesized compounds, three (7b, 7d and 7f) were found to have better binding affinity and enzyme inhibition activity in µM range as shown by fluorescence binding, ITC and kinase assays. Here we used functional assays of selected potential lead molecules with commercially available panel of 26 kinases of same family. A distinctive kinase selectivity profile was observed for each compound. The selective compounds were identified with submicromolar cellular activity against MARK4. Furthermore, in vitro antitumor evaluation against cancerous cells (MCF-7 and HepG2) revealed that compounds 7b, 7d and 7f inhibit cell proliferation and predominantly induce apoptosis in MCF-7 cells, with IC₅₀ values of 5.2 ± 1.2 μM, 6.3 ± 1.2 μM, and 5.8 ± 1.4 μM respectively. In addition, these compounds significantly upsurge the oxidative stress in cancerous cells. Our observations support our approach for the synthesis of effective inhibitors against MARK4 that can be taken forward for the development of novel anticancer molecules targeting MARK4.

Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A) Inhibitors as Potential Therapeutics

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a member of an evolutionarily conserved family of protein kinases that belongs to the CMGC group of kinases. DYRK1A, encoded by a gene located in the human chromosome 21q22.2 region, has attracted attention due to its association with both neuropathological phenotypes and cancer susceptibility in patients with Down syndrome (DS). Inhibition of DYRK1A attenuates cognitive dysfunctions in animal models for both DS and Alzheimer's disease (AD). Furthermore, DYRK1A has been studied as a potential cancer therapeutic target because of its role in the regulation of cell cycle progression by affecting both tumor suppressors and oncogenes. Consequently, selective synthetic inhibitors have been developed to determine the role of DYRK1A in various human diseases. Our perspective includes a comprehensive review of potent and selective DYRK1A inhibitors and their forthcoming therapeutic applications.

Synthesis of 3-Methylidene-1-tosyl-2,3-dihydroquinolin-4(1H)-ones as Potent Cytotoxic Agents

An efficient synthetic strategy to 3-methylidene-2,3-dihydroquinolin-4(1H)-ones variously substituted in position 2 has been developed. The title compounds were synthesized in the reaction sequence involving reaction of diethyl methylphosphonate with methyl 2-(tosylamino)benzoate, condensation of thus formed diethyl 2-oxo-2-(2-N-tosylphenyl)ethylphosphonate with various aldehydes followed by successful application of the obtained 3-(diethoxyphosphoryl)-1,2-dihydroquinolin-4-ols as Horner-Wadsworth-Emmons reagents for the olefination of formaldehyde. Also, enantioselective approach to the target compounds has been evaluated using 3-dimenthoxyphosphoryl group as a chiral auxiliary. Single X-ray crystal analysis of (2S)-3-(dimenthoxyphosphoryl)-2-phenyl-1-tosyldihydroquinolin-4-ol revealed the presence of strong resonance-assisted hydrogen bond (RAHB). The obtained 3-methylidene-2,3-dihydroquinolin-4(1H)-ones were then tested for their cytotoxic activity against two leukemia cell lines NALM-6 and HL-60 and a breast cancer MCF-7 cell line. All compounds showed very high cytotoxic activity with the IC₅₀ values mostly below 1 μm in all three cancer cell lines. The selected analogs were also tested on human umbilical vein endothelial cells (HUVEC) and on human mammary gland/breast cells (MCF-10A) to evaluate their influence on normal cells. Since one of the most serious problems in cancer chemotherapy is the development of drug resistance, the mRNA levels and activity of ABCB1 transporter considered to be the most important factor engaged in drug resistance, were evaluated in MCF-7 cells treated with two selected analogs. Both compounds were strong ABCB1 transporter inhibitors that could prevent efflux of anticancer drugs from cancer cells.

Synthesis of 2-aminobenzophenones through acylation of anilines with α-oxocarboxylic acids assisted by tert-butyl nitrite

A highly facile all-in-one-pot synthesis of 2-aminobenzophenones directly from anilines, tert-butyl nitrite and α-oxocarboxylic acids under the catalysis of Pd(OAc)₂ is presented.

Multi-step virtual screening to develop selective DYRK1A inhibitors

Developing selective inhibitors for a particular kinase remains a major challenge in kinase-targeted drug discovery. Here we performed a multi-step virtual screening for dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) inhibitors by focusing on the selectivity for DYRK1A over cyclin-dependent kinase 5 (CDK5). To examine the key factors contributing to the selectivity, we constructed logistic regression models to discriminate between actives and inactives for DYRK1A and CDK5, respectively, using residue-based binding free energies. The residue-based parameters were calculated by molecular mechanics-generalized Born surface area (MM-GBSA) decomposition methods for kinase-ligand complexes modeled by computer ligand docking. Based on the findings from the logistic regression models, we built a three-dimensional (3D) pharmacophore model and chose filter criteria for the multi-step virtual screening. The virtual hit compounds obtained from the screening were assessed for their inhibitory activities against DYRK1A and CDK5 by in vitro assay. Our screening identified two novel selective DYRK1A inhibitors with IC50 values of several μM for DYRK1A and >100μM for CDK5, which can be further optimized to develop more potent selective DYRK1A inhibitors.

Transition-metal-free oxidative intermolecular cyclization reaction: synthesis of 2-aryl-4-quinolones

Herein, a novel and efficient intermolecular cyclization of 2-aminoacetophenones with aldehydes was developed for the synthesis of 2-aryl-4-quinolones through C–C and C–N bond formation.

Recent developments in the synthesis and biological activity of acridine/acridone analogues

Many people in the world struggle with cancer or bacterial, parasitic, viral, Alzheimer's and other diseases.

Current pharmacotherapy and putative disease-modifying therapy for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease of the central nervous system correlated with the progressive loss of cognition and memory. β-Amyloid plaques, neurofibrillary tangles and the deficiency in cholinergic neurotransmission constitute the major hallmarks of the AD. Two major hypotheses have been implicated in the pathogenesis of AD namely the cholinergic hypothesis which ascribed the clinical features of dementia to the deficit cholinergic neurotransmission and the amyloid cascade hypothesis which emphasized on the deposition of insoluble peptides formed due to the faulty cleavage of the amyloid precursor protein. Current pharmacotherapy includes mainly the acetylcholinesterase inhibitors and N-methyl-D-aspartate receptor agonist which offer symptomatic therapy and does not address the underlying cause of the disease. The disease-modifying therapy has garnered a lot of research interest for the development of effective pharmacotherapy for AD. β and γ-Secretase constitute attractive targets that are focussed in the disease-modifying approach. Potentiation of α-secretase also seems to be a promising approach towards the development of an effective anti-Alzheimer therapy. Additionally, the ameliorative agents that prevent aggregation of amyloid peptide and also the ones that modulate inflammation and oxidative damage associated with the disease are focussed upon. Development in the area of the vaccines is in progress to combat the characteristic hallmarks of the disease. Use of cholesterol-lowering agents also is a fruitful strategy for the alleviation of the disease as a close association between the cholesterol and AD has been cited. The present review underlines the major therapeutic strategies for AD with focus on the new developments that are on their way to amend the current therapeutic scenario of the disease.

DYRK1A inhibition as potential treatment for Alzheimer's disease

In total, 47,500,000 people worldwide are affected by dementia and this number is estimated to double by 2030 and triple within 2050 resulting in a huge burden on public health. Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia, accounting for 60-70% of all the cases. The cause of AD is still poorly understood but several brain abnormalities (e.g., loss of neuronal connections and neuronal death) have been identified in affected patients. In addition to the accumulation of β-amyloid plaques in the brain tissue, aberrant phosphorylation of tau proteins has proved to increase neuronal death. DYRK1A phosphorylates tau on 11 different Ser/Thr residues, resulting in the formation of aggregates called 'neurofibrillary tangles' which, together with amyloid plaques, could be responsible for dementia, neuronal degeneration and cell death. Small molecule inhibition of DYRK1A could thus represent an interesting approach toward the treatment of Alzheimer's and other neurodegenerative diseases. Herein we review the current progress in the identification and development of DYRK1A inhibitors.

A concise and efficient synthesis of benzimidazo[1,2-c]quinazolines through CuI-catalyzed intramolecular N-arylations

A series of functionalized benzimidazo[1,2-c]quinazoline derivatives was obtained in excellent yields under mild conditions through a CuI-catalyzed Ullmann N-arylation starting from easily available starting materials.

Luciferin and derivatives as a DYRK selective scaffold for the design of protein kinase inhibitors

D-Luciferin is widely used as a substrate in luciferase catalysed bioluminescence assays for in vitro studies. However, little is known about cross reactivity and potential interference of D-luciferin with other enzymes. We serendipitously found that firefly luciferin inhibited the CDK2/Cyclin A protein kinase. Inhibition profiling of D-luciferin over a 103-protein kinase panel showed significant inhibition of a small set of protein kinases, in particular the DYRK-family, but also other members of the CMGC-group, including ERK8 and CK2. Inhibition profiling on a 16-member focused library derived from D-luciferin confirms that D-luciferin represents a DYRK-selective chemotype of fragment-like molecular weight. Thus, observation of its inhibitory activity and the initial SAR information reported here promise to be useful for further design of protein kinase inhibitors with related scaffolds.

Several human cyclin-dependent kinase inhibitors, structurally related to roscovitine, are new anti-malarial agents

In Africa, malaria kills one child each minute. It is also responsible for about one million deaths worldwide each year. Plasmodium falciparum, is the protozoan responsible for the most lethal form of the disease, with resistance developing against the available anti-malarial drugs. Among newly proposed anti-malaria targets, are the P. falciparum cyclin-dependent kinases (PfCDKs). There are involved in different stages of the protozoan growth and development but share high sequence homology with human cyclin-dependent kinases (CDKs). We previously reported the synthesis of CDKs inhibitors that are structurally-related to (R)-roscovitine, a 2,6,9-trisubstituted purine, and they showed activity against neuronal diseases and cancers. In this report, we describe the synthesis and the characterization of new CDK inhibitors, active in reducing the in vitro growth of P. falciparum (3D7 and 7G8 strains). Six compounds are more potent inhibitors than roscovitine, and three exhibited IC₅₀ values close to 1 µM for both 3D7 and 7G8 strains. Although, such molecules do inhibit P. falciparum growth, they require further studies to improve their selectivity for PfCDKs.