DNA topoisomerase-I Research Articles

Determination of T Cell Responses in Thai Systemic Sclerosis Patients.

Objectives This study is aimed at determining the role of T cells by assessing the numbers of IFN-γ- and IL-2-secreting T cells following stimulation with peptides derived from DNA topoisomerase-I protein in Thai SSc patients. Methods Fifty Thai SSc patients and 50 healthy controls (HC) joined this study. IFN-γ and IL-2 levels upon stimulation of T cells with 6 peptides derived from DNA topoisomerase-I protein were determined. Anti-nuclear antibodies (ANA) and anti-Scl-70 antibodies were determined by using the ELISA method. Results In SSc patients, we detected a significantly higher number of IFN-γ- and IL-2-secreting CD8+ T cells than IFN-γ- and IL-2-secreting CD4+ T cells after stimulation with pooled peptides derived from DNA topoisomerase-I protein. A similar percentage of CD4+IL-2+, CD4+IFN-γ+, and CD8+IL-2+ were detected following stimulation with DNA topoisomerase-I protein -in SSc patients with anti-Scl-70 antibody (SSc/anti-Scl-70+) and those without. In contrast, the amount of CD8+IFN-γ+ cells was significantly higher in SSc/anti-Scl-70+ than those without. Stimulation with individual peptides showed that CSLRVEHINLHPELD (sPep3; 15 amino acids; position 505-519 of DNA topoisomerase-I protein) was the optimal epitope that induced T cells secreting the highest levels of IFN-γ and IL-2. A higher percentage of IFN-γ+CD4+ T cells was detected in SSc/anti-Scl-70+ than those without the following stimulation with peptides 2 (amino acid position 475-486 [RAVALYFIDKLA] of protein DNA topoisomerase). Conclusion The results from this study emphasize the critical role of DNA topoisomerase-I peptides on the activation of T cells in SSc patients. The findings provide a better understanding of SSc's immunopathogenesis and may lead to the development of diagnostic tools and specific treatments for SSc in the future.

In-silico Studies and Wet-Lab Validation of Camptothecin Derivatives for Anti-Cancer Activity Against Liver (HepG2) and Lung (A549) Cancer Cell Lines.

In the present study, we have explored the utility of QSAR modelling, in silico ADMET, docking, chemical semi-synthesis, and in vitro evaluation studies for the identification of active camptothecin (CPT) derivatives against cancer-targeting human liver (HepG2) and lung (A549) cancer cell lines. Two QSAR models were developed as screenings tools using the multiple linear regression (MLR) method followed by ADMET and docking studies. The regression coefficient (r2) and cross-validation regression coefficients (rCV2T) of the QSAR model for the HepG2 cell line was 0.95 and 0.90, respectively, and for the A549 cell line, it was 0.93 and 0.81, respectively. In silico studies show that CPT derivatives (CPT-1 and CPT-6) possess drug-like properties. Docking performed on DNA Topoisomerase-I showed significant binding affinity. Finally, predicted active derivatives were chemically semi synthesized, spectroscopically characterized, and evaluated in-vitro for cytotoxic/anticancer activity against HepG2 and A549 cell lines. The experimental results are consistent with the predicted results. These findings may be of immense importance in the anticancer drug development from an inexpensive and widely available natural product, camptothecin.

Copper(I)-Catalyzed Nitrile-Addition/N-Arylation Ring-Closure Cascade: Synthesis of 5,11-Dihydro-6H-indolo[3,2-c]quinolin-6-ones as Potent Topoisomerase-I Inhibitors.

In this paper, we present a copper(I)-catalyzed nitrile-addition/N-arylation ring-closure cascade for the synthesis of 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones from 2-(2-bromophenyl)-N-(2-cyanophenyl)acetamides. Using CuBr and t-BuONa in dimethylformamide (DMF) as the optimal reaction conditions, the cascade reaction gave the target products, in high yields, with a good substrate scope. Application of the cascade reaction was demonstrated on the concise total syntheses of alkaloid isocryptolepine. Further optimization of the products from the cascade reaction led to 3-chloro-5,12-bis[2-(dimethylamino)ethyl]-5,12-dihydro-6H-[1,3]dioxolo[4',5':5,6]indolo[3,2-c]quinolin-6-one (2k), which exhibited the characteristic DNA topoisomerase-I inhibitory mechanism of action with potent in vitro anticancer activity. Compound 2k actively inhibited ARC-111- and SN-38-resistant HCT-116 cells and showed in vivo activity in mice bearing human HCT-116 and SJCRH30 xenografts. The interaction of 2k with the Top-DNA cleavable complex was revealed by docking simulations to guide the future optimization of 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones as topoisomerase-I inhibitors.

A preliminary study on molecular target identification of drugs in individualized treatment of malignant solid tumors in children

Objective: To explore the role of drug-related molecular target identification in the individualized treatment of malignant solid tumors in children. Methods: The clinical data of 40 patients diagnosed with malignant solid tumors from Beijing Tongren Hospital, Capital Medical University, between June 2017 and March 2019 were retrospectively analyzed. Immunohistochemistry, polymerase chain reaction and sequencing methods were used to determine the expression levels and mutations of tumor drug molecular targets, and to compare the efficiency as well as the incidence of toxic side effects of chemotherapy using anti-tumor drugs with various molecular targets. Results: A total of 4 tumor drug-related targets were identified in 40 tumor tissue samples, namely DNA topoisomerase-ⅡA (TOPOⅡA), β(3)-tubulin (Tubulinβ(3)), DNA topoisomerase-Ⅰ(TOPOⅠ) and dihydrofolate reductase gene polymorphisms [DHFR (C829T)]. The effective rates of platinum-based agents, methotrexate, irinotecan, vinblastine and anthracycline for malignant solid tumors in children were 90.0% (36/40), 85.0% (34/40), 70.0% (28/40), 67.5% (27/40), 62.5% (25/40), respectively. The effective rates of chemotherapy with irinotecan, methotrexate, and vinblastine in mesenchymal tumors were 68.9% (20/29), 62.1% (18/29), 68.9% (20/29), respectively, which were considerably higher than 18.2% (2/11), 36.4% (4/11) and 36.4% (4/11) in non-mesenchymal tumors, with significant differences (χ(2)=5.487, 15.345, 17.278, all P<0.05). The effective rate of chemotherapy of platinum-based drugs for non-mesenchymal tumors was 72.3% (8/11), which was significantly higher than 58.6% (17/29) in mesenchymal tumors, and the difference was statistically significant (χ(2)=11.231, P<0.05). The intensity of toxic side effects in order from high to low was anthracycline > platinum > methotrexate > vinblastine > irinotecan. Conclusion: Tumor drug-related molecular targets and the sensitivity of tumors of different origins to the same anti-tumor drug as well as side effects are predicted, which provides a theoretical and clinical basis for individualized treatment of malignant tumors in children.

Activity of Topotecan toward the DNA/Topoisomerase I Complex: A Theoretical Rationalization.

Topotecan (TPT) is a nontoxic anticancer drug characterized by a pH-dependent lactone/carboxyl equilibrium. TPT acts on the covalently bonded DNA/topoisomerase I (DNA/TopoI) complex by intercalating between two DNA bases at the active site. This turns TopoI into a DNA-damaging agent and inhibits supercoil relaxation. Although only the lactone form of the drug is active and effectively inhibits TopoI, both forms have been co-crystallized at the same location within the DNA/TopoI complex. To gain further insights into the pH-dependent activity of TPT, the differences between two TPT:DNA/TopoI complexes presenting either the lactone (acidic pH) or the carboxyl (basic pH) form of TPT were studied by means of molecular dynamic simulations, quantum mechanical/molecular mechanical calculations, and topological analysis. We identified two specific amino acids that have a direct relationship with the activity of the drug, i.e., lysine 532 (K532) and asparagine 722 (N722). K532 forms a stable hydrogen bond bridge between TPT and DNA only when the drug is in its active lactone form. The presence of the active drug triggers the formation of an additional stable interaction between DNA and protein residues, where N722 acts as a bridge between the two fragments, thus increasing the binding affinity of DNA for TopoI and further slowing the release of DNA. Overall, our results provide a clear understanding of the activity of the TPT-like class of molecules and can help in the future design of new anticancer drugs targeting topoisomerase enzymes.

Strategic Perspectives on Improved Anti-Tumor Drug Effects in Combination with Clinically Equivalent or Lower Concentrations of Epigenetic Modifiers, DNA Methyltransferase Inhibitors, and Histone Deacetylase Inhibitors

The aim of this research is to facilitate the pursuit of improved chemotherapeutic drugs in combination with epigenetic modifiers. Both in vitro studies and a clinical study have described the combinations of DNA methyltransferase inhibitors with irinotecan and histone deacetylase inhibitors with 5-fluorouracil or gemcitabine to enhance their anti-cancer activities. The molecular mechanisms involved in the potentiation of anti-tumor activities were apoptosis regulation, cellular metabolism, DNA topoisomerase-I upregulation, cell-cell adhesion, regulation of transcription (DNA-templated), DNA repair, and the PI3K/AKT signaling pathway. More importantly, the priming effects and long-lasting effects induced by DNA methyltransferase inhibitors, when applied as a pretreatment, sensitized cancer cells to subsequent anti-cancer drug treatments. The combinations of 5-fluorouracil and gemcitabine with histone deacetylase inhibitors (depsipeptide and valproic acid, respectively), increased the expression of major histocompatibility complex class II, which may warrant further investigation for possible accurate biomarkers and therapeutic targets. As valproic acid downregulated histone deacetylase in patients recruited in a clinical phase I/II study, the activity of valproic acid may be associated with the enhanced anti-tumor activity in combination with 5-fluorouracil. This research provides a positive perspective on the combination therapy of anticancer drugs with epigenetic modifiers.

Enhanced cytotoxic effect of camptothecin nanosponges in anaplastic thyroid cancer cells in vitro and in vivo on orthotopic xenograft tumors

Anaplastic carcinoma of the thyroid (ATC) is a lethal human malignant cancer with median survival of 6 months. To date, no treatment has substantially changed its course, which makes urgent need for the development of novel drugs or novel formulations for drug delivery. Nanomedicine has enormous potential to improve the accuracy of cancer therapy by enhancing availability and stability, decreasing effective doses and reducing side effects of drugs.Camptothecin (CPT) is an inhibitor of DNA topoisomerase-I with several anticancer properties but has poor solubility and a high degradation rate. Previously, we reported that CPT encapsulated in β-cyclodextrin-nanosponges (CN-CPT) increased solubility, was protected from degradation and inhibited the growth of prostate tumor cells both in vitro and in vivo. The aim of this study was to extend that work by assessing the CN-CPT effectiveness on ATC both in vitro and in vivo.Results showed that CN-CPT significantly inhibited viability, clonogenic capacity and cell-cycle progression of ATC cell lines showing a faster and enhanced effect compared to free CPT. Moreover, CN-CPT inhibited tumor cell adhesion to vascular endothelial cells, migration, secretion of pro-angiogenic factors (IL-8 and VEGF-α), expression of β-PIX, belonging to the Rho family activators, and phosphorylation of the Erk1/2 MAPK.Finally, CN-CPT significantly inhibited the growth, the metastatization and the vascularization of orthotopic ATC xenografts in SCID/beige mice without apparent toxic effects in vivo. This work extends the previous insight showing that β-cyclodextrin-nanosponges are a promising tool for the treatment of ATC.

In Vitro and In Vivo Therapeutic Evaluation of Camptothecin-Encapsulated β-Cyclodextrin Nanosponges in Prostate Cancer.

Camptothecin (CPT), a pentacyclic alkaloid, is an inhibitor of DNA Topoisomerase-I and shows a wide spectrum of anti-cancer activities. The use of CPT has been hampered by poor aqueous solubility and a high degradation rate. Previously, it has been reported that CPT encapsulated in β-cyclodextrin-nanosponges (CN-CPT) overcomes these disadvantages and improves the CPT's inhibitory effect on DU145 prostate tumor cell lines, and PC-3 growth in vitro. This work extends these observations by showing that CN-CPT significantly inhibits the adhesion and migration of these tumor cells and their STAT3 phosphorylation. The anti-adhesive effect is exerted also in human endothelial cells, in which CN-CPT also inhibits the angiogenic activity as assessed by the tubulogenesis and sprouting assays. Finally, CN-CPT substantially delays the growth of PC-3 cell engraftment in SCID mice in vivo without apparent toxic effects. These results support the use of β-cyclodextrin nanosponge nanotechnology as a potential nanocarrier for delivery of anticancer drugs in the treatment of prostate cancers.

Unraveling the mode of binding of the anticancer drug topotecan with dsDNA

The binding interactions between antitumor drugs and DNA are of burgeoning interest due to increasing demand in medicinal science. In the present work, we have tried to examine the mode of binding of topotecan (TPT) with DNA. TPT, an eminent anti-cancer drug from the Camptothecin family, is found to interact with DNA Topoisomerase-I and inhibits the DNA replication process. Steady state, time resolved fluorescence, circular dichroism and thermal melting studies have been utilized to explore the mode of binding of TPT with synthetic polynucleotides ((dA-dT)15, (dG-dC)15) and natural DNA (CT-DNA). The mode of binding of TPT with the DNA double helix has been substantiated to be principally groove binding. It is found that even though the ground state cationic form (C) of the drug binds to dsDNA irrespective of DNA sequences, the emission mainly appears from Z*, and it is attributed to the intermolecular excited state proton transfer (ESPT) reaction between the drug and surrounding water molecules. However, in the case of (dA-dT)15, the emission profile indicates the existence of a small population of excited state cationic form (C*) of the drug in the minor groove of DNA. The different photophysical behavior of TPT in the case of (dA-dT)15 compared to others is attributed to the narrower and deeper minor groove of (dA-dT)15 than that of the others. The exact molecular picture of the binding interaction between the drug and DNAs has been explored from molecular modeling studies.

Antileishmanial activity evaluation of bis-lawsone analogs and DNA topoisomerase-I inhibition studies

For the development of potent novel antileishmanial agents, 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4 dione) derivatives were synthesized from lawsone and evaluated for cytotoxicity on Leishmania donovani promastigotes as well as on leishmanial DNA topoisomerase-I. Enzyme inhibition studies were conducted with simultaneous and preincubation conditions. Total inhibition is compared to camptothecin (CPT), which was taken as positive control on both the systems of enzyme inhibition. The range of activity varied from 37.5 to 70 µM in simultaneous assay and 13–16 µM in preincubation assay. Furthermore, when evaluated against L. donovani promastigotes, the synthesized compounds exhibited the activity ranging from 2 to 14 µM. The results revealed that all the compounds exhibit promising antileishmanial activity.

Docking and QSAR Studies of Camptothecin Derivatives as Inhibitor of DNA Topoisomerase-I

AbstractCamptothecin (CPT) is a cytotoxic quinoline alkaloid which inhibits the DNA enzyme Topoisomerase-I (Topo-I) and has shown remarkable anticancer activity in preliminary clinical trials. The major limitation is its low solubility and high adverse reaction. In the studied work, we performed molecular docking of CPT derivatives against Topo-I and developed the quantitative structure activity relationship (QSAR) model for anticancer activity screening. For QSAR, we used CPT and other anticancer drugs with its IC50 values. We used a total of forty seven anticancer drugs as training set and eight compounds as test set and thirty derivatives of CPT as query set. Total of fifty two chemical descriptors were used for the quantitative data calculation. Only four showed good correlation with the experimental activity. Forward feed regression method was used for development of multiple linear regression (MLR) QSAR model. Model showed acceptable regression coefficient (r2) 0.89 (i.e., 89% of correlation) and cross validation coefficient (rCV2) 0.86 (i.e., 86 % of prediction accuracy). After drug likeness test, ten compounds namely, MSB3a, MSB3b, MSB19, MSB22L, MSB22M, MSB22O, MSB22R, MSB25D, MSB37G and MSB39D, showed promising predicted anticancer activity and drug likeness properties. Out of ten, only six compounds namely, MSB19, MSB22L, MSBM, MSB22O, MSB22R and MSB37D indicate two times more activity than the parent CPT compound. In molecular docking studies, all the identified active CPT derivatives showed high binding affinity with Topo-I. QSAR study indicates that connectivity index, electron affinity, mol.wt. &amp; ether group count highly contribute to inhibitory activity of CPT derivatives. These results can offer useful references for directing the molecular design of Topo-I inhibitor with improved anticancer activity.

Docking and QSAR Studies of Camptothecin Derivatives as Inhibitor of DNA Topoisomerase-I

Docking and QSAR Studies of Camptothecin Derivatives as Inhibitor of DNA Topoisomerase-I

Neurotoxic activity of a Topoisomerase-I inhibitor, camptothecin, in cultured cerebellar granule neurons

DNA Topoisomerase-I (Topo-I) is an enzyme involved in DNA rearrangements, transcription and replication and is a potential target for cancer chemotherapy. Camptothecin is one of the chemotherapeutic agents inhibiting the catalytic activity of Topo-I through the formation of single-strand protein–DNA cross-links. Here, we show that camptothecin is toxic to primary cerebellar granule neurons (CGNs), and camptothecin-induced toxicity is not solely due to the inhibition of Topo-I. An analysis of the effect of camptothecin on CGNs in culture showed that camptothecin inhibits the viability of CGNs. The observed inhibition of cell viability is through the induction of a pro-apoptotic pathway that leads to neuronal degeneration. Furthermore, results show that camptothecin inhibits both protein synthesis and the neuritic outgrowth of CGNs. To determine if the observed neurotoxicity was due to inhibition of Topo-I alone, siRNA-mediated Topo-I-downregulated CGNs were analyzed for cell viability, apoptosis, protein synthesis and neurite outgrowth. The results of these experiments demonstrate that Topo-I downregulation affects only neurite outgrowth and has no significant effect on viability, apoptosis and protein synthesis in granule neurons. In conclusion, camptothecin-induced neurotoxicity may be due to the induction of protein–DNA cross-links and other unknown drug-related interactions rather than the inhibition of Topo-I activity alone.

Ataxia telangiectasia mutated activation by transcription‐ and topoisomerase I‐induced DNA double‐strand breaks

Ataxia telangiectasia mutated (ATM), the deficiency of which causes a severe neurodegenerative disease, is a crucial mediator for the DNA damage response (DDR). As neurons have high rates of transcription that require topoisomerase I (TOP1), we investigated whether TOP1 cleavage complexes (TOP1cc)-which are potent transcription-blocking lesions-also produce transcription-dependent DNA double-strand breaks (DSBs) with ATM activation. We show the induction of DSBs and DDR activation in post-mitotic primary neurons and lymphocytes treated with camptothecin, with the induction of nuclear DDR foci containing activated ATM, gamma-H2AX (phosphorylated histone H2AX), activated CHK2 (checkpoint kinase 2), MDC1 (mediator of DNA damage checkpoint 1) and 53BP1 (p53 binding protein 1). The DSB-ATM-DDR pathway was suppressed by inhibiting transcription and gamma-H2AX signals were reduced by RNase H1 transfection, which removes transcription-mediated R-loops. Thus, we propose that Top1cc produce transcription arrests with R-loop formation and generate DSBs that activate ATM in post-mitotic cells.

RETRACTED: A computational docking study for prediction of binding mode of diospyrin and derivatives: Inhibitors of human and leishmanial DNA topoisomerase-I

A computational approach was utilized to study the relative binding modes of diospyrin (bisnaphthoquinonoid) with the crystal structure of human DNA-TopoI and the recently reported Leishmania donavani DNA-TopoI. Additionally, the binding site interactions of amino derivatives of diospyrin with human TopoI were studied extensively. Based on the docking results, binding modes of diospyrin with the human and leishmanial TopoI catalytic core were predicted. The parallel use of two efficient and predictive docking programs, GOLD and Ligandfit, allowed mutual validation of the predicted binding poses. A reasonably good correlation coefficient between the calculated docking scores and the experimentally determined cytotoxicity helped in validating the docking method. Furthermore, a structure-based pharmacophore model was developed for L. donavani DNA-TopoI inhibition which helped in elucidating the topological and spatial requirements of the ligand-receptor interactions. This study provides an understanding of the structural basis of ligand binding to the topoisomerase receptor, which may be used for the structure-based design of potent and novel ligands for anticancer and antileishmanial therapy. To our knowledge, this is the first report of a binding mode exploration study for diospyrin and its derivatives as inhibitors of the leishmanial and human TopoI enzymes.

Naphthofuroquinone Derivatives: DNA Topoisomerase‐I Inhibition and Cytotoxicity.

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Naphthofuroquinone Derivatives: DNA Topoisomerase-I Inhibition and Cytotoxicity

The naphthoquinone skeleton is found in many natural products and has been employed as a synthetic intermediate for the preparation of numerous heterocyclic compounds with interesting biological properties such as antitumor, antibacterial, antifungal and antiinflammatory agents. The quinone core of streptonigrin and lavendamycin has been proposed to be a determining factor in their antitumor activity. Recently, the linearly substituted quinolinediones have revealed the importance of the quinone framework for potent antitumor activity against the cell lines. Furthermore, Cheng et al. designed the fused benzofuroquinone that possesses a characteristic “2-phenylnaphthalene-type” structural framework in which the two rings are coplanar. They found that the designed benzo[b]naphtho[2,3-d]furan6,11-dione derivatives exhibited strong inhibitory activity throughout the entire series of cancer cell lines. A decade ago, dinaphtho[1,2-b;2',3'-d]furan-7,12-dione 3 was isolated from stems of Paulownia tomentos, a perennial tree widely distributed in China, Japan, and Korea. The naphthofuroquinone 3 significantly reduced viral cytopathic effect in a standard in vitro antiviral assay with HeLa cells. It is also interesting that this structural pattern is commonly observed in other biologically active compounds including camptothecin, ellipticine, and mappicine, a class of DNA Topoisomerase-I (Topo-I) inhibitors that exhibit efficious antitumor activity. Here, we would like to report the synthesis of naphthofuroquinone derivatives, and their DNA TopoI inhibition and cytotoxicity against various cancer cell lines.

Molecular Modeling for Generation of Structural and Molecular Electronic Descriptors for QSAR Using Quantum Mechanical Semiempirical and ab initio Methods

The major thrust of scienti c research is to understand and explain the biological functions of biologi-cal systems in molecular terms. The development of techniques of molecular modeling has opened theprospects for understanding the function, reactivity and properties of biological systems in terms ofmolecularstructure. QSARsquantifytheconnectionbetweenthestructureandpropertiesofmoleculesand allow the prediction of properties from structural and electronic parameters. The QSAR studiesemploy electronic, hydrophobic, structural and topological parameters of the compounds. In partic-ular, electronic parameters are considered important in the establishment of QSAR models and arehelpful to quantify di erent types of intermolecular and intramolecular interactions, as these interac-tions are usually responsible for properties of biological systems. The hydroxy substituted quinonesand their derivatives are of considerable practical importance in the eld of biology and pharmacol-ogy, as prominent family of pharmaceutically active and biologically relevant chromophores. Hydroxynaphthoquinone derivatives, in particular, have shown inhibitory e ect on DNA topoisomerase-I andantiproliferative activity and cytotoxic activity [1, 5, 6]. We have generated the molecular electronicdescriptors like the energies of HOMO and LUMO, dipole moment  ionization potentials, heat offormation, total energy E

Naphthazarin derivatives (VIII): Synthesis, inhibitory effect on DNA topoisomerase-I, and antiproliferative activity of 6-(1-acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones.

6-(1-Acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinone (DMNQ; 5,8-dimethoxy-1,4-naphthoquinone) derivatives were synthesized and examined for their inhibitory effect on DNA topoisomerase-I (Topo I) and their antiproliferative activity against L1210 cells. The Topo-I inhibitory effect of 6-(1-hydroxyalkyl)-DMNQ derivatives was found to be dependent on the size of the alkyl chains, suggesting that lipophilicity might be one important factor influencing the inhibitory effect. It was found that acylation of 6-(1-hydroxyalkyl)-DMNQ derivatives possessing alkyl chains of C2-C5 enhanced both bioactivities, suggesting that an increase of electrophilicity in the quinoid moiety makes the electrophilic arylation of bionucleophiles more favorable. It is noteworthy that 6-(1-heptanoyloxyethyl)-DMNQ exhibited both the most potent Topo I inhibitory activity (IC50, 11.5 microM) and the greatest antiproliferative activity (ED50, 0.05 microM) upon L1210 cells.

Naphthazarin derivatives (VIII): Synthesis, inhibitory effect on DNA topoisomerase-I, and antiproliferative activity of 6-(1-acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones

Naphthazarin derivatives (VIII): Synthesis, inhibitory effect on DNA topoisomerase-I, and antiproliferative activity of 6-(1-acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones