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Organic compounds with antibacterial and antiparasitic properties are gaining significance for biomedical applications. This study focuses on the solvent-free synthesis (green synthesis) of 1,4-naphthoquinone or 2,3-dichloro-1,4-naphthoquinone with different phenylamines using silica gel as an acid solid support. The study also includes in silico PASS predictions and the discovery of antibacterial and antiparasitic properties of phenylaminonaphthoquinone derivatives 1 - 12 , which can be further applied in drug discovery and development. These activities were discussed in terms of molecular descriptors such as hydrophobicity, molar refractivity, and half-wave potentials. The in vitro antimicrobial potential of the synthesized compounds 1 - 12 was evaluated against a panel of six bacterial strains (three Gram-positive: Staphylococcus aureus , Proteus mirabilis , and Enterococcus faecalis ; and three Gram-negative bacteria: Escherichia coli , Salmonella typhimurium , and Klebsiella pneumoniae ). Six compounds ( 1 , 3 , 5 , 7 , 10, and 11 ) showed better activity toward S. aureus with MIC values between 3.2 and 5.7 μg/mL compared to cefazolin (MIC = 4.2 μg/mL) and cefotaxime (MIC = 8.9 μg/mL), two cephalosporin antibiotics. Regarding in vitro antiplasmodial activity, compounds 1 and 3 were the most active against the Plasmodium falciparum strain 3D7 (chloroquine-sensitive), displaying IC 50 values of 0.16 and 0.0049 μg/mL, respectively, compared to chloroquine (0.33 μg/mL). In strain FCR-3 (chloroquine-resistant), most of the compounds showed good activity, with compounds 3 (0.12 μg/mL) and 11 (0.55 μg/mL) being particularly noteworthy. Additionally, docking studies were used to better rationalize the action and prediction of the binding modes of these compounds. Finally, absorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions were performed.

Psoriasis is a troublesome scaling skin disease with no high-effective medication available by far. Signal transducer and activator of transcription 3 (STAT3) has recently been revealed as a crucial player in the pathogenesis and progression of psoriasis and emerged as an intriguing antipsoriatic drug target. Naturally occurring lapachol and its quinone analogs had been discovered as effective STAT3 inhibitors, however, their antipsoriatic effects are not well investigated. Previously, we have reported a series of isothiazoloquinone lapachol derivatives. Here, the antipsoriastic potentials of these isothiazoloquinones were investigated and, in addition, 35 novel isoxazoloquinone derivatives were prepared and studied for their anti-psoriasis properties. Among them, the most potent antipsoriatic compound B20 determined by in vitro test on HaCaT cells could directly bind to STAT3, reduce STAT3 level and inhibit STAT3 nuclear translocation. In vivo studies showed that topical application of B20 could effectively alleviate IMQ-induced psoriasis in mice with no obvious side effects. In addition, B20 inhibited the production of interleukin 17 (IL-17A), a STAT3-downstream cytokine essential for the progression of psoriasis, both in vitro and in vivo. Thus, isoxazoloquinone B20 is a potent STAT3-targeting antipsoriatic agent worth of further investigation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Total syntheses of borolithochromes H1, H2, I1, and I2, the red pigments isolated from fossils of Jurassic putative red alga Solenopora jurassica, have been achieved. The naphthoquinone possessing a chiral sec-butyl side chain has been synthesized from (S)-2-methylbutanol. The Diels-Alder reaction of the chiral naphthoquinone and the previously reported diene was followed by one pot S-methylation/intramolecular Corey-Chaykovsky reaction/epoxide rearrangement to provide the benzo[gh]tetraphene skeleton. Complexation of the resulting ligand with trimethyl borate and the following O-demethylation furnished a 1:1 mixture of borolithochromes I1 and I2, which were separated by HPLC using CHIRALPAK IC® to afford optically pure borolithochromes I1 (6) and I2 (7). On the other hand, borolithochromes H1 and H2 were not separated by HPLC in our laboratory. Fortunately, the mixture of the methyl ethers of borolithochromes H1 and H2 were separated and O-demethylation with magnesium iodide furnished optically pure borolithochromes H1 (4) and H2 (5)., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, and STAT3 has emerged as an effective drug target for TNBC treatment. Herein, we employed a scaffold-hopping strategy of natural products to develop a series of naphthoquinone-furopiperidine derivatives as novel STAT3 inhibitors. The in vitro assay showed that compound 10g possessed higher antiproliferative activity than Cryptotanshinone and Napabucasin against TNBC cell lines, along with lower toxicity and potent antitumor activity in a TNBC xenograft model. Mechanistically, 10g could inhibit the phosphorylation of STAT3 and the binding affinity was determined by the SPR assay ( K D = 8.30 μM). Molecule docking studies suggested a plausible binding mode between 10g and the SH2 domain, in which the piperidine fragment and the terminal hydroxy group of 10g played an important role in demonstrating the success of this evolution strategy. These findings provide a natural product-inspired novel STAT3 inhibitor for TNBC treatment.

1,4-naphthoquinones hydroxyderivatives belong to an important class of natural products and have been known as a favored scaffold in medicinal chemistry due to their multiple biological properties. Juglone is one of the most important 1,4-naphthoquinone extracted from juglandaceae family showing a good antibacterial activity. In this study, we report the synthesis of aminojuglone derivatives through Michael addition reaction using Cerium (III) chloride heptahydrate (CeCl 3 ·7H 2 O) as catalyst. The synthesized aminojuglone derivatives were evaluated for their antibacterial properties against sensitive, clinical resistant Gram-positive and Gram-negative bacterial strains. Compound 3c showed a good antibacterial activity similar to cloxacillin (2 µg/mL) against the clinically resistant S.aureus. The antibiotic adjuvant activity of compounds was evaluated in combination with three clinically use antibiotics. The combination of compounds 3a, 3b, 3e, 3 h-3 l, 3n and 3o with cloxacillin showed remarkable adjuvant activity against clinically resistant S. aureus (66-fold potentiation of cloxacillin activity). 3e is the only compound consistent with the concept of antibiotic adjuvant, presenting insufficient antibacterial activity (MIC > 128 µg/mL) and potentiate the activity of cloxacillin (66-fold) with synergistic effect. A structural characterization of 3e was carried out for the first time using X-ray diffraction technic. Moreover, compound 3e did not show a cytotoxic activity on sheep red blood cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The signal transducer and activator of transcription 3 (STAT3) has been established as a crucial drug target in the development of antitumor agents. In this study, a series of 21 derivatives of the STAT3 inhibitor napabucasin were designed and synthesized. Through preliminary screening against tumor cell lines, SZ6 emerged as the most potent compound with half maximal inhibitory concentration (IC 50 ) values of 46.3 nM, 66.4 nM, and 53.8 nM against HCT116, HepG2, and Hela cells respectively. Furthermore, SZ6 effectively suppressed tumor invasion and migration in HCT116 cell assays by inducing S-phase arrest and apoptosis through inhibition of Protein Kinase B (PKB/AKT) activity and induction of reactive oxygen species (ROS). The mechanism underlying SZ6's action involves inhibition of STAT3 phosphorylation, which was confirmed by western blotting analysis. Additionally, surface plasmon resonance (SPR) and cellular thermal shift assay (CETSA) demonstrated direct binding between SZ6 and STAT3. Notably, in vivo studies revealed that SZ6 significantly inhibited tumor growth without any observed organ toxicity. Collectively, these findings identify SZ6 as a promising STAT3 inhibitor for colorectal cancer treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Waldiomycin is an inhibitor of histidine kinases (HKs). Although most HK inhibitors target the ATP-binding region, waldiomycin binds to the intracellular dimerization domain (DHp domain) with its naphthoquinone moiety presumed to interact with the conserved H-box region. To further develop inhibitors targeting the H-box, various 2-aminonaphthoquinones with cyclic, aliphatic, or aromatic amino groups and naphtho [2,3-d] isoxazole-4,9-diones were synthesized. These compounds were tested for their inhibitory activity (IC 50 ) against WalK, an essential HK for Bacillus subtilis growth, and their minimum inhibitory concentrations (MIC) against B. subtilis. As a result, 11 novel HK inhibitors were obtained as naphthoquinone derivatives (IC 50 : 12.6-305 µM, MIC: 0.5-128 µg ml -1 ). The effect of representative compounds on the expression of WalK/WalR regulated genes in B. subtilis was investigated. Four naphthoquinone derivatives induced the expression of iseA (formerly yoeB), whose expression is negatively regulated by the WalK/WalR system. This suggests that these compounds inhibit WalK in B. subtilis cells, resulting in antibacterial activity. Affinity selection/mass spectrometry analysis was performed to identify whether these naphthoquinone derivatives interact with WalK in a manner similar to waldiomycin. Three compounds were found to competitively inhibit the binding of waldiomycin to WalK, suggesting that they bind to the H-box region conserved in HKs and inhibit HK activity., (© 2024. The Author(s).)

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 IC 50 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In pursuit of potential agents to treat Chagas disease and leishmaniasis, we report the design, synthesis, and identification novel naphthoquinone hydrazide-based molecular hybrids. The compounds were subjected to in vitro trypanocide and leishmanicidal activities. N'-(1,4-Dioxo-1,4-dihydronaphthalen-2-yl)-3,5-dimethoxybenzohydrazide (13) showed the best performance against Trypanosoma cruzi (IC50 1.83 µM) and Leishmania amazonensis (IC50 9.65 µM). 4-Bromo-N'-(1,4-dioxo-1,4-dihydronaphthalen-2-yl)benzohydrazide (16) exhibited leishmanicidal activity (IC50 12.16 µM). Regarding trypanocide activity, compound 13 was low cytotoxic to LLC-MK2 cells (SI = 95.28). Furthermore, through molecular modeling studies, the cysteine proteases cruzain, rhodesain and CPB2.8 were identified as the potential biological targets.

Background: This study investigates the potential of eleven 1H-1,2,3-triazol-1,4-naphthoquinone conjugates as virulence factor inhibitors (like Pyocyanin) and their affinity for PhzM, a crucial enzyme for Pyocyanin biosynthesis in Pseudomonas aeruginosa infections., Methods: A straightforward synthetic pathway enabled the production of these compounds, which were characterized and structurally confirmed through spectroscopic analyses. Evaluation of their impact on PhzM thermal stability identified promising candidates for PhzM binders., Results: Concentration-response behavior elucidated their binding affinity, revealing them as the first reported micromolar affinity ligands for PhzM. Structure-activity relationship analysis emphasized the role of specific molecular moieties in binding affinity modulation, paving the way for future advanced inhibitors' development., Conclusion: These findings highlight the potential of naphthoquinone-triazole derivatives as leads for novel therapeutics against P. aeruginosa infections., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Cancer is a malignant disease that causes millions of deaths each year worldwide. As one of the cancer therapeutic strategies, chemotherapy is a means to destroy rapidly dividing cells. The main problem with cancer chemotherapy is the lack of selectivity of conventional chemotherapeutic drugs, leading to toxicity towards normal cells. Therefore, the discovery of anti-cancer agents with selectivity for fast-growing cancer cells is desirable., Objective: In this study, we report the synthesis and identification of synthesized 5-benzyl juglone as a potential anticancer agent with selectivity toward certain cancer cell lines., Methods: An efficient synthetic method for 5-benzyl juglone was established. The proliferation of cancer cell lines and a normal cell line treated by the target compound was studied using an MTT assay. In addition, the cell cycle arrest and apoptosis were determined by flow cytometry., Results: Based on the Diels-Alder (D-A) reaction between 3,6-dimethoxy benzyne intermediate and furan, further acid-catalyzed intramolecular rearrangement, and CAN-mediated oxidation, a convenient synthesis of 5-benzyl juglone was achieved with high overall yield. The results from in vitro biological evaluation indicated that the juglone derivative exhibited potent antiproliferative activity against HCT-15 human colorectal cancer cells with an IC50 value of 12.27 μM. It exerted high inhibitory activity toward MCF-7 human breast cancer cells and, to a much lesser extent, to corresponding MCF-10A human breast epithelial normal cells with an IC50 ratio (IC50 in MCF-7 divided by IC50 in MCF-10A) of 0.62., Conclusion: The mechanistic investigations indicated that 5-benzyl juglone could induce cell cycle arrest at the G0/G1 phase and promote apoptosis of HCT-15 cells. The apoptotic effects possibly contributed to its higher selectivity toward cancer cells than normal cell lines., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

In this study, a series of novel shikonin N-benzyl matrinic acid ester derivatives (PMMB-299-PMMB-310) were synthesized and tested for their ability to inhibit the proliferation of cancer cells. Compared with shikonin and matrine, some of the ester derivatives were found to exhibit better anti-proliferative activity against seven different cancer cell lines, with less cytotoxicity toward non-cancerous cells. The strongest anti-proliferative activity was exhibited by PMMB-302, which had an IC 50 value of 2.71 μM against A549 cells. The compound caused cell cycle arrest in the G2/M phase and induced apoptosis. Effects on the expression of apoptosis-related molecules such as Bcl2, Bcl-XL, caspase-3, caspase-9 and FADD suggested that PMMB-302 has tumor suppressive roles in lung cancer cells. In addition, PMMB-302 inhibited expression of telomerase core proteins, dyskerin and NHP2, and telomerase reverse transcriptase RNA. Moreover, molecular docking of PMMB-302 was subsequently conducted to determine the probable binding mode with telomerase. Taken together, the results indicate that PMMB-302 acts as a tumor suppressor in lung cancer cells by negatively regulating telomerase expression., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

We synthesized ten enamine naphthoquinones with yields ranging from 43 to 76%. These compounds were screened for their in vitro antiproliferative activities by MTT assay against four types of human cancer cell lines: HCT116, PC3, HL60 and SNB19. The naphthoquinones bearing the picolylamine (7) and quinoline (12) moieties were the most actives (IC 50  < 24 μM for all the cell lines), which were comparable or better to the values obtained for the control drugs. In silico evaluations allowed us to develop a qualitative Structure-Activity Relationship which suggest that electrostatic features, particularly the C 2 -C 3 internuclear repulsion and the molecular dipole moment, relate to the biological response. Furthermore, Molecular Docking simulations indicate that the synthetic compounds have the potential to act as anticancer molecules by inhibiting topoisomerase-II and thymidylate synthase., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Since NQO1 is overexpressed in many cancer cells, it can be used as a biomarker for cancer diagnosis and targeted therapy. NQO1 substrates show potent anticancer activity through the redox cycle mediated by NQO1, while the NQO1 probes can monitor NQO1 levels in cancers. High sensitivity of probes is needed for diagnostic imaging in clinic. In this study, based on the analysis of NQO1 catalytic pocket, the naphthoquinone trigger group 13 rationally designed by expanding the aromatic plane of the benzoquinone trigger group 10 shows significantly increased sensitivity to NQO1. The sensitivity of the naphthoquinone trigger group-based probe A was eight times higher than that of benzoquinone trigger group-based probe B in vivo. Probe A was selectively and efficiently sensitive to NQO1 with good safety profile and plasma stability, enabling its combination with NQO1 substrates in vivo for NQO1-overexpressing cancer theranostics for the first time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Two series of (hetero)arylamino-naphthoquinones and benzo-fused carbazolequinones were considered for study with the rationale that related structural motifs are present in numerous drugs, clinical trial agents, natural products and hTopoIIα inhibitors. Total 42 compounds were synthesized by reactions including dehydrogenative CN and Pd-catalyzed CC bond forming transformations. These compounds were screened against numerous cancer cells including highly metastatic one (MCF-7, MDA-MB-231, H-357 and HEK293T), and normal cells (MCF 10A). Some of the active compounds were evaluated for clonogenic cell survival and apoptotic effects in cancer cells (DAPI nuclear staining, Comet assay, Annexin-V-FITC/PI dual staining, flow cytometry, and western blot analysis with relevant proteins). All compounds were tested for hTopoIIα inhibitory activity. The investigated series compounds showed important properties like significant apoptotic antiproliferation in cancer cells with cell cycle arrest at S-phase and downregulation of NF- κβ signaling cascade, relatively less cytotoxicity to normal cells, and hTopoIIα inhibition with more efficiency compared to an anticancer drug etoposide., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A principal factor that contributes towards the failure to eradicate leishmaniasis and tuberculosis infections is the reduced efficacy of existing chemotherapies, owing to a continuous increase in multidrug-resistant strains of the causative pathogens. This accentuates the dire need to develop new and effective drugs against both plights. A series of naphthoquinone-triazole hybrids was synthesized and evaluated in vitro against Leishmania (L.) and Mycobacterium tuberculosis (Mtb) strains. Their cytotoxicities were also evaluated, using the human embryonic kidney cell line (HEK-293). The hybrids were found to be non-toxic towards human cells and had demonstrated micromolar cellular antileishmanial and antimycobacterial potencies. Hybrid 13, i.e. 2-{[1-(4-methylbenzyl)-1H-1,2,3-triazol-4-yl]methoxy}naphthalene-1,4-dione was the most active of all. It was found with MIC 90 0.5 µM potency against Mtb in a protein free medium, and with half-maxima inhibitory concentrations (IC 50 ) of 0.81 µM and 1.48 µM against the infective promastigote parasites of L. donavani and L. major, respectively, with good selectivity towards these pathogens (SI 22 - 65). Comparatively, the clinical naphthoquinone, atovaquone, although less cytotoxic, was found to be two-fold less antimycobacterial potent, and six- to twelve-fold less active against leishmania. Hybrid 13 may therefore stand as a potential anti-infective hit for further development in the search for new antitubercular and antileishmanial drugs. Elucidation of its exact mechanism of action and molecular targets will constitute future endeavour., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Some metabolic enzyme inhibitors can be used as Multi-target-Directed-Ligands (MTDL) in Medicinal chemistry therefore, synthesis and determination of alternative inhibitors are essential. In this study, novel bis-napthoquinone derivatives (5a-o) were synthesized through a multi-component cascade reaction of two molecules of 2-hydroxy-1,4-naphthoquinone with an aromatic aldehyde in basic media using triethylamine as a catalyst. This novel heterocyclic derivatives (5a-o) are applied to inhibit the carbonic anhydrase (hCA I and hCA II) isoform in low levels of nano molecules with Ki values exist between 4.62 ± 1.01 to 70.45 ± 9.03 nM for hCA I and for hCA II which is physiologically dominant K i s values are in the range of 5.61 ± 1.04 to 73.26 ± 10.25 nM. Further these novel derivatives (5a-o) efficiently inhibit AChE with Ki values in the range of 0.13 ± 0.02 to 3.16 ± 0.56 nM. The compounds are also applied for BChE with Ki values varying between 0.50 ± 0.10 to 9.23 ± 1.15 nM. For α-glycosidase, the most efficient Ki values of 5e and 5f are 76.14 ± 9.60 and 95.27 ± 12.55 nM respectively. Finally, molecular docking calculations against enzymes (acetylcholinesterase, butyrylcholinesterase, and the human carbonic anhydrase I and II) are compared using biological activities of heterocyclic derivatives. After these calculations, an ADME/T analysis is performed to study the future medicinal use of heterocyclic derivatives from lawsone., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A series of novel 3-(1-benzotriazole)-nor-β-lapachones 5a-5l were synthesized as the NQO1-targeted anticancer agents. Most of these compounds displayed good antiproliferative activity against the breast cancer MCF-7, lung cancer A549 and hepatocellular carcinoma HepG2 cells in agreements with their NQO1 activity. Among them, compound 5k was identified as a favorable NQO1 substrate. It could activate the ROS production in a NQO1-dependent manner, arrest tumor cell cycle at G0/G1 phase, promote tumor cell apoptosis, and decrease the mitochondrial membrane potential. In HepG2 xenograft models, 5k significantly suppressed the tumor growth with no influences on animal body weights. Therefore, 5k could be a good lead for further anticancer drug developments., (Copyright © 2021. Published by Elsevier Inc.)

Discrimination of cancer cells/tissues from normal ones is of critical importance for early diagnosis and treatment of cancers. Herein, we present a new strategy for high-contrast fluorescence diagnosis of cancer cells/tissues based on β-Lapachone (β-Lap, an anticancer agent) triggered ROS (reactive oxygen species) amplification specific in cancer cells/tissues. With the strategy, a wide range of cancer cells/tissues, including surgical tissue specimens harvested from patients, were distinguished from normal ones by using a combination of β-Lap and a Si-rhodamine-based NIR fluorescent ROS probe PSiR3 developed in this work with average tumor-to-normal (T/N) ratios up to 15 in cell level and 24 in tissue level, far exceeding the clinically acceptable threshold of 2.0. What's more, the strategy allowed the fluorescence discrimination of tumor tissues from inflammatory ones based on whether a marked fluorescence enhancement could be induced when treated with PSiR3 and β-Lap/PSiR3 combination, respectively., (© 2021 Wiley-VCH GmbH.)

A series of 1,4-naphthoquinone derivatives of lawsone (1), 6-hydroxy-1,4-naphthoquinone (2), and juglone (3) were synthesized by alkylation, acylation, and sulfonylation reactions. The yields of lawsone derivatives 1a-1k (type A), 6-hydroxy-1,4-naphthoquinone derivatives 2a-2j (type B), and juglone derivatives 3a-3h (type C) were 52-99%, 53-96%, and 28-95%, respectively. All compounds were tested in vitro for the cytotoxicity against human oral epidermoid carcinoma (KB) and cervix epithelioid carcinoma (HeLa) cells and their structure-activity relationship was studied. Compound 3c was found to be most potent in KB cell line (IC 50  = 1.39 µM). Some compounds were evaluated for DNA topoisomerase I inhibition. Compounds 2c, 3, 3a, and 3d showed topoisomerase inhibition activity with IC 50 values of 8.3-91 µM. Standard redox potentials (E°) of all naphthoquinones in phosphate buffer at pH 7.2 were examined by means of cyclic voltammetry. A definite correlation has been found between the redox potentials and inhibitory effects of type A compounds., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In order to expand structural diversity and improve antitumor efficiency, forty new naphthoquinone phenacylimidazolium derivatives were designed, synthesized and evaluated. Good synthetic yields were obtained under mild conditions using easily available starting materials. Cytotoxicity of these compounds was evaluated in vitro against a panel of human tumor cell lines: human breast carcinoma cell lines (MCF-7), human cervical carcinoma cell lines (HeLa), and human lung carcinoma cell lines (A549). Among them, the optimal compound 7m showed splendid antiproliferative activity with low to 50 nM IC 50 values against MCF-7 and excellent selectivity of 256-fold compared with the normal cell lines L929. Compound 7m induced apoptosis in a dose-dependent manner. Further mechanism experiments showed that compound 7m dramatically inhibited the expression of survivin and activated the pro-apoptotic protein caspase-3. Our results indicated that the structural modification on the 1,3-substituents of naphthoquinone imidazoliums without 2-substituent is also promising to obtain new antitumor compounds., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Triple-negative breast cancer (TNBC) has an unfavorable prognosis attribute to its low differentiation, rapid proliferation and high distant metastasis rate. PI3K/Akt/mTOR as an intracellular signaling pathway plays a key role in the cell proliferation, migration, invasion, metabolism and regeneration. In this work, we designed and synthesized a series of anilide (dicarboxylic acid) shikonin esters targeting PI3K/Akt/mTOR signaling pathway, and assessed their antitumor effects. Through three rounds of screening by computer-aided drug design method (CADD), we preliminarily obtained sixteen novel anilide (dicarboxylic acid) shikonin esters and identified them as excellent compounds. CCK-8 assay results demonstrated that compound M9 exhibited better antiproliferative activities against MDA-MB-231, A549 and HeLa cell lines than shikonin (SK), especially for MDA-MB-231 (M9: IC 50  = 4.52 ± 0.28 μM; SK: IC 50  = 7.62 ± 0.26 μM). Moreover, the antiproliferative activity of M9 was better than that of paclitaxel. Further pharmacological studies showed that M9 could induce apoptosis of MDA-MB-231 cells and arrest the cell cycle in G2/M phase. M9 also inhibited the migration of MDA-MB-231 cells by inhibiting Wnt/β-catenin signaling pathway. In addition, western blot results showed that M9 could inhibit cell proliferation and migration by down-regulating PI3K/Akt/mTOR signaling pathway. Finally, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model was also constructed to provide a basis for further development of shikonin derivatives as potential antitumor drugs through structure-activity relationship analysis. To sum up, M9 could be a potential candidate for TNBC therapy., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A method for the synthesis of fused 1,2-naphthoquinones, as analogues of biologically active natural terpene quinones, is described. The intermediate polycyclic naphthalenes were prepared by a one-pot palladium-catalysed process from simple alkynes, one of which was made from an optically pure biomass-derived levoglucosenone. The prepared methoxy-substituted naphthalenes were subsequently transformed in one step to 1,2-naphthoquinones by a trivalent-iodine-mediated oxidation. The naphthoquinone products were found to have cytotoxic properties.

A series of novel podophyllotoxin-naphthoquinone compounds 5a-p were synthesized in good yields using microwave-assisted four-component reactions of 2-hydroxy-1,4-naphthoquinone, aromatic benzaldehydes, tetronic acid and ammonium acetate. All the synthesized compounds were fully characterized by spectral data and evaluated for their cytotoxicity activities against KB, HepG2, Lu1, MCF7, and non-cancerous Hek-293 cell lines. Among 16 new compounds screened, compounds 5a, 5d, 5h, and 5k displayed high potent inhibitory activities with IC 50  < 40 nM against HepG2 and SK-Lu-1 cell lines, and showed lower toxicity for non-cancerous Hek-293 cell line, demonstrating the potential importance of these compounds in the development of potential anticancer agents., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

We developed a novel method for the synthesis of bis-naphthoquinones (BNQ), which are hybrids of lawsone (2-hydroxy-1,4-naphthoquinone) and 3-hydroxy-juglone (3,5-dihydroxy-1,4-naphthoquinone). The anticancer activity of three synthesized compounds, named 4 (RC10), 5 (RCDFC), and 6 (RCDOH) was evaluated in vitro against two metastatic prostate cancer (PCa) cell lines, DU145 and PC3, using MTT assays. We found that 4 (RC10) and 5 (RCDFC) induced cytotoxicity against DU145 and PC3 cells. Flow cytometry analysis revealed that these two compounds promoted cell cycle arrest in G1/S and G2/M phases, increased Sub-G1 peak and induced inhibition in cell viability. We also showed that these effects are cell-type context dependent and more selective for these tested PCa cells than for HUVEC non-tumor cells. The two BNQ compounds 4 (RC10) and 5 (RCDFC) displayed promising anticancer activity against the two tested metastatic PCa cell lines, DU145 and PC3. Their effects are mainly associated with inhibition of cell viability, possibly through apoptotic cell death, besides altering the SubG1, G1/S and G2/M phases of cell cycle. 5 (RCDFC) compound was found to be more selective than 4 (RC10), when comparing their cytotoxic effects in relation to HUVEC non-tumoral cells. Future work should also test these compounds in combination with other chemotherapeutic drugs to evaluate their effects on further sensitizing drug-resistant metastatic PCa cells.

Melanoma is the deadliest form of skin cancer and accounts for about three quarters of all skin cancer deaths. Especially at an advanced stage, its treatment is challenging, and survival rates are very low. In previous studies, we showed that the constituents of the roots of Onosma paniculata as well as a synthetic derivative of the most active constituent showed promising results in metastatic melanoma cell lines. In the current study, we address the question whether we can generate further derivatives with optimized activity by synthesis. Therefore, we prepared 31, mainly novel shikonin derivatives and screened them in different melanoma cell lines (WM9, WM164, and MUG-Mel2 cells) using the XTT viability assay. We identified ( R )-1-(1,4-dihydro-5,8-dihydroxy-1,4-dioxonaphthalen-2-yl)-4-methylpent-3-enyl 2-cyclopropyl-2-oxoacetate as a novel derivative with even higher activity. Furthermore, pharmacological investigations including the ApoToxGlo TM Triplex assay, LDH assay, and cell cycle measurements revealed that this compound induced apoptosis and reduced cells in the G1 phase accompanied by an increase of cells in the G2/M phase. Moreover, it showed hardly any effects on the cell membrane integrity. However, it also exhibited cytotoxicity against non-tumorigenic cells. Nevertheless, in summary, we could show that shikonin derivatives might be promising drug leads in the treatment of melanoma.

A series of 3-substituted-2-hydroxy-1,4-naphthoquinone derivatives with a variety of side chains were successfully synthesized by Mannich reaction of 2-hydroxy-1,4-naphthoquinone (lawsone) with selected amines and aldehydes. All substances (1-16) were evaluated for in-vitro antimalarial activity against strains of Plasmodium falciparum by microculture radioisotope technique. Bioassay data revealed that ten derivatives (1-8, 11 and 13) displayed significantly good activity with values of IC 50 ranging from 0.77 to 4.05 µg/mL. The best biological profile (IC 50  = 0.77 µg/mL) was observed in compound 1, possessing a n-butyl substituted aminomethyl group. Experimental results support the potential use of our active Mannich components as promising antimalarial agents in the fight against malaria infections and multidrug resistance problems.

Napabucasin, undergoing multiple clinical trials, was reported to inhibit the signal transducer and transcription factor 3 (STAT3). To better elucidate its mechanism of action, we designed a napabucasin-based proteolysis targeting chimera (PROTAC), XD2-149 that resulted in inhibition of STAT3 signaling in pancreatic cancer cell lines without inducing proteasome-dependent degradation of STAT3. Proteomics analysis of XD2-149 revealed the downregulation of the E3 ubiquitin-protein ligase ZFP91. XD2-149 degrades ZFP91 with DC 50 values in the nanomolar range. The cytotoxicity of XD2-149 was significantly, but not fully, reduced with ZFP91 knockdown providing evidence for its multi-targeted mechanism of action. The NQO1 inhibitor, dicoumarol, rescued the cytotoxicity of XD2-149 but not ZFP91 degradation, suggesting that the NQO1-induced cell death is independent of ZFP91. ZFP91 plays a role in tumorigenesis and is involved in multiple oncogenic pathways including NF-κB and HIF-1α.

The P2X7 receptor (P2X7R) is an ATP-gated ion channel and potential therapeutic target for new drug development. In this study, we synthesized a series of new 1,4-naphthoquinone (1,4-NQ) derivatives and investigated their antagonistic effects against mouse P2X7R. We explored the ability of the tested substances to block ATP-induced Ca 2+ influx into mouse Neuro-2a cells and selected the four most effective substances: the 1,4-naphthoquinone thioglucosides U-548 and U-557 and their tetracyclic conjugates U-286 and U-556. Biological analysis of these compounds revealed significant in vitro inhibition of murine P2X7R. This inhibition resulted in marked blockade of ethidium bromide (EtBr) and YO-PRO-1 fluorescent dye uptake, pronounced decreases in ROS and NO production and protection of neuronal cell viability against the toxic action of high ATP concentrations. In silico analysis indicated favorable molecular docking results of these 1,4-NQs, pointing to their potential to bind in an allosteric site located in the extracellular region of P2X7R. These findings suggest compounds U-286, U-548, U-556 and U-557 as potential scaffolds for the design of new P2X7R blockers and drugs effective against neuropathic pain and neurodegenerative diseases., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

A series of novel 4-aminobenzensulfonamide/carboxamide derivatives bearing naphthoquinone pharmacophore were designed, sythesized and evaluated for their proteasome inhibitory and antiproliferative activities against human breast cancer cell line (MCF-7). The structures of the synthesized compounds were confirmed by spectral and elemental analyses. The proteasome inhibitory activity studies were carried out using cell-based assay. The antiproteasomal activity results revealed that most of the compounds exhibited inhibitory activity with different percentages against the caspase-like (C-L, β1 subunit), trypsin-like (T-L, β2 subunit) and chymotrypsin-like (ChT-L, β5 subunit) activities of proteasome. Among the tested compounds, compound 14 bearing 5-chloro-2-pyridyl ring on the nitrogen atom of sulfonamide group is the most active compound in the series and displayed higher inhibition with IC 50 values of 9.90 ± 0.61, 44.83 ± 4.23 and 22.27 ± 0.15 μM against ChT-L, C-L and T-L activities of proteasome compared to the lead compound PI-083 (IC 50  = 12.47 ± 0.21, 53.12 ± 2.56 and 26.37 ± 0.5 μM), respectively. The antiproliferative activity was also determined by MTT (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay in vitro. According to the antiproliferative activity results, all of the compounds exhibited cell growth inhibitory activity in a range of IC 50  = 1.72 ± 0.14-20.8 ± 0.5 μM and compounds 13 and 28 were found to be the most active compounds with IC 50 values of 1.79 ± 0.21 and 1.72 ± 0.14 μM, respectively. Furthermore, molecular modeling studies were carried out for the compounds 13, 14 and 28 to investigate the ligand-enzyme binding interactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

In continuation with the previous work, a series of 5-hydroxy-2-amidomethoxy-1,4-naphthoquinones were prepared to establish the structure-activity relationship studies toward anticancer activity (IC 50 in µM) against three cell lines; colo205 (colon adenocarcinoma), T47D (breast ductal carcinoma) and K562 (chronic myelogenous leukemia). Among the synthesized compounds, naphthoquinone amines, 5 (0.8; 0.6; 0.8), 14 (0.8; 0.6; 0.5) and the amine precursor, 4 (1.3; 0.3; 1.0) displayed potent anticancer activities. A tumor targeting drug delivery system was achieved by synthesizing the conjugate 6 (1.4; 0.5; 1.1) of naphthoquinone-amine 5 and Biotin which also proved its potency. Finally, to introduce polyamine conjugate, spermidine was attached with 2-amidomethoxy-1,4-naphthoquinone. The naphthoquinone-spermidine conjugate 27 (1.2; 1.7; 1.7) also retained the activity. Thus, potent naphthoquinone amines were explored and Biotin/polyamine conjugate was developed as tumor targeting drug delivery system., (Copyright © 2020. Published by Elsevier Ltd.)

Background: Naphthoquinones are a class of aromatic compounds relevant for their chemical characteristics, structural properties, and biological activity. These compounds are found in nature with a wide range of effects, highlighting their antibacterial, antifungal, and antiprotozoal properties. Additionally, naphthoquinones are used as a scaffold to obtain new derivatives with pharmacological potential, mainly compounds against parasitic diseases., Objective: The purpose of this work was to carry out a comprehensive review of naphthoquinones and their derivatives obtained from both natural and synthetic sources, also, to analyze their biological activity against Leishmania spp. (Leishmaniasis), Trypanosoma cruzi (Chagas disease), Plasmodium falciparum (Malaria), Toxoplasma gondii (Toxoplasmosis), and Toxocara canis (Toxocariasis). All of these agents are responsible for relevant diseases worldwide., Results: Natural naphthoquinones, such as plumbagin, diospyrin, burmanin, lapachol, lawsone and psychorubrin, show an antiprotozoal activity similar or enhanced antiprotozoal activity to reference drugs. Some naphthoquinones obtained by synthesis or semi-synthesis showed better biological activity or less toxic effects than natural compounds., Conclusion: In this review, natural and synthetic naphthoquinones showed antiparasitic activity, in most cases, with improved results than current drugs currently used in clinical trials. A modification of their structure with different functional groups can enhance their biological effects, improve solubility, and reduce undesirable side effects. Therefore, naphthoquinones are important molecules in the development of new chemotherapeutic agents against parasitic diseases., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

In this study, based on our previous study, derivatives of naphtho[2,3-b]furan-4,9-diones were synthesized and their antimicrobial activities were evaluated. The screening of these naphthoquinones revealed that the fluorine-containing NQ008 compound exhibited potent and broad antimicrobial activities against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacteria, and fungi. The results of the ratio of the minimum bactericidal concentration (MBC) to the minimum inhibitory concentrations (MICs) and time-kill assays suggest that the mode of action of NQ008 is bactericidal. Additionally, the results of a drug resistance study revealed that NQ008 exhibited potent antibacterial activity and may delay the development of bacteria resistance. Furthermore, NQ008 exhibited preliminary antiviral activity against the swine influenza virus and Feline calicivirus.

Naphthoquinones are important molecules belonging to the general class of quinones, and many of these compounds have become drugs that are in the pharmaceutical market for the treatment of several diseases. A special subclass of compounds is that of the bis(naphthoquinones), which have two linked naphthoquinone units. In the last few years, several synthetic approaches toward such valuable compounds have been described, as well as their evaluation against numerous important biological targets. In this review, we provide a thorough discussion on the various synthetic methods reported for the synthesis of bis(naphthoquinone) analogues, also highlighting the biological activities of these substances., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The 2,6'-bijuglone natural product diospyrin and its unnatural 3,6'-isomer idospyrin have been synthesized in seven steps each from N , N -diethylsenecioamide in overall yields of 12% and 13%, respectively. The syntheses diverge from ramentaceone (7-methyljuglone) and include a key Suzuki-Miyaura cross-coupling. Diospyrin, idospyrin, and several synthetic precursors exhibit potent and selective cytotoxicity to the murine myeloma NS-1 cell line over neonatal foreskin cells.

Lindbladione (1) is a neural stem cell differentiation activator isolated from Lindbladia tubulina by our group. Hes1 dimerization inhibitory activity of lindbladione (1) was discovered using our original fluorescent Hes1 dimer microplate assay. We also found that lindbladione (1) accelerates the differentiation of neural stem cells. We conducted the first total synthesis of lindbladione (1) via Heck reaction of 1-hexene-3-one 7 with iodinated naphthoquinone 12, which was provided by Friedel-Crafts acylation followed by Claisen condensation, in the presence of Pd (II) acetate. Careful deprotection of the benzyl groups of 13 successively provided lindbladione (1). Synthesized lindbladione (1) exhibited potent Hes1 dimer inhibition (IC 50 of 2.7 μM) in our previously developed fluorescent Hes1 dimer microplate assay. Synthesized lindbladione (1) also accelerated the differentiation of C17.2 mouse neural stem cells into neurons dose dependently, increasing the number of neurons by 59% (2.5 μM) and 112% (10 μM) compared to the control. These activities are comparable to those of naturally occurring lindbladione (1) isolated from L. tublina.

A series of novel 1,4-naphthoquinone-triazole hybrids, N-(3-amino-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-2-(4-R-1H-1,2,3-triazol-1-yl)acetamide, was synthesized by click chemistry in the presence of sodium ascorbate and copper(II) sulfate pentahydrate in 81-94% yield. Various biological properties of the synthesized compounds including DNA binding/cleavage, antioxidant, antibacterial and antifungal properties were evaluated. The DNA binding study was performed using dsDNA and G-quadruplex DNA. All of the compounds showed fluorescence increase in the presence of DNA, regardless of the structure. Up to 2.9 and 2.5 times fluorescence increase upon incubation with double stranded or G-quadruplex DNA was detected for 5f and 5g, respectively. The docking studies performed on dsDNA and G-quadruplex structures suggested compounds' mode of interactions were populated around the grooves. All of the compounds showed excellent DNA cleavage activity and 5e was almost degraded the plasmid DNA. The highest radical scavenging activity was obtained as 89.9% at 200 mg/L with 5d. However, the highest ferrous chelating activity was obtained as 68.1% at 200 mg/L with 5g. The compounds exhibited antimicrobial activity against Bacillus cereus, Legionella pneumophila subsp. pneumophila, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus hirae as bacteria strains and Candida albicans and Candida tropicalis as microfungus strains. The compounds exhibited antibacterial and antifungal activity in the range of 4-128 μg/mL and 16-128 μg/mL, respectively. The best antimicrobial activity was obtained with 5d and 5e with a MIC value of 4 μg/mL against Enterococcus hirae. The acid dissociation constants (pK a ) were determined potentiometrically in 20% (v/v) dimethyl sulfoxide-water hydro-organic solvent at an ionic background of 0.1 mol/L of NaCl, at 25 ± 0.1 °C. Five pK a values were obtained for each ligand., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Basis on molecular docking and pharmacophore analysis of naphthoquinone moiety, a total of 23 compounds were designed and synthesised. With the help of reverse targets searching, anti-cancer activity was preliminarily evaluated, most of them are effective against some tumour cells, especially compound 12 : 1-(5,8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-en-1-yl-4-oxo-4-((4-phenoxyphenyl)amino) butanoate whose IC 50 against SGC-7901 was 4.1 ± 2.6 μM. Meanwhile the anticancer mechanism of compound 12 had been investigated by AnnexinV/PI staining, immunofluorescence, Western blot assay and molecular docking. The results indicated that this compound might induce cell apoptosis and cell autophagy through regulating the PI3K signal pathway.

Based on 6,7-substituted 2,5,8-trihydroxy-1,4-naphtoquinones (1,4-NQs) derived from sea urchins, five new acetyl- O -glucosides of NQs were prepared. A new method of conjugation of per- O -acetylated 1-mercaptosaccharides with 2-hydroxy-1,4-NQs through a methylene spacer was developed. Methylation of 2-hydroxy group of quinone core of acetylthiomethylglycosides by diazomethane and deacetylation of sugar moiety led to 28 new thiomethylglycosidesof 2-hydroxy- and 2-methoxy-1,4-NQs. The cytotoxic activity of starting 1,4-NQs (13 compounds) and their O - and S -glycoside derivatives (37 compounds) was determined by the MTT method against Neuro-2a mouse neuroblastoma cells. Cytotoxic compounds with EC 50 = 2.7-87.0 μM and nontoxic compounds with EC 50 > 100 μM were found. Acetylated O - and S -glycosides 1,4-NQs were the most potent, with EC 50 = 2.7-16.4 μM. Methylation of the 2-OH group innaphthoquinone core led to a sharp increase in the cytotoxic activity of acetylated thioglycosidesof NQs, which was partially retained for their deacetylated derivatives. Thiomethylglycosides of 2-hydroxy-1,4-NQs with OH and MeO groups in quinone core at positions 6 and 7, resprectively formed a nontoxic set of compounds with EC 50 > 100 μM. A quantitative structure-activity relationship (QSAR) model of cytotoxic activity of 22 1,4-NQ derivatives was constructed and tested. Descriptors related to the cytotoxic activity of new 1,4-NQ derivatives were determined. The QSAR model is good at predicting the activity of 1,4-NQ derivatives which are unused for QSAR models and nontoxic derivatives.

Extracellular ATP activates purinergic receptors such as P2X7, cationic channels for Ca 2+ , K + , and Na + . There is robust evidence of the involvement of these receptors in the immune response, so P2X7 receptors (P2X7R) are considered a potential therapeutic target for the development of anti-inflammatory drugs. Although there are many studies of the anti-inflammatory properties of naphthoquinones, these molecules have not yet been explored as P2X7 antagonists. In previous work, our group prepared 3-substituted (halogen or aryl) 2-hydroxy-1,4-naphthoquinones and studied their action on P2X7R. In this paper, eight 2-amino-3-aryl-1,4-naphthoquinones were evaluated to identify the inhibitory activity on P2X7R and the toxicological profile. Three analogues (AD-4CN, AD-4Me, and AD-4F) exhibited reduced toxicity for mammalian cells with CC 50 values higher than 500 µM. These three 3-substituted 2-amino-1,4-naphthoquinones inhibited murine P2X7R (mP2X7R) in vitro. However, the analogues AD-4CN and AD-4Me showed low selectivity index values. AD-4F inhibited both mP2X7R and human P2X7R (hP2X7R) with IC 50 values of 0.123 and 0.93 µM, respectively. Additionally, this analogue exhibited higher potency than BBG at inhibiting the ATP-induced release of IL-1β in vitro. Carrageenan-induced paw edema in vivo was reversed for AD-4F with an ID 50 value of 11.51 ng/kg. Although AD-4F was less potent than previous 3-substituted (halogen or aryl) 2-hydroxy-1,4-naphthoquinones such as AN-04in vitro, this 3-substituted 2-amino-1,4-naphthoquinone revealed higher potency in vivo to reduce the edematogenic response. In silico analysis suggests that the binding site of the novel 2-amino-3-aryl-1,4-naphthoquinone derivatives, including all the tautomeric forms, is located in the pore area of the hP2X7R model. Based on these results, we considered AD-4F to be a satisfactory P2X7R inhibitor. AD-4F might be used as a scaffold structure to design a novel series of inhibitors with potential inhibitory activity on murine (mP2X7R) and human (hP2X7R) P2X7 receptors., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Based on the structure of signal transducer and activator of transcription 3 (STAT3), a series of 1,4-naphthoquinones derived from plumbagin (PL) with STAT3 inhibition potential were designed, synthesized, and biologically evaluated in vitro against several human cancer cell lines (MDA-MB-231, HepG2 and A549 cells) and three normal cells. The structure-activity relationship (SAR) and molecular docking result showed that the presence of hydroxyl group at C-5 of PL might interact with STAT3 in the form of hydrogen bonds, which is conducive to the binding of this kind structures with STAT3. Among the target compounds, 7a displayed the most potent inhibition against cancer cells and weaker cytotoxicity on normal cells than PL. The western bolting analysis showed that 7a could suppress the phosphorylation of STAT3 as well as the downstream genes instead of affecting its upstream tyrosine kinases (Src and JAK2) levels and p-STAT1 expression. Furthermore, molecular docking indicated that 7a bound to STAT3 more tightly than PL, and it could significantly induce the apoptosis of cancer cells in vitro. All these results may provide reference for the discovery of effective STAT3 inhibitors., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Covering: Up to January 2020Meroterpenoids derived from the polyketide 1,3,6,8-tetrahydroxynaphthalene (THN) are complex natural products produced exclusively by Streptomyces bacteria. These antibacterial compounds include the napyradiomycins, merochlorins, marinones, and furaquinocins and have inspired many attempts at their chemical synthesis. In this review, we highlight the role played by biosynthetic studies in the stimulation of biomimetic and, ultimately, chemoenzymatic total syntheses of these natural products. In particular, the application of genome mining techniques to marine Streptomyces bacteria led to the discovery of unique prenyltransferase and vanadium-dependent haloperoxidase enzymes that can be used as highly selective biocatalysts in fully enzymatic total syntheses, thus overcoming the limitations of purely chemical reagents.

Menaquinones are a class of isoprenoid molecules that have important roles in human biology and bacterial electron transport, and multiple methods have been developed for their synthesis. These compounds consist of a methylnaphthoquinone (MK) unit and an isoprene side chain, such as found in vitamin K 1 (phylloquinone), K 2 , and other lipoquinones. The most common naturally occurring menaquinones contain multiple isoprene units and are very hydrophobic, rendering it difficult to evaluate the biological activity of these compounds in aqueous assays. One way to overcome this challenge has been the application of truncated MK-derivatives for their moderate solubility in water. The synthesis of such derivatives has been dominated by Friedel-Crafts alkylation with BF 3 ∙OEt 2 . This attractive method occurs over two steps from commercially available starting materials, but it generally produces low yields and a mixture of isomers. In this review, we summarize reported syntheses of both truncated and naturally occurring MK-derivatives that encompass five different synthetic strategies: Nucleophilic ring methods, metal-mediated reactions, electrophilic ring methods, pericyclic reactions, and homologation and side chain extensions. The advantages and disadvantages of each method are discussed, identifying methods with a focus on high yields, regioselectivity, and stereochemistry leading to a detailed overview of the reported chemistry available for preparation of these compounds.

Novel heterocyclic dichloronaphthoquinone derivatives have been synthesized by chlorine atom substitution in 2,3-dichloro-1,4-naphthoquinone to pyrazole or pyrimidine fragments. The structures of these compounds have been confirmed by FT-IR, ESI-MS, 1H?NMR, 13C-NMR and elementary analysis. Synthesized compounds were evaluated for their anticonvulsant action in a pentylenetetrazole (PTZ)-convulsion model and antidepressant activity in the forced swimming test (FST). All naphthoquinone derivatives at a dose 100 mg/kg indicated anticonvulsant effect in PTZ-induced test at 3 h and 24 h after oral administration. In addition, these compounds possessed prolonged antidepressant properties significantly reducing the duration of immobility time when compared to the reference drug amitriptyline.

Persistently activated signal transducer and activator of transcription 3 (STAT3) plays an important role in the development of multiple cancers, and therefore is a potential therapeutic target for cancer prevention. Herein, we report the rational design, synthesis, and biological evaluation of novel potent STAT3 inhibitors based on BBI608. Among them, compound A11 exhibited the most potent in vitro tumor cell growth inhibitory activities toward MDA-MB-231, MDA-MB-468 and HepG2 cells with IC 50 values as low as 0.67 ± 0.02 μM, 0.77 ± 0.01 μM and 1.24 ± 0.16 μM, respectively. Fluorescence polarization (FP) assay validated the binding of compound A11 in STAT3 SH2 domain with the IC 50 value of 5.18 μM. Further mechanistic studies indicated that A11 inhibited the activation of STAT3 (Y705), and thus reduced the expression of STAT3 downstream genes CyclinD1 and C-Myc. Simultaneously, it induced cancer cell S phase arrest and apoptosis in a concentration-dependent manner. An additional in vivo study revealed that A11 suppressed the MDA-MB-231 xenograft tumor growth in mice at the dose of 10 mg/kg (i.p.) without obvious body-weight loss. Finally, molecular docking study further elucidated the binding mode of A11 in STAT3 SH2 domain., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Rhodium-catalyzed [2 + 2 + 2] cycloadditions, sulfonyl phthalide annulations and nitroalkene reactions have been employed for the synthesis of 56 quinone-based compounds. These were evaluated against Trypanosoma cruzi, the parasite that causes Chagas disease. The reactions described here are part of a program that aims to utilize modern, versatile and efficient synthetic methods for the one or two step preparation of trypanocidal compounds. We have identified 9 compounds with potent activity against the parasite; 3 of these were 30-fold more potent than benznidazole (Bz), a drug used for the treatment of Chagas disease. This article provides a comprehensive outline of reactions involving over 120 compounds aimed at the discovery of new quinone-based frameworks with activity against T. cruzi., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Human dihydroorotate dehydrogenase ( h DHODH) is an attractive target for cancer therapy. Based on its crystal structure, we designed and synthesized a focused compound library containing the structural moiety of 1,4-benzoquinone, which possesses reactive oxygen species (ROS) induction capacity. Compound 3s with a naphtho[2,3- d ][1,2,3]triazole-4,9-dione scaffold exhibited inhibitory activity against h DHODH. Further optimization led to compounds 11k and 11l , which inhibited h DHODH activity with IC 50 values of 9 and 4.5 nM, respectively. Protein-ligand cocrystal structures clearly depicted hydrogen bond and hydrophobic interactions of 11k and 11l with h DHODH. Compounds 11k and 11l significantly inhibited leukemia cell and solid tumor cell proliferation and induced ROS production, mitochondrial dysfunction, apoptosis, and cell cycle arrest. Nanocrystallization of compound 11l displayed significant in vivo antitumor effects in the Raji xenograft model. Overall, this study provides a novel bifunctional compound 11l with h DHODH inhibition and ROS induction efficacy, which represents a promising anticancer lead worthy of further exploration.

The respiratory chain of Escherichia coli contains two different types of terminal oxidase that are differentially regulated as a response to changing environmental conditions. These oxidoreductases catalyze the reduction of molecular oxygen to water and contribute to the proton motive force. The cytochrome bo 3 oxidase (cyt bo 3 ) acts as the primary terminal oxidase under atmospheric oxygen levels, whereas the bd-type oxidase is most abundant under microaerobic conditions. In E. coli, both types of respiratory terminal oxidase (HCO and bd-type) use ubiquinol-8 as electron donor. Here, we assess the inhibitory potential of newly designed and synthesized 3-alkylated Lawson derivatives through L-proline-catalyzed three-component reductive alkylation (TCRA). The inhibitory effects of these Lawson derivatives on the terminal oxidases of E. coli (cyt bo 3 and cyt bd-I) were tested potentiometrically. Four compounds were able to reduce the oxidoreductase activity of cyt bo 3 by more than 50 % without affecting the cyt bd-I activity. Moreover, two inhibitors for both cyt bo 3 and cyt bd-I oxidase could be identified. Based on molecular-docking simulations, we propose binding modes of the new Lawson inhibitors. The molecular fragment benzyl enhances the inhibitory potential and selectivity for cyt bo 3 , whereas heterocycles reduce this effect. This work extends the library of 3-alkylated Lawson derivatives as selective inhibitors for respiratory oxidases and provides molecular probes for detailed investigations of the mechanisms of respiratory-chain enzymes of E. coli., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Isoplumbagin (5-hydroxy-3-methyl-1,4-naphthoquinone), a naturally occurring quinone from Lawsonia inermis and Plumbago europaea , has been reported to have anti-inflammatory and antimicrobial activity. Inflammation has long been implicated in cancer progression. In this study, we examined the anticancer effect of chemically synthesized isoplumbagin. Our results revealed that isoplumbagin treatment suppressed cell viability and invasion of highly invasive oral squamous cell carcinoma (OSCC) OC3-IV2 cells, glioblastoma U87 cells, non-small cell lung carcinoma H1299 cells, prostate cancer PC3 cells, and cervical cancer HeLa cells by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Boyden chamber assays. In vivo studies demonstrate the inhibitory effect of 2 mg/kg isoplumbagin on the growth of orthotopic xenograft tumors derived from OSCC cells. Mechanistically, isoplumbagin exerts its cytotoxic effect through acting as a substrate of reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] dehydrogenase quinone 1 (NQO1) to generate hydroquinone, which reverses mitochondrial fission phenotype, reduces mitochondrial complex IV activity, and thus compromises mitochondrial function. Collectively, this work reveals an anticancer activity of isoplumbagin mainly through modulating mitochondrial dynamics and function.

The phenomenon of high sugar consumption by tumor cells is known as Warburg effect. It results from a high glycolysis rate, used by tumors as preferred metabolic pathway even in aerobic conditions. Targeting the Warburg effect to specifically deliver sugar conjugated cytotoxic compounds into tumor cells is a promising approach to create new selective drugs. We designed, synthesized, and analyzed a library of novel 6-S-(1,4-naphthoquinone-2-yl)-d-glucose chimera molecules (SABs)-novel sugar conjugates of 1,4-naphthoquinone analogs of the sea urchin pigments spinochromes, which have previously shown anticancer properties. A sulfur linker (thioether bond) was used to prevent potential hydrolysis by human glycoside-unspecific enzymes. The synthesized compounds exhibited a Warburg effect mediated selectivity to human prostate cancer cells (including highly drug-resistant cell lines). Mitochondria were identified as a primary cellular target of SABs. The mechanism of action included mitochondria membrane permeabilization, followed by ROS upregulation and release of cytotoxic mitochondrial proteins (AIF and cytochrome C) to the cytoplasm, which led to the consequent caspase-9 and -3 activation, PARP cleavage, and apoptosis-like cell death. These results enable us to further clinically develop these compounds for effective Warburg effect targeting., Competing Interests: The authors declare no conflict of interest.