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pK a of a compound is crucial for determining the contributions of different forms of it towards overall binding with DNA. Hence it is important to use correct pK a values in DNA interaction studies. This study takes a look at the importance of pK a values to realize binding of compounds with DNA. Since pK a of a compound determined in the presence of DNA is quite different from that determined in its absence hence, presence of different forms of a compound during interaction with DNA is different from that realized if the determination of pK a is done in normal aqueous solution in absence of DNA. Hence, calculations determining contributions of different forms of a compound interacting with DNA are affected accordingly. Two simple analogues of anthracyclines, alizarin and purpurin, were used to investigate the influence DNA has on pK a values. Indeed, they were different in presence of DNA than when determined in normal aqueous solution. pK a1 for alizarin and purpurin determined in the absence and presence of calf thymus DNA were used in equations that determine contributions of two forms (neutral and anionic) towards overall binding with DNA. The study concludes that correct pK a values, determined correctly i.e. under appropriate conditions, must be used for DNA binding experiments to evaluate contributions of individual forms., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A 1 : 2 copper(II) complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) having the molecular formula CuQ2 was prepared and characterized by elemental analysis, NMR, FTIR, UV-vis and mass spectroscopy. The powder diffraction of the solid complex, magnetic susceptibility and ESR spectra were also recorded. The presence of the planar anthraquinone moiety in the complex makes it extremely difficult to obtain a single crystal suitable for X-ray diffraction studies. To overcome this problem, density functional theory (DFT) was used to evaluate an optimized structure of CuQ2. In the optimized structure, it was found that there is a tilt of the two planar aromatic anthraquinone rings of the complex with respect to each other in the two planes containing the O-Cu(II)-O plane. The present study is an important addition to the understanding of the structural aspects of metal-anthracyclines because there are only a few reports on the actual structures of metal-anthracyclines. The theoretical vibrational spectrum of the complex was assigned with the help of vibrational energy distribution analysis (VEDA) using potential energy distribution (PED) and compared with experimental results. Being important in producing the biochemical action of this class of molecules, the electrochemical behavior of the complex was studied in aqueous and non-aqueous solvents to find certain electrochemical parameters. In aqueous media, reduction involves a kinetic effect during electron transfer at an electrode surface, which was characterized very carefully using cyclic voltammetry. Electrochemical studies showed a significant modification in the electrochemical properties of 1-amino-4-hydroxy-9,10-anthraquinone (QH) when bound to Cu(II) in the complex compared to those observed for free QH. This suggests that the copper complex might be a good choice as a biologically active molecule, which was reflected in the lack of stimulated superoxide generation by the complex.

Copper(II) forms a complex with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaQSH(2)), an analogue of the core unit of anthracycline antibiotics used in the treatment of cancer. The 1:2 metal-ligand complex is formed in aqueous solution at neutral and acidic pH while in alkaline pH both 1:1 and 1:2 species are formed. The effective stability constant of the 1:2 metal-ligand complex is 9.64x10(16) while that of the 1:1 metal-ligand complex is 9.4x10(9). The 1:2 complex Cu(NaQSH)(2)(H(2)O)(2) was synthesized and characterized by different techniques in solid state and in solution. The complex Cu(NaQSH)(2)(H(2)O)(2) interacts with calf thymus DNA which was studied by fluorescence spectroscopy. The binding constant and site size for the interaction with DNA were determined.

A 1 : 2 copperII complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) having the molecular formula CuQ2 was prepared and characterized by elemental analysis, NMR, FTIR, UV-vis and mass spectroscopy. The powder diffraction of the solid complex, magnetic susceptibility and ESR spectra were also recorded. The presence of the planar anthraquinone moiety in the complex makes it extremely difficult to obtain a single crystal suitable for X-ray diffraction studies. To overcome this problem, density functional theory (DFT) was used to evaluate an optimized structure of CuQ2. In the optimized structure, it was found that there is a tilt of the two planar aromatic anthraquinone rings of the complex with respect to each other in the two planes containing the O–Cu(ii)–O plane. The present study is an important addition to the understanding of the structural aspects of metal-anthracyclines because there are only a few reports on the actual structures of metal-anthracyclines. The theoretical vibrational spectrum of the complex was assigned with the help of vibrational energy distribution analysis (VEDA) using potential energy distribution (PED) and compared with experimental results. Being important in producing the biochemical action of this class of molecules, the electrochemical behavior of the complex was studied in aqueous and non-aqueous solvents to find certain electrochemical parameters. In aqueous media, reduction involves a kinetic effect during electron transfer at an electrode surface, which was characterized very carefully using cyclic voltammetry. Electrochemical studies showed a significant modification in the electrochemical properties of 1-amino-4-hydroxy-9,10-anthraquinone (QH) when bound to CuII in the complex compared to those observed for free QH. This suggests that the copper complex might be a good choice as a biologically active molecule, which was reflected in the lack of stimulated superoxide generation by the complex. [ABSTRACT FROM AUTHOR]

Hydroxy-9,10-anthraquinones resemble anthracycline-based anticancer drugs. By varying the pH of the solution, the proton dissociation constants of 1,2,5,8-tetrahydroxy-9,10-anthraquinone (THAQ) were determined. Interaction of THAQ with calf thymus DNA (ct DNA) was studied by UV-Vis spectroscopy to determine the overall binding constant and site size of interaction. The binding constant values (~104) for THAQ interacting with ct DNA at different pH were an order less than that known for anthracyclines. From knowledge of the overall binding constants at different pH values and the first pK of THAQ, the contribution of each form (neutral and monoanionic) towards overall binding with ct DNA could be obtained under physiological conditions. Hence, knowing the contributions of the neutral and monoanionic forms, it now becomes possible to know the overall binding constant for an interaction of THAQ with ct DNA at any pH. The calculated parameters help in understanding the role of the negative charge on the monoanionic form during interaction and suggests suitable chemical modifications that could prevent the development of such negative charges. This could lead to an increase in binding of THAQ to ct DNA. The study also helps to recognize the importance of sugar units in anthracycline anticancer drugs in DNA interaction. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Anthracyclines are broad-spectrum antibiotics that are used against several human cancers. Hydroxy-9,10-anthraquinone compounds closely resemble anthracycline antibiotics from a structural and functional viewpoint. High cost and aspects of toxicity introduce limitations on its use. On complex formation the toxicities of anthracyclines decrease. A close analogue is sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (AS), which is a comparatively cheaper molecule and resembles a good number of anthracycline derivatives. It forms a complex with CuII, [Cu(AS)2]. The complex interacts with calf thymus DNA that was studied by UV/Vis spectroscopy and cyclic voltammetry. The experimental data obtained from the two techniques was analyzed for binding constant and size of the binding site. These results not only corroborate each other but also justify earlier data obtained using fluorescence spectroscopy. An important aspect to this study was that nonlinear curve fitting, which is usually applied for analyzing DNA interaction using fluorescence and absorption spectroscopy, was used for the first time to analyze the interaction of the complex with DNA using cyclic voltammetry by monitoring the change in the reduction peak current ( Ip). The DNA binding data provides an insight into a probable mode of action of the hydroxy-9,10-anthraquinones within cells as modification of DNA that leads to cell death is an important aspect in cancer research. [ABSTRACT FROM AUTHOR]

The anthracycline drug adriamycin and its metal complexes are efficient in treating several forms of human cancers with recognized antineoplastic activity attributed to strong interactions with DNA within the target cells. The hydroxy-9,10-anthraquinone unit present in the molecule controls and regulates drug action. Metal ions when linked to adriamycin help to reduce the generation of radicals responsible for toxic side effects. A complex of adriamycin with Ni(II) was prepared and its physicochemical characteristics and DNA-binding ability were compared to a Ni(II) complex of sodium-1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (NaLH2), an analog of adriamycin. Interactions with calf thymus DNA of both complexes were studied by UV-Vis and fluorescence spectroscopy. Binding parameters determined for both complexes agree with each other. Binding of the Ni(II)-adriamycin complex to DNA was five to eight times stronger than for the Ni(II) complex of the hydroxy-9,10-anthraquinone analog, Na2[Ni(NaLH)2Cl2] · 2H2O, i.e., Ni(NaLH)2. The difference in binding was attributed to the presence of sugar units in adriamycin and to its absence in NaLH2. Although the Ni(II) complex of the hydroxy-9,10-anthraquinone analog of adriamycin [Ni(NaLH)2] was slightly weaker in binding DNA than the drug and its Ni(II) complex, a much lower cost of the former justifies its consideration as a substitute for the anthracycline drugs that are now in use. [ABSTRACT FROM PUBLISHER]

Anthracycline drugs show anticancer activity, an ability to inhibit DNA replication and RNA transcription but are costly. This study attempts to see if cheaper hydroxy-9,10-anthraquinones (1,2,4-trihydroxy-9,10-anthraquinone) that structurally resemble anthracyclines mimic its biological interactions and whether it can be a suitable substitute. Proton dissociation at 298 K for THA, pK1 = 4.82 ± 0.05 (phenolic OH at C2) and particularly pK2 = 9.22 ± 0.05 (phenolic OH at C1 and C4) closely resemble those of the anthracyclines. THA undergoes a single step two-electron reduction in aqueous media (pH 7.36) having E1/2 = −0.69 V and two successive single-electron reduction in DMF having E1/2 values −0.70 V and −1.06 V, respectively. CV data showed quasi-reversible nature of THA in aqueous media. E1/2 values of THA were comparable to anthracycline drugs suggesting similarity in redox behavior. Binding studies of THA to ct DNA using UV-Vis and fluorescence spectroscopy were analyzed. Intrinsic binding constant and site size of interaction were (4.80 ± 0.2) × 104 M−1 and (5.96 ± 0.3) bases, respectively. THA, approximately three to five times weaker in binding ct DNA than anthracycline anticancer drugs suggests a role for sugar moieties present in anthracyclines. Anti-leukemic activity studies of THA on cultured MOLT-4 cell lines were performed and apoptosis measured by MTT assay. Result indicates THA to be a potent inducer of apoptosis in MOLT-4 cell line having an IC50 value of 33.8 µM. THA therefore possesses anti-leukemic activity that is comparable to anthracyclines on P388 leukemia and the study reveals that 1,2,4-trihydroxy-9,10-anthraquinone to be a suitable substitute to the costlier anthracyclines. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The anthracycline drugs adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficacy and toxicity of such anticancer drugs are governed by biochemical reactions of the core dihydroxy-9,10-anthraquinone unit. The high cost and toxic side effects of anthracycline drugs limit their use in cancer therapy. For a few decades, efforts have been made to find cheap, less toxic yet efficient analogues of anthracyclines. This work on 1,4-dihydroxy-9,10-anthraquinone (QH), a simple analogue of the anthracyclines, was carried out to compare its biochemical properties with anthracyclines. UV-Vis and fluorescence spectroscopic methods were used to analyze interaction of the compound with calf thymus DNA. The data were used to evaluate the binding constant and site size. [ABSTRACT FROM AUTHOR]

The anthracycline drugs, adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficiency and toxic properties of the drugs are associated with electron transfer processes, which correlate well with the redox behaviour of the compounds. Sodium 1,4-dihydroxy 9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaLH2) (Na-Qz-2S) is a molecule that resembles anthracycline drugs and has a simpler structure in comparison to these drugs. Two electrons in the course of chemical action reduce this molecule like the anthracyclines. Electrochemical methods were used to identify this process. UV-Vis and fluorescence spectroscopy were used to analyse binding of the compound to calf thymus DNA. The binding constant and site size were evaluated for Na-Qz-2S and the same compared to that of the anthracyclines. Such comparisons are essential in order to understand whether the simpler hydroxy-anthraquinones can be a substitute for anthracycline drugs in cancer chemotherapy. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Ionizing radiation when allowed to fall upon cells or DNA, the radicals produced modify the base-pair region of the double strands. Radiation-induced double-strand modifications in calf thymus DNA were detected using Ni(II) and Fe(III) complexes of 1,2 dihydroxy 9,10 anthraquinone (DHA). 60Co was used as the source for γ-radiation and ethidium bromide (EB) as the fluorescent dye for detecting double-strand modifications caused in DNA. Results show that the Fe(III)–DHA complex is more efficient in modifying the base-pair region in double-stranded DNA in comparison to DHA or the Ni(II)–DHA complex. [Copyright &y& Elsevier]