Pyranonaphthoquinone derivatives of eleutherin, ventiloquinone L, thysanone and nanaomycin A possessing a diverse topoisomerase II inhibition and cytotoxicity spectrum

Improved synthesis, molecular modeling and anti-inflammatory activity of new fluorinated dihydrofurano-naphthoquinone compounds

A series of new fluorinated dihydrofurano-napthoquinone compounds were sucessfully synthesized in good yields using microwave-assisted multi-component reactions of 2-hydroxy-1,4-naphthoquinone, fluorinated aromatic aldehydes, and pyridinium bromide. The products were fully characterized using spectroscopic techniques and evaluated for their anti-inflammatory activity using lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Among 12 new compounds, compounds 8b, 8d, and 8e showed high potent NO inhibitory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells with IC50 values ranging from 1.54 to 3.92 µM. The levels of pro-inflammatory cytokines IL-1β and IL-6 in LPS-stimulated RAW264.7 macrophages were remarkably decreased after the application of 8b, 8d, 8e and 8k. Molecular docking simulations revealed structure-activity relationships of 8b, 8d, and 8e toward NO synthase, cyclooxygenase (COX-2 over COX-1), and prostaglandin E synthase-1 (mPGES-1). Further physicochemical and pharmacokinetic computations also demonstrated the drug-like characteristics of synthesized compounds. These findings demonstrated the importance of fluorinated dihydrofurano-napthoquinone moieties in the development of potential anti-inflammatory agents.

Benzochromenopyrimidines: Synthesis, Antiproliferative Activity against Colorectal Cancer and Physicochemical Properties

Ten new differently substituted 3-benzyl-5-aryl-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidin-4,6,11-triones 3 were synthesized by a simple and cost-efficient procedure in a one-pot, three-component reaction from readily available ethyl 2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromene-3-carboxylates, benzylamine and triethyl orthoformate under solvent- and catalyst-free conditions. All the new compounds were screened for their antiproliferative activity against two colorectal-cancer-cell lines. The results showed that the compounds 3-benzyl-5-phenyl-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidine-4,6,11-trione (3a) and 3-benzyl-5-(3-hydroxyphenyl)-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidine-4,6,11-trione (3g) exhibited the most potent balanced inhibitory activity against human LoVo and HCT-116 cancer cells.

Recent Developments of Coumarin-based Hybrids in Drug Discovery

Coumarin scaffold is a highly significant O-heterocycle, namely benzopyran-2-ones, form an elite class of naturally occurring compounds that possess promising therapeutic perspectives. Based on its broad spectrum of biological activities, the privileged coumarin scaffold is applied to medicinal and pharmacological treatments by several rational design strategies and approaches. Structure-activity relationships of the coumarin-based hybrids with various bioactivity fragments revealed significant information toward the further development of highly potent and selective disorder therapeutic agents. The molecular docking studies between coumarins and critical therapeutic enzymes demonstrated mode of action by forming noncovalent interactions with more than one receptor, further rationally confirm information about structure-activity relationships. This review summarizes recent developments relating to coumarin-based hybrids with other pharmacophores aiming to numerous feasible therapeutic enzymatic targets to combat various therapeutic fields, including anticancer, antimicrobic, anti-Alzheimer, anti-inflammatory activities.

4-(Dimethylamino)pyridine as an Efficient Catalyst for One-Pot Synthesis of 1,4-Pyranonaphthoquinone Derivatives viaMicrowave-Assisted Sequential Three Component Reaction in Green Solvent

Novel 1,4-pyranonaphthoquinone derivatives were successfully synthesized via the microwave-assisted three-component reaction of 1,4-naphthoquinone, malononitrile, and various arylaldehydes in ethanol in the presence of 4-(dimethylamino)pyridine (DMAP) as a catalyst, and subsequently evaluated in terms of their antimicrobial and antifungal activities. This synthetic procedure has the notable advantages of environmental friendliness, short reaction time, good yield, and convenient operation.

Secondary metabolites from hypocrealean entomopathogenic fungi: novel bioactive compounds

Covering: 2014 up to the third quarter of 2019 Entomopathogens constitute a unique, specialized trophic subgroup of fungi, most of whose members belong to the order Hypocreales (class Sordariomycetes, phylum Ascomycota). These Hypocrealean Entomopathogenic Fungi (HEF) produce a large variety of secondary metabolites (SMs) and their genomes rank highly for the number of predicted, unique SM biosynthetic gene clusters. SMs from HEF have diverse roles in insect pathogenicity as virulence factors by modulating various interactions between the producer fungus and its insect host. In addition, these SMs also defend the carcass of the prey against opportunistic microbial invaders, mediate intra- and interspecies communication, and mitigate abiotic and biotic stresses. Thus, these SMs contribute to the role of HEF as commercial biopesticides in the context of integrated pest management systems, and provide lead compounds for the development of chemical pesticides for crop protection. These bioactive SMs also underpin the widespread use of certain HEF as nutraceuticals and traditional remedies, and allowed the modern pharmaceutical industry to repurpose some of these molecules as life-saving human medications. Herein, we survey the structures and biological activities of SMs described from HEF, and summarize new information on the roles of these metabolites in fungal virulence.

Cytotoxic Heptaketides from the Endolichenic Fungus Ulospora bilgramii

Eleven new metabolites including nine heptaketides, ulosporin A-G (1a-7b), one diphenyl compound, ulophenol (8), and one spirobisnaphthalene, palmarumycin P5 (9), were isolated from the endolichenic fungus Ulospora bilgramii, which inhabits the lichen Umbilicaria sp. The structures of these compounds were elucidated based on comprehensive analysis of their spectroscopic, electronic circular dichroism (ECD), and single-crystal X-ray diffraction data. Ulosporin G (7) inhibited the growth of the human cancer cell lines A549, MCF-7, and KB with IC₅₀ values of 1.3, 1.3, and 3.0 μM, respectively. Additionally, it induced A549 cell apoptosis through G0/G1 cell cycle arrest caused by DNA damage.

Induction of apoptosis by Xiakemycin A in human hepatoma HepG2 cells

Xiakemycin A (XKA), a new antibiotic in the pyranonaphthoquinone family, shows antitumor activity. However, the type of cell death induced by XKA remains elusive. In this study, we aim to investigate the type of death induced by XKA in hepatic cancer.The apoptotic features, such as chromatic agglutination, reactive oxygen species generation and membrane potential of mitochondria, in HepG2 cells treated by XKA were measured by Hoechst 33342 staining and flow cytometry. Apoptosis of HepG2 cells treated with XKA was determined by Annexin V-FITC/propidium iodide double staining and Western blot analysis, respectively.XKA had a significant dose-dependent elevation of chromatic agglutination, reactive oxygen species generation, Annexin V and propidium iodide staining, decrease of membrane potential. Meanwhile, in apoptotic HepG2 cells induced by XKA, robust increment was noticed in p53 expression, cleavage of PARP, caspase-3, and caspase-9.XKA showed potent inhibitory effects on the proliferation of HepG2 cells. Such phenomenon may be related to activation of the apoptotic pathway.

Bifunctional Naphthoquinone Aromatic Amide-Oxime Derivatives Exert Combined Immunotherapeutic and Antitumor Effects through Simultaneous Targeting of Indoleamine-2,3-dioxygenase and Signal Transducer and Activator of Transcription 3

Indoleamine-2,3-dioxygenase 1 (IDO1) and signal transducer and activator of transcription 3 (STAT3) are important targets in the tumor microenvironment for cancer therapy. In the present study, a set of naphthoquinone aromatic amide-oxime derivatives were designed, which stimulated the immune response via IDO1 inhibition and simultaneously displayed powerful antitumor activity against three selected cancer cell lines through suppressing STAT3 signaling. The representative compound 8u bound effectively to IDO1, with greater inhibitory activity relative to the commercial IDO1 inhibitor 4-amino-N-(3-chloro-4-fluorophenyl)-N'-hydroxy-1,2,5-oxadiazole-3-carboximidamide (IDO5L) in addition to the efficient suppression of nuclear translocation of STAT3. Consistently, in vivo assays demonstrated a higher antiproliferative activity of compound 8u in both wild-type B16-F10 isograft tumors and an athymic HepG2 xenograft model relative to 1-methyl-l-tryptophan (1-MT) and doxorubicin (DOX). This bifunctional compound with dual immunotherapeutic and anticancer efficacy may represent a new generation of highly efficacious drug candidates for cancer therapy.

Pyranonaphthoquinone and anthraquinone derivatives from Ventilago harmandiana and their potent anti-inflammatory activity

The chemical study on the heartwoods extract of Ventilago harmandiana (Rhamnaceae) resulted in the isolation of ten previously undescribed pyranonaphthoquinones (ventilanones A-J), an undescribed anthraquinone (ventilanone K), together with eight known anthraquinone derivatives. Their structures were elucidated by extensive analysis of their spectroscopic data. The absolute configuration of ventilanone A was established from single crystal X-ray crystallographic analysis of its p-bromobenzenesulfonate ester derivative using Cu Kα radiation. The absolute configurations of the other related compounds were identified by comparison of their ECD data with those of ventilanone A and related known compounds. Cytotoxic and anti-inflammatory activities of some of the isolated compounds were evaluated. Ventilanone A and ventilanone C exhibited moderate cytotoxicity against P-388 cell line. Ventilanone D exhibited significant anti-inflammatory activity while ventilanone A and ventilanone C showed moderate activity.

Pyranonaphthoquinones - isolation, biology and synthesis: an update

Covering: 2008 to 2015. A review on the isolation, biological activity and synthesis of pyranonaphthoquinone natural products from 2008-2015 is providedThis review discusses the isolation, biological activity and synthesis of pyranonaphthoquinone natural products, covering the years 2008-2015. The pyranonaphthoquinones are a group of metabolites sharing a common naphtho[2,3-c]pyran-5,10-dione ring system that have been isolated from a wide range of microorganisms, plants and insects. In addition to their synthetically challenging molecular structures, pyranonaphthoquinones exhibit a wide array of biological activity, including anti-bacterial, anti-fungal and anti-cancer properties. The therapeutic potential of these compounds has led to a dynamic interplay between total synthesis and biological evaluation.

Synthesis and biological evaluation of naphthoquinone-coumarin conjugates as topoisomerase II inhibitors

Based on previous Topoisomerase II docking studies of naphthoquinone derivatives, a series of naphthoquinone-coumarin conjugates was synthesized through a multicomponent reaction from aromatic aldehydes, 4-hydroxycoumarin and 2-hydroxynaphthoquinone. The hybrid structures were evaluated against the α isoform of human topoisomerase II (hTopoIIα), Escherichia coli DNA Gyrase and E. coli Topoisomerase I. All tested compounds inhibited the hTopoIIα-mediated relaxation of negatively supercoiled circular DNA in the low micromolar range. This inhibition was specific since neither DNA Gyrase nor Topoisomerase I were affected. Cleavage assays pointed out that naphthoquinone-coumarins act by catalytically inhibiting hTopoIIα. ATPase assays and molecular docking studies further pointed out that the mode of action is related to the hTopoIIα ATP-binding site.

Synthesis and cytotoxicity of pyranonaphthoquinone natural product analogues under bioreductive conditions

We have synthesised a focused library of derivatives of natural products containing the pyranonaphthoquinone moiety including the first report of such a scaffold with an appended tetrazole functionality. Examples include kalafungin derivatives as well as analogues of nanaomycin and eleutherin. These compounds were assessed for cytotoxic activation by breast cancer cell lines engineered to express the prototypic human one- and two-electron quinone bioreductive enzymes, NADPH: cytochrome P450 oxidoreductase (POR) and

NAD(P)H

quinoneoxidoreductase 1 (NQO1; DT-diaphorase), respectively. Several compounds were observed to be cytotoxic at sub-micromolar level and a pattern of increased aerobic potency was observed in cells over expressing POR. A subset of analogues was assessed under anoxic conditions, where cytotoxicity was reduced, implicating redox cycling as a major mechanism of toxicity. The substrate specificity for reductive enzymes is relevant to the future design of bioreductive prodrugs to treat cancer.

Nature as a source of metabolites with cholinesterase-inhibitory activity: an approach to Alzheimer's disease treatment

Objectives

Alzheimer's disease (AD) is the most common cause of dementia, being responsible for high healthcare costs and familial hardships. Despite the efforts of researchers, no treatment able to delay or stop AD progress exists. Currently, the available treatments are only symptomatic, cholinesterase inhibitors being the most widely used drugs. Here we describe several natural compounds with anticholinesterase (acetylcholinesterase and butyrylcholinesterase) activity and also some synthetic compounds whose structures are based on those of natural compounds.

Key findings

Galantamine and rivastigmine are two cholinesterase inhibitors used in therapeutics: galantamine is a natural alkaloid that was extracted for the first time from Galanthus nivalis L., while rivastigmine is a synthetic alkaloid, the structure of which is modelled on that of natural physostigmine. Alkaloids include a high number of compounds with anticholinesterases activity at the submicromolar range. Quinones and stilbenes are less well studied regarding cholinesterase inhibition, although some of them, such as sargaquinoic acid or (+)-α-viniferin, show promising activity. Among flavonoids, flavones and isoflavones are the most potent compounds. Xanthones and monoterpenes are generally weak cholinesterase inhibitors.

Summary

Nature is an almost endless source of bioactive compounds. Several natural compounds have anticholinesterase activity and others can be used as leader compounds for the synthesis of new drugs.

Synthesis of the griseusin B framework via a one-pot annulation-methylation-double deprotection-spirocyclization sequence

A highly convergent synthesis of the griseusin B scaffold is described. The key step involves an efficient one-pot Hauser-Kraus annulation-methylation-double deprotection-spirocyclization sequence that directly affords the target parent tetracyclic ring system.

Natural Product-Inspired Pyranonaphthoquinone Inhibitors of Indoleamine 2,3-Dioxygenase-1 (IDO-1)

A series of pyranonaphthoquinone derivatives possessing structural features present in both natural products annulin B and exiguamine A have been shown to exhibit low micromolar inhibition of indoleamine 2,3-dioxygenase-1 (IDO-1). These inhibitors retain activity against the enzyme in a cellular context with an approximate one-log loss of dose potency against IDO-1 in cells. One particular analogue, triazole 8 shows good inhibition of IDO-1 along with little loss of cell viability at low drug concentrations. These results have extended the naphthoquinone series of novel IDO-1 inhibitors based on lead compounds from nature.

Exploring the DNA binding/cleavage, cellular accumulation and topoisomerase inhibition of 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinone Mannich bases and their platinum(II) complexes

Several chlorido and amino Pt(2+) complexes of 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinone Mannich bases HL exhibiting moderate to high cytotoxicity against cancer cell lines were studied in order to investigate their modes of DNA binding, in vitro DNA strand breaks, mechanism of topoisomerase (Topo I) inhibition and cellular accumulation. DNA model base studies have shown that complex 1a [Pt(HL1)Cl(2)] was capable of binding covalently to 9-ethylguanine (9-EtG) and 5'-GMP. (1)H NMR and mass spectrometry studies have shown that both chlorides were substituted by 9-EtG ligands, whereas 5'-GMP was able to replace only one chlorido ligand, due to steric hindrance. The chlorido Pt(2+) complexes [Pt(HL)Cl(2)] highly accumulate in prostate (PC-3) and melanoma (MDA-MB-435) cell lines, being able to induce DNA strand breaks in vitro and inhibit Topo I by a catalytic mode. On the other hand, the free 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinones HL and the amino Pt(2+) complexes [Pt(L(-))(NH(3))(2)]NO(3) neither cause DNA strand breakage nor exhibit strong DNA interaction, nevertheless the latter were also found to be catalytic inhibitors of Topo I at 100μM. Thus, coordination of the Mannich bases HL to the "PtCl(2)" fragment substantially affects the chemical and biophysical properties of the pro-ligands, leading to an improvement of their DNA binding properties and generating compounds that cleave DNA and catalytically inhibit Topo I. Finally, the high cytotoxicity exhibited by the free (uncomplexed) 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinones might be associated with their decomposition in solution, which is not observed for the Pt(2+) complexes.