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Daily ingestion of fresh produce has increased tremendously due to a rise in awareness of its nutritional benefits that contribute to reducing health risks and disease. However, these commodities are highly perishable and prone to significant post-harvest losses. Conventional methods have been scrutinized in the production of undesirable by-products. Ozone technology has emerged as an efficient sterilization technique. Additionally, it stimulated the synthesis of bioactive and antioxidant compounds by activating secondary metabolic pathways. However, there are conflicting findings in the literature related to their impact on the quality and physiological processes of fruits and vegetables (F&V). This scientific literature review focuses on key studies examining the effects of ozonation on the growth of microorganisms and the quality preservation of different F&V. This review also enlarges our understanding of eco-friendly technologies which not only extend the shelf life of F&V but also uphold their quality without introducing harmful chemicals., 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.)

Ligand binding to G-quadruplex (G4) structures at human telomeric DNA ends promotes thermal stabilization, disrupting the interaction of the telomerase enzyme, which is found active in 80-85% of cancers and serves as a molecular marker. Anthraquinone compounds are well-known G-quadruplex (G4) binders that inhibit telomerase and induce apoptosis in cancer cells. Our current investigation is based on 1,5-bis[3-(diethylamino)propionamido]anthracene-9,10-dione, a derivative of anthraquinone and its binding characterization with two different human telomeric DNA structures, wHTel26 and HTel22, in the effect of K + and Na + by using an array of biophysical, calorimetry, molecular docking and cell viability assay techniques. Binding constants ( K b ) in the range of ∼10 5 -10 7 M -1 and stoichiometries of 1:1, 2:1 & 4:1 were obtained from the absorbance, fluorescence, and circular dichroism study. Remarkable hypochromism (55, 97%) and ∼17 nm shift in absorbance, fluorescence quenching (95, 97%), the unaltered value of fluorescence lifetime, restoration of Circular Dichroism bands, absence of ICD band, indicated the external groove binding/binding somewhere at loops. This is also evident in molecular docking results, the ligand binds to groove forming base (G4, G5, G24, T25) and in the vicinity to TTA loop (G14, G15, T17) bases of wHTel26 and HTel22, respectively. Thermal stabilization induced by ligand was found greater in Na + ion (27.5 °C) than (19.1 °C) in K + ion. Ligand caused cell toxicity in MCF-7 cancer cell lines with an IC 50 value of ∼8.4 µM. The above findings suggest the ligand, 1,5-bis[3-(diethylamino)propionamido]anthracene-9,10-dione could be a potent anticancer drug candidate and has great therapeutic implications.Binding of disubstituted amido anthraquinone derivative, 1,5-bis[3-(diethylamino)propionamido]anthracene-9,10-dione to human telomere HTel22 antiparallel conformation induced thermal stabilization.

Secondary metabolites are essential components for the survival of plants. Secondary metabolites in complex mixtures from plants have been adopted and documented by different traditional medicinal systems worldwide for the treatment of various human diseases. The extraction strategies are the key components for therapeutic development from natural sources. Polarity-dependent solvent-selective extraction, acidic and basic solution-based extraction, and microwave- and ultrasound-assisted extraction are some of the most important strategies for the extraction of natural products from plants. The method needs to be optimized to isolate a specific class of compounds. Therefore, to establish the mechanism of action, the characterization of the secondary metabolites, in a mixture or in their pure forms, is equally important. LC-MS, GC-MS, and extensive NMR spectroscopic strategies are established techniques for the profiling of metabolites in crude extracts. Various protocols for the extraction and characterization of a wide range of classes of compounds have been developed by various research groups and are described in this review. Additionally, the possible means of characterizing the compounds in the mixture and their uniqueness are also discussed. Hyphenated techniques are crucial for profiling because of their ability to analyze a vast range of compounds. In contrast, inherent chemical shifts make NMR an indispensable tool for structure elucidation in complex mixtures.

Occurrence of non-canonical G-quadruplex (G4) DNA structures in the genome have been recognized as key factors in gene regulation and several other cellular processes. The mosR and ndhA genes involved in pathways of oxidation sensing regulation and ATP generation, respectively, make Mycobacterium tuberculosis ( Mtb ) bacteria responsible for oxidative stress inside host macrophage cells. Circular Dichroism spectra demonstrate stable hybrid G4 DNA conformations of mosR / ndhA DNA sequences. Real-time binding of mitoxantrone to G4 DNA with an affinity constant ~10 5 -10 7 M -1 , leads to hypochromism with a red shift of ~18 nm, followed by hyperchromism in the absorption spectra. The corresponding fluorescence is quenched with a red shift ~15 nm followed by an increase in intensity. A change in conformation of the G4 DNA accompanies the formation of multiple stoichiometric complexes with a dual binding mode. The external binding of mitoxantrone with a partial stacking with G-quartets and/or groove binding induces significant thermal stabilization, ~20-29 °C in ndhA/mosR G4 DNA. The interaction leads to a two/four-fold downregulation of transcriptomes of mosR / ndhA genes apart from the suppression of DNA replication by Taq polymerase enzyme, establishing the role of mitoxantrone in targeting G4 DNA, as an alternate strategy for effective anti-tuberculosis action in view of deadly multi-drug resistant tuberculosis disease causing bacterial strains t that arise from existing therapeutic treatments.

According to current research, anti-cancer anthraquinones impact telomere disruption and may interact with G-quadruplex DNA that triggers signaling to apoptosis. The present study represents the biophysical investigation of oxidative stress, late apoptosis, and induced senescence among cancer cells after binding laboratory synthesized piperidine-based anthraquinone derivatives, 2, 6- Bis [(3-piperidino)acetamido)]anthracene-9,10-dione (N1P) and 2, 6-Bis [piperidino)propionamido]anthracene-9,10-dione (N2P), with G-quadruplex DNA. We employed biophysical approaches to explore the interaction of synthetic anthraquinone derivatives with quadruplex DNA sequences to influence biological activities in the presence of K + and Na + cations. The binding affinity for N2P and N1P are K b  = 5.8 × 10 6  M -1 and K b  = 1.0 × 10 6  M -1 , respectively, leading to hypo-/hyper-chromism with 5-7 nm red shift and significant fluorescence quenching and changes in ellipticity resulting in external binding of both the ligands to G-quadruplex DNA. Ligand binding induced enhancement of thermostability of G4 DNA is greater in Na + environment (ΔT m  = 34 °C) as compared to that in K + environment (ΔT m  = 21 °C), thereby restricting telomerase binding access to telomeres. Microscopic images of treated cells indicated cellular shape, nuclear condensation, and fragmentation alterations. The findings pave the path for therapeutic research, given the great potential of modifying anthraquinone substituent groups towards improved efficacy, ROS generation, and G-quadruplex DNA selectivity., Competing Interests: Declaration of competing interest All the authors declare that they do not have any financial or personal relationship and any conflicting interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

G-quadruplex is a non-canonical secondary structure identified in the telomeric region and the promoter of many oncogenes. Anthraquinone derivatives, a well-known inducer of telomere disruption in malignant cells and activate the apoptotic pathway. We used biophysical and biochemical studies to confirm the interaction of synthesized anthraquinone derivatives with the human telomeric G-quadruplex sequence. The binding affinity of N-2DEA and N-1DEA are K b  = 4.8 × 10 6 M -1 and K b  = 7.6 × 10 5 M -1 , respectively, leading to hypochroism, fluorescence quenching with minor redshift and ellipticity variations indicating ligand binding in the external groove. We found that sodium ions induced stabilization more rather than potassium ions. Molecular docking of complex demonstrates a molecule's exterior binding to a quadruplex. The investigation of ROS activity indicated that the cell initiates mortality in response to the IC 50 concentration. Cellular morphology, nuclear condensation, and fragmentation were altered in the treated cell, impairing cellular function. Finally, the transcriptional regulatory study paves the way for drug design as an anti-cancer agent because of the tremendous possibilities of changing substituent groups on anthraquinones to improve efficacy and selectivity for G-quartet DNA. Our research focused on how ligand binding to telomere sequences induces oxidative stress and inhibits the growth of malignant cells., Competing Interests: The authors declare no competing interests., (© 2022.)

Besides inhibiting DNA duplication, DNA dependent RNA synthesis and topoisomerase-II enzyme action, anticancer drug adriamycin is found to cause telomere dysfunction and shows multiple strategies of action on gene functioning. We present evidence of binding of adriamycin to parallel stranded intermolecular [d-(TTAGGGT)] 4 G-quadruplex DNA comprising human telomeric DNA by proton and phosphorus-31 nuclear magnetic resonance spectroscopy. Diffusion ordered spectroscopy shows formation of complex between the two molecules. Changes in chemical shift and line broadening of DNA and adriamycin protons suggest participation of specific chemical groups/moieties in interaction. Presence of sequential nuclear Overhauser enhancements at all base quartet steps and absence of large downfield shifts in 31 P resonances give clear proof of absence of intercalation of adriamycin chromophore between base quartets. Restrained molecular dynamics simulations using observed 15 short intermolecular inter proton distance contacts depict stacking of ring D of adriamycin with terminal G6 quartet by displacing T7 base and external groove binding close to T1-T2-A3 bases. The disappearance of imino protons monitored as a function of temperature and differential scanning calorimetry experiments yield thermal stabilization of 24 °C, which is likely to come in the way of telomerase association with telomeres. The findings pave the way for design of alternate anthracycline based drugs with specific modifications at ring D to enhance induced thermal stabilization and use alternate mechanism of binding to G-quadruplex DNA for interference in functional pathway of telomere maintenance by telomerase enzyme besides their well known action on duplex DNA. Communicated by Ramaswamy H. Sarma.

Anthracycline anticancer drugs show multiple strategies of action on gene functioning by regulation of telomerase enzyme by apoptotic factors, e.g. ceramide level, p53 activity, bcl-2 protein levels, besides inhibiting DNA/RNA synthesis and topoisomerase-II action. We report binding of epirubicin with G-quadruplex (G4) DNA, [d-(TTAGGGT)] 4 , comprising human telomeric DNA sequence TTAGGG, using 1 H and 31 P NMR spectroscopy. Diffusion ordered spectroscopy, sequence selective changes in chemical shift (~0.33 ppm) and line broadening in DNA signals suggest formation of a well-defined complex. Presence of sequential nuclear Overhauser enhancements at all base quartet steps and absence of large downfield shifts in 31 P resonances preclude intercalative mode of interaction. Restrained molecular dynamics simulations using AMBER force field incorporating intermolecular drug to DNA interproton distances, involving ring D protons of epirubicin depict external binding close to T1-T2-A3 and G6pT7 sites. Binding induced thermal stabilization of G4 DNA (~36 °C), obtained from imino protons and differential scanning calorimetry, is likely to come in the way of telomerase association with telomeres. The findings pave the way for drug-designing with modifications at ring D and daunosamine sugar., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Prosthetic valve thrombosis (PVT) is an uncommon but serious cause of morbidity and mortality after cardiac valve implantation. The most common cause leading to PVT is inadequate anticoagulation. Royal Darwin Hospital is a major referral centre for the Top End of Australia and is unique in having a high burden of rheumatic heart disease (RHD) requiring valve surgery, issues with adherence with oral anticoagulants, and the absence of onsite cardiothoracic facility., Methods: We report clinical characteristics and outcomes of consecutive patients presenting with PVT to a single centre without on-site cardiothoracic surgery., Results: Thirty-two (32) episodes involving 21 patients were retrospectively identified between 2000 and 2017. Our cohort had an average age of 37 years. Nineteen (19) patients were of Aboriginal or Torres Strait Islander descent. All valves were mechanical, except for one bioprosthetic mitral valve, with average time from implantation to initial PVT 5.1 years. The majority of patients were in New York Heart Association (NYHA) class III and IV (6%, and 66%, respectively). Anti-coagulation was sub-therapeutic in 88% of presentations. Eleven (11) (34%) presentations were recurrent PVT involving eight patients. Twenty-six (26) (82%) episodes were treated with thrombolytic therapy which achieved complete success in 65% and partial success in 19%. Five (5) patients received a second dose of the lytic agent. Of the four patients not responding to thrombolytic therapy, two died and two were urgently transferred to a facility with on-site cardiothoracic surgery. Five (5) out of 32 episodes resulted in death (16%) with overall mortality 24% for the cohort over the entire time period. Thrombolytic therapy was associated with five major bleeding episodes (16%) including two fatal bleeds., Conclusions: Prosthetic valve thrombosis is a rare but life-threatening complication of prosthetic valves, with the vast majority of patients found to be inadequately anticoagulated. Despite differences in thrombolytic agents these were successful in the majority of patients., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)

Adriamycin is known to exert its anti cancer action by inhibiting DNA duplication, RNA transcription and topoisomerase-II enzyme action. Recent findings of its binding to G-quadruplex DNA resulting in telomere dysfunction indicated multiple strategies of its action. The interaction of anticancer drug adriamycin with parallel stranded inter molecular G-quadruplex DNA [d-(TTAGGGT)] 4 comprising human telomeric DNA sequence TTAGGG was investigated by absorption, fluorescence, circular dichroism and nuclear magnetic resonance spectroscopy to understand mode of their interaction. The adriamycin binds as monomer to G-quadruplex DNA with affinity (K b1 = 9.8x10 5 M -1 and K b2 = 6.7x10 5 M -1 ) higher than that reported for daunomycin, at two independent sites, mainly in terminal stacking and groove binding modes. The bound complex formed as a result of specific interactions induces thermal stabilization of DNA by 12.5-28.1°C, which is likely to hinder telomere association with telomerase enzyme and contribute significantly to adriamycin-induced apoptosis in cancer cell lines. The findings have therapeutic potential towards drug designing by way of altering substituent groups on anthracyclines to enhance efficacy using additional mechanism of targeting pathway of telomere maintenance by disrupting telomerase association with telomeres., (© 2019 John Wiley & Sons, Ltd.)

Epirubicin exerts its anti cancer action by blocking DNA/RNA synthesis and inhibition of topoisomerase-II enzyme. Recent reports on its influence on telomere maintenance, suggest interaction with G-quadruplex DNA leading to multiple strategies of action. The binding of epirubicin with parallel stranded inter molecular G-quadruplex DNA [d-(TTAGGGT)] 4 comprising human telomeric DNA sequence TTAGGG was investigated by absorption, fluorescence, circular dichroism and nuclear magnetic resonance spectroscopy. The epirubicin binds as monomer to G-quadruplex DNA with affinity, K b1  = 3.8 × 10 6 M -1 and K b2  = 2.7 × 10 6 M -1 , at two independent sites externally. The specific interactions induce thermal stabilization of DNA by 13.2-26.3 °C, which is likely to come in the way of telomere association with telomerase enzyme and contribute to epirubicin-induced apoptosis in cancer cell lines. The findings pave the way for drug designing in view of the possibility of altering substituent groups on anthracyclines to enhance efficacy using alternate mechanism of its interaction with G4 DNA, causing interference in telomere maintenance pathway by inducing telomere dysfunction., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Coralyne is an important alkaloid due to its anti-cancer and other medicinal properties. It targets DNA in cells and acts as human topoisomerase-I poison, telomerase inhibitor and nucleic acid intercalator. It has high tendency to undergo self-association, which is a matter of concern for therapeutic applications. The understanding of its interaction with DNA requires precise knowledge of chemical shifts in Nuclear Magnetic Resonance (NMR) spectra besides self-association. The present study is the first report of a complete assignment of all 1 H/ 13 C resonances in NMR spectra of coralyne in DMSO-d 6 using one dimensional 1 H/ 13 C and two dimensional NMR experiments. The chemical shift of all proton and several 13 C resonances have also been obtained in D 2 O and ethanol-d 6 . The same has been calculated using Density Functional Theory (DFT). NMR spectra of coralyne show upfield shift of 0.6-1.2 ppm in aromatic ring protons suggesting stacking interactions. Apart from 11 intra molecular NOE cross peaks in 2D 1 H- 1 H ROESY spectra, 3 short distance NOE correlations, H6-10OCH 3 , H5-10OCH 3 and H12-16CH 3 , give direct independent evidence of the formation of a stacked dimer. The absorbance, fluorescence, circular dichroism and fluorescence lifetime experiments conducted in the present investigations corroborate results obtained by NMR., (© 2019 Xi'an Jiaotong University. Production and hosting by Elsevier B.V.)

Recent reports suggest influence of anti-cancer anthracyclines on telomere dysfunction and their possible interaction with G-quadruplex (G4) DNA as an alternate pathway to apoptosis. We have investigated interaction of epirubicin and adriamycin with G4 DNA [d-AGGG(TTAGGG) 3 ] comprising human telomeric DNA sequence by surface plasmon resonance, absorption, fluorescence, circular dichroism and thermal denaturation. Epirubicin and adriamycin bind with affinity, K b , = 2.5×10 5 and 5.2×10 5 M -1 , respectively in monomeric form leading to decrease in absorbance, fluorescence quenching and ellipticity changes without any significant shift in absorption emission maxima with corresponding induced thermal stabilization by 13.0 and 11.6°C in K + rich solution. Na + ions did not induce any thermal stabilization. Molecular docking confirmed external binding at grooves and loops of G4 DNA involving 4OCH 3 of ring D, 9COCH 2 OH of ring A, 4'OH/H and 3'NH 3 + of daunosamine sugar. Thermal stabilization induced by specific interactions is likely to hamper telomere association with telomerase enzyme and contribute to drug-induced apoptosis in cancer cell lines besides causing damage to duplex DNA. The findings pave the way for drug designing in view of immense possibilities of altering substituent groups on anthracyclines for enhancement of efficacy, reduced cell toxicity as well as specificity towards G-quadruplex DNA., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Guanine rich DNA sequences form four stranded G-quadruplex structures found in telomeric DNA and oncogene promoters. Small molecules binding and stabilizing the G-quadruplex disrupt telomere maintenance and gene regulation, thereby limiting the proliferation of cancer cells. The anti-cancer drug daunomycin binds to both G-quadruplex DNA and duplex DNA. We have undertaken a study of interaction of daunomycin to [d-(TTGGGGT)] 4 comprising telomeric DNA sequence from Tetrahymena thermophilia to understand the mechanisms of its action. Absorbance, fluorescence and circular dicroism spectra show significant change on interaction with no change in wavelength maxima. The daunomycin dimers present in free state in solution are disrupted on binding. Presence of all sequential short inter proton distance contacts in nuclear magnetic resonance spectra confirm external binding. The observed inter molecular nuclear Overhauser enhancements, changes in chemical shift and molecular docking studies establish well defined binding of daunomycin at two different sites of G-quadruplex DNA. Thermal stabilization of [d-(TTGGGGT)] 4 by 10-15 °C upon daunomycin binding is expected to reduce access of telomerase to its functional site at telomeres. The present studies on mode of action pave the way for alternate derivatives/analogues by chemical modification of anthracyclines to arrive at a more potent telomerase inhibitor., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The anticancer drug daunomycin exerts its influence by multiple strategies of action to interfere with gene functioning. Besides inhibiting DNA/RNA synthesis and topoisomerase-II, it affects the functional pathway of telomere maintenance by the telomerase enzyme. We present evidence of the binding of daunomycin to parallel-stranded tetramolecular [d-(TTGGGGT)]₄ guanine (G)-quadruplex DNA comprising telomeric DNA from Tetrahymena thermophilia by surface plasmon resonance and Diffusion Ordered SpectroscopY (DOSY). Circular Dichroism (CD) spectra show the disruption of daunomycin dimers, suggesting the end-stacking and groove-binding of the daunomycin monomer. Proton and phosphorus-31 Nuclear Magnetic Resonance (NMR) spectroscopy show a sequence-specific interaction and a clear proof of absence of intercalation of the daunomycin chromophore between base quartets or stacking between G-quadruplexes. Restrained molecular dynamics simulations using observed short interproton distance contacts depict interaction at the molecular level. The interactions involving ring A and daunosamine protons, the stacking of an aromatic ring of daunomycin with a terminal G6 quartet by displacing the T7 base, and external groove-binding close to the T1⁻T2 bases lead to the thermal stabilization of 15 °C, which is likely to inhibit the association of telomerase with telomeres. The findings have implications in the structure-based designing of anthracycline drugs as potent telomerase inhibitors.

Interaction of mitoxantrone (MTX) with G-quadruplex, leading to inhibition of telomerase enzyme and anticancer action, is not understood. Titrations of MTX with [d-(TTAGGGT)] 4 , comprising human telomere single repeat sequence, have been monitored by fluorescence and 1 H/ 31 P NMR spectroscopy. Binding induces chemical shift changes in GNH (~0.3ppm), T2/T7/A3 base protons and sequence specific shifts in 31 P resonances. Absence of large downfield shifts in 31 P signals and presence of all sequential NOEs show that classical intercalation of drug between base quartets does not occur. The upfield shift (~0.53ppm) in 2/3H, 1/4OH and minor shift in 6/7H aromatic protons of MTX in complex rule out end stacking as a possible mode of interaction. The 26 short inter molecular contacts of 1/4OH, 11NH, 6/7H and 12CH 2 protons of MTX with T1, T2, G6, G7 protons in the structure of complex obtained by restrained Molecular Dynamics simulations show binding at grooves accompanied by 4 hydrogen bonds and partial stacking of MTX with base pairs. Interaction causes thermal stabilization, ΔT m =35°C, which may be attributed to telomerase inhibition. The present study is the first report on solution structure of mitoxantrone-[d-(TTAGGGT)] 4 complex and is significant for structure based designing of anthraquinone derivatives as future drugs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Plant derived small molecules, which interact with and stabilize G-quadruplex DNA, act as inhibitors of telomere elongation and oncogene expression in humans. The inhibition of telomerase enzyme has immense potential since it is over expressed in most cancer cells. Interaction of palmatine, an antitumor alkaloid, to parallel G-quadruplex DNA, [d(TTGGGGT)] 4 and [d(TTAGGGT)] 4 , has been investigated using Nuclear Magnetic Resonance (NMR), fluorescence and Circular Dichroism (CD) spectroscopy. Titrations were monitored by 1 H and 31 P NMR spectra and solution structure of palmatine-[d(TTGGGGT)] 4 complex was obtained by restrained Molecular Dynamics (rMD) simulations using distance restraints from 2D NOESY spectra. Thermal stabilization of DNA was determined by CD, 1 H NMR and Differential Scanning Calorimetry (DSC). Binding of palmatine induces 98% enhancement of fluorescence accompanied by blue shift ∼8 nm. CD spectral bands of DNA show minor changes. Diffusion NMR studies confirm formation of a stable complex. Proton NMR signals of palmatine shift upfield upon binding and NOE cross peaks of H10, H3, H28, 5OCH 3 protons with T2, A3/G3, G6 and T7 residues reveal dual recognition sites in both G-quadruplex DNA sequences, resulting in thermal stabilization of G-quadruplex by ∼13-17 °C. Restrained molecular dynamics simulations using NOE distance restraints for 2:1 palmatine-[d(TTGGGGT)] 4 complex reveal end-stacking of palmatine at G6pT7 step and groove binding along T2pG3 step. Binding to [d(TTAGGGT)] 4 takes place at T2pA3pG4 and G6pT7 steps. Structural features of molecular recognition of two different G-quadruplex DNA sequences by palmatine have relevance in rational drug development for anti-cancer therapy., (Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.biochi.2018.02.002. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal., (Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

Background: Telomere elongation by telomerase gets inhibited by G-quadruplex DNA found in its guanine rich region. Stabilization of G-quadruplex DNA upon ligand binding has evolved as a promising strategy to target cancer cells in which telomerase is over expressed., Methods: Interaction of anti-leukemic alkaloid, coralyne, to tetrameric parallel [d(TTGGGGT)] 4 (Ttel7), [d(TTAGGGT)] 4 (Htel7) and monomeric anti-parallel [dGGGG(TTGGGG) 3 ] (Ttel22) G-quadruplex DNA has been studied using Circular Dichroism (CD) spectroscopy. Titrations of coralyne with Ttel7 and Htel7 were monitored by 1 H and 31 P NMR spectroscopy. Solution structure of coralyne-Ttel7 complex was obtained by restrained Molecular Dynamics (rMD) simulations using distance restraints from 2D NOESY spectra. Thermal stabilization of DNA was determined by absorption, CD and 1 H NMR., Results and Conclusions: Binding of coralyne to Ttel7/Htel7 induces negative CD band at 315/300nm. A significant upfield shift in all GNH, downfield shift in T2/T7 base protons and upfield shift (1.8ppm) in coralyne protons indicates stacking interactions. 31 P chemical shifts and NOE contacts of G3, G6, T2, T7 protons with methoxy protons reveal proximity of coralyne to T2pG3 and G6pT7 sites. Solution structure reveals stacking of coralyne at G6pT7 and T2pG3 steps with two methoxy groups of coralyne located in the grooves along with formation of a hydrogen bond. Binding stabilizes Ttel7/Htel7 by ~25-35°C in 2:1 coralyne-Ttel7/Htel7 complex., General Significance: The present study is the first report on solution structure of coralyne-Ttel7 complex showing stacking of coralyne with terminal guanine tetrads leading to significant thermal stabilization, which may be responsible for telomerase inhibition., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Binding of coralyne to tetra-molecular parallel G-quadruplex DNA [d(TTGGGGT)] 4 was evaluated for the first time using biophysical techniques. Absorbance titrations show hypo/hyper-chromism accompanied by 12nm red shift with binding constant K b =0.2-4.0×10 6 M -1 . Binding induces a negative circular dichroism band of coralyne at 315nm. Quenching of fluorescence (~64%) along with 10nm blue shift in emission maxima indicates proximity of coralyne to guanine bases. Job plot indicates existence of multiple complexes. The observed two fluorescence life times, 6 and 12ns, with relative abundance 33% and 63%, respectively suggest two binding sites/conformations in complex. 1D 1 H NMR spectra reveal significant broadening and upfield shift of G3NH, G6NH and G3H8 proton signals upon binding. The NOESY spectra reveal sequence specific non-intercalative interaction of coralyne in monomeric form at two sites close to A3/G3 and G6 bases of [d(TTGGGGT)] 4 and [d(TTAGGGT)] 4 , which has implications in anti-cancer drug action., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Stabilization of G-quadruplex DNA structures in human telomeric and proto-oncogenic promoter regions upon ligand binding has evolved as a viable anti-cancer strategy. We have studied interaction of coralyne, a human telomerase inhibiting protoberberine alkaloid, with parallel stranded tetrameric G-quadruplex DNA [d(T 2 G 4 T)] 4 using Circular Dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. Appearance of induced CD band and the Diffusion Ordered NMR Spectroscopy (DOSY) experiments confirm the formation of well defined coralyne-DNA complex. 1 H and 31 P NMR studies reveal that coralyne specifically recognizes T2pG3 and G6pT7 steps in DNA. Guanine imino protons indicate that coralyne binding induces thermal stabilization of the G-quadruplex DNA by >20°C. The observed specific changes and thermal stabilization of DNA upon binding may be attributed to inhibition of telomerase by coralyne., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Small molecule ligands which specifically bind and stabilize G-quadruplex structures in telomeric ends inhibit the activity of telomerase enzyme, an important marker for cancer. Understanding of the binding mode of ligand-G quadruplex complex is important for evaluating relative efficacy of anti-tumor drugs. The present study is focused on interaction of anti-tumor drug mitoxantrone (MTX) with tetra-molecular parallel stranded G-quadruplex sequence d-TTGGGGT using absorbance, fluorescence and circular dichroism spectroscopy techniques. Absorbance of mitoxantrone shows hypochromism up to MTX (D)/DNA quadruplex (N) ratio ~5, followed by hyperchromism up to D/N=0.21 accompanied by a red shift of 15nm. The fluorescence emission of MTX shows decrease up to D/N ~5 and then increases with red shift of 8nm. The two observed fluorescent lifetimes, 0.17ns (91%) and 0.44ns (9%), indicate dual binding mode. Absence of isobestic and isoemissive point indicates presence of multiple complexes. Circular Dichroism spectra showing positive induced band at 645nm and two exciton bands centered at 619 and 664nm suggest binding of mitoxantrone as a dimer. Proton NMR studies show intermolecular MTX-MTX short contacts confirming existence of stacked dimer of MTX. Thermal melting transitions of DNA saturate at D/N=4 with ΔTm=25°C. The results establish highly specific external groove binding of 4 molecules of mitoxantrone as two dimers at two distinct sites of DNA., (Copyright © 2015. Published by Elsevier B.V.)

The formation of complex between anti-cancer drug mitoxantrone (MTX) and tetra-molecular parallel G-quadruplex DNA [d-(TTGGGGT)]4 has been studied by solution state one and two dimensional NMR spectroscopy. Mitoxantrone forms a head-to-tail dimer and binds at two opposite grooves of the G-quadruplex. The Job's method of continuous variation and thermal melting studies independently ascertain binding stoichiometry of 4:1 in mitoxantrone:DNA complex. The existence of only four guanine NH peaks corresponding to the four G-quartets during the course of titration shows that C4 symmetry of G-quadruplex is intact upon binding of mitoxantrone. The specific inter molecular short distance contacts between protons of two mitoxantrone molecules of dimer, that is, ring A protons with ring C and side chain methylene protons, confirms the formation of mitoxantrone head-to-tail dimer. The observed 38 Nuclear Overhauser Enhancement (NOE) cross peaks between MTX and G-quadruplex DNA indicate formation of a well-defined complex. The three dimensional structure of 4:1 mitoxantrone:[d-(TTGGGGT)]4 complex computed by using experimental distance restraints followed by restrained Molecular Dynamics (rMD) simulations envisages the critical knowledge of specific molecular interactions within ligand-G-quadruplex complex. The findings are of direct interest in development of anti-cancer therapeutic drug based on G-quadruplex stabilization, resulting in telomerase inhibition., (Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

The interaction of the anthraquinone derivative mitoxantrone, a semisynthetic anti-cancer drug with two non-planar side chains, with heptamer G-quadruplex d(TTAGGGT)4 , which contains the human telomere DNA sequence, was evaluated by differential scanning calorimetry, fluorescence Job plotting, absorption, and NMR and CD spectroscopy. Binding led to thermal stabilization of DNA (ΔTm =13-20 °C). The spectra revealed that two mitoxantrone molecules bind externally at two sites of the DNA quadruplex as monomers, by partial insertion of the chromophore and side-chain interaction at the grooves. The inhibition of telomerase (IC50 =2 μM), as determined by a TRAP assay, can be attributed to thermal stabilization of the DNA quadruplex because of the interactions with mitoxantrone. The studies revealed highly specific molecular recognition between a ligand and a parallel-stranded G-quadruplex; this might serve as a platform for the rational design of new drugs., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hoppea fastigiata, an annual medicinal herb belonging to the Gentianaceae, is mostly found in South Asian countries, and is used by local tribes for various brain-related ailments. The genus possesses a unique class of compounds, xanthones, which are known for their potential against Alzheimer's and Parkinson's diseases. Limited availability and the potential pharmacological significance of the plants has led to the establishment of in vitro cultures of H. fastigiata and study of its neuroprotective principles. In vitro plantlets were established from the apical meristem of the plant in Murashige and Skoog medium with a combination of the phytohormones 6-benzylaminopurine (1 mg/L) and kinetin (0.1 mg/L), which was found to be efficacious with a growth index of 0.9 ± 0.01 after 30 days. Four different solvent extracts of in vitro cultures were evaluated for acetylcholinesterase (AChE) and monoamine oxidase A and B (MAO-A and MAO-B) inhibitory activities, amongst which the ethanolic extract showed the lowest IC50 value in all the assays. Three major compounds were isolated from the ethanolic extract and structurally confirmed as 1,5,7-trihydroxy-3-methoxyxanthone (1), 1,5-dihydroxy-3,7-dimethoxyxanthone (2) and 1,3,5-trihydroxy-8-methoxyxanthone (3). Compound 3 showed the strongest AChE inhibitory activity with mixed-type inhibition. Compounds 1 and 2 also showed promising AChE inhibitory properties with mixed and non-competitive types of inhibition, respectively. Compounds 1 and 2 showed inhibition of MAO-A (mixed and competitive, respectively) and compounds 2 and 3 showed inhibition of MAO-B (competitive and mixed, respectively). Extracts and isolated compounds showed good antioxidant capacities. The ethanolic extract and compound 2 showed the strongest antioxidant activities among the other solvent extracts and compounds, respectively.

Mitoxantrone is a promising antitumor drug having considerably reduced cardiotoxicity as compared to anthracyclines. Its binding to deoxyhexanucleotides sequence d-(ATCGAT)2 has been studied by proton and phosphorous-31 nuclear magnetic resonance spectroscopy. The stoichiometry reveals that 1:1 and 2:1 mitoxantrone-d(ATCGAT)2 complexes are formed in solution. Significant upfield shifts in 6H/7H, 2H/3H, 11NH, and 12NH protons (∼.5 ppm) of mitoxantrone and T6NH imino protons (∼.3 ppm) are observed. The phosphorous resonances do not shift significantly indicating that the base pairs do not open at any nucleotide step along the sequence of hexamer. Several inter-molecular Nuclear Overhauser Enhancement connectivities between mitoxantrone and hexanucleotide protons indicate that mitoxantrone chromophore stacks with terminal A1-T6 base pair and side chains involving 12CH2, 12NH, and 14OH protons are in close proximity of A1, T2, A5, and T6 bases. Absorption and emission spectra show red shift in wavelength maxima, which is characteristic of stacking interaction. At higher mitoxantrone to nucleic acid ratios, electrostatic interactions are dominant. The 2:1 drug/DNA stoichiometric structure obtained by restrained Molecular Dynamics simulations shows considerable distortions in backbone torsional angles and helicoidal parameters although structural fluctuations in 25 ps analysis of trajectory are found to be negligible. Mitoxantrone binds as a monomer at either or both ends of hexamer externally with side chains interacting specifically with DNA. The findings are relevant to the understanding of pharmacological action of drug.

The interaction of mitoxantrone with alternating Poly(dG-dC).Poly(dG-dC) and Poly(dA-dT).Poly(dA-dT) duplex has been studied by absorption, fluorescence and Circular Dichroism (CD) spectroscopy at Drug to Phosphate base pair ratios D/P=20.0-0.04. Binding to GC polymer occurs in two distinct modes: partial stacking characterized by red shifts of 18-23nm at D/P=0.2-0.8 and external binding at D/P=1.0-20.0 whereas that to AT polymer occurs externally in the entire range of D/P. The binding constant and number of binding sites is 3.7×10(5)M(-1), 0.3 and 1.3× 10(4)M(-1), 1.5 in GC and AT polymers, respectively at low D/P ratios. CD binding isotherms show breakpoints at D/P=0.1, 0.5 and 0.25, 0.5 in GC and AT polymers, respectively. The intrinsic CD bands indicate that the distortions in GC polymer are significantly higher than that in AT polymer. Docking studies show partial insertion of mitoxantrone rings between to GC base pairs in alternating GC polymer. Side chains of mitoxantrone interact specifically with base pairs and DNA backbone. The studies are relevant to the understanding of suppression or inhibition of DNA cleavage on formation of ternary complex with topoisomerase-II enzyme and hence the anti cancer action., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The interaction of mitoxantrone with d-(CTCGAG)2 has been studied by absorption, fluorescence and circular dichroism (CD) spectroscopy. The hypochromism and quenching of fluorescence showed that about four mitoxantrone molecules may be binding externally to DNA hexamer sequence at high drug to nucleic (D/N) acid duplex ratios (28.0-1.1). At lower D/N ratios (1.0-0.2), a red shift in absorption maxima at 610 and 660 nm by 15 and 20 nm, respectively and a red shift in emission maxima by 11 nm accompanied by increase in absorbance and emission has been observed. The equilibrium constant for binding at low (1.0-0.2) and high (28.0-1.1) D/N ratios is 1.8×10(5) M(-1) and 1.38×10(6) M(-1), respectively. The CD spectra show change in intensity of bands accompanied by appearance of induced bands at 325 nm and 650-700 nm. The 251 nm band shows blue shift at D/N ratio of 0.25 and 0.5. The binding isotherms show stoichiometry of 0.25 and 0.5 mitoxantrone molecules binding per duplex. The results suggest stacking of aromatic chromophore of mitoxantrone with terminal base pair of DNA strand forming a sandwiched structure of mitoxantrone between four and two duplex molecules. These investigations are relevant to the formation of ternary complex with topoisomerase enzyme and hence an understanding of anti tumor action of mitoxantrone., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Fluorescence studies on the indole alkaloids vinblastine sulfate, vincristine sulfate, vincamine and catharanthine have demonstrated the DNA binding ability of these molecules. The binding mode of these molecules in the minor groove of DNA is non-specific. A new parameter of the purine-pyrimidine base sequence specificty was observed in order to define the non-specific DNA binding of ligands. Catharanthine had shown 'same' pattern of 'Pu-Py' specificity while evaluating its DNA binding profile. The proton resonances of a DNA decamer duplex were assigned. The models of the drug:DNA complexes were analyzed for DNA binding features. The effect of temperature on the DNA binding was also evaluated.

Trans activation response (TAR) region is an RNA target of considerable importance in controlling the replication cycle of the human immunodeficiency virus (HIV). At a transcriptional level, HIV-1 is regulated by means of the interaction between Tat protein and TAR RNA. The TAR-Tat complex is an attractive target for developing novel antiviral drugs. Herein, the recognition modes of 8 structurally different ligands, as mimics of Tat protein, in complex with a TAR RNA are investigated using the DOCK 6.4 flexible docking protocol in association with the newly-implemented scoring function AMBER including solvation implicitly through the generalized Born solvent-accessible surface area (GB/SA) continuum model. The TAR RNA-ligand interactions are further characterized and contrasted using the nature of separate contributions to the stability of the complexes. Several interesting implications for the key challenge, the development of low molecular weight ligands binding to HIV-1 TAR RNA with high affinity and specificity, are discussed.

Numbers of drugs are being synthesized every year to meet the target of safe and disease-free society. Presently molecular modeling technique is used to unfold the mechanism of action of drugs alone or in conjunction with experimental methodologies. There are a number of drugs which are successfully developed using this methodology. Mitoxantrone (MTX) - 1, 4-dihydroxy-5, 8-bis {[2-(2-hydroxyethyl) amino] amino}-9, 10-anthracenedione is marketed under the name Novantrone, an anticancer drug used in chemotherapy. Its important analog ametantrone and various other analogs differ from one another in the position of side chain or functionalities on the chromophore eventually exhibit varied biological activities. DNA binding is an important phenomenon for anticancer activity of these drugs. In order to understand the interactions of the drug molecules with its receptor site, at atomic level, we have carried out computer simulations of drug and DNA alone and also in complex mode in water as a medium. All the simulations are being carried out using molecular operating environment (MOE) and X3DNA software tools on SUN SOLARIS platform. Interaction energy of all the drug molecules with DNA is determined and compared. Also the structural changes in DNA and drug before and after complex formation are studied extensively.

The complexes of adriamycin-d-(TGATCA)(2) and 4'-epiadriamycin-d-(CGATCG)(2) are studied by one- and two-dimensional (31)P nuclear magnetic resonance spectroscopy (NMR) at 500 MHz in the temperature range 275-328 K and as a function of drug to DNA ratio (0.0-2.0). The binding of drug to DNA is clearly evident in (31)P-(31)P exchange NOESY spectra that shows two sets of resonances in slow chemical exchange. The phosphate resonances at the intercalating steps, T1pG2/C1pG2 and C5pA6/C5pG6, shift downfield up to 1.7 ppm and that at the adjacent step shift downfield up to 0.7 ppm, whereas the central phosphate A3pT4 is relatively unaffected. The variations of chemical shift with drug to DNA ratio and temperature as well as linewidths are different in each of the two complexes. These observations reflect change in population of B(I)/B(II) conformation, stretching of backbone torsional angle zeta, and distortions in O-P-O bond angles that occur on binding of drug to DNA. To the best of our knowledge, there are no solution studies on 4'-epiadriamycin, a better tolerated drug, and binding of daunomycin or its analogue to d-(TGATCA)(2) hexamer sequence. The studies report the use of (31)P NMR as a tool to differentiate various complexes. The specific differences may well be the reasons that are responsible for different antitumor action of these drugs due to different binding ability and distortions in DNA., (Copyright (c) 2009 John Wiley & Sons, Ltd.)