Synthesis, and cytotoxic activity of some novel indolo[2,3-b]quinoline derivatives: DNA topoisomerase II inhibitors

A series of new 5H-indolo[2,3-b]quinoline derivatives bearing methoxy and methyl groups at C-2 and C-9 was synthesized (according to the modified Graebe-Ullmann reaction). These compounds were evaluated for their antimicrobial and cytotoxic activity and tested as inhibitors of DNA topoisomerase II. Lipophilic and calf thymus DNA binding properties of these compounds were also established. In the SAR studies we used quantum-mechanical methodology to analyze the molecular properties of the drugs. All of the 5H-indolo[2,3-b]quinolines tested were found to inhibit the growth of gram-positive bacteria and pathogenic fungi at MIC ranging between 2.0 and 6.0 microM. They showed also cytotoxic activity in vitro against several human cancer cell lines of different origin (ID50 varied from 0.6 to 1.4 microM), and stimulated the formation of topoisomerase-II-mediated pSP65 DNA cleavage at concentration between 0.2 and 0.5 microM. The most active indolo[2,3-b]quinolines which had the greatest contribution to the increase in the Tm of DNA displayed also the highest DNA binding constants and the highest cytotoxic activity. The differences in DNA binding properties and cytotoxic activity seem to be more related to steric than electrostatic effects.     

Synthesis and in vitro antiproliferative activity of new 11-aminoalkylamino-substituted 5H- and 6H-indolo[2,3-b]quinolines; structure-activity relationships of neocryptolepines and 6-methyl congeners

The present report describes the synthesis and antiproliferative evaluation of certain 11-aminoalkylamino-substituted 5H- and 6H-indolo[2,3-b]quinolines and their methylated derivatives. These 5-Me- and 6-Me-indolo[2,3-b]quinoline derivatives 10-14, 20 were prepared by amination at the C-11 position of the 11-chloro-5-methyl-5H- and 11-chloro-6-methyl-6H-indolo[2,3-b]quinolines with different substituents on the quinoline ring. The 11-aminoalkylaminomethylated 23, the homologue of 11, was prepared from the same intermediate for a further SAR study. These intermediates are accessible from 4-substituted anilines or their N-methylated analogues and methyl indole-3-carboxylate as a counterpart. The in vitro antiproliferative assay indicated that the 5-methylated derivatives 10-14 are more cytotoxic than their respective 6-methylated 6H-indolo[2,3-b]quinoline derivatives 20. Among them, N-(3-aminopropyl)-2-bromo-5-methyl-5H-indolo[2,3-b]quinolin-11-amine 12f was the most cytotoxic with a mean IC(50) value of 0.12 μM against human leukemia MV4-11 cell line, and also exhibited selective cytotoxicities against A549 (lung cancer), HCT116 (colon cancer) cell lines and normal fibroblast BALB/3T3 with IC(50) values of 0.543, 0.274 and 0.869 μM, respectively. The binding constant of products 12f and 20f to salmon fish sperm DNA were also evaluated using UV-vis absorption spectroscopy, indicating intercalation binding with a constant of 2.93×10(5) and 3.28×10(5)Lmol(-1), respectively.     

DNA interaction and cytotoxicity of a new series of indolo[2,3-b]quinoxaline and pyridopyrazino[2,3-b]indole derivatives.

Absorption, melting temperature and linear dichroism measurements were performed to investigate the interaction with DNA of a series of 16 tricyclic and tetracyclic compounds related to the antiviral agent B-220. The relative DNA affinity of the test compounds containing an indolo[2,3-b]quinoxaline, pyridopyrazino[2,3-b]indoles or pyrazino[2,3-b]indole planar chromophore varies significantly depending on the nature of the side chain grafted onto the indole nitrogen. Compounds with a dimethylaminoethyl chain strongly bind to DNA and exhibit a preference for GC-rich DNA sequences, as revealed by DNase I footprinting. Weaker DNA interactions were detected with those bearing a morpholinoethyl side chain. The incorporation of a 2,3-dihydroxypropyl side chain does not reinforce the DNA interaction compared with the unsubstituted analogues. Both the DNA relaxation assay and cytotoxicity study using two human leukemia cell lines sensitive (HL-60) or resistant (HL-60/MX2) to the antitumor drug mitoxantrone, indicate that topoisomerase II is not a privileged target for the test compounds which only weakly interfere with the catalytic activity of the DNA cleaving enzyme. Cytometry studies showed that the most cytotoxic compounds induce a massive accumulation of cells in the G2/M phase of the cell cycle. Collectively, the data show a relationship between DNA binding and cytotoxicity in the indolo[2,3-b]quinoxaline series.     

Cytotoxic activity toward KB cells of 2-substituted naphtho[2,3-b]furan-4,9-diones and their related compounds

We investigated the cytotoxic activity of 2-substituted naphtho[2,3-b]furan-4,9-diones. We have previously synthesized 33 types of 2-substituted and related compounds, and the cytotoxic activity of these compounds was then examined by a KB cell culture assay. 2-(3-Furanoyl)benzoic acids and 1,4-naphthoquinones had no activity. 2-Acetyl-4,9-dimethoxynaphtho[2,3-b]furan 4 showed low activity. However, parent naphtho[2,3-b]furan-4,9-dione 2 and most 2-substituted derivatives exhibited cytotoxic activity. The parent structure was therefore for cytotoxicity. 2-Formylnaphtho[2,3-b]furan-4,9-dione 11 had particularly potent activity (ED50=0.09 microg/ml).     

Antibacterial profile against drug-resistant Staphylococcus epidermidis clinical strain and structure-activity relationship studies of 1H-pyrazolo[3,4-b]pyridine and thieno[2,3-b]pyridine derivatives

Antibacterial resistance is a complex problem that contributes to health and economic losses worldwide. The Staphylococcus epidermidis is an important nosocomial pathogen that affects immunocompromised patients or those with indwelling devices. Currently, there are several resistant strains including S. epidermidis that became an important medical issue mainly in hospital environment. In this work, we report the biological and theoretical evaluations of a 4-(arylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acids series (1, 1a-m) and the comparison with a new isosteric ring nucleus series, 4-(arylamino)thieno[2,3-b]pyridine-5-carboxylic acids derivatives (2, 2a-m). Our results revealed the 1H-pyrazolo[3,4-b]pyridine derivatives significant antibacterial activity against a drug-resistant S. epidermidis clinical strain in contrast to the thieno[2,3-b]pyridine series. The minimal inhibitory concentration (MIC) of the most active derivatives (1a, 1c, 1e, and 1f) against S. epidermidis was similar to that of oxacillin and twofold better than chloramphenicol. Interestingly, the position of the functional groups has a great impact on the activity as observed in our structure-activity relationship (SAR) study. The SAR of 1H-pyrazolo[3,4-b]pyridine derivatives shows that the highest inhibitory activity is observed when the meta position is occupied by electronegative substituents. The molecular modeling analysis of frontier molecular orbitals revealed that the LUMO density is less intense in meta than in ortho and para positions for both series (1 and 2), whereas HOMO density is overconcentrated in 1H-pyrazolo[3,4-b]pyridine ring nucleus compared to the thieno[2,3-b]pyridine system. The most active derivatives of series 1 were submitted to in silico ADMET screening, which confirmed these compounds as potential antibacterial candidates.     

Isolation and identification of the intermediates during pyrazole formation of some carbohydrate hydrazone derivatives

Reaction of the oxidation product of L-ascorbic acid, dehydro-L-ascorbic acid, with o-phenylenediamine, followed by 2,4,6-trichlorophenylhydrazine (3) afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-L-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one (4), whose structure was deduced from studying its periodate oxidation, which gave the glyoxal derivative 3-[1-(2,4,6-trichlorophenylhydrazono)glyoxal-1-yl]quinoxalin-2(1H)one (5) that upon reduction afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-2-hydroxyethy-1-yl]quinoxalin-2(1H)one (6). The reaction of 5 with 3 afforded the bishydrazone 3-[1,2-bis(2,4,6-trichlorophenylhydrazono)glyoxal-1-yl]quinoxalin-2(1H)one. The reaction of 5 with acetic anhydride in pyridine afforded the 2,3-dihydrofuro[2,3-b]quinoxaline derivative 2-acetoxy-3-[2-acetyl-2-(2,4,6-trichlorophenyl)hydrazono)]-2,3-dihydrofuro[2,3-b]quinoxaline. Acetylation of 4 with acetic anhydride in pyridine afforded the acyclic diacetate intermediate 3-[3,4-di-O-acetyl-2-deoxy-1-(2,4,6-trichlorophenylhydra-zono)but-2-en-1-yl]quinoxalin-2(1H)one (12), which was also obtained from the reaction of 4 with boiling acetic anhydride. Compound 12 rearranged under the reaction conditions to give the pyrazole derivatives 3-[5-(ace-toxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin-2(1H)one (14) and 2-acetoxy-3-[5-(acetoxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl)]quinoxaline (15), as well as the 2,3-dihydrofuro[2,3-b]quinoxaline derivative 2-(2-acetoxyethen-2-yl)-3-[2-(2,4,6-trichlorophenyl)hydrazono]-2,3-dihydrofuro[2,3-b]quinoxaline. Acetylation of 3-[5-(hydroxymethyl)-l-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin-2(1H)one (16) with acetic anhydride in pyridine or 12 with boiling acetic anhydride afforded 15 and 16, respectively. Treatment of 4 with diluted sodium hydroxide afforded the pyrazolo[2,3-b]quinoxaline (flavazole) derivative 1-(2,4,6-trichlorophenyl)-3-(L-threo-glycerol-1-yl)pyrazolo[2,3-b]quinoxaline whose acetylation afforded the acetyl derivative 3-(2,3,4-tri-O-acetyl-L-threo-glycerol-1-yl)-1-(2,4,6-trichlorophenyl)pyrazolo[2,3-b]quinoxaline. The assigned structures were based on spectral analysis. The activity of compound 4 against hepatitis B virus has been studied.     

Novel 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines as 5-HT6 agonists and antagonists

1-Aminoethyl-3-arylsulfonyl-1H-indoles 1 are 5-HT(6) receptor ligands with modest activity in a 5-HT(6) cyclase assay. Introduction of an additional nitrogen in the indole ring provides 1-aminoethyl-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines 2 with both enhanced 5-HT(6) affinity and cyclase activity, many acting as 5-HT(6) agonists. We constrained the basic side chain as part of a ring to make 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines incorporating a pyrrolidinyl 3 or piperidinyl 4 ring system. Preparation of compounds 3 and 4 required synthesis of the key intermediates, 1-(pyrrolidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 7 and 1-(piperidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 8, respectively. Intermediates 7 were prepared through alkylation of 7-azaindole while the intermediates 8 required an alternate synthesis. The compounds of both series 3 and 4 were shown to have high binding affinities for the 5-HT(6) receptor. The in vitro functional activity at the 5-HT(6) receptor varied depending on various functionalities including the selection of the arylsulfonyl, the substitution on the arylsulfonyl group, the ring size, and the substitution on the basic amine moiety producing either 5-HT(6) receptor agonists or antagonists.     

Synthesis and biological evaluation of tetracyclic thienopyridones as antibacterial and antitumor agents

A facile synthesis of model 4-oxopyrido[3',2':4,5]thieno[3,2-b]indole-3-carboxylic acids 9a-e was achieved via Stille arylation of 2-chloro-3-nitro-4-oxothieno[2,3-b]pyridine-5-carboxylate and a subsequent microwave-assisted phosphite-mediated Cadogan reaction. The new compounds were tested for their in vitro antimicrobial and antiproliferative activity. Compounds 9a-c and 9e exhibited very high potency against Gram positive Bacillus subtilis and Bacillus megaterium at concentrations 0.000015-0.007 μg/mL. They also displayed excellent activity towards other Gram positive bacilli and staphylococci and Gram negative Haemophilus influenzae, being in most cases superior or equal to commercial fluoroquinolones. Both 9a and 9c were inhibitors of the DNA gyrase activity. As concerns antitumor properties, compounds 9b-e showed growth inhibition of MCF-7 breast tumor and A549 non-small cell lung cancer cells with IC(50) 1.6-2.8 μM and 2.6-6.9 μM, respectively, coupled with absence of cytotoxicity towards normal cells. These compounds are promising as dual acting chemotherapeutics.     

Novel cyano- and amidino-substituted derivatives of thieno[2,3-b]- and thieno[3,2-b]thiophene-2-carboxanilides and thieno[3',2':4,5]thieno- and thieno[2',3':4,5]thieno [2,3-c]quinolones: synthesis, photochemical synthesis, DNA binding, and antitumor evaluation

A series of cyano- and amidino-substituted derivatives of thieno[2,3-b]- and thieno[3,2-b]thiophene-2-carboxanilides and their 'cyclic' derivatives (quinolones) were synthesized. 'Cyclic' compounds displayed a rather strong and differential antiproliferative effect on various cell lines, while the 'acyclic' amidino-substituted compounds were much more active, but showing mostly non-differential cytotoxicity, whereas cyano-substituted compounds (2a,b) produced a strikingly strong effect selectively on HeLa and Hep-2 cell lines. Antiproliferative activity of 'cyclic' derivatives is very likely caused by intercalation into DNA, while their 'acyclic' analogues use other target(s) and/or mechanisms of action.     

Furanonaphthoquinones,atraric acid and a benzofuran from the stem barks of Newbouldia laevis

The series of naturally occurring furanonaphthoquinones is extended by identification of the derivatives 2-(1'-methylethenyl)-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)-7-hydroxynaphtho[2,3-b]furan-4,9-dione. They are accompanied in the stem barks of Newbouldia laevis by the known analogues 5-hydroxy-dehydro-iso-alpha-lapachone, 2-acetyl-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)naphtho[2,3-b]furan-4,9-dione along with the rare atraric acid and the new 2-(1'-methylethenyl)-6-hydroxy-2,3-dihydrobenzofuran. The structures of these compounds were established from spectroscopic studies.     

Synthesis of new aromatic pyrrolo[2,1-c] [1,4]benzodiazepines and pyrrolo[1,2-a]thieno[3,2-e] [1,4]diazepines as anti-tumoral agents

Diazepine analogs of thieno[2,3-b]pyrrolizin-8-ones were synthesized by aromatization of 2-hydroxypyrrolo[1,2-a]thieno[3,2-e][1,4]diazepines. These compounds were evaluated in vitro for their antiproliferative activity against the L1210 leukemia cell line. The activity of these compounds was in the micromolar range, the best result being for the mixture of the isomers 5 and 6 which showed a 0.35 microM IC50 against cell growth.     

Synthesis and biological evaluation of 7-azaindole derivatives, synthetic cytokinin analogues

Cytokinins, N6-substituted adenine derivatives, are plant hormones playing important roles in various processes in plant development. Furthermore, cytokinins and their derivatives are able to control mammalian cell apoptosis and differentiation. The aim of our study was the synthesis of 7-azaindole derivatives as cytokinin analogues with the Hartwig-Buchwald coupling reaction in order to evaluate their biological properties on human myeloblastic leukaemia cells (HL-60 cell line). All these compounds presented a cytotoxic activity on HL-60 cells especially the 4-phenylaminopyrrolo[2,3-b]pyridine and the 4-phenethylaminopyrrolo[2,3-b]pyridine.     

Synthesis and anti-inflammatory evaluation of 9-phenoxyacridine and 4-phenoxyfuro[2,3-b]quinoline derivatives. Part 2

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 9-phenoxyacridine and 4-phenoxyfuro[2,3-b]quinoline derivatives and evaluated their anti-inflammatory activities. The title compounds were synthesized by reaction of either 9-chloroacridine or 3,4-dichlorofuro[2,3-b]quinoline with appropriate Ar-OH and their anti-inflammatory activities were studied on inhibitory effects on the activation of mast cells, neutrophils and macrophages. Four 9-(4-formylphenoxy)acridine derivatives 2b-2e 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 6.1, 5.9, 13.5, and 4.7 microM, respectively. Compounds 2c, 3b, 3c, and 5a also showed potent inhibitory activity (IC(50)=4.3-18.3 microM) for the secretion of lysosomal enzyme and beta-glucuronidase from neutrophils. In addition, 2d, 3a, and 4 inhibited TNF-alpha formation from the N9 cells (the brain resident macrophages) with IC(50) vales less then 10 microM. These results indicated that acridine derivatives exhibited more potent anti-inflammatory activities than their respective furo[2,3-b]quinoline counterparts (4 vs 9; 5a vs 10a; 5b vs 10b).     

Microbial transformation of azacarbazoles X: Regioselective hydroxylation of 5,11-dimethyl-5H-indolo [2,3-b]quinoline, a novel DNA topoisomerase II inhibitor, by Rhizopus arrhizus

Summary Microbial transformation of cytotoxic 5,11-dimethyl-5H-indolo[2,3-b]quinoline (a compound displaying antitumor activity and affecting the activity of calf thymus DNA topoisomerase II) was performed by the Rhizopus arrhizus strain and yielded a 9-hydroxy derivative. The metabolite obtained displayed a stronger cytotoxity against KB cells than the parent compound (ID₅₀=0.001 mol/mL), and stimulated also the formation of calf thymus topoisomerase II mediated pSP65 DNA cleavage in vitro at the concentration of 3 M. Being analogous to 9-hydroxyellipticine (which is an antitumor alkaloid), this novel indolo[2,3-b] quinoline derivative can be regarded as a novel potential antitumor agent.     

Synthesis and cytotoxicity evaluation of 6,11-dihydro-pyridazo- and 6,11-dihydro-pyrido[2,3-b]phenazine-6,11-diones

The 6,11-dihydro-pyridazo[2,3-b]phenazine-6,11-dione and 6,11-dihydro-pyrido[2,3-b]phenazine-6,11-dione derivatives were synthesized from 6,7-dichloro-5,8-phthalazinedione and 6,7-dichloro-5,8-quinolinedione, respectively, producing a series of new anticancer drugs. The cytotoxic activities of the prepared compounds were evaluated by a SRB (Sulforhodamine B) assay against the following tumor cell lines: A459 (human lung), SK-OV-3 (human ovarian), SK-MEL-2 (human melanoma), XF498 (human CNS), and HCT 15 (human colon). Almost all the derivatives of the 6,11-dihydro-pyridazo[2[,3-b]phenazine-6,11-dione and 6,11-dihydro-pyrido[2,3-b]phenazine-6,11-dione, tetracyclic heteroquinone analogues with four or three nitrogen atoms, exhibited excellent cytotoxicity on almost all the human tumor cell lines tested. Specifically, 6,11-dihydro-pyridazo[2,3-b]phenazine-6,11-dione (4a) exhibited potent activity against all the tumor cell lines, and in particular, its cytotoxic effect against HCT 15 (ED(50)=0.004 microg/mL) was 25 times greater than that of doxorubicin (ED(50)=0.093 microg/mL).     

DNA adduct formation of 14 heterocyclic aromatic amines in mouse tissue after oral administration and characterization of the DNA adduct formed by 2-amino-9H-pyrido[2,3-b]indole (AalphaC), analysed by 32P_HPLC.

Heterocyclic aromatic amines (HAAs) are produced during cooking of proteinaceous food such as meat and fish. Humans eating a normal diet are regularly exposed to these food-borne substances. HAAs have proved to be carcinogenic in animals and to induce early lesions in the development of cancer. DNA adduct levels in mouse liver have been measured by 32P-HPLC after oral administration each of 14 different HAAs. The highest DNA adduct levels were detected for 3-amino-1-methyl-5H-pyrido[4,3-b]-indole (Trp-P-2), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 2-amino-9H-pyrido[2,3-b]indole (AalphaC), respectively. To assess a relative risk in a human population, a relative risk index was calculated by combining the DNA adduct levels in mouse liver with human daily intake of heterocyclic amines in a US and in a Swedish population. Such calculations suggest that AalphaC presents the highest risk for humans, e.g. nine-fold higher compared with the most abundant amines in food, 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP). Therefore, the distribution of DNA adducts in different tissues of mouse was investigated after oral administration of AalphaC. The highest AalphaC-DNA adduct levels were found in liver (137 adducts/10(8) normal nucleotides) followed by heart, kidney, lung, large intestine, small intestine, stomach and spleen, in descending order. To characterize the chemical structure of the major DNA adduct, chemical synthesis was performed. The major DNA adduct from the in vivo experiments was characterized by five different methods. On the basis of these results, the adduct was characterized as N2-(deoxyguanin-8-yl)-2-amino-9H-pyrido [2,3-b]indole. Considering the abundance of AalphaC not only in grilled meat, but also in other products like grilled chicken, vegetables and cigarette smoke and in light of the results of the present study, it is suggested that the human cancer risk for AalphaC might be underestimated.     

Bacterial Transformations of Naphthothiophenes

Naphthothiophenes are minor components of fossil fuels, and they can enter the environment from oil spills. Naphtho[2,1-b]thiophene, naphtho[2,3-b]thiophene, and 1-methylnaphtho[2,1-b]thiophene were synthesized and used in biodegradation studies with 1-methylnaphthalene (1-MN)-degrading Pseudomonas strains W1, F, and BT1. Cultures were incubated with one of the naphthothiophenes with or without 1-MN, acidified, and extracted with CH(inf2)Cl(inf2). The extracts were analyzed by gas chromatography with flame photometric and mass detectors to characterize sulfur-containing metabolites and with an atomic emission detector for quantification. Only strain W1 was able to grow on naphtho[2,1-b]thiophene, but strains F and BT1 cometabolized this compound if 1-MN was present. 1-MN was required by all three strains to metabolize naphtho[2,3-b]thiophene, which was more resistant to biodegradation than the [2,1-b] isomer. Two metabolites of naphtho [2,1-b]thiophene were purified, analyzed by (sup1)H nuclear magnetic resonance spectroscopy, and found to be 4-hydroxybenzothiophene-5-carboxylic acid (metabolite I) and 5-hydroxybenzothiophene-4-carboxylic acid (metabolite II). In cultures of strain W1 grown for 7 days on 52 (mu)mol of naphtho[2,1-b]thiophene, >84% of the substrate was degraded and metabolites I and II accounted for 19 and 9%, respectively, of the original amount of naphtho[2,1-b]thiophene. When 1-MN was present, strain W1 degraded >97% of the naphtho[2,1-b]thiophene and similar amounts of metabolite II were produced, but metabolite I did not accumulate. 1-MN was shown to promote the further degradation of metabolite I, but not of metabolite II, by strain W1. Thus, 1-MN enhanced the biodegradation of naphtho[2,1-b]thiophene. Approximately 70% of the 1-methylnaphtho [2,1-b]thiophene added to cultures of strain W1 with 1-MN was recovered as 4-hydroxy-3-methylbenzothiophene-5-carboxylic acid, the 3-methyl analog of metabolite I. The methyl substitution hindered further metabolism of 3-methyl-metabolite I even in the presence of 1-MN. Cometabolism of naphtho[2,3-b]thiophene yielded two products that were tentatively identified as 5-hydroxybenzothiophene-6-carboxylic and 6-hydroxybenzothiophene-5-carboxylic acids.     

Synthesis, cytotoxic activity, NMR study and stereochemical effects of some new pyrano[3,2-b]thioxanthen-6-ones and pyrano[2,3-c]thioxanthen-7-ones

Some new substituted pyrano[3,2-b]thioxanthen-6-ones and pyrano[2,3-c]thioxanthen-7-ones were prepared and their cytotoxic activity was evaluated using acronycine as the reference compound. The conformation of the molecules was also investigated in an effort to correlate this parameter with the biological activity.     

DNA adduct formation of 14 heterocyclic aromatic amines in mouse tissue after oral administration and characterization of the DNA adduct formed by 2-amino-9H-pyrido[2,3-b]indole (AαC), analysed by 32 P-HPLC

Heterocyclic aromatic amines (HAAs) are produced during cooking of proteinaceous food such as meat and fish. Humans eating a normal diet are regularly exposed to these food-borne substances. HAAs have proved to be carcinogenic in animals and to induce early lesions in the development of cancer. DNA adduct levels in mouse liver have been measured by ³²P-HPLC after oral administration each of 14 different HAAs. The highest DNA adduct levels were detected for 3-amino-1-methyl-5H-pyrido[4,3-b]-indole (Trp-P-2), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 2-amino-9H-pyrido[2,3-b]indole (AαC), respectively. To assess a relative risk in a human population, a relative risk index was calculated by combining the DNA adduct levels in mouse liver with human daily intake of heterocyclic amines in a US and in a Swedish population. Such calculations suggest that AαC presents the highest risk for humans, e.g. nine-fold higher compared with the most abundant amines in food, 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP). Therefore, the distribution of DNA adducts in different tissues of mouse was investigated after oral administration of AαC. The highest AαC–DNA adduct levels were found in liver (137 adducts/10⁸ normal nucleotides) followed by heart, kidney, lung, large intestine, small intestine, stomach and spleen, in descending order. To characterize the chemical structure of the major DNA adduct, chemical synthesis was performed. The major DNA adduct from the in vivo experiments was characterized by five different methods. On the basis of these results, the adduct was characterized as N²-(deoxyguanin-8-yl)-2-amino-9H-pyrido[2,3-b]indole. Considering the abundance of AαC not only in grilled meat, but also in other products like grilled chicken, vegetables and cigarette smoke and in light of the results of the present study, it is suggested that the human cancer risk for AαC might be underestimated.     

2-substituted-4-aryl-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one as a structurally new NK1 antagonist

The structurally novel pyrimido[4,5-b][1,5]oxazocine derivative 3, a hybrid compound of pyrido[4,3-b]- and [2,3-b]-1,5-oxazocine (1 and 2, respectively), was designed and synthesized. We examined the atropisomeric property and the NK1 antagonist activity of 3. Compound 3 was found to possess both a feature of 1, free rotation about the biaryl bond, and a feature of 2, potent in vivo activity.