Microbial transformation of quinoline by a Pseudomonas sp.

A Pseudomonas sp. isolated from sewage by enrichment culture on quinoline metabolized this substrate by a novel pathway involving 8-hydroxycoumarin. During early growth of the organism on quinoline, 2-hydroxyquinoline accumulated as the intermediate; 8-hydroxycoumarin accumulated as the major metabolite on further incubation. 2,8-Dihydroxyquinoline and 2,3-dihydroxyphenylpropionic acid were identified as the other intermediates. Inhibition of quinoline metabolism by 1 mM sodium arsenite led to the accumulation of pyruvate, whereas inhibition by 5 mM arsenite resulted in the accumulation of 2-hydroxyquinoline as the major metabolite and 2,8-dihydroxyquinoline as the minor metabolite. Coumarin was not utilized as a growth substrate by this bacterium, but quinoline-grown cells converted it to 2-hydroxyphenylpropionic acid, which was not further metabolized. Quinoline, 2-hydroxyquinoline, 8-hydroxycoumarin, and 2,3-dihydroxyphenylpropionic acid were rapidly oxidized by quinoline-adapted cells, whereas 2,8-dihydroxyquinoline was oxidized very slowly. Quinoline catabolism in this Pseudomonas sp. is therefore initiated by hydroxylation(s) of the molecule followed by cleavage of the pyridine ring to yield 8-hydroxycoumarin, which is further metabolized via 2,3-dihydroxyphenylpropionic acid.     

Microbial transformation of quinoline by a Pseudomonas sp

A Pseudomonas sp. isolated from sewage by enrichment culture on quinoline metabolized this substrate by a novel pathway involving 8-hydroxycoumarin. During early growth of the organism on quinoline, 2-hydroxyquinoline accumulated as the intermediate; 8-hydroxycoumarin accumulated as the major metabolite on further incubation. 2,8-Dihydroxyquinoline and 2,3-dihydroxyphenylpropionic acid were identified as the other intermediates. Inhibition of quinoline metabolism by 1 mM sodium arsenite led to the accumulation of pyruvate, whereas inhibition by 5 mM arsenite resulted in the accumulation of 2-hydroxyquinoline as the major metabolite and 2,8-dihydroxyquinoline as the minor metabolite. Coumarin was not utilized as a growth substrate by this bacterium, but quinoline-grown cells converted it to 2-hydroxyphenylpropionic acid, which was not further metabolized. Quinoline, 2-hydroxyquinoline, 8-hydroxycoumarin, and 2,3-dihydroxyphenylpropionic acid were rapidly oxidized by quinoline-adapted cells, whereas 2,8-dihydroxyquinoline was oxidized very slowly. Quinoline catabolism in this Pseudomonas sp. is therefore initiated by hydroxylation(s) of the molecule followed by cleavage of the pyridine ring to yield 8-hydroxycoumarin, which is further metabolized via 2,3-dihydroxyphenylpropionic acid.     

Microbial metabolism of quinoline and related compounds. II. Degradation of quinoline by Pseudomonas fluorescens 3, Pseudomonas putida 86 and Rhodococcus spec. B1

Quinoline catabolism was investigated with different bacterial strains, able to use quinoline as sole source of carbon, nitrogen and energy. Some degradation products of quinoline were isolated from the culture fluids and identified. With Pseudomonas fluorescens and Pseudomonas putida we found 2-oxo-1,2-dihydroquinoline, 8-hydroxy-2-oxo-1,2-dihydroquinoline, 8-hydroxycoumarin and 2,3-dihydroxyphenylpropionic acid as intermediates. With a Rhodococcus strain 2-oxo-1,2-dihydroquinoline, 6-hydroxy-2-oxo-1,2-dihydroquinoline, a red meta-cleavage product and a blue fluorescent compound were isolated. The red compound was identified as 5-hydroxy-6-(3-carboxy-3-oxopropenyl)-1H-2-pyridone. From this the blue fluorescent azacoumarin 2H-pyrano-2-one-[3,2b]-5H-6-pyridone is formed by chemical decomposition. Therefore it can be considered a by-product of quinoline-degradation in Rhodococcus spec. With the present results two different degradation pathways for quinoline in different microorganisms are proposed.     

Aerobic biodegradation characteristics and metabolic products of quinoline by a Pseudomonas strain

A bacterial strain, BW003, which utilized quinoline as its sole C, N and energy source, was isolated and identified as Pseudomonas sp. BW003 degraded 192–911 mg/l quinoline within 3–8 h with removal rates ranging from 96% to 98%. The optimum conditions for the degradation were 30 °C and pH 8. In the process of biodegradation, at least 43% of quinoline was transformed into 2-hydroxyquinoline, then 0.69% of 2-hydroxyquinoline was transformed into 2,8-dihydroxyquinoline, and then, presumably, into 8-hydroxycoumarin. Meanwhile, at least 48% of the nitrogen in quinoline was directly transformed into ammonia-N. An extra carbon source enhanced the nitrogen transformation from ammonia-N. Further experiments showed that, besides cell synthesis, BW003 transformed less than 6% of ammonia-N into nitrate through heterotrophic nitrification. In addition, BW003 contained a large plasmid, which may be involved in quinoline metabolism. The study indicates that quinoline and its metabolic products can be eliminated from wastewater by controlling the C/N ratio using BW003 as the bioaugmentation inoculum.     

Xenobiotic reductase A in the degradation of quinoline by Pseudomonas putida 86: physiological function, structure and mechanism of 8-hydroxycoumarin reduction

A continuous evolutionary pressure of the biotic and abiotic world has led to the development of a diversity of microbial pathways to degrade and biomineralize aromatic and heteroaromatic compounds. The heterogeneity of compounds metabolized by bacteria like Pseudomonas putida indicates the large variety of enzymes necessary to catalyse the required reactions. Quinoline, a N-heterocyclic aromatic compound, can be degraded by microbes along different pathways. For P. putida 86 quinoline degradation by the 8-hydroxycoumarin pathway has been described and several intermediates were identified. To select enzymes catalysing the later stages of the 8-hydroxycoumarin pathway P. putida 86 was grown with quinoline. The FMN-containing enzyme xenobiotic reductase A (XenA) was isolated and analysed for its reactivity with intermediates of the 8-hydroxycoumarin pathway. XenA catalyses the NADPH-dependent reduction of 8-hydroxycoumarin and coumarin to produce 8-hydroxy-3,4-dihydrocoumarin and 3,4-dihydrocoumarin, respectively. Crystallographic analysis of XenA alone and in complex with the two substrates revealed insights into the mechanism. XenA shows a dimeric arrangement of two (beta/alpha)(8) barrel domains each binding one FMN cofactor. High resolution crystal structures of complexes with 8-hydroxycoumarin and coumarin show different modes of binding for these molecules in the active site. While coumarin is ideally positioned for hydride transfer from N-5 of the isoalloxazine ring to C-4 of coumarin, 8-hydroxycoumarin forms a non-productive complex with oxidised XenA. Orientation of 8-hydroxycoumarin in the active site appears to be dependent on the electronic state of the flavin. We postulate that XenA catalyses the last step of the 8-hydroxycoumarin pathway before the heterocyclic ring is hydrolysed to yield 3-(2,3-dihydroxyphenyl)-propionic acid. As XenA is also found in P. putida strains unable to degrade quinoline, it appears to have more than one physiological function and is an example of how enzymes with low substrate specificity can help to explain the variety of degradation pathways possible.     

Quinoline biodegradation and its nitrogen transformation pathway by a <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain

A Pseudomonas sp. strain, which can utilize quinoline as its sole carbon, nitrogen and energy source, was isolated from activated sludge in a coking wastewater treatment plant. Quinoline can be degraded via the 8-hydroxycoumarin pathway. We quantified the first two organic intermediates of the biodegradation, 2-hydroxyquinoline and 2,8-dihydroxyquinoline. We tracked the transformation of the nitrogen in quinoline in two media containing different C/N ratios. At least 40.4% of the nitrogen was finally transformed into ammonium when quinoline was the sole C and N source. But addition of an external carbon source like glucose promoted the transformation of N from NH₃ into NO₃ ⁻, NO₂ ⁻, and then to N₂. The product analysis and gene characteristics indicated that the isolate accomplished heterotrophic nitrification and aerobic denitrification simultaneously. The study also demonstrated that quinoline and its metabolic products can be eliminated if the C/N ratio is properly controlled in the treatment of quinoline-containing wastewater.     

Monoamine oxidase inhibition by pyrrole quinoline derivatives

The effect of 1-(beta-aminoethyl)-3H-pyrrole[2,3-h]quinoline (I), 3-(beta-aminoethyl)-1H-pyrrole[2,3-h]quinoline (I'), 8-amino-3H-pyrrole[2,3-h]quinoline (II), 6-amino-3H-pyrrole[2,3-h]quinoline (II') and 8-amino-1H-pyrrole[2,3-h]quinoline (III) on tyramine, serotonin and 2-phenylethylamine deaminase activities of mitochondrial monoamine oxidase from bovine brain were studied. All the compounds tested appeared to be reversibly inhibit MAO without preliminary incubation. Compounds II, II' and III specifically inhibited type A MAO; compound III exhibited the highest selectivity. The inhibition was of a mixed type. The effects of compounds I and I' were competitive and inconsistent with a classical concept on the dual activity of MAO, i. e., deamination of tyramine, a substrate common for MAO type A and MAO type B was inhibited in a greater degree than the deamination of specific substrates of MAO type A (serotonin) or type B (2-phenylethylamine). Possible reasons for the observed phenomenon are discussed.     

Microbial metabolism of quinoline and related compounds. III. Degradation of 3-chloroquinoline-8-carboxylic acid by Pseudomonas spec. EK III

Bacteria have been isolated with the ability to use 3-chloroquinoline-8-carboxylic acid as sole source of carbon and energy. According to their physiological properties, these bacteria have been classified as Pseudomonas spec. Two metabolites of the degradation pathway have been isolated and identified. The first metabolite was 3-(3-carboxy-3-oxopropenyl)-2-hydroxy-5-chloropyridine, the meta-cleavage product of 3-chloro-7,8-dihydroxyquinoline. The second metabolite, 5-chloro-2-hydroxynicotinic acid, was not further metabolized by this organisms.     

Synthesis and anticancer evaluation of certain indolo[2,3-b]quinoline derivatives

The present report describes the synthesis and anticancer evaluation of certain 11-substituted 6H-indolo[2,3-b]quinolines and their methylated derivatives. These 6H-indolo[2,3-b]quinoline derivatives 11–13 were prepared from the commercially available 1,4-dihydroxyquinoline through alkylation, chlorination, nucleophilic reaction, and ring cyclization. Depending on the ratio of 11, (MeO)₂SO₂, and K₂CO₃, alkylation occurred primarily on N-5 (1:0.8:0.8) or N-6 (1:1.5:1.5) leading to the isolation of 14a or 14b as a major product. Accordingly, major product 15a (2/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 15b (1:1:1), respectively, was obtained by alkylation of 12 while 16a (13/(MeO)₂SO₂/K₂CO₃ = 1:2:2) or 16b (1:1:1), respectively, was obtained by alkylation of 13. The in vitro anticancer assay indicated 5-methylated derivatives 14a, 15a, 16a are more cytotoxic than their respective 6-methylated counterparts 14b, 15b, 16b and 6H-indolo[2,3-b]quinoline precursors 11, 12, 13. Among them, 11-(4-methoxyanilino)-6-methyl-6H-indolo[2,3-b]quinoline (16a) was the most cytotoxic with a mean GI₅₀ value of 0.78 μM and also exhibited selective cytotoxicities for HL-60 (TB), K-562, MOLT-4, RPMI-8226, and SR with GI₅₀ values of 0.11, 0.42, 0.09, 0.14, and 0.19 μM, respectively.     

Selective removal of nitrogen from quinoline and petroleum by Pseudomonas ayucida IGTN9m

Enrichment culture experiments employing soil and water samples obtained from petroleum-contaminated environments succeeded in the isolation of a pure culture possessing the ability to utilize quinoline as a sole nitrogen source but did not utilize quinoline as a carbon source. This culture was identified as Pseudomonas ayucida based on a partial 16S rRNA gene sequence, and the strain was given the designation IGTN9m. Examination of metabolites using thin-layer chromatography and gas chromatography-mass spectrometry suggests that P. ayucida IGTN9m converts quinoline to 2-quinolinone and subsequently to 8-hydroxycoumarin. Resting cells of P. ayucida IGTN9m were shown to be capable of selectively removing about 68% of quinoline from shale oil in a 16-h treatment time. These results suggest that P. ayucida IGTN9m may be useful in petroleum biorefining for the selective removal of organically bound nitrogen from petroleum.     

Biotransformation of quinoline and methylquinolines in anoxic freshwater sediment

Quinoline (Q) and some isomers of methylquinoline (MQ) were transformed to hydroxylated products in freshwater sediment slurries incubated under methanogenic conditions at 25 °C. Methylquinoline transformation was not affected by a methyl group on the C-3 or C-4 carbon atom of the pyridine ring; 2-MQ, however, was not transformed. All isomers of dimethylquinoline (DMQ) tested (2,4-, 2,6-, 2,7-, and 2,8-DMQ) with a methyl group at the number 2 carbon also persisted in sediments after anaerobic incubation for one year at 25 °C.In most experiments, quinoline initially was transformed to 2-hydroxyquinoline (2-OH-Q), which was further metabolized to unidentified products. A second product, 4-CH₃-2-OH-Q, was detected in some experiments. This product accumulated and was not further transformed. 6-, 7-, and 8-Methylquinoline (6-, 7-, 8-MQ) were hydroxylated to form the respective 2-OH-MQ products. These hydroxylated products accumulated and were not further transformed. Hydroxylation of Q and 6-, 7- and 8-MQ at the 2-carbon position was confirmed by GC/FTIR and GC/MS analyses. The transformations of Q and MQs were pH dependent with an optimal pH of 7–8.The results of this study suggest that two pathways may exist for the anaerobic transformation of quinoline; one pathway leads to the formation of a hydroxylated intermediate and the other to a methylated and hydroxylated intermediate. In addition, our results suggest that a methyl substituent on the number 2 carbon inhibits the anaerobic transformation of quinoline derivatives.Abbreviations GC gas chromatography - GC/FTIR gas chromatography/Fourier transform infrared spectrometry - GC/MS gas chromatography/mass spectrometry - HPLC high performance liquid chromatography - MQ methylquinoline - Q quinoline     

Transformation of 2-chloroquinoline to 2-chloro-cis-7,8-dihydro-7,8-dihydroxyquinoline by quinoline-grown resting cells of Pseudomonas putida 86

Abstract Resting cells of Pseudononas putida strain 86 were grown on quinoline transformed 2-chloroquinoline to 2-chloro- cis -7,8-dihydro-7,8-dihydroxyquinoline which was not converted further. 7,8-Dioxygenating activity was present when the enzymes of quinoline catabolism were induced. Quinoline-grown cells of strain 86 treated simultaneously with 2-chloroquinoline and D-(-)- threo -chloramphenicol to prevent protein biosynthesis also formed the cis -7,8-dihydrodiol of 2-chloroquinoline. Succinate-grown resting cells did not oxidize 2-chloroquinoline. Acid-catalyzed decomposition of 2-chloro- cis -7,8-dihydro-7,8-dihydroxyquinoline predominantly yielded 2-chloro-8-hydroxyquinoline. By analogy, accumulation of the putative dead-end metabolite 1 H -8-hydroxy-2-oxoquinoline during growth of P. putida 86 on quinoline is suggested to likewise result from dehydration of the 7,8-dihydrodiol of 1 H -2-oxoquinoline.     

Isolation of a Pseudomonas stutzeri strain that degrades o-xylene.

A Pseudomonas stutzeri strain capable of growing on o-xylene was isolated from enrichment cultures. The organism grew on 2,3- and 3,4-dimethylphenol but not on 2-methylbenzyl alcohol, o-tolualdehyde, or o-toluate. P. stutzeri was not able to utilize m-xylene, p-xylene, or 1,2,4-trimethylbenzene, but growth was observed in the presence of the corresponding alcohols and acids. From the Pseudomonas cultures supplied with o-xylene, 2,3-dimethylphenol was isolated and identified. When resting P. stutzeri cells were incubated with 2,3-dimethylphenol, the reaction mixture turned greenish yellow and showed spectral properties identical to those of the 3,4-dimethylcatechol meta ring fission product. Catechol 2,3-oxygenase was induced by growth on o-xylene or on 2,3- or 3,4-dimethylphenol. The suggested hypothesis is that the first metabolic steps of growth on o-xylene involve the direct oxygenation of the aromatic nucleus, followed by meta pathway reactions.     

Isolation of a Pseudomonas stutzeri strain that degrades o-xylene

A Pseudomonas stutzeri strain capable of growing on o-xylene was isolated from enrichment cultures. The organism grew on 2,3- and 3,4-dimethylphenol but not on 2-methylbenzyl alcohol, o-tolualdehyde, or o-toluate. P. stutzeri was not able to utilize m-xylene, p-xylene, or 1,2,4-trimethylbenzene, but growth was observed in the presence of the corresponding alcohols and acids. From the Pseudomonas cultures supplied with o-xylene, 2,3-dimethylphenol was isolated and identified. When resting P. stutzeri cells were incubated with 2,3-dimethylphenol, the reaction mixture turned greenish yellow and showed spectral properties identical to those of the 3,4-dimethylcatechol meta ring fission product. Catechol 2,3-oxygenase was induced by growth on o-xylene or on 2,3- or 3,4-dimethylphenol. The suggested hypothesis is that the first metabolic steps of growth on o-xylene involve the direct oxygenation of the aromatic nucleus, followed by meta pathway reactions.     

Microbial metabolism of quinoline and related compounds. IX. Degradation of 6-hydroxyquinoline and quinoline by Pseudomonas diminuta 31/1 Fa1 and Bacillus circulans 31/2 A1

Two strains, using 6-hydroxyquinoline as sole source of energy, carbon and nitrogen, have been isolated. These bacteria, designated 31/1 Fa1 and 31/2 A1, are also able to degrade quinoline. According to their physiological properties strain 31/1 Fa1 has been identified as Pseudomonas diminuta and strain 31/2 A1 as Bacillus circulans. 6-Hydroxy-2-oxo-1,2-dihydroquinoline was found as intermediate in the degradation of 6-hydroxyquinoline and quinoline. 2-Oxo-1,2-dihydroquinoline was the first metabolite in the degradation of quinoline.     

Synthesis and anti-inflammatory evaluation of 4-anilinofuro[2,3-b]quinoline and 4-phenoxyfuro[2,3-b]quinoline derivatives. Part 3

Mast cells, neutrophils and macrophages are important inflammatory cells that have been implicated in the pathogenesis of acute and chronic inflammatory diseases. To explore a novel anti-inflammatory agent, we have synthesized certain 4-anilinofuro[2,3-b]quinoline and 4-phenoxyfuro[2,3-b]quinoline derivatives and evaluated their anti-inflammatory activities by reaction of 3,4-dichlorofuro[2,3-b]quinoline with appropriate Ar-NH(2) or Ar-OH. Compounds 6a and 15 were proved to be more potent than the reference inhibitor, mepacrine for the inhibition of rat peritoneal mast cell degranulation with IC(50) values of 6.5 and 16.4 microM, respectively. Compounds 2b, 6a, 10, and 15 also showed potent inhibitory activity (IC(50)=7.2-29.4 microM) for the secretion of lysosomal enzyme and beta-glucuronidase from neutrophils. These results also indicated that oxime derivatives are more potent than the respective ketone precursors (6a> or =2a; 7a> or =3), and the substituent such as Me at the oxime decreased inhibitory activity (6a> or =6b; 7a> or =7b). Among these derivatives, compound 6a showed the most potent activity with IC(50) values of 6.5-11.6 microM for the inhibition of mast cell degranulation and neutrophil degranulation.     

Isolation of Zeanic Acid,a Natural Plant Growth-regulator from Corn Steep Liquor and Its Chemical Structure

Corn steep liquor markedly inhibited the growth of the grass, alfalfa, as previously reported. The active principles from corn steep liquor were isolated. From the acidic fraction of corn steep liquor, white needles and yellow needles were isolated. The compound of white needles, which inhibited the germination of alfalfa seeds at the concentrations above 500 ppm, was found to be identical with ferulic acid known as germination inhibitor of plant seeds. The compound of yellow needles did not inhibit the germination of alfalfa seeds, but stimulated the growth of the plant. It has a structure related to β-acid which has been isolated from rice-bran and has been identified as 2,6-dihydroxycinchoninic acid. This active substance is a new quinoline, 2,8-dihydroxycinchoninic acid and was named zeanic acid.     

X-ray and molecular modelling in fragment-based design of three small quinoline scaffolds for HIV integrase inhibitors

Crystal structures of three small molecular scaffolds based on quinoline, 2-methylquinoline-5,8-dione, 5-hydroxy-quinaldine-6-carboxylic acid and 8-hydroxy-quinaldine-7-carboxylic acid, were characterised. 5-Hydroxy-quinaldine-6-carboxylic acid was co-crystallized with cobalt(II) chloride to form a model of divalent metal cation-ligand interactions for potential HIV integrase inhibitors. Molecular docking into active site of HIV IN was also performed on 1WKN PDB file. Selected ligand-protein interactions have been found specific for active compounds. Studied structures can be used as scaffolds in fragment-based design of new potent drugs.     

Microbial degradation of quinoline and methylquinolines

Several bacterial cultures were isolated that are able to degrade quinoline and to transform or to degrade methylquinolines. The degradation of quinoline by strains of Pseudomonas aeruginosa QP and P. putida QP produced hydroxyquinolines, a transient pink compound, and other undetermined products. The quinoline-degrading strains of P. aeruginosa QP and P. putida QP hydroxylated a limited number of methylquinolines but could not degrade them, nor could they transform 2-methylquinoline, isoquinoline, or pyridine. Another pseudomonad, Pseudomonas sp. strain MQP, was isolated that could degrade 2-methylquinoline. P. aeruginosa QP was able to degrade or to transform quinoline and a few methylquinolines in a complex heterocyclic nitrogen-containing fraction of a shale oil. All of the quinoline- and methylquinoline-degrading strains have multiple plasmids including a common 250-kilobase plasmid. The 225-, 250-, and 320-kilobase plasmids of the P. aeruginosa QP strain all contained genes involved in quinoline metabolism.