Cytotoxicity, redox cycling and photodynamic action of two naturally occurring quinones

From main chain conjugated polymer photosensitizer to hyperbranched one: the expansion of polymerization-enhanced photosensitization effect for photodynamic therapy

Three conjugated polymers with the same donor-acceptor structure but totally different architectures are design to show both Type-I and Type-II photosensitization abilities simultaneously, among which the hyperbranched polymer shows the...

9,10-Phenanthrenequinone: A Promising Kernel to Develop Multifunctional Antitumor Systems for Efficient Type I Photodynamic and Photothermal Synergistic Therapy

Synergistic phototherapy provides a promising strategy to conquer the hypoxia and heterogeneity of tumors and realize a better therapeutic effect than monomodal photodynamic therapy (PDT) or photothermal therapy (PTT). The development of efficient multifunctional organic phototheranostic systems still remains a challenging task. Herein, 9,10-phenanthrenequinone (PQ) with strong electron-withdrawing ability is conjugated with the rotor-type electron-donating triphenylamine derivatives to create a series of tailor-made photosensitizers. The highly efficient Type I reactive oxygen species generation and outstanding photothermal conversion capacity are tactfully integrated into these PQ-cored photosensitizers. The underlying photophysical and photochemical mechanisms of the combined photothermal and Type I photodynamic effects are deciphered by experimental and theoretical methods and are closely associated with the active intramolecular bond stretching vibration, facilitated intersystem crossing, and specific redox cycling activity of the PQ core. Both in vitro and in vivo evaluations demonstrate that the nanoagents fabricated by these PQ-based photosensitizers are excellent candidates for Type I photodynamic and photothermal combined antitumor therapy. This study thus broadens the horizon for the development of high-performance PTT/Type I PDT nanoagents for synergistic phototheranostic treatments.

Interaction of emodin, aloe-emodin, and rhein with human serum albumin: a fluorescence spectroscopic study

The interaction of the dihydroxyanthraquinones, emodin (1), aloe-emodin (2), and rhein (3) with human serum albumin (HSA) has been studied through fluorescence spectroscopy. Quenching studies and the association constant of the anthraquinoid compounds 1, 2, and 3 in the presence of HSA were estimated. The binding and quenching studies suggest that only emodin (1) may serve as a useful fluorescence probe for structure/function studies of different emodin binding proteins. No photoinduced binding was observed after irradiation of compounds 1, 2, and 3 in presence of human serum albumin.

Electrochemical Reduction of Quinones in Different Media: A Review

The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.

9-Nitroanthracene derivative as a precursor of anthraquinone for photodynamic therapy

Anthraquinones are typical photosensitizers used in photodynamic therapy (PDT). However, systemic toxicity is a major problem for anthraquinones due to their ability not only to bind DNA but also to cause oxidative stress even without photoirradiation. To avoid such disadvantages in cancer therapy, we designed and synthesized a novel 9-nitroanthracene derivative (1) as a precursor of anthraquinone. Under photoirradiation, 1 is converted into anthraquinone via generation of nitric oxide as confirmed by ESR. Strong DNA cleavage specifically at guanine under photoirradiation was also observed, characteristic of DNA-cleaving reactions by photoirradiated anthraquinones. We propose development of 1 as an alternative approach toward PDT that reduces the systemic toxicity of anthraquinone.

Synthesis, X-ray crystal structure, antimicrobial activity and photodynamic effects of some thiabendazole complexes

An interesting series of metal complexes of thiabendazole (tbz) is synthesized and characterized by elemental analyses and spectroscopic studies. The crystal structure of the hydrogen bonded one dimensional Co(II) complex, namely [Co(tbz)(2)(NO(3))(H(2)O)](NO(3)) is solved by single crystal X-ray diffraction. The complex crystallizes in monoclinic space group P2(1)/a with unit cell parameters, a=14.366(2), b=11.459(4), c=15.942(3) A, beta=113.78(3) degrees and z=4. The unit cell packing reveals an extensive hydrogen bonding involving a water molecule, nitrate ligands and the protonated nitrogen atoms of the tbz ligands, resulting in a one dimensional hydrogen bonding pattern. The antimicrobial activity of the complexes against selected bacteria (Escherichia coli and Bacillus subtilis) and yeast (Aspergillus flavues) is estimated. The relationship between the enzymatic production of ROS and antimicrobial activity of the complexes is examined, and a good correlation between two factors is found. Photodynamic quantum yields of singlet oxygen production (RNO bleaching assay) and rate of superoxide generation (SOD inhibitable ferricytochrome c reduction assay and EPR spin trapping experiments using 5,5-dimethyl-1-pyrroline-N-oxide as spin trap) by the metal complexes have been studied.

Among substituted 9,10-dihydro-9,10-[1,2]benzenoanthracene-1,4,5,8-tetraones, the lead antitumor triptycene bisquinone TT24 blocks nucleoside transport, induces apoptotic DNA fragmentation and decreases the viability of L1210 leukemic cells in the nanomolar range of daunorubicin in vitro

In contrast to their inactive parent compound triptycene (code name TT0), several new synthetic analogs (TT code number) have antileukemic activities and remain effective in daunorubicin (DAU)-resistant tumor sublines in vitro. Among variously substituted 9,10-dihydro-9,10-[1,2]benzenoanthracene-1,4,5,8-tetraones, a total of six lead antitumor compounds have been identified, and their code names are TT2, TT13, TT16, TT19, TT21 and TT24. These active antitumor triptych structures have bisquinone functionality, and various bromo, methoxy, methylamino and/or dimethylamino substitutions with or without longer alkyl chains on the amino function. Like the anthracycline quinone antibiotic DAU, these triptycene (TT) bisquinones also inhibit DNA synthesis and induce DNA cleavage in relation with their cytotoxic activities, but have the additional advantage of blocking the cellular transport of purine and pyrimidine nucleosides, an effect which DAU cannot do. As demonstrated by intact chromatin precipitation and agarose gel electrophoresis, the ability of TT bisquinones and DAU to induce DNA fragmentation is biphasic with a peak that shifts to lower concentrations with increasing times of drug exposure. The most effective lead antitumor compound, TT24, induces DNA cleavage in the same concentration-dependent manner as DAU at 24 h (similar peak in response to 1.6 microM) and is nearly equipotent to DAU against L1210 tumor cell viability at day 4 (IC50 values of TT24 and DAU: 48 and 25 nM, respectively). The mechanism by which TT24 induces DNA fragmentation is inhibited by actinomycin D, cycloheximide, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, benzyloxycarbonyl-Ile-Glu-Thr-Asp-fluoromethyl ketone, N-tosyl-L-phenylalanine chloromethyl ketone and ZnSO4, suggesting that TT bisquinones trigger apoptosis by caspase and endonuclease activation. Since TT24 is cytotoxic in the nanomolar range of DAU, but might have a more versatile mechanism of action than DAU in wild-type and multidrug-resistant tumor cells, this new class of DNA-damaging quinone antitumor drugs inhibiting nucleoside transport might be valuable to develop new means of polychemotherapy.

Synthetic 1,4-anthracenediones, which block nucleoside transport and induce DNA fragmentation, retain their cytotoxic efficacy in daunorubicin-resistant HL-60 cell lines

Anthracene-1,4-dione and 6,7-dichloro-1,4-anthracenedione (code names AQ1 and AQ4, respectively) are cytostatic (IC50: 53 and 110 nM, respectively) and cytotoxic (IC50: 100 and 175 nM, respectively) in wild-type drug-sensitive HL-60-S tumor cells at day 4 in vitro. Therefore, the antitumor effects of these drugs were assessed and compared to those of daunorubicin (DAU) in HL-60-RV and HL-60-R8 tumor cells, which are, respectively, P-glycoprotein-positive and -negative multidrug-resistant (MDR) sublines. In contrast to DAU, which loses its cytostatic [resistance factors (RFs): 30.3-31.8] and cytotoxic (RFs: 48.8-58.1) activities in MDR sublines, AQ1 inhibits cell proliferation (RFs: 0.9-1.3) and cell viability (RFs: 1.4-1.6) as effectively in HL-60-RV and HL-60-R8 as in HL-60-S cells. Similarly, DAU decreases the rate of DNA synthesis less effectively in MDR sublines (RFs: 8.0-13.3) but AQ1 inhibits the incorporation of [3H]thymidine into DNA to the same degree in HL-60-S as in HL-60-RV and HL-60-R8 cells (RFs: 0.9-1.1). In contrast to DAU, which is ineffective, the advantage of AQ1 is its ability to block the cellular transport of purine and pyrimidine nucleosides in HL-60-S cells, an effect which persists in the MDR sublines (RFs: 1.1). AQ4, which mimics to a lesser degree all the antitumor effects of AQ1, except the inhibition of adenosine transport, also retains its effectiveness in MDR sublines (RFs: 1.1-3.1). The peaks of DNA cleavage caused by DAU and AQ1 in HL-60-S cells shift to lower concentrations with increasing times of drug exposure but DAU loses most of its ability to induce DNA fragmentation in MDR sublines, whereas the levels of AQ1-induced DNA cleavage at 16 and 24 h are nearly equivalent in HL-60-S, HL-60-RV and HL-60-R8 cells. Because they not only mimic the antitumor effects of DAU in the nM range but also block nucleoside transport and remain effective in tumor cells that have developed different mechanisms of MDR, AQ1 and AQ4 analogs might be valuable to develop new means of polychemotherapy.