New tryptophanase inhibitors: towards prevention of bacterial biofilm formation

Tryptophanase (tryptophan indole-lyase, Tnase, EC 4.1.99.1), a bacterial enzyme with no counterpart in eukaryotic cells, produces from L-tryptophan pyruvate, ammonia and indole. It was recently suggested that indole signaling plays an important role in the stable maintenance of multicopy plasmids. In addition, Tnase was shown to be capable of binding Rcd, a short RNA molecule involved in resolution of plasmid multimers. Binding of Rcd increases the affinity of Tnase for tryptophan, and it was proposed that indole is involved in bacteria multiplication and biofilm formation. Biofilm-associated bacteria may cause serious infections, and biofilm contamination of equipment and food, may result in expensive consequences. Thus, optimal and specific factors that interact with Tnase can be used as a tool to study the role of this multifunctional enzyme as well as antibacterial agents that may affect biofilm formation. Most known quasi-substrates inhibit Tnase at the mM range. In the present work, the mode of Tnase inhibition by the following compounds and the corresponding Ki values were: S-phenylbenzoquinone-L-tryptophan, uncompetitively, 101 microM; alpha-amino-2-(9,10-anthraquinone)-propanoic acid, noncompetitively, 174 microM; L-tryptophane-ethylester, competitively, 52 microM; N-acetyl-L-tryptophan, noncompetitively, 48 microM. S-phenylbenzoquinone-L-tryptophan and alpha-amino-2-(9,10-anthraquinone)-propanoic acid were newly synthesized.     

9,10-Anthraquinone Reduces the Photosynthetic Efficiency of Oscillatoria perornata and Modifies Cellular Inclusions

The natural compound 9,10-anthraquinone was found to inhibit the growth of the musty odor-producing cyanobacterium Oscillatoria perornata at a low concentration (1 μM) in previous laboratory studies. In this study, the mode of action of 9,10-anthraquinone was investigated by observing ultrastructural changes in O. perornata and by monitoring chlorophyll fluorescence as an indicator of photosynthetic efficiency. Results indicate that 9,10-anthraquinone inhibits photosynthetic electron transport, probably at PSII, and thereby affects growth. Moreover, 9,10-anthraquinone treatment caused thylakoid disorganization and reduced the number of ribosomes in O. perornata. The thylakoid disorganization is identical to reported modification in a cyanobacterium treated with simazine, a PSII inhibitor.     

Design, synthesis and cytotoxic effect of hydroxy- and 3-alkylaminopropoxy-9,10-anthraquinone derivatives

In previous paper, we have reported the synthesis and the cytotoxic effect of 1,3-dihydroxy-9,10-anthraquinone derivatives. For further design of more potent compounds, a new series of 1-hydroxy-3-(3-alkylaminopropoxy)-9,10-anthraquinones and 3-(3-alkylaminopropoxy)-9,10-anthraquinones have been synthesized. The cytotoxicity of synthetic compounds were evaluated against human Hep G2, Hep 3B and HT-29 cells. Almost all compounds indicated significant inhibitory activity against Hep G2, Hep 3B and HT-29 cell lines in vitro. Compound 5 exhibited selective cytotoxicity against Hep G2 in a concentration-dependent manner with ED50 value of 1.23 +/- 0.05 microM. Structure-activity analysis revealed that most of the 1-hydroxy-3-(3-alkylamino-2-hydroxypropoxy)-9,10-anthraquinone showed stronger cytotoxic effects than those of 1-hydroxy-3- or 3-(3-alkylaminopropoxy)-9,10-anthraquinones against Hep 3B cell line in vitro. A sub-G1 cell stage and DNA fragmentation in MCF-7 cells were significantly observed after 72 h incubation with selective compound 16. The results show that 16 causes cell death by apoptosis.     

降龙草的蒽醌类化学成分

为了解降龙草(Hemiboea subcapitata Clarke)的化学成分,从降龙草全草的乙醇提取物的石油醚和乙酸乙酯萃取部位分离得到了5个蒽醌类化合物。经波谱学分析鉴定为digiferruginol(1)、1,4-二羟基-2-羟甲基-9,10-蒽醌(2)、1,7-二羟基-2-羟甲基-9,10-蒽醌(3)、1-羟基-7-甲氧基-2-羟甲基-9,10-蒽醌(4)和1,4,7-三羟基-2-甲基-9,10-蒽醌(5)。其中化合物4和5为新化合物,其它3个化合物为首次从降龙草中分离得到。     

Isolation of glucosyltransferase fromStreptomyces aureofaciens

Streptomyces aureofaciens B 96 grown on a synthetic medium glucosylated exogenous 1,2-dihydroxy-9, 10-anthraquinone (alizarin). The glucosylation was inhibited by 2,4-dinitrophenol added to the cultivation medium. A cell-free preparation was obtained from the mycelium isolated after 16 h of growth and was found to catalyze the transfer of glucose from glucosyluridyl diphosphate to 1,2-dihydroxy-9, 10-anthraquinone, giving rise to l-hydroxy-2-(β-D-glueopyranosyloxy)-9,10-anthraquinone.     

Esters of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinones with melphalan as multifunctional anticancer agents

Eight esters of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone with melphalan were prepared and tested for their antitumor activity (S-180) and cytotoxicity. 2-[1-[4-(p-Bis(2-chloroethyl)-aminophenyl)-butanoyloxy]methyl]-1,4-dihydroxy-9,10-anthraquinone and 2-[1-[4-(p-bis(2-chloroethyl)-aminophenyl)-butanoyloxy]ethyl]-1,4-dihydroxy-9,10-anthraquinone showed remarkable antitumor activity (T/C, 265 and 272%).     

Identification of two pigments and a hydroxystilbene antibiotic from Photorhabdus luminescens.

Two yellow pigments were isolated for the first time from the entomopathogenic bacterium Photorhabdus luminescens in liquid culture and were identified as the anthraquinone derivatives 3,8-dimethoxy-1-hydroxy-9,10-anthraquinone (minor) and 1,3-dimethoxy-8-hydroxy-9,10-anthraquinone (major). A known antibiotic, 3,5-dihydroxy-4-isopropylstilbene, was also detected and for the first time showed strong fungicidal activity against several fungi of medical and agricultural importance.     

Anthraquinone derivatives induce G2/M cell cycle arrest and apoptosis in NTUB1 cells

Thirteen anthraquinone derivatives 5-17 including two 3-(3-alkylaminopropoxy)-9,10-anthraquinone (NHA) derivatives 5 and 6, and 11 1-hydroxy-3-(3-alkylaminopropoxy)-9,10-anthraquinone (MHA) derivatives 7-17 were synthesized, evaluated for cytotoxicities against two cancer cell lines, and assayed the generation of reactive oxygen species (ROS) in NTUB1 cells (a human bladder carcinoma cell line). Compound 9 bearing a pyrrolidinyl group induced the stronger cytotoxic effect than those of other synthesized NHA and MHA derivatives. Exposure of NTUB1 cells to 9, 13, and 17 for 24h significantly increased the production of ROS, respectively. Flow cytometric analysis exhibited that the exposure of NTUB1 cells to the selective 9 led to the G2/M phase arrest accompanied by an increase of apoptotic cell death after the incubation for 24h. Compound 9 induced up-regulation of cyclinB1 and p21 expressions. Biological results suggested that the induction of G2/M arrest, apoptosis, and cell death by 9 may associate with increased expression of p21 and cyclin B1, elevation of Bax and p53 levels, and generation of ROS in the cell. In conclusion, these series of compounds may be used as anticancer agents.     

Solvent effect on the physical quenching of singlet molecular oxygen by p-quinones.

Rate constants for the interaction between singlet molecular oxygen [O2(1 delta g)] and the p-quinones 1,4-benzoquinone (BQ), duroquinone (DQ), 9,10-anthraquinone (AQ) and 1,8-dihydroxy-9,10-anthraquinone (OHAQ) are reported for several solvents at room temperature. The solvent effect on the total quenching rate constant (kt) was analysed employing the semiempirical solvatochromic equation proposed by Kamlet and Taft. The higher values of kt (2-7 x 10(7) M(-1) s(-1)) were obtained when the hydrogen-bond donor solvent ability is increased (higher alpha parameter values). The results indicate the importance of specific solvent interactions in governing the rates of the quenching.     

One- and two-electron reduction of hydroxy-1,4-naphthoquinones and hydroxy-9,10-anthraquinones: The role of internal hydrogen bonding and its bearing on the redox chemistry of the anthracycline antitumour quinones

First and second half-wave reduction potentials of 11 1,4-naphthoquinones and 42 9,10-anthraquinones have been measured for solutions in dimethylformamide. The presence of hydroxy groups at the 5- and 8-positions of the 1,4-naphthoquinone nucleus, and at the 1-, 4-, 5- and 8-positions of the 9,10-anthraquinone (the α-positions) markedley raises both reduction potentials. Measurements on the corresponding methoxy- and acetoxyquinones indicate that internal hydrogen bonding in the α-hydroxyquinones makes a major contribution to stabilisation of the semiquinone, probably as a result of increased delocalisation due to exchange of the hydroxy hydrogen between the two neighbouring oxygen atoms. The bearing of this phenomenon on the mechanism of action off anthracycline antitumour quinones is discussed, and the stabilising effect on the semiquinone of hydroxy groups at the 1- adn 5-positions of the 9,10-anthraquinone nucleus is highlighted.     

Evaluation of complementary effects of 9,10-anthraquinone and fumaric acid on methanogenesis and ruminal fermentation in vitro

The objective of the present study was to investigate the hypothesis that 9,10-anthraquinone (AQ) in combination with fumaric acid (FMA) may provide complementary effects to inhibit methanogens and enhance rumen's capacity for better utilisation of FMA towards propionate production. Three levels of AQ and four levels of FMA were tested in a 3 x 4 factorial design using in vitro gas production technique. AQ reduced the total gas and methane production significantly. The combination of 4 ppm AQ with FMA had additive effect on concentration of propionate. Supplementation of AQ alone resulted in hydrogen accumulation (p < 0.001), whereas presence of FMA (up to 6.5 mM) along with AQ declined hydrogen concentration (p < 0.001). The level of 4 ppm AQ did not affect in vitro digestibility, however, a reduction of organic matter digestibility was caused by 8 ppm AQ (p < 0.001), which was partially compensated by the addition of FMA (p = 0.06). The optimum FMA level depended on the AQ concentration. At 4 ppm AQ, a FMA level of 3.5 mM had best possible effect on partitioning factor and microbial biomass production (p < 0.001), though, at 8 ppm AQ the higher level of FMA (6.5 mM) responded better. Overall, FMA in combination with AQ provided an alternative hydrogen sink and might be introduced as a novel strategy for mitigation of enteric methane emission. Nevertheless, the result should be proved by in vivo experiments.     

One- and two-electron reduction of hydroxy-1,4-naphthoquinones and hydroxy-9,10-anthraquinones. The role of internal hydrogen bonding and its bearing on the redox chemistry of the anthracycline antitumour quinones

First and second half-wave reduction potentials of 11 1,4-naphthoquinones and 42 9,10-anthraquinones have been measured for solutions in dimethylformamide. The presence of hydroxy groups at the 5- and 8-positions of the 1,4-naphthoquinone nucleus, and at the 1-, 4-, 5- and 8-positions of the 9,10-anthraquinone (the alpha-positions) markedly raises both reduction potentials. Measurements on the corresponding methoxy- and acetoxyquinones indicate that internal hydrogen bonding in the alpha-hydroxyquinones makes a major contribution to stabilisation of the semiquinone, probably as a result of increased delocalisation due to exchange of the hydroxy hydrogen between the two neighbouring oxygen atoms. The bearing of this phenomenon on the mechanism of action of anthracycline antitumour quinones is discussed, and the stabilising effect on the semiquinone of hydroxy groups at the 1- and 5-positions of the 9,10-anthraquinone nucleus is highlighted.     

Novel derivatives of 9,10-anthraquinone are selective algicides against the musty-odor cyanobacterium Oscillatoria perornata

Musty "off-flavor" in pond-cultured channel catfish (Ictalurus punctatus) costs the catfish production industry in the United States at least 30 million US dollars annually. The cyanobacterium Oscillatoria perornata (Skuja) is credited with being the major cause of musty off-flavor in farm-raised catfish in Mississippi. The herbicides diuron and copper sulfate, currently used by catfish producers as algicides to help mitigate musty off-flavor problems, have several drawbacks, including broad-spectrum toxicity towards the entire phytoplankton community that can lead to water quality deterioration and subsequent fish death. By use of microtiter plate bioassays, a novel group of compounds derived from the natural compound 9,10-anthraquinone have been found to be much more selectively toxic towards O. perornata than diuron and copper sulfate. In efficacy studies using limnocorrals placed in catfish production ponds, application rates of 0.3 micro M (125 micro g/liter) of the most promising anthraquinone derivative, 2-[methylamino-N-(1'-methylethyl)]-9,10-anthraquinone monophosphate (anthraquinone-59), dramatically reduced the abundance of O. perornata and levels of 2-methylisoborneol, the musty compound produced by O. perornata. The abundance of green algae and diatoms increased dramatically 2 days after application of a 0.3 micro M concentration of anthraquinone-59 to pond water within the limnocorrals. The half-life of anthraquinone-59 in pond water was determined to be 19 h, making it much less persistent than diuron. Anthraquinone-59 appears to be promising for use as a selective algicide in catfish aquaculture.     

Degradation of anthracene by laccase of Trametes versicolor in the presence of different mediator compounds

 Laccase of Trametes versicolor was generally able to oxidize anthracene in vitro. After 72 h incubation about 35% of the anthracene was transformed stoichiometrically to 9,10-anthraquinone. Transformation of anthracene increased rapidly in the presence of different mediators that readily generate stable radicals: 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 1-hydroxybenzotriazole. For the reaction, the presence of both the laccase and the mediator was necessary. In the presence of 0.005 mM 1-hydroxybenzotriazole this conversion had removed 47% of the anthracene after 72 h; 75% of the substrate was oxidized during this period when ABTS (1 mM) was used as mediator. In contrast to reactions without or with only low concentrations of a mediator, there was a discrepancy between the disappearance of anthracene and the formation of 9,10-anthraquinone in mediator-forced reactions. Coupling-products of mediators with anthracene degradation products were found. Anthracene disappeared nearly completely after incubation for 72 h with laccase in a 0.1 mM solution of 1-hydroxybenzotriazole and was transformed to 9,10-anthraquinone in about 80% yield; 90% of the substrate was transformed in the presence of ABTS (2.0 mM) resulting again in 80% quinone. Phenothiazine was not effective in this system. Received: 9 April 1996/Received last revision: 7 June 1996/Accepted: 10 June 1996     

Novel Derivatives of 9,10-Anthraquinone Are Selective Algicides against the Musty-Odor Cyanobacterium Oscillatoria perornata

Musty “off-flavor” in pond-cultured channel catfish (Ictalurus punctatus) costs the catfish production industry in the United States at least $30 million annually. The cyanobacterium Oscillatoria perornata (Skuja) is credited with being the major cause of musty off-flavor in farm-raised catfish in Mississippi. The herbicides diuron and copper sulfate, currently used by catfish producers as algicides to help mitigate musty off-flavor problems, have several drawbacks, including broad-spectrum toxicity towards the entire phytoplankton community that can lead to water quality deterioration and subsequent fish death. By use of microtiter plate bioassays, a novel group of compounds derived from the natural compound 9,10-anthraquinone have been found to be much more selectively toxic towards O. perornata than diuron and copper sulfate. In efficacy studies using limnocorrals placed in catfish production ponds, application rates of 0.3 μM (125 μg/liter) of the most promising anthraquinone derivative, 2-[methylamino-N-(1′-methylethyl)]-9,10-anthraquinone monophosphate (anthraquinone-59), dramatically reduced the abundance of O. perornata and levels of 2-methylisoborneol, the musty compound produced by O. perornata. The abundance of green algae and diatoms increased dramatically 2 days after application of a 0.3 μM concentration of anthraquinone-59 to pond water within the limnocorrals. The half-life of anthraquinone-59 in pond water was determined to be 19 h, making it much less persistent than diuron. Anthraquinone-59 appears to be promising for use as a selective algicide in catfish aquaculture.     

Anthraquinones from the Genus cortinarius

The anthraquinones 6-methylxanthopurpurin-3-methyl ether, xanthorin, and 1,4-dihydroxy-2-methoxy-7-methyl-9,10-anthraquinone (austrocortinin) have been isolated from fruit bodies of a red Australian toadstool belonging to the genus Cortinarius; austrocortinin is reported for the first time as a natural product.     

4-aminophyscion,an anthraquinone derivative from dermocybe (Agaricales)

The anthraquinones physcion, erythroglaucin and 4-aminophyscion (4-amino-1,8-dihydroxy-6-methoxy-3-methyl-9,10-anthraquinone) have been isolated from the fungal species Dermocybe canaria Horak (ined.). 4-Aminophyscion is reported for the first time as a natural product and represents the first fungal anthraquinone with an amino group.     

Chloroplast cytochrome b-563, hydrophobic environment and lack of direct reaction with ferredoxin.

1. The reaction of electron donors with cytochrome b-563 in chloroplasts was studied by investigating their effects on the rate of its reduction in the presence of dithionite, which reacts only slowly with the cytochrome. The relative effects of 9,10-anthraquinone and 9,10-anthraquinone 2-sulphonate in the presence of dithionite suggested that the site of attack of redox reagents was protected behind a hydrophobic barrier from the external medium. 2. Ferredoxin had no measurable effect on the rate of reduction of the cytochrome in the presence of dithionite. 3. The reduction of pigment P700 in the dark after illumination in the presence of the inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea was stimulated by a combination of NADPH and ferredoxin, although NADPH alone had little effect. The same combination was unable to reduce cytochrome b-563 at a measurable rate. 4. It is concluded that the cytochrome is unlikely to be part of a linear pathway of electron flow between ferredoxin and pigment P700.     

New tryptophanase inhibitors: Towards prevention of bacterial biofilm formation

Tryptophanase (tryptophan indole-lyase, Tnase, EC 4.1.99.1), a bacterial enzyme with no counterpart in eukaryotic cells, produces from L-tryptophan pyruvate, ammonia and indole. It was recently suggested that indole signaling plays an important role in the stable maintenance of multicopy plasmids. In addition, Tnase was shown to be capable of binding Rcd, a short RNA molecule involved in resolution of plasmid multimers. Binding of Rcd increases the affinity of Tnase for tryptophan, and it was proposed that indole is involved in bacteria multiplication and biofilm formation. Biofilm-associated bacteria may cause serious infections, and biofilm contamination of equipment and food, may result in expensive consequences. Thus, optimal and specific factors that interact with Tnase can be used as a tool to study the role of this multifunctional enzyme as well as antibacterial agents that may affect biofilm formation. Most known quasi-substrates inhibit Tnase at the mM range. In the present work, the mode of Tnase inhibition by the following compounds and the corresponding Ki values were: S-phenylbenzoquinone-L-tryptophan, uncompetitively, 101 μM; α-amino-2-(9,10-anthraquinone)-propanoic acid, noncompetitively, 174 μM; L-tryptophane-ethylester, competitively, 52 μM; N-acetyl-L-tryptophan, noncompetitively, 48 μM. S-phenylbenzoquinone-L-tryptophan and α-amino-2-(9,10-anthraquinone)-propanoic acid were newly synthesized.     

Isolation and characterization of Anthraquinone from Streptomyces sp. ERINLG-26 with anticancer activity Against adenocarcinoma cell line COLO320

Applied Biochemistry and Microbiology - Anticancer activity of 9,10-anthraquinone isolated from soil-derived (Doddabetta forest, Nilgiris, Tamil Nadu, India) filamentous bacterium Streptomyces sp....