naphthoquinones and diospyrin

The genus Diospyros is one of the most important sources of bioactive compounds, exclusively 1,4-naphthoquinones. The following information is an attempt to cover the developments in the biology and phytochemistry of 1,4-naphthoquinones isolated from this genus, as well as the studies done and the suggested mechanisms regarding their activities. During the past 60 years, many of these agents have been isolated from Diospyros L. Twelve considerable bioactive structures are reported in this review. The basic 1,4-naphthoquinone skeletons, on which a large number of studies have been done, are plumbagin and diospyrin. Today, the potential for development of leads from 1,4-naphthoquinones obtained from Diospyros L. is growing dramatically, mainly in the area of anticancer and antibacterial investigations. The data prepared and described here are intended to be served as a reference tool to the natural products and chemistry specialists in order to expand the rational drug design.

Topics: Anti-Bacterial Agents; Antineoplastic Agents, Phytogenic; Diospyros; Naphthoquinones

Natural products have played a vital role in drug discovery and development process for cancer. Diospyrin, a plant based bisnaphthoquinonoid, has been used as a lead molecule in an effort to develop anti-cancer drugs. Several derivatives/analogues have been synthesized and screened for their pro-apoptotic/anti-cancer activities so far. Our review is focused on the pro-apoptotic/anti-cancer activities of diospyrin, its derivatives/analogues and the different mechanisms potentially involved in the bioactivity of these compounds. Particular focus has been placed on the different mechanisms (both chemical and molecular) thought to underlie the bioactivity of these compounds. A brief bioinformatics analysis at the end of the article provides novel insights into the new potential mechanisms and pathways by which these compounds might exert their effects and lead to a better realization of the full therapeutic potential of these compounds as anti-cancer drugs.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Computational Biology; Humans; Naphthoquinones

Among the various strategies of curbing tuberculosis, suppression of Mycobacterium tuberculosis (Mtb) is a primary goal of the WHO to stop its infection, which is further strengthened by the presence of a massive reservoir of latently infected individuals. Several efforts have been made to explore potential candidates, including drug-repurposing, phytomolecules evaluation, and de novo designs. Compared to other strategies, investigation of phytomolecules with known experimental evidence represents a highly cost-effective and less time-consuming approach. Interestingly, some of the phytomolecules, previously known to show anti-tuberculosis effects, are known. While, these compounds have not yet been tested for their additional abilities to interact with resuscitation-promoting factor B (RpfB), an essential protein involved in revoking of Mtb dormancy. We, therefore, performed an initial computational study to evaluate the binding affinity of 38 phytomolecules to select the most effective ligands against RpfB. The studies were carried out using AutoDock and associated tools for static interaction analysis, while molecular dynamics (MD) simulations were performed to examine the stability of predicted protein-ligand complexes using the Desmond MD package. As an outcome of this study, we have reported four potential compounds, viz. diospyrin, 2'-Nortiliacorinine, 5,4'-dihydroxy-3,7,8,3'-tetramethoxyflavone, and tiliacorine which showed a putative binding affinity with significant intermolecular interactions, docking energy of -8.0 kcal/mol or higher, and vital complex stability (~2.4 Å RMSD) during 100 ns MD simulation. The findings of this study indicated that phytomolecules are capable to efficiently inhibit the RpfB, which is vital for reactivation of dormant Mtb. Characterization of the molecular targets for hits with intriguingly selective activity against dormant Mtb would be helpful to elucidate the essential mechanisms underlying the survival of dormant Mtb during latent infections.

Topics: Antitubercular Agents; Bacterial Proteins; Benzylisoquinolines; Humans; Latent Tuberculosis; Molecular Docking Simulation; Molecular Dynamics Simulation; Mycobacterium tuberculosis; Naphthoquinones; Plants; Structure-Activity Relationship

The 2,6'-bijuglone natural product diospyrin and its unnatural 3,6'-isomer idospyrin have been synthesized in seven steps each from

Topics: Antineoplastic Agents; Antitubercular Agents; Isomerism; Naphthoquinones

Two new dimeric naphthoquinones, 5',8'-dihydroxy-6,6'-dimethyl-7,3'-binaphthyl-1,4,1',4'-tetraone (1; Di-naphthodiospyrol D) and 5',8'-dihydroxy-5,8-dimethoxy-6,6'-dimethyl-7,3'-binaphthyl-1,4,1',4'-tetraone (2; Di-naphthodiospyrol E), along with known naphthoquinones diospyrin (3) and 8-hydroxy diospyrin (4) were isolated from the chloroform fraction of extract of Diospyros lotus roots. Their structures were elucidated by advanced spectroscopic analyses, including HSQC, HMBC, NOESY, and J-resolved NMR experiments. The fractions and compounds 1-4 were evaluated for urease activity and phosphodiesterase-I, carbonic anhydrase-II and α-chymotrypsin enzyme inhibitory activities. Compounds 1 and 2 and their corresponding fractions showed significant and selective inhibitory effects on urease activities. The IC

Topics: Biological Assay; Diospyros; Enzyme Inhibitors; Molecular Structure; Naphthoquinones; Plant Extracts; Plant Roots; Urease

Anticancer activity of diospyrin and its derivatives (1-5) was evaluated against thirteen human cell lines. Compared to diospyrin (1), the acetylamine derivative (4) exhibited increase in cytotoxicity, particularly in HT-29 colon cancer cells, showing GI50 values of 33.90 and 1.96 μM, respectively. Also, enhanced toxicity was observed when cells, pre-treated with compound 4, were exposed to radiation. In vivo assessment of 4 was undertaken on tumour-bearing Nod-Scid mice treated at 4 mg/kg/day. Significant reduction in relative tumour volume (~86-91 %) was observed during the 12th-37th days after drug treatment. Increased caspase-3 activity and DNA ladder formation was observed in HT-29 cells after treatment with 4, suggesting induction of apoptotic death after drug treatment. Moreover, flow cytometric determination of Annexin V- FITC positive and PI negative cells demonstrated 17.4, 26.4, and 27.9 % of early apoptosis, respectively, upon treatment with 5, 10 and 25 μM of 4. HT-29 cells after treatment with 4 (1-25 μM) revealed ~2.5- 3- folds generation of ROS. Furthermore, concentration dependent decrease of mitochondrial trans-membrane potential (∆ψm), and expression of Bcl-2/Bax and other marker proteins suggested involvement of mitochondrial pathway of cell death. Overall, our results demonstrated the underlying cell-death mechanism of the plant-derived naphthoquinonoid (4), and established it as a prospective chemotherapeutic 'lead' molecule against colon cancer.

Topics: Animals; Antineoplastic Agents, Phytogenic; Caspase 3; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Colonic Neoplasms; DNA Fragmentation; Humans; Membrane Potential, Mitochondrial; Mice, Inbred NOD; Mice, SCID; Naphthoquinones; Tumor Burden; Xenograft Model Antitumor Assays

Density functional theory (DFT) and phytochemical study of a natural product, Diospyrin (DO) have been carried out. A suitable level of theory was developed, based on correlating the experimental and theoretical data. Hybrid DFT method at B3LYP/6-31G (d,p) level of theory is employed for obtaining the electronic, spectroscopic, inter-molecular interaction and thermodynamic properties of DO. The exact structure of DO is confirmed from the nice validation of the theory and experiment. Non-covalent interactions of DO with different atmospheric gases such as NH3, CO2, CO, and H2O were studied to find out its electroactive nature. The experimental and predicted geometrical parameters, IR and UV-vis spectra (B3LYP/6-31+G (d,p) level of theory) show excellent correlation. Inter-molecular non-bonding interaction of DO with atmospheric gases is investigated through geometrical parameters, electronic properties, charge analysis, and thermodynamic parameters. Electronic properties include, ionization potential (I.P.), electron affinities (E.A.), electrostatic potential (ESP), density of states (DOS), HOMO, LUMO, and band gap. All these characterizations have corroborated each other and confirmed the presence of non-covalent nature in DO with the mentioned gases.

Topics: Atmosphere; Computer Simulation; Electrons; Gases; Models, Molecular; Molecular Conformation; Naphthoquinones; Phytochemicals; Quantum Theory; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Static Electricity

The cell wall of Mycobacterium tuberculosis interacts with the host counterpart during the pathogenesis of tuberculosis. L-rhamnosyl (L-Rha) residue, a linker connects the arabinogalactan and peptidoglycan moieties in the bacterial cell wall. The biosynthesis of L-rhamnose utilizes four successive enzymes RmlA, RmlB, RmlC and RmlD. Neither rhamnose nor the genes responsible for its synthesis are observed in humans. Thus, drugs inhibiting enzymes of this pathway are unlikely to interfere with metabolic pathways in humans. The adverse drug effects of first and second line drugs along with the development of multi-drug resistance tuberculosis have stimulated the research in search of new therapeutic drugs. Thus, it is attractive to hypothesize that inhibition of the biosynthesis of L-Rha would be lethal to the mycobacteria. Nature provides innumerable secondary metabolites with novel structural architectures with reported activity against M. tuberculosis. Combination of structure based virtual screening with physicochemical and pharmacokinetic studies against rhamnose pathway enzymes identified potential leads. The crucial screening studies recognized four phytocompounds butein, diospyrin, indicanine, and rumexneposide A with good binding affinity towards the rhamnose pathway proteins. Furthermore, the high throughput screening methods recognized butein, a secondary metabolite from Butea monosperma with strong anti-tubercular bioactive spectrum. Butein displayed promising anti-mycobacterial activity which is validated by Microplate alamar blue assay (MABA). The focus on novel agents like these phytocompounds which exhibit preference toward the successive enzymes of a single pathway can prevent the development of bacterial resistance.

Topics: Antitubercular Agents; Bacterial Proteins; Biosynthetic Pathways; Chalcones; Humans; Molecular Docking Simulation; Mycobacterium tuberculosis; Naphthoquinones; Rhamnose; Tuberculosis, Multidrug-Resistant

Allergic disorders are characterized by an abnormal immune response towards non-infectious substances, being associated with life quality reduction and potential life-threatening reactions. The increasing prevalence of allergic disorders demands for new and effective anti-allergic treatments. Here we test the anti-allergic potential of monomeric (juglone, menadione, naphthazarin, plumbagin) and dimeric (diospyrin and diosquinone) naphthoquinones. Inhibition of RBL-2H3 rat basophils' degranulation by naphthoquinones was assessed using two complementary stimuli: IgE/antigen and calcium ionophore A23187. Additionally, we tested for the inhibition of leukotrienes production in IgE/antigen-stimulated cells, and studied hyaluronidase and lipoxidase inhibition by naphthoquinones in cell-free assays. Naphthazarin (0.1 µM) decreased degranulation induced by IgE/antigen but not A23187, suggesting a mechanism upstream of the calcium increase, unlike diospyrin (10 µM) that reduced degranulation in A23187-stimulated cells. Naphthoquinones were weak hyaluronidase inhibitors, but all inhibited soybean lipoxidase with the most lipophilic diospyrin, diosquinone and menadione being the most potent, thus suggesting a mechanism of competition with natural lipophilic substrates. Menadione was the only naphthoquinone reducing leukotriene C4 production, with a maximal effect at 5 µM. This work expands the current knowledge on the biological properties of naphthoquinones, highlighting naphthazarin, diospyrin and menadione as potential lead compounds for structural modification in the process of improving and developing novel anti-allergic drugs.

Topics: Animals; Anti-Allergic Agents; Antigens; Basophils; Calcimycin; Cell Degranulation; Cell Line, Tumor; Cell-Free System; Enzyme Inhibitors; Hyaluronoglucosaminidase; Immunoglobulin E; Leukotriene C4; Lipoxygenase; Naphthoquinones; Rats; Vitamin K 3

Diospyros lotus L. is traditionally used in various diseases including pain and sleep disorders. The pain and inflammation are the common problems, which are treated with various synthetic analgesic drugs, and associated the side effects. The natural products have gained significant importance over synthetic drugs. The importance of phyto-medicine the current study has been designed with the aim to investigate the analgesic and anti-inflammatory effects of Diospyros lotus and bioassay guided isolation from its crude fractions. Seven known compounds; lupeol (1), 7-methyljuglone (2), β-Sitosterol (3), stigmasterol (4) betulinic acid (5), diospyrin (6; DS) and 8-hydroxyisodiospyrin (7; HDS) which were hitherto unreported from D. lotus. The chloroform fraction (CFDL) and isolated compounds DS and HDS were evaluated for anti-nociceptive, sedative and anti-inflammatory effects. The acetic acid induced writing was significantly (p<0.001) protected by CFDL (72.43%), DS (40.87%) and HDS (65.76%) at higher doses which exhibited peripheral and central analgesic effects in acetic acid and hot-plat pain paradigms. Regarding the anti-inflammatory effect the CFDL (77.43%), DS (80.54%) and HDS (75.87%) protected the carrageenan paw edema after 3rd h. The central analgesic effect was significantly antagonized with naloxone (0.5 mg/kg), showing opiodergic mechanism of action. The CFDL, DS and HDS were also proved sedative in open field animal models. In acute toxicity study the chloroform fraction [CFDL (50, 100 and 150 mg/kg)], DS (5 and 10 mg/kg) and HDS (5 and 10 mg/kg) were found safe. Our study concluded that CFDL, DS and HDS have marked anti-nociceptive, anti-inflammatory and sedative effect. The anti-nociceptive and anti-inflammatory effects of the roots of D. lotus are partially attributed due to the presence of analgesic constituents like diospyrin (DS), 8-hydroxyisodiospyrin (HDS) and strongly supports the ethno-pharmacological uses of D. lotus as anti-nociceptive, anti-inflammatory and sedative.

Topics: Acetic Acid; Analgesics; Animals; Anti-Inflammatory Agents; Carrageenan; Chloroform; Diospyros; Drug Evaluation, Preclinical; Edema; Female; Hypnotics and Sedatives; Male; Mice, Inbred BALB C; Naphthoquinones; Plant Extracts; Toxicity Tests, Acute

World health organization has called for academic research and development of new chemotherapeutic strategies to overcome the emerging resistance and side effects exhibited by the drugs currently used against leishmaniasis. Diospyrin, a bis-naphthoquinone isolated from Diospyros montana Roxb., and its semi-synthetic derivatives, were reported for inhibitory activity against protozoan parasites including Leishmania. Presently, we have investigated the antileishmanial effect of a di-epoxide derivative of diospyrin (D17), both in vitro and in vivo. Further, the safety profile of D17 was established by testing its toxicity against normal macrophage cells (IC₅₀∼20.7 μM), and also against normal BALB/c mice in vivo. The compound showed enhanced activity (IC₅₀∼7.2 μM) as compared to diospyrin (IC₅₀∼12.6 μM) against Leishmania donovani promastigotes. Again, D17 was tested on L. donovani BHU1216 isolated from a sodium stibogluconate-unresponsive patient, and exhibited selective inhibition of the intracellular amastigotes (IC₅₀∼0.18 μM). Also, treatment of infected BALB/c mice with D17 at 2mg/kg/day reduced the hepatic parasite load by about 38%. Subsequently, computational docking studies were undertaken on selected enzymes of trypanothione metabolism, viz. trypanothione reductase (TryR) and ornithine decarboxylase (ODC), followed by the enzyme kinetics, where D17 demonstrated non-competitive inhibition of the L. donovani ODC, but could not inhibit TryR.

Topics: Animals; Antiprotozoal Agents; Cell Line; Female; Gene Expression Regulation, Enzymologic; Inhibitory Concentration 50; Kidney; Leishmania donovani; Liver; Macrophages; Mice; Mice, Inbred BALB C; Naphthoquinones; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Random Allocation

Tuberculosis and other bacterial diseases represent a significant threat to human health. The DNA topoisomerases are excellent targets for chemotherapy, and DNA gyrase in particular is a well-validated target for antibacterial agents. Naphthoquinones (e.g. diospyrin and 7-methyljuglone) have been shown to have therapeutic potential, particularly against Mycobacterium tuberculosis. We have found that these compounds are inhibitors of the supercoiling reaction catalyzed by M. tuberculosis gyrase and other gyrases. Our evidence strongly suggests that the compounds bind to the N-terminal domain of GyrB, which contains the ATPase active site, but are not competitive inhibitors of the ATPase reaction. We propose that naphthoquinones bind to GyrB at a novel site close to the ATPase site. This novel mode of action could be exploited to develop new antibacterial agents.

Topics: Adenosine Triphosphate; Anti-Infective Agents; Binding Sites; Catalytic Domain; DNA; DNA Gyrase; Escherichia coli; Humans; Inhibitory Concentration 50; Mass Spectrometry; Models, Chemical; Mycobacterium tuberculosis; Naphthoquinones; Protein Binding; Protein Structure, Tertiary; Staphylococcus aureus; Surface Plasmon Resonance; Tuberculosis

Previous studies have demonstrated that diospyrin (1), a quinonoid plant product, can inhibit the growth of Leishmania donovani parasites. Here, several derivatives of 1 were evaluated by the MTT assay and it was observed that the ethanolamine analogue (10) exhibited maximum cytotoxicity [50% inhibitory concentration (IC(50))=2.9 microM] against L. donovani promastigotes. Subsequently, the mode of cell death in promastigotes was investigated through externalisation of membrane-associated phosphatidylserine, mitochondrial membrane depolarisation, DNA laddering and in situ labelling of DNA fragmentation by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) methods. Whilst both 1 and 10 were found to induce apoptosis-like death in promastigotes, the effect of 10 was evidently stronger even at a lower concentration. Hence, the ethanolamine derivative (10) of diospyrin (1) may be a prospective 'lead' for the development of novel cytotoxic agents inducing apoptosis in L. donovani parasites.

Topics: Animals; Antiprotozoal Agents; Apoptosis; DNA Fragmentation; Ethanolamines; Inhibitory Concentration 50; Leishmania donovani; Naphthoquinones; Parasitic Sensitivity Tests

The synthesis and tumor-inhibitory activity of a series of aminonaphthoquinone derivatives of diospyrin, which was isolated from Diospyros montana Roxb., are presented here for the first time. An aminoacetate derivative showed the maximum (approximately 93%) increase in life span in vivo against murine Ehrlich ascites carcinoma (EAC) at a dose of 1 mg kg(-1)day(-1) (ip; five doses), and the lowest IC50 (0.06 microM) in vitro. Further, the same analogue also exhibited considerable enhancement in antiproliferative activity when evaluated against human cell lines, viz. malignant skin melanoma and epidermoid laryngeal carcinoma (IC50=0.06 and 0.92 microM, respectively) in comparison to the natural precursor, diospyrin (IC50=0.82 and 3.58 microM, respectively). Moreover, diospyrin and all its derivatives were found to show significantly greater (approximately 17- to 1441-fold) cytotoxicity against the tumor cells as compared to normal human lymphocytes. All these quinonoids generated substantial amounts of reactive oxygen species in EAC cells, more or less commensurate to their respective IC50 values.

Topics: Animals; Antineoplastic Agents; Benzoquinones; Carcinoma, Ehrlich Tumor; Cell Line, Tumor; Cell Proliferation; Drug Design; Electrochemistry; Humans; Mice; Naphthoquinones; Neoplasms; Oxidation-Reduction; Reactive Oxygen Species

Alkyl ethers (D2 and D7) synthesized from diospyrin (D1), a naphthoquinonoid isolated from Diospyros montana Roxb., were evaluated for cytotoxicity and capacity to generate reactive oxygen species (ROS) in tumour cells.. The tumour inhibitory activity of the quinonoids was assessed in vivo against Ehrlich ascites carcinoma (EAC), while cytotoxicity was determined in vitro on EAC and MCF-7 cancer cells by MTT assay. ROS generated by quinonoids in MCF-7 cells was measured fluorimetrically.. The tumour inhibitory activity, cytotoxicity and ROS generation capacity of quinonoids were found to be D7 > D2 > D1.. Alkyl ethers of D1 were more cytotoxic against tumour cells in vitro as well as in vivo.

Topics: Animals; Antineoplastic Agents, Phytogenic; Carcinoma, Ehrlich Tumor; Cell Line, Tumor; Ethers; Humans; Lipid Peroxidation; Mice; Naphthoquinones; Reactive Oxygen Species; Xenograft Model Antitumor Assays

Derivatisation of diospyrin, a bisnaphthoquinonoid isolated from Diospyros montana Roxb., led to the modification of its inhibitory activity, in vitro, towards a murine tumour model, Ehrlich ascites carcinoma (EAC), and two human cancer cell lines, viz., malignant skin melanoma (A375) and epidermoid laryngeal carcinoma (Hep2). Among the novel derivatives, an epoxide exhibited the maximum antiproliferative activity (IC(50) values in the range of 0.03-0.21 microM) and a comparatively lower toxicity (IC(50) approximately 98 microM) in normal human peripheral blood mononuclear cells (PBMC). This compound might provide a novel 'lead' for the development of clinically effective antiproliferative agents against cancer.

Topics: Animals; Antineoplastic Agents; Cell Proliferation; Diospyros; Disease Models, Animal; Humans; Inhibitory Concentration 50; Leukocytes, Mononuclear; Mice; Naphthoquinones; Plant Bark; Tumor Cells, Cultured

The development of radio-resistant tumor cells might be overcome by the use of tumor selective cytotoxic agents in combination with radiation treatment of cancer. Thus, we are exploring the radiomodifying potential of D7, a tumor-inhibitory compound derived from a plant product, diospyrin, in breast carcinoma cells, MCF-7. The present study indicated that D7 could enhance the radiation-induced cytotoxicity and apoptosis through down-regulation of the anti-apoptotic Bcl-2 and COX-2 gene expression, and up-regulation of pro-apoptotic genes, like p53 and p21. The higher expression of PUMA, a pro-apoptotic protein was also observed in the combination treatment. Effect of D7 on up-regulation of p21 expression in irradiated MCF-7 cells was concomitant with the cell cycle arrest in the G1 phase. Thus, it was concluded that D7 could sensitize the effect of radiation in breast carcinoma by regulating the gene expression involved in cell cycle and apoptosis.

Topics: Breast Neoplasms; Carcinoma; Cell Cycle; Cell Line, Tumor; Cyclooxygenase 2; Drug Evaluation, Preclinical; Gene Expression Regulation, Neoplastic; Genes, bcl-2; Genes, p53; Humans; Models, Biological; Naphthoquinones; Radiation Tolerance; Radiation-Sensitizing Agents; Reactive Oxygen Species

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.

Topics: Animals; Cell Line, Tumor; Computer Simulation; DNA Topoisomerases, Type I; Humans; Hydrogen Bonding; Leishmania donovani; Ligands; Models, Molecular; Molecular Conformation; Naphthoquinones; Protein Binding; Software; Topoisomerase I Inhibitors

Glycoside derivatives of diospyrin (1) were synthesized for the first time, and the cytotoxicity of the novel compounds vis-à-vis their precursors were evaluated against two human cancer cell lines, viz. malignant melanoma (A375) and laryngeal carcinoma (Hep2). The IC(50) values were in the low micromolar range for all the compounds tested, and A375 cells showed comparatively greater sensitivity than Hep2. Most of the compounds exhibited enhanced activity as compared to the plant-derived quinonoid precursor of the series (1), while the aminophenyl mannosyl (6) was found to be the most effective derivative. In A375 cells, 6 (IC(50) = 0.02 microM) showed the maximum increase in cytotoxicity (approximately 35-fold) over that of 1 (IC(50) = 0.82 microM). Again, when the glycosides were evaluated at a given concentration (0.1 microM) for their relative capacity to generate ROS from A375 cells, the compound 6 could produce the highest amount of ROS. Incidentally, this derivative also showed a comparatively lower toxicity (IC(50) approximately 41 microM) when tested against normal human peripheral blood mononuclear cells, indicating a fair prospect of its development as a novel chemotherapeutic agent for the treatment of malignant melanoma.

Topics: Antineoplastic Agents, Phytogenic; Cell Line, Tumor; Glycoconjugates; Humans; Laryngeal Neoplasms; Melanoma; Naphthoquinones; Reactive Oxygen Species

Chemical investigation of the roots of Diospyros assimilis had led to the isolation and characterization of six naphthalene derivatives, two 2-naphthaldehyes, namely 4-hydroxy-3,5-dimethoxy-2-naphthaldehyde 1, 4-hydroxy-5-methoxy-2-naphthaldehye 2, its related isomer 5-hydroxy-4-methoxy-2-naphthaldehyde 3 and three commonly occurring naphthoquinones, diospyrin 4, 8'-hydroxyisodiospyrin 5 and the simple monomer, plumbagin 6. Their chemical structures were established by detailed NMR investigations including 1H and 13C NMR, HSQC, HMBC and NOESY experiments. In addition, the naphthalene derivatives 1-5 were evaluated for their in vitro antiprotozoal activity against protozoan parasites belonging to the genera Trypanosoma, Leishmania and Plasmodium. Among the tested compounds, naphthaldehyde 1 showed moderate inhibition of the growth of the parasites, T. brucei, T. cruzi, L. donovani with IC50 values of 19.82, 12.28 and 38.78 microM and displayed cytotoxicity towards rat skeletal myoblasts (L-6 cells) with IC50 of 174.94 microM, while 2 and 3 were found to be comparatively less active to 1. The dimeric quinones 4 and 5 exhibited good activity against T. brucei and L. donovani with IC50 of 1.12 and 8.82 microM and 12.94 and 16.66 microM respectively.

Topics: Aldehydes; Animals; Antiprotozoal Agents; Cell Survival; Cells, Cultured; Diospyros; Inhibitory Concentration 50; Leishmania donovani; Magnetic Resonance Spectroscopy; Molecular Structure; Naphthalenes; Naphthoquinones; Plant Roots; Rats; Trypanosoma cruzi

Pre-mRNA splicing is an essential step of the expression of most metazoan protein-coding genes, which is often regulated in a cell type-specific or developmental manner. We have demonstrated previously that human DNA topoisomerase I, an extensively studied target for anticancer drugs, also has an intrinsic protein kinase activity that specifically phosphorylates proteins involved in splice site selection. Therefore, DNA topoisomerase I was recently shown to play a critical role in alternative splicing. Here, we have exploited these novel properties of DNA topoisomerase I to develop entirely novel diospyrin derivatives targeting its protein kinase activity and thereby modulating pre-mRNA splicing. Although some derivatives indeed inhibit kinase activity of topoisomerase I, they did not block reactions of topoisomerase I on DNA. However, these drugs interfere with camptothecin-dependent topoisomerase I-mediated DNA cleavage, implying that diospyrin derivatives mediate a conformational change of topoisomerase I. It is note-worthy that in vitro splicing reactions revealed that diospyrin derivatives alter various steps of splicing. Some diospyrin derivatives inhibit either the first or the second catalytic step of splicing but not spliceosome assembly, whereas diospyrin itself prevents the formation of full spliceosome. Our data revealed for the first time that diospyrin derivatives are able to stall the dynamic assembly of the spliceosome and open the exciting possibility of using these derivatives to correct aberrant splicing in human genetic diseases.

Topics: DNA; Enzyme Inhibitors; Naphthoquinones; Phosphorylation; RNA Splicing; Spliceosomes; Structure-Activity Relationship; Topoisomerase I Inhibitors

Diospyrin, a bisnaphthoquinonoid plant product, shows inhibitory activity against murine tumour in vivo and human cancer cell lines in vitro. Efforts have further been made to obtain synthetic derivatives of diospyrin with the objective of improved therapeutic effects. With the goal to reduce the toxicity towards normal cells and enhance the efficacy to tumour cells, diospyrin was encapsulated in liposomal vesicle and its antitumour potential was observed on the growth of Ehrlich ascites tumour in Swiss mice. It was found that the longevity of the tumour-bearing mice was significantly enhanced by treatment with liposomal diospyrin as compared with the free drug. Biochemical assay of liver function enzymes, viz. LDH, AP, GOT and GPT in blood serum of the tumour-bearing mice showed substantial alterations in the activity of these enzymes. These parameters were, however, restored to near normal level when the drug treatment was given encapsulated in a liposome. Histopathological studies on the liver tissues indicated a near normal pathological status in the treated animals despite being challenged by tumour cells. This study on diospyrin has shown, for the first time, an enhancement of its antitumour effect in vivo through liposomal encapsulation.

Topics: Animals; Antineoplastic Agents, Phytogenic; Carcinoma, Ehrlich Tumor; Diospyros; Drug Compounding; Drug Screening Assays, Antitumor; Liposomes; Liver; Liver Function Tests; Male; Mice; Naphthoquinones; Neoplasm Transplantation

The interaction of geshoidin, diospyrin and ergothioneine, with heterologously expressed human glutathione transferases (GSTs) was investigated in vitro. Diospyrin and geshoidin inhibited the three GST isoforms tested, with IC50 values in the range 0.1-0.5 microm, whereas ergothioneine had no effect on the GSTs. The predominant mode of inhibition was noncompetitive with respect to both glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). Diospyrin, however, competitively inhibited A1-1 and M1-1 with respect to GSH and geshoidin displayed mixed inhibition toward A1-1 with respect to GSH. The Ki values for diospyrin with respect to both GSH and CDNB were in the range 0.08-0.6 microM and those for geshoidin were in the range 16-173 microM. These results indicate that diospyrin is a potent inhibitor of heterologously expressed human GSTs A1-1, M1-1 and P1-1. Diospyrin and geshoidin were also found to inactivate P1-1 with diospyrin being a potent inactivator. Given these inhibitory properties, diospyrin may be a potential GST chemomodulator. Ergothioneine inactivated P1-1 only after preincubation and it enhanced ethacrynic acid inactivation of P1-1. Inactivation of P1-1 by ergothioneine may have implications for the antioxidant roles of P1-1 and ergothioneine in vivo.

Topics: Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Ergothioneine; Glucosides; Glutathione Transferase; Humans; Inhibitory Concentration 50; Naphthalenes; Naphthoquinones; Phytotherapy; Plants, Medicinal

Three derivatives and one structural analogue of diospyrin were synthesized and investigated for their inhibitory activity against Mycobacterium tuberculosis employing the rapid radiometric method in vitro. A novel aminoacetate derivative was found to be more active than the parent compound, the MICs being 50 and 100 mg/L, respectively, for a drug-susceptible strain, H37Rv, of M. tuberculosis. This derivative also exhibited an MIC of 50 mg/L for a few multidrug-resistant strains of M. tuberculosis. The other two derivatives and the analogue did not show any significant antimycobacterial activity at the highest concentration (100 mg/L) tested.

Topics: Antibiotics, Antitubercular; Antitubercular Agents; Ethambutol; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Naphthoquinones; Oxygen Consumption; Plant Bark; Plant Stems; Streptomycin

Isocratic reversed-phase liquid chromatography (LC) method was developed using acetonitrile and water for the determination of diospyrin, a pharmacologically important bisnaphthoquinonoid plant-product. The method was validated for precision, accuracy and reproducibility, and was found to be linear over the concentration range of 1-1000 microg/ml; the limits of detection and quantitation were 8 and 20 ng, respectively. The technique was used to determine the amount of diospyrin in plant extracts from four climatic regions in India. It was also applied for differentiation and separation of 27 naphthyl compounds. While a composition of 50:50 was preferable for dimeric compounds, the composition 40:60 was a better choice for the monomers. Also, the isomeric alpha- and beta-naphthols and their dimers could be distinguished by conversion into the respective methyl ethers.

Topics: Dimerization; Naphthols; Naphthoquinones; Plant Extracts; Reproducibility of Results; Sensitivity and Specificity

Diospyrin, a bisnaphthoquinonoid natural product, and three synthetic derivatives have been tested for their action in four human cancer cell lines: acute myeloblastic leukemia (HL-60), chronic myelogenic leukemia (K-562), breast adenocarcinoma (MCF-7) and cervical epithelial carcinoma (HeLa). In cells grown in appropriate media several derivatives elicited cytotoxicity as assessed by Trypan Blue dye exclusion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide reduction and DNA synthesis. Diethyl ether derivative (D7) was most effective in this regard while the parent compound diospyrin (D1) was least active (D7>D3>D2>D1). D7 was not cytotoxic toward normal human lymphocytes, suggesting its action is specific for tumor cells. On microscopic examination D7-treated cells exhibited characteristic morphological features of apoptosis, such as cell shrinkage and formation of apoptotic bodies. Fluorescent staining with propidium iodide revealed distinct chromatin condensation and nuclear fragmentation. The apoptotic index paralleled cytotoxic parameters, and fragmented DNA extracted free of genomic DNA displayed on gel electrophoresis a typical ladder pattern. D7-induced apoptosis was mediated via activation of caspase 3 and caspase 8.

Topics: Antineoplastic Agents; Apoptosis; Caspase 3; Caspase 8; Caspase 9; Caspases; Cell Division; Diospyros; Humans; Microscopy, Fluorescence; Naphthoquinones; Neoplasms; Plant Bark; Tumor Cells, Cultured

Plumbagin, a plant-derived bioactive naphthoquinonoid compound, was converted to a hydroquinonoid derivative, which was studied for its tumour-inhibitory and antileishmanial activities for the first time. A similar chemical transformation was undertaken on an analogous dimeric compound, diospyrin, and its bioassay results were compared with those of the plumbagin derivative. Synthesis of the derivative of plumbagin did not result in a marked enhancement of the tumour-inhibitory activity, whereas the improvement was obvious in the case of diospyrin vis à vis its hydroquinonoid analogue. The conversion of diospyrin to the hydroquinonoid compound also led to a substantial increase in the antileishmanial activity, while a similar conversion of plumbagin failed to do so.

Topics: Animals; Antineoplastic Agents, Phytogenic; Antiparasitic Agents; Carcinoma, Ehrlich Tumor; Cell Division; Inhibitory Concentration 50; Leishmania donovani; Male; Mice; Molecular Structure; Naphthoquinones; Phytotherapy; Plant Extracts; Plant Roots; Plumbaginaceae

The binaphthoquinoid, diospyrin, was isolated from Euclea natalensis A.DC., and evaluated for its activity against drug-sensitive and drug-resistant strains of Mycobacterium tuberculosis. The minimal inhibitory concentration (MIC) of diospyrin was found to be 100 microg/ml for all the M. tuberculosis strains.

Topics: Drug Resistance, Multiple; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Naphthoquinones; Plant Extracts

The naphthoquinone atovaquone is effective against Plasmodium and Pneumocystis carinii carinii. In Plasmodium, the primary mechanism of drug action is an irreversible binding to the mitochondrial cytochrome bc(1) complex as an analog of ubiquinone. Blockage of the electron transport chain ultimately inhibits de novo pyrimidine biosynthesis since dihydroorotate dehydrogenase, a key enzyme in pyrimidine biosynthesis, is unable to transfer electrons to ubiquinone. In the present study, the effect of atovaquone was examined on Pneumocystis carinii carinii coenzyme Q biosynthesis (rather than electron transport and respiration) by measuring its effect on the incorporation of radiolabeled p-hydroxybenzoate into ubiquinone in vitro. A triphasic dose-response was observed, with inhibition at 10 nM and then stimulation up to 0.2 microM, followed by inhibition at 1 microM. Since other naphthoquinone drugs may also act as analogs of ubiquinone, diospyrin and two of its derivatives were also tested for their effects on ubiquinone biosynthesis in P. carinii carinii. In contrast to atovaquone, these drugs did not inhibit the incorporation of p-hydroxybenzoate into P. carinii carinii ubiquinone.

Topics: Antifungal Agents; Atovaquone; Dose-Response Relationship, Drug; Naphthoquinones; Oxygen Consumption; Parabens; Pneumocystis; Ubiquinone

Atovaquone (also called Mepron, or 566C80) is a napthoquinone used for the treatment of infections caused by pathogens such as Plasmodium spp. and Pneumocystis carinii. The mechanism of action against the malarial parasite is the inhibition of dihydroorotate dehydrogenase (DHOD), a consequence of blocking electron transport by the drug. As an analog of ubiquinone (coenzyme Q [CoQ]), atovaquone irreversibly binds to the mitochondrial cytochrome bc(1) complex; thus, electrons are not able to pass from dehydrogenase enzymes via CoQ to cytochrome c. Since DHOD is a critical enzyme in pyrimidine biosynthesis, and because the parasite cannot scavenge host pyrimidines, the drug is lethal to the organism. Oxygen consumption in P. carinii is inhibited by the drug; thus, electron transport has also been identified as the drug target in P. carinii. However, unlike Plasmodium DHOD, P. carinii DHOD is inhibited only at high atovaquone concentrations, suggesting that the organism may salvage host pyrimidines and that atovaquone exerts its primary effects on ATP biosynthesis. In the present study, the effect of atovaquone on ATP levels in P. carinii was measured directly from 1 to 6 h and then after 24, 48, and 72 h of exposure. The average 50% inhibitory concentration after 24 to 72 h of exposure was 1.5 microgram/ml (4.2 microM). The kinetics of ATP depletion were in contrast to those of another family of naphthoquinone compounds, diospyrin and two of its derivatives. Whereas atovaquone reduced ATP levels within 1 h of exposure, the diospyrins required at least 48 h. After 72 h, the diospyrins were able to decrease ATP levels of P. carinii at nanomolar concentrations. These data indicate that although naphthoquinones inhibit the electron transport chain, the molecular targets in a given organism are likely to be distinct among members of this class of compounds.

Topics: Adenosine Triphosphate; Animals; Antifungal Agents; Atovaquone; Dose-Response Relationship, Drug; Male; Naphthoquinones; Pentamidine; Pneumocystis; Pneumocystis Infections; Rats; Rats, Inbred BN; Rats, Long-Evans

Two dimeric naphthoquinones, diospyrin and isodiospyrin, isolated from the root of Diospyros piscatoria (Gurke), a common ingredient in several folk medicines, have been shown to have a broad spectrum of antibacterial activity. The minimum inhibitory concentrations (MICs) of diospyrin against Streptococcus pyogenes ATCC 12344 and Streptococcus pneumoniae ATCC 33400 ranged from 1.56 to 50 microg/mL. While those against Salmonella choleraesuis serotype typhi (S. typhi), ATCC 6539 and Mycobacterium chelonae ATCC 19977 were between 25 and 100 microg/mL. Isodiospyrin was more active than its racemic isomer diospyrin. The MICs against Gram-positive bacteria ranged from 0.78 to 50 microg/mL. While those against Pseudomonas aeruginosa ATCC 15443 and S. typhi ranged from 50 to 100 microg/mL. The MIC for M. chelonae was between 6.25 and 25 microg/mL. MICs were found to increase with the concentration of cells used for the inoculum. The MICs for Bacillus subtilis ATCC 6633 increased up to the highest concentration of cells tested. The same phenomenon was observed on M. chelonae, but with better effect in the latter. The kinetics of bacteria studies against both B. subtilis and M. chelonae increases with increasing concentration of isodiospyrin tested. Two tetrameric forms of plumbagin were isolated. The naphthoquinone bisisodiospyrin, gave MIC values between 300 and 400 micro g/mL. The second, as yet unidentified tetramer, was not active at 500 micro g/mL.

Topics: Anti-Bacterial Agents; Bacillus; Microbial Sensitivity Tests; Mycobacterium; Naphthoquinones; Plant Extracts; Plant Roots; Salmonella; Streptococcus

Diospyrin, a tumour inhibitory agent from the stem bark of Diospyros montana was isolated and characterised. A sensitive high-performance thin-layer chromatographic (HPTLC) method was developed for the estimation of diospyrin. The method was validated for precision (intra- and inter-day), repeatability and accuracy. The method was found to be precise, with the RSDs for intra-day in the range of 0.72-1.85% and RSDs for inter-day in the range of 1.06-2.95%, for different concentrations. Instrumental precision and repeatability of the method were found to be 0.086 and 0.937 (% CV), respectively. Accuracy of the method was checked by performing the recovery study at two levels and average percentage recovery was found to be 97.87%. The developed HPTLC method was adopted for the estimation of diospyrin content of the stem bark of D. montana from different regions, which varied from 0.35 to 0.47% (w/w) in the samples.

Topics: Antineoplastic Agents, Phytogenic; Chromatography, Thin Layer; Magnoliopsida; Naphthoquinones; Plant Stems; Reproducibility of Results; Sensitivity and Specificity; Spectrophotometry, Ultraviolet

Diospyrin is a plant product that has significant inhibitory effect on the growth of Leishmania donovani promastigotes. This compound inhibits the catalytic activity of DNA topoisomerase I of the parasite. Like camptothecin, it induces topoisomerase I mediated DNA cleavage in vitro. Treatment of DNA with diospyrin before addition of topoisomerase I has no effect. Preincubation of topoisomerase I with diospyrin before the addition of DNA in the relaxation reaction increases this inhibition. Our results suggest that this bis-naphthoquinone compound exerts its inhibitory effect by binding with the enzyme and stabilizing the topoisomerase I-DNA "cleavable complex." Diospyrin is a specific inhibitor of the parasitic topoisomerase I. It does not inhibit type II topoisomerase of L. donovani and requires much higher concentrations to inhibit type I topoisomerase of calf thymus. The potent inhibitory effect of diospyrin on type I DNA topoisomerase from L. donovani can be exploited for rational drug design in human leishmaniasis.

Topics: Animals; Antiprotozoal Agents; DNA Damage; DNA Topoisomerases, Type I; DNA Topoisomerases, Type II; Dose-Response Relationship, Drug; Leishmania donovani; Naphthoquinones; Topoisomerase I Inhibitors

Diospyrin, a bis-naphthoquinone derivative, isolated from a plant, known for its antitumour properties against Ehrlich ascites carcinoma in Swiss A mice, exhibits antiprotozoal activity towards L. donovani promastigotes in culture.

Topics: Animals; Dose-Response Relationship, Drug; Leishmania donovani; Naphthoquinones; Oxygen Consumption; Time Factors

Topics: Animals; Antineoplastic Agents, Phytogenic; Carcinoma, Ehrlich Tumor; Hemoglobins; Leukocyte Count; Mice; Mice, Inbred A; Naphthoquinones