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Acridone derivatives, which have been shown to have in vitro and in vivo activity against Plasmodium spp, inhibit Toxoplasma gondii proliferation at picomolar concentrations. Using enzymatic assays, we show that acridones inhibit both T. gondii cytochrome bc1 and dihydroorotate dehydrogenase and identify acridones that bind preferentially to the Qi site of cytochrome bc1. We identify acridones that have efficacy in a murine model of systemic toxoplasmosis. Acridones have potent activity against T. gondii and represent a promising new class of preclinical compounds.

A total of 21 novel xanthone and acridone derivatives were synthesized using the reactions of 1,2,4-triazine derivatives with 1-hydroxy-3-methoxy-10-methylacridone, 1,3-dimethoxy-, and 1,3-dihydroxanthone, followed by optional dihydrotiazine ring aromatization. The synthesized compounds were evaluated for their anticancer activity against colorectal cancer HCT116, glioblastoma A-172, breast cancer Hs578T, and human embryonic kidney HEK-293 tumor cell lines. Five compounds (7a, 7e, 9e, 14a, and 14b) displayed good in vitro antiproliferative activities against these cancer cell lines. Compounds 7a and 7e demonstrated low toxicity for normal human embryonic kidney (HEK-293) cells, which determines the possibility of further development of these compounds as anticancer agents. Annexin V assay demonstrated that compound 7e activates apoptotic mechanisms and inhibits proliferation in glioblastoma cells.

The global impact of malaria remains staggering despite extensive efforts to eradicate the disease. With increasing drug resistance and the absence of a clinically available vaccine, there is an urgent need for novel, affordable, and safe drugs for prevention and treatment of malaria. Previously, we described a novel antimalarial acridone chemotype that is potent against both blood-stage and liver-stage malaria parasites. Here, we describe an optimization process that has produced a second-generation acridone series with significant improvements in efficacy, metabolic stability, pharmacokinetics, and safety profiles. These findings highlight the therapeutic potential of dual-stage targeting acridones as novel drug candidates for further preclinical development.

Nitric oxide (NO) is an important signaling molecule involved in a wide range of physiological and pathological processes. Fluorescent imaging is a useful tool for monitoring NO concentration, which could be essential in various biological and biochemical studies. Here, we report the design of a novel small-molecule fluorescent probe based on 9(10H)acridone moiety for nitric oxide sensing. 7,8-Diamino-4-carboxy-10-methyl-9(10H)acridone reacts with NO in aqueous media in the presence of O2, yielding a corresponding triazole derivative with fivefold increased fluorescence intensity. The probe was shown to be capable of nitric oxide sensing in living Jurkat cells.

Background: The lack of efficacious therapy for advanced melanoma and neuroblastoma makes new approaches necessary. Therefore, many scientists seek new, more effective, more selective and less toxic anticancer drugs. Objective: We propose the synthesis of the new functionalized analogs of 1-nitroacridine/4- nitroacridone connected to tuftsin/retro-tuftsin derivatives as potential anticancer agents. Methods: Acridine and acridone analogues were prepared by Ullmann condensation and then cyclization reaction. As a result of nucleophilic substitution reaction 1-nitro-9-phenoxyacridine or 1- chloro-4-nitro-9(10H)-acridone with the corresponding peptides, the planned acridine derivatives (10a-c, 12, 17-a-d, 19) have been obtained. The cytotoxic activity of the newly obtained analogs were evaluated against melanotic (Ma) and amelanotic (Ab) melanoma cell lines and neuroblastoma SH-SY5Y by using the XTT method. Apoptosis and cell cycle were analyzed by flow cytometry. Results: Among the investigated analogs compound 12 exhibited the highest potency comparable to dacarbazine action for amelanotic Ab melanoma cells. FLICA test (flurochrome-labeled inhibitors of caspases) showed that this analog significantly increased the content of cells with activated caspases (C+) among both neuroblastoma lines and only Ab melanoma line. Using phosphatidylserine (PS) externalization assay, 12 induced changes in the Ab melanoma plasma membrane structure as the externalization of phosphatidylserine (An+ cells). These changes in neuroblastoma cells were less pronounced. Conclusion: Analog 12 could be proposed as the new potential chemotherapeutic against amelanotic melanoma form especially.

Based on the molecular modelling studies, a rational modification of the lead molecule was made to develop highly potent compounds showing anti-cancer activity against human breast cancer cell lines MCF 7, MDA-MB-468 and T-47D. The most potent compounds have Log P and total polar surface area 4.4–5.4 and 59.8 A, respectively and they also exhibited promising ADME profile.

A new coumarin-acridone fluorescent probe S was designed and synthesized, and the structure was confirmed with 1H/13C NMR spectrometry, single-crystal X-ray diffraction, and high-resolution mass spectrometry. This probe has high sensitivity and selectivity for Fe3+ over other testing metal ions at 420 or 436 nm in acetonitrile–MOPS (3-Morpholinopropanesulfonic Acid) buffer solution (20.0 μM, pH = 6.9, 8:2 (v/v)). Under physiological conditions, the probe displayed satisfying time stability with a detection limit of 1.77 µM. In addition, probe S was successfully used to detect intracellular iron changes through a fluorescence-off mode, and the imaging results of cells and zebrafish confirmed their low cytotoxicity and satisfactory cell membrane permeability, as well as their potential biological applications.

Upregulation of platelet-derived growth factor receptor β (PDGFR-β) has been found to be associated with development of various types of cancers, which has become an attractive target for anti-tumor treatment. Previously, we have synthesized and studied an acridone derivative B19, which can selectively bind to and stabilize oncogene c-myc promoter i-motif, resulting in down-regulation of c-myc transcription and translation, however its effect on tumor cells apoptosis requires improvement. In the present study, we synthesized a variety of B19 derivatives containing a known anti-cancer fluorescent chromophore naphthalimide for the purpose of enhancing anti-cancer activity. After screening, we found that acridone-naphthalimide derivative WZZ02 could selectively stabilize PDGFR-β promoter G-quadruplex and destabilize its corresponding i-motif structure, without significant interaction to other oncogenes promoter G-quadruplex and i-motif. WZZ02 down-regulated PDGFR-β gene transcription and translation in a dose-dependent manner, possibly due to above interactions. WZZ02 could significantly inhibit cancer cell proliferation, and induce cell apoptosis and cycle arrest. WZZ02 exhibited tumor growth inhibition activity in MCF-7 xenograft tumor model, which could be due to its binding interactions with PDGFR-β promoter G-quadruplex and i-motif. Our results suggested that WZZ02 as a dual G-quadruplex/i-motif binder could be effective on both oncogene replication and transcription, which could become a promising lead compound for further development with improved potency and selectivity. The wide properties for the derivatives of 1,8-naphthalimide could facilitate further in-depth mechanistic studies of WZZ02 through various fluorescent physical and chemical methods, which could help to further understand the function of PDGFR-β gene promoter G-quadruplex and i-motif.

This study investigates the application of the paramagnetic shift reagent tris(dipivaloylmethanato)-europium(III) in NMR spectral studies of permethoxyacridone alkaloids (1&ndash, 3) and pyranoacridone alkaloids (4&ndash, 6). The induced chemical shifts (∆&delta, ) of all protons were observed for the same molecule, and were compared to deduce the positions resulting from the distance nearby the Eu(dpm)3. Assignment of the H-2, H-4 and H-8 of polysubstituted acridones could be distinguished based on the least-squares method of lanthanide-induced shifts plotted against the mole ratios of Eu(dpm)3 to the substrate. The developed method is not only potentially useful for determining the planar structures of polysubstituted compounds, such as acridones, anthraquinones, xanthones, flavonoids, and phenanthrenes, but also applicable for their stereochemistry.

As part of our continuing search for potent inhibitors of tubulin polymerization, two novel series of 42 10-(4-phenylpiperazine-1-carbonyl)acridin-9(10H)-ones and N-benzoylated acridones were synthesized on the basis of a retrosynthetic approach. All newly synthesized compounds were tested for antiproliferative activity and interaction with tubulin. Several analogs potently inhibited tumor cell growth. Among the compounds tested, 10-(4-(3-methoxyphenyl)piperazine-1-carbonyl)acridin-9(10H)-one (17c) exhibited excellent growth inhibitory effects on 93 tumor cell lines, with an average GI50 value of 5.4 nM. We were able to show that the strong cytotoxic effects are caused by disruption of tubulin polymerization, as supported by the EBI (N,N'-Ethylenebis(iodoacetamide)) assay and the fact that the most potent inhibitors of cancer cell growth turned out to be the most efficacious tubulin polymerization inhibitors. Potencies were nearly comparable or superior to those of the antimitotic reference compounds. Closely related to this, the most active analogs inhibited cell cycling at the G2/M phase at concentrations down to 30 nM and induced apoptosis in K562 leukemia cells. We believe that our work not only proves the excellent suitability of the acridone scaffold for the design of potent tubulin polymerization inhibitors but also enables synthetic access to further potentially interesting N-acylated acridones.

Unlike other DNA topoisomerase II (topo II) inhibitors, our recently identified acridone derivative E17 exerted strong cytotoxic activity by inhibiting topo II without causing topo II degradation and DNA damage, which promoted us to explore more analogues of E17 by expanding its chemical diversification and enrich the structure–activity relationship (SAR) outcomes of acridone-oriented chemotypes. To achieve this goal, 42 novel acridone derivatives were synthesized and evaluated for their antiproliferative efficacies. SAR investigations revealed that orientation and spatial topology of R3 substituents make greater contributions to the bioactivity, exemplified by compounds E24, E25 and E27, which has provided valuable information for guiding further development of acridone derivatives as promising drug candidates.

International audience; By starting from a common substrate, 2-aminobenzaldehyde, both acridines and acridones were prepared. The former were generated in high yields by copper-catalyzed N-arylation followed by acid-mediated cyclization while the latter were obtained by double copper-catalyzed N-arylation followed by cyclization under the same reaction conditions. Moreover, acridine was subjected to deprotometalation by recourse to a lithium-zinc base and converted to the corresponding 4-iodo derivative, which was involved in copper-catalyzed couplings with pyrrolidinone and pyrazole. Finally, addition of pyrazole, indole and carbazole onto the 9 position of bare acridine was improved. While moderate biological activity was noticed in melanoma cells growth inhibition, the newly prepared compounds feature interesting photophysical properties which were evaluated in a preliminary study.

Amyloid-β (Aβ) and tau protein are two crucial hallmarks in Alzheimer's disease (AD). Their aggregation forms are thought to be toxic to the neurons in the brain. A series of new 1,2,3,4-tetrahydro-1-acridone analogues were designed, synthesized, and evaluated as potential dual inhibitors for Aβ and tau aggregation. In vitro studies showed that compounds 25-30 (20 μM) with N-methylation of the quinolone ring effectively inhibited Aβ1-42 aggregation by 84.7%-99.5% and tau aggregation by 71.2%-101.8%. Their structure-activity relationships are discussed. In particular, 30 could permeate the blood-brain barrier, bind to Aβ1-42 and tau, inhibit Aβ1-42 β-sheets formation, and prevent tau aggregation in living cells.

A facile protocol for the synthesis of acridone derivatives has been developed through palladium-catalyzed carbonylation/C H activation sequence from 2-bromo-diarylamines in moderate to excellent yields. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates converted to the corresponding acridones.

Sorafenib was the only small-molecule drug approved by FDA for treatment of the advanced hepatocellular carcinoma (HCC). Recent study indicated that YM155 was a promising agent for HCC cells with high survivin expression, however, the antitumor activity needs to be further improved. Based on molecular docking and rational design method, a series of multi-substituted benzyl acridone derivatives were designed and synthesized. MTT assay indicated that some of the synthesized compounds displayed better antiproliferative activity against HepG2 cells than YM155. Later study indicated that the representive compound 8u may directly interact with survivin protein and induce HepG2 cells apoptosis, which is different from YM155. In addition, ADME property was predicted in silico, and it performed well. Moreover, in vivo preliminary experiments showed that 8u may be a good lead compound in the treatment of HCC.

Quinacrine-the drug based on 9-aminoacridine-failed in clinical trials for prion diseases, whereas it was active in in vitro studies. We hypothesize that aromatic nucleophilic substitution at C9 could be contributing factor responsible for this failure because of the transfer of acridine moiety from quinacrine to abundant glutathione. Here, we described the semi-large-scale synthesis of the acridinylated glutathione and the consequences of its formation on biological and biophysical activities. The acridinylated glutathione is one order of magnitude weaker prion protein binder than the parent quinacrine. Moreover, according to log DpH 7.4 , the glutathione conjugate is two orders of magnitude more hydrophilic than quinacrine. Its higher hydrophilicity and higher dsDNA binding potency will significantly decrease its bioavailability in membrane-like environment. The glutathione deactivates quinacrine not only directly but also decreases its bioavailability. Furthermore, the conjugate can spontaneously decompose to practically insoluble acridone, which is precipitated out from the living systems.

Hybrid systems of acridones with substituted pyrimidines were designed with an objective of discovering next generation anticancer agents targeting multiple mechanisms in the cancer cell. Hybrid compounds were synthesized by simple and convenient methods in the lab, characterized by NMR and Mass spectral methods and screened for cytotoxicity against A549 (lung), Hela (cervical), MCF7 (breast) and MDA-MB-231 (breast) cancer cell lines respectively. Evaluation of compounds for cell proliferation identified active compounds 11b, 11d and 11h against MCF7, MDA-MB-231 and A549 cell lines. Further absorption titrations with CT-DNA and gel electrophoresis identified that hybrid molecules displayed anticancer activity partly by DNA intercalation. Also further results of western blotting assay with Akt kinase identified that hybrid compounds have the ability to inhibit the Akt kinase activity and induce apoptosis, with ABCC1 suggests that active compounds too have the ability to modulate multidrug resistance (MDR) associated with ABCC1/MRP1. Selective Akt1 kinase assay have identified 11a, 11b, 11d and 11h as potential inhibitors. Molecular docking studies identified the orientation and binding interactions at the active site of Akt1 and DNA. Compounds 12e and 12f have shown good cytotoxicity profile against lung cancer cell lines of sensitive and resistant type. Acute toxicity study of compound 12f at the dose of 5000 mg/kg has identified no signs of clinical toxicity. Prediction of ADMET properties and oral toxicity of the drug likeness features of new hybrid systems were carried out using software's. This experimental data suggests that hybrid systems of acridone with substituted pyrimidines can be taken as a lead for the design of efficient inhibitors and active compounds which can be taken up for further studies.

STING (Stimulator of Interferon Genes) has become a focal point in immunology research and a target in drug discovery. The discovery of a potent human-STING agonist is expected to revolutionize current anti-virus or cancer immunotherapy. Inspired by the structure and function of murine STING-specific agonists (DMXAA and CMA), we rationally designed and synthesized four series of novel compounds for the enhancement of human sensitivity. In the cell-based assay, we identified six compounds from all the synthetic small molecules: 2g, 9g, and 12b are STING agonists that are efficacious across species, and all have the skeleton of acridone; 1b, 1c, and 12c just function in the murine STING pathway. Notably, 12b exhibits the best activity among the six agonists, and its inductions of both human and murine STING-dependent signalling are similar to that of 2′3′-cGAMP, which is a well-known STING inducer. While a protein assay indicated that 2 g, 9 g, and 12b could activate the pathway by directly binding human STING, 12b also displayed the strongest binding affinity. Additionally, our studies show that 12b can induce faster, more powerful, and more durable responses of assorted cytokines in a native system than 2′3′-cGAMP. Consequently, our team is the first to successfully modify murine STING agonists to obtain human sensitivity, and these results suggest that 12b is a potent direct-human-STING agonist. Additionally, the acridone analogues demonstrate tremendous potential in the treatment of tumours or viral infections.

Malaria remains one of the deadliest diseases in the world today. Novel chemoprophylactic and chemotherapeutic antimalarials are needed to support the renewed eradication agenda. We have discovered a novel antimalarial acridone chemotype with dual-stage activity against both liver-stage and blood-stage malaria. Several lead compounds generated from structural optimization of a large library of novel acridones exhibit efficacy in the following systems: (1) picomolar inhibition of in vitro Plasmodium falciparum blood-stage growth against multidrug-resistant parasites; (2) curative efficacy after oral administration in an erythrocytic Plasmodium yoelii murine malaria model; (3) prevention of in vitro Plasmodium berghei sporozoite-induced development in human hepatocytes; and (4) protection of in vivo P. berghei sporozoite-induced infection in mice. This study offers the first account of liver-stage antimalarial activity in an acridone chemotype. Details of the design, chemistry, structure-activity relationships, safety, metabolic/pharmacokinetic studies, and mechanistic investigation are presented herein.

A synthetic route to new heterocyclic 1,1-donor–acceptor-substituted alkenes starting with N-methyl-acridone, xanthone, and thioxanthone was investigated, leading to the acridone- and xanthone-derived products methyl 2-methoxy-2-(10-methylacridin-9 (10H)-ylidene)acetate (7) and methyl 2-methoxy-2-(9H-xanthen-9-ylidene)acetate (10) in low yields with the de-methoxylated product methyl 2-(10-methylacridin-9 (10H)-ylidene)acetate (8) and the reduced compound methyl 2-methoxy-2-(9H-xanthen-9-yl)acetate (11) as the major products from N-methyl acridone and xanthone. From thioxanthone, only the rearrangement and reduction products (14) and (15) resulted. The photophysical properties of compounds (7), (8), and (10) were investigated in the presence and absence of the Brønsted acid TFA by NMR, UV–VIS absorption, and fluorescence spectroscopy. Protonation of the acridone-derived alkenes (7) and (8) led to strong bathochromic and hyperchromic fluorescence shifts and a substantial increase in Stokes shift. The photooxygenation experiments with these substrates showed an unusual reactivity pattern in the singlet oxygen processes: whereas the electron-rich enolether (7) was chemically unreactive, (8) and (10) were oxidatively cleaved, presumably via intermediate 1,2-dioxetanes.

Acridone derivatives have much attracted attention due to their objective photoelectric properties. However, their applications in nonlinear optical (NLO) materials are rarely studied. In this work, we designed and synthesized four D-π-A-π-D acridone derivatives and one D-A-D type derivative as comparison. The effects of the structure on photophysics, electrochemistry and the third-order nonlinear optics were analyzed by UV spectrophotometer, fluorescence spectrophotometer, cyclic voltammetry and Z-scan technique. The results show that the introduction of acetylene group as a bridge is conducive to intramolecular charge transfer and can maintain the planarity of the molecule and enhances the third-order NLO properties. In the four target products, YA4 has the best third-order NLO properties, with its second-order hyperpolarizability γ (γ = 5.792 × 10−33 esu) 1.36 times that of YA1 (γ = 4.262 × 10−33 esu) and 6267 times that of urea (γ = 0.68 × 10−36 esu). The study showed that introducing an appropriate length of alkane chain into acridone derivatives can effectively reduce the intermolecular interference and improve their third-order NLO performance.

A weak external magnetic field, very close to the hyperfine interactions of the system, can acts as a tool to monitor spin dynamics and assess distance between the components of the spin-correlated transient radical pair or radical ion pair (RIP). The present review focuses on the magnetic field effect (MFE) on the photo-induced electron-transfer (PET) reactions among acridine derivatives and classical as well as biological electron acceptor or donor moieties, which produce spin-correlated RIPs, in homogeneous solvents, heterogeneous micellar media and in biological nanocavities of proteins. Although a confined medium is preferred to observe prominent MFE, yet unanticipated MFE on PET between acridine derivatives [Acridone (AD) and Acridine Yellow (AY)] and classical electron donors is obtained even in homogeneous medium when it consists of impurities like water molecules. In a comparative study of interaction of another acridine derivative, Proflavin (PF+) with two electron donors which are amines of aromatic nature, MFE on PET reveal that the bulk and the structure of the electron donor govern the mechanism as well as the spin dynamics of PET. While studying interaction of PF+ with a different amine which is aliphatic in nature, MFE on PET implies that it is the nature of the solvent matrix which determines the spin dynamics of PET. The cause of discrepancy in the experimental and calculated values of B1/2 for 9-amino acridine – methyl viologen system has been delineated. Apart from micellar medium, prominent MFE on PET is also observed while studying the interaction of PF+, AY and AD with tryptophan residues present in the nanocavities of serum albumins since the inter-radical distance within primary geminate RIP is enough to make exchange interaction negligible.

The present study was carried out in an attempt to synthesize a new class of potential antibacterial agents. In this context, novel isoxazoles were synthesized and evaluated for their potential antibacterial behavior against four pathogenic bacterial strains. The synthesized compounds exhibited moderate-to-good antibacterial activity against these strains. The highest antibacterial activity was observed against the Escherichia coli strains, particularly for compounds 4a and 4e with phenyl and para-nitrophenyl groups on the isoxazole-acridone skeleton; they showed promising minimum inhibitory concentration values of 16.88 and 19.01 μg/ml, respectively, compared with the standard drug chloramphenicol (22.41 µg/ml). The synthesized compounds were subjected to in silico docking studies to understand the mode of their interactions with the DNA topoisomerase complex (PDB ID: 3FV5) of E. coli. The molecular docking results showed that compounds 4a-l occupy the active site of DNA topoisomerase (PDB ID: 3FV5), stabilized via hydrogen bonding and hydrophobic interactions, which may be the reason behind their interesting in vitro antibacterial activity.

A one-pot synthesis of N -alkyl acridone via rhodium catalyzed decomposition of N -phenyl-2-(1-sulfonyl-1 H -1,2,3-triazol-4-yl)aniline and subsequent oxidative C–C bond fragmentation has been developed. 14 examples are presented and the yields range from 30% to 80%.

Frequent fungal infections in immunocompromised patients and mortality due to invasive mycosis are important clinical problems. Opportunistic pathogenic Candida species remain one of the leading causes of systemic mycosis worldwide. The repertoire of antifungal chemotherapeutic agents is very limited. Although new antifungal drugs such as lanosterol 14α-demethylase and β-glucan synthase inhibitors have been introduced into clinical practice, the development of multidrug resistance has become increasingly significant. The urgency to expand the range of therapeutic options for the treatment of fungal infections has led researchers in recent decades to seek alternative antifungal targets to the conventional ones currently used. Among them, many compounds containing an acridine scaffold have been synthesized and tested. In this review, the applicability of acridines and their functional analogues acridones as antifungal agents is described. Acridine derivatives usage in photoantifungal chemotherapy, interactions with fungal transporters resulting in modulation of efflux/influx pumps and the effect of acridine derivatives on fungal topoisomerases are discussed. This article explores new perspectives on the mechanisms of antifungal acridine-peptide conjugates and acridine-based hybrid molecules to effectively combat fungal infections.

This mini-review focuses on fluorescent optically active crown ethers (polymeric derivatives are not included) reported in the literature (according to our knowledge), of which enantiomeric recognition ability, and in some cases, also inorganic cation complexation properties, were investigated by the sensitive and versatile fluorescence spectroscopy. These crown ether-based chemosensors contain various fluorophore signaling units such as binaphthyl, anthracene, pyrene, tryptophan, benzimidazole, terpyridine, acridine, phenazine, acridone, BODIPY, and another conjugated aromatic one.

'Acridine' along with its functional analogue 'Acridone' is the most privileged pharmacophore in medicinal chemistry with diverse applications ranging from DNA intercalators, endonuclease mimics, ratiometric selective ion sensors, and P-glycoprotein inhibitors in countering the multi-drug resistance, enzyme inhibitors, and reversals of neurodegenerative disorders. Their interaction with DNA and ability of selectively identifying numerous biologically useful ions has cemented exploitability of the acridone nucleus in modern day therapeutics. Additionally, most derivatives and salts of acridine are planar, crystalline, and stable displaying a strong fluorescence which, when coupled with their marked bio selectivity and low cytotoxicity, enables the studying and monitoring of several biochemical, metabolic, and pharmacological processes. In this review, a detailed picture covering the important therapeutic aspects of the acridone nucleus and its functional analogues is discussed.

Five new compounds named buxifoximes A–C (1–3), buxifobenzoate (4), and 7-O-(7′-peroxygeranyl) coumarin (5), together with 25 known compounds, were identified from the twigs of Atalantia buxifolia. Compounds 1–3 are unique secondary metabolites with the aldoxime functionality. The structures of the isolates were determined on the basis of spectroscopic data analyses, and the structure of 1 was confirmed by an X-ray single-crystallographic analysis. With respect to bioactivity, antidengue virus, anti-inflammatory, and cytotoxic activities of all purified compounds were tested and evaluated. Compound 1 showed a significant anti-inflammatory effect by inhibiting superoxide anion generation with an IC50 value of 4.8 ± 0.7 μM. Among the acridone alkaloids, 5-hydroxy-N-methylseverifoline (23) exhibited antidengue activity (IC50 = 5.3 ± 0.4 μM), and atalaphyllinine (20) demonstrated cytotoxicity (IC50 = 6.5 ± 0.0 μM) against the human liver cancer cell line, HepG2.

Ethnopharmacological relevance: Citrus aurantium L. (Rutaceae) is used, either singly or as a part of a polyherbal preparation, in Nigerian traditional medicine for the management of cancer and inflammatory diseases. Currently, there is a dearth of knowledge demonstrating its anticancer potential.\ud Aim of the study: This study was carried out to determine the in vitro cytotoxicity of the crude extract of the stem bark of C. aurantium, identify and isolate the bioactive constituents and to establish the cytotoxicity of such constituents.\ud Material and Methods The powdered bark of C. aurantium was extracted with methanol at room temperature (25-34 °C) and the crude extract was partitioned successively, with nhexane, dichloromethane (DCM) and methanol. Amongst the fractions, the DCM fraction was the most active and compounds were isolated from this fraction using several chromatographic techniques. The structures of the isolated compounds were elucidated by spectroscopic means (mass spectrometry, one-dimensional and two-dimensional nuclear magnetic resonance). The cytotoxicity of the extract, and the isolated compounds were evaluated by the MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium) assay against four human cancer cell lines: A549 (lung), HepG2 (liver), MCF7 (breast) and PC3 (prostate). The selectivity of the isolated compounds was assessed using the normal human prostate epithelium cells (PNT2).\ud Results and Discussion: Of the three plant fractions, the DCM fraction showed significant cytotoxicity, with its highest activity against A549 cells (IC50 = 3.88 µg/mL) and the least activity on HepG2 cells (IC50 = 5.73 µg/mL). Six acridone alkaloids: citrusinine-I (1), citracridone-I (2), 5-hydroxynoracronycine (3), natsucitrine-I (4), glycofolinine (5) and citracridone-III (6), were isolated from the DCM fraction of C. aurantium. The isolated compounds demonstrated potent to moderate cytotoxicity ((IC50 = 12.65 – 50.74 µM) against the cancer cells under investigation. It is noteworthy that the compounds exerted cytotoxicity at least four times more selective towards the carcinoma cells than the PNT2 cells.\ud Conclusion: The results obtained from this study have provided some evidence for the ethnomedicinal use of C. aurantium against cancer and the acridone alkaloids present in its stem bark, have appeared to be responsible for this effect. Further research to explore the underlying molecular mechanism of the isolated acridone alkaloids is needful.

Introduction Chemotherapy is one of the preferred mode of treatment of malignancies, but is complicated by the expression of diverse resistance mechanisms of cancer cells. Methods In the present study, we investigated the cytotoxicity of five alkaloids including a furoquinoline montrofoline (1) and four acridones namely 1-hydroxy-4-methoxy-10-methylacridone (2), norevoxanthine (3), evoxanthine (4), 1,3-dimethoxy-10-methylacridone (5) against 9 drug-sensitive and multidrug-resistant (MDR) cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of these compounds, whilst caspase-Glo assay was used to detect caspase activation. Cell cycle, mitochondrial membrane potential (MMP) and levels of reactive oxygen species (ROS) were all analyzed via flow cytometry. Results Furoquinoline 1 as well as the acridone alkaloids 2–5 displayed cytotoxic effects with IC50 values below 138 µM on all the 9 tested cancer cell lines. The IC50 values ranged from 41.56 µM (towards hepatocarinoma HepG2 cells) to 90.66 µM [towards colon carcinoma HCT116 (p53−/−) cells] for 1, from 6.78 µM [towards HCT116 (p53−/−) cells) to 106.47 µM [towards breast adenocarcinoma MDA-MB-231-pcDNA cells] for 2, from 5.72 µM (towards gliobastoma U87MG.ΔEGFR cells) to 137.62 µM (towards leukemia CCRF-CEM cells] for 3, from 6.11 µM [towards HCT116 (p53+/+) cells] to 80.99 µM (towards HepG2 cells] for 4, from 3.38 µM (towards MDA-MB-231-BCRP cells) to 58.10 µM (towards leukemia CEM/ADR5000 cells] for 5 and from 0.20 µM (against CCRF-CEM cells) to 195.12 µM (against CEM/ADR5000 cells) for doxorubicin. Acridone alkaloid 5 induced apoptosis in CCRF-CEM leukemia cells, mediated by increased ROS production. Conclusions The five tested alkaloids and mostly acridone 5 are potential cytotoxic natural products that deserve more investigations to develop novel cytotoxic compounds against multifactorial drug-resistant cancers.

In the past decades, tricyclic acridone ring system has become one of the major research interests of the medicinal chemists due to the biological significance of this moiety in drug design and drug discovery. Acridone scaffold has substantial bio-potential since it possess crucial activities such as antibacterial, antimalarial, antiviral and anti-neoplastic. The diverse biological activity of acridone and its prospective in reversal of multi-drug resistance has attracted attention of medicinal chemists to explore this scaffold especially to treat multi-drug resistance in cancer. Considering this potential in this review we have summarized the synthesis and the antitumor activities of different acridone derived compounds reported from 2000 to 2014.

In this study, novel acridone-1,2,4-oxadiazole-1,2,3-triazole hybrids were designed, synthesized, and evaluated for their acetylcholinesterase and butyrylcholinesterase inhibitory activity. Among various synthesized compounds, 10-((1-((3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)acridin-9(10H)-one 10b showed the most potent anti-acetylcholinesterase activity (IC50 = 11.55 μm) being as potent as rivastigmine. Also docking outcomes were in good agreement with in vitro results confirming the dual binding inhibitory activity of compound 10b.

A new series of 9(10H)-acridinone-1,2,3-triazole derivatives were designed, synthesized and evaluated for their cytotoxic activity against human breast cancer cell lines. The acridone skeleton was prepared through the Ullman condensation of 2-bromobenzoic acid and anilines. Subsequently, it was functionalized with propargyl bromide. Then, a click reaction of the latter compound and in situ prepared 1-(azidomethyl)-4-methoxybenzene derivatives led to the formation of the desired triazole products. Finally, all products were investigated for their capability to cause cytotoxicity against MCF-7, T-47D, and MDA-MB-231 cell lines. Among them, 2-methoxy-10-((1-(4-methoxybenzyl)-1H-1,2,3-triazol-4-yl)methyl)acridin-9(10H)-one 8c exhibited the most potency [Formula: see text] against MCF-7 cells, being more potent than etoposide [Formula: see text]. Also, apoptosis induced by compound 8c was confirmed via acridine orange/ethidium bromide and Annexin V-FITC/propidium iodide (PI) double staining.

A novel series of l0-(3,5-dimethoxy)benzyl-9(10H)-acridone derivatives with terminal ammonium substituents at C2 and C7 positions on the acridone ring were successfully synthesized as antiproliferation agents. The biologic activity of the acridone compounds against leukemia CCRF-CEM cells demonstrated that some of the compounds displayed good antiproliferative activity, among which compound 6a containing dimethylamine substituents at the terminal C2 and C7 positions exhibited the highest cytotoxicity with IC50 at 0.3μM. In addition compound 6a showed little toxicity against normal 293T cells proliferation with IC50 more than 100μM. Further study indicated that compound 6a had strong binding activity to human telomeric G-quadruplex DNA, as detected by mass spectrometry, CD spectroscopy, UV absorption, FRET and fluorescence quenching assays. Our data suggested that the activity of 6a might be associated with its stabilization of G-quadruplex DNA, which can be developed as potent antitumor agent.

Three new limonoids, limonophyllines A-C (1, 4 and 5), along with two known limonoids (2 and 3) and 11 acridone alkaloids (6-16) were isolated from the stems of Atalantia monophylla. All isolates were evaluated against cholangiocarcinoma, KKU-M156, and HepG2 cancer cell lines. Compounds 12, 14 and 16 displayed cytotoxicity against KKU-M156 cell line with IC50 ranging from 3.39 to 4.1 μg/mL while cytotoxicity against HepG2 cell line with IC50 ranging from 1.43 to 8.4 μg/mL. The structures of all isolated compounds were established by spectroscopic methods including 1D and 2D NMR, IR and mass spectrometry.

Drug resistance in cancer is an unmet medical challenge and a major drawback for the failure of many chemotherapeutic drugs. Search for targeted, effective drug with minimum toxicity is an urgent need. Acridone which is an alkaloid derivative has been attributed as molecule in reversing drug resistance in cancer cells for a long time now. In the present investigation, an attempt has been made to explore the chemosensitizing ability of 2,4-dimethylacridones with alkyl side chain containing terminally substituted tertiary amino groups. Considering the structural features required for the MDR reversal activity, acridone derivatives have been synthesized with propyl and butyl side chain containing morpholinyl, piperidinyl, N-methylpiperazinyl, N,N-diethylamino, N-diethanolamino, N-[(β-hydroxylethyl)]piperazino at the terminus of the alkyl side chain. cLogP values for the synthesized compounds ranged from 2.96 to 4.72 for the propyl derivatives and 3.41 to 5.15 for the butyl derivatives. All the compounds were screened against breast cancer sensitive MCF7 and resistant MCF7/ADR cell lines. Compounds 12e and 12f have shown better cytotoxicity profiles with IC50 of 4 ± 0.05 and 2 ± 0.03 μM against MCF7 cells, 5.21 ± 0.13 and 2.56 ± 0.05 μM against MCF7/ADR cells. Photolabelling studies with [3H]-azidopine and molecular docking studies have identified that 2,4-dimethylacridones have potential to modulate the P-gp mediated multidrug resistance. Docking studies identified that compounds have shown favorable interactions with P-gp. QSAR equation was derived for cytotoxicity vs molecular descriptors of acridone derivatives. Best models with good predictive ability have been generated with very high square correlation coefficient (R2) values of 0.889, 0.964 and 0.983.

Fluorescence lifetime (FLT)-based assays have developed to become highly attractive tools in drug discovery. All recently published examples of FLT-based assays essentially describe their use for monitoring enzyme-mediated peptide modifications, such as proteolytic cleavage or phosphorylation/dephosphorylation. Here we report the development of competitive binding assays as novel, inhibitor-centric assays, principally employing the FLT of the acridone dye Puretime 14 (PT14) as the readout parameter. Exemplified with two case studies on human serine proteases, the details of the rationale for both the design and synthesis of probes (i.e., active site-directed low-molecular-weight inhibitors conjugated to PT14) are provided. Data obtained from testing inhibitors with the novel assay format match those obtained with alternative formats such as FLT-based protease activity and time-resolved fluorescence resonance energy transfer-based competitive binding assays.

In a quest for finding potent cytotoxic molecules, we have designed and synthesized a new scaffold by tagging quinazolinones with an acridone moiety. The new acridone-4-carboximide derivatives were evaluated for their cytotoxic potentials against the MCF7 breast cancer cell line and three colon cancer cell lines (LS174T, SW1398, and WiDr). Compound 26 showed relatively potent cytotoxic activity among the derivatives, against all the cell lines tested. Mechanistic studies for the selected derivatives 7, 8, 16, 17, 25, and 26 were conducted through in vitro EGFR tyrosine kinase inhibition studies. The results indicate that compound 26 has a better EGFR tyrosine kinase inhibitory profile. The in vitro EGFR inhibition data was correlated with the cytotoxic properties, and molecular docking studies were performed with regard to the receptor autophosphorylation sites of the protein kinase domain of the EGFR.

Targeting dihydrofolate reductase, here, we report the tumor growth inhibitory activity of substituted acridones. The screening of the molecules over 60 cell line panel of human cancer cells identified (S)-oxiran-2-ylmethyl 9-oxo-9,10-dihydroacridine-4-carboxylate (19) with average GI50 0.3 μM. The specificity of the compound to CCRF-CEM, MOLT-4 and SR cell lines of leukemia and SW-620, SF268, LOXIMVI, ACHN and MCF7 cancerous cells exhibiting GI50 in the nM range was observed. C6 Glioma cells treated with compound 19 showed differentiated cell morphology and cell cycle arrest in G2/M phase. The interactions of the compound with dihydrofolate reductase were ascertained with the help of enzyme immunoassays, molecular docking and molecular dynamic studies.

Two new acridone alkaloids, 3-methoxy-1,4,5-trihydroxy-10-methylacridone (1) and 2,3-dimethoxy-1,4,5-trihydroxy-10-methylacridone (2), were isolated from the ethanol extract of the branch of Atalantia buxifolia. Their structures were elucidated by spectroscopic methods including 1D and 2D NMR. Compounds 1 and 2 exhibited significant antibacterial activity against Staphylococcus aureus and weak inhibitory effect on acetylcholinesterase.

A class of 9(10 H )-acridone derivatives with terminal ammonium substituents at C2 (and C7) position(s) on the acridone ring were successfully synthesized. The relative affinities of the acridone compounds to G-quadruplex DNA have been investigated and the results showed that these compounds had a binding specificity for G-quadruplex over duplex sequences. The acridones with two terminal ammonium substituents had much more effects on the human telomeric G-quadruplex DNA than the corresponding acridone derivatives with one terminal ammonium substituent, and more positive charges introduced to the side chains can improve the formation and stabilization of the G-quadruplex.

Hybrid pharmacophore anti-proliferative compounds, comprised of mycophenolic acid (MPA) and 1-nitroacridine/4-nitroacridone derivative have been synthesized and evaluated as inhibitors of five different leukemia cell lines (Jurkat, Molt-4, HL-60, CCRF-CEM, L1210) and human peripheral blood mononuclear cells from healthy donors. These conjugates possess different length of the linker between MPA and heterocyclic units. The type of heterocyclic part influenced their cytotoxic and anti-proliferative properties. Coupling of MPA 1 with 9-(ω-aminoalkyl)amino-1-nitroacridines 2 and 1-[(ω-aminoalkyl)-4-nitro-9(10 H )]-acridones 3 was tested. Although all tested conjugates were active, compounds 4a – e exhibited the highest potency. Preliminary experiments with GMP suggested that the tested compounds acted as IMPDH inhibitors.

Double (spin and fluorescence) labeled pyrroline derivatives of crown ethers containing an acridone or an acridine fluorophore unit ( 1 and 2 ) and their diamagnetic analogues ( 3 and 4 ) were synthesized. Their fluorescent behavior as well as their complexation properties toward selected metal ions (Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ ) were examined.

On the basis of the chemical structures of psorospermin with a xanthone template and acronycine derivatives with an acridone template, rac-1 and rac-2 constructed on an 1,2-dihydrobenzofuro[4,5-b][1,8]naphthyridin-6(11H)-one scaffold were designed and synthesized as potential anticancer agents. Their anticancer activities were evaluated against five human cancer cell lines. Rac-2 showed similar anticancer activity to doxorubicin and rac-1 exhibited even higher anticancer activity against LNCaP (IC(50)=0.14 μM), DU145 (IC(50)=0.15 μM), PC3 (IC(50)=0.30 μM) and MCF-7 (IC(50)=0.26 μM) cancer lines than doxorubicin and rac-2. Also, rac-1 revealed very potent anticancer activity (IC(50)=0.15 μM) against MCF-7/ADR cell (doxorubicin-resistant breast cancer cell) lines and induced G2/M phase arrest of the cell cycle in MCF-7/ADR cells.

Heme is an important prosthetic molecule for various hemoproteins and serves important function in living aerobic organisms. But degradation of hemoprotein, for example, hemoglobin during different pathological conditions leads to the release of heme, which is very toxic as it induces oxidative stress and inflammation due to its pro-oxidant nature. Thus, synthesis of compound that will detoxify free heme by interacting with it would be fruitful for the management of heme-induced pathogenesis. Here, we report the synthesis of a novel natural product arborinine and some other acridone derivatives, which interact with free heme. These acridones in vitro block heme-mediated protein oxidation and degradation, markers for heme-induced oxidative stress.

The structure elucidation and complete 1H- and 13C-NMR assignments are reported for two new compounds: the ceramide citropremide (1), and the acridone alkaloid citropridone (2). Both of these secondary metabolites were isolated from the stem bark of Citropsis gabunensis. High-resolution mass, IR and UV spectrometry, and NMR experiments including COSY, HMQC, and HMBC were used for the determination of the structures and NMR spectral assignments.

Since emergence of chloroquine-resistant Plasmodium falciparum and reports of parasite resistance to alternative drugs, there has been renewed interest in the antimalarial activity of acridines and their congeners, the acridinones. This article presents literature compilation of natural acridinone alkaloids and synthetic 9-substituted acridines, acridinediones, haloalcoxyacridinones and 10-N-substituted acridinones with antimalarial activity. The review also provides an outlook to antimalarial modes of action of some described compounds.