CTBT (7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine) producing ROS affects growth and viability of filamentous fungi

CTBT (7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine) causes intracellular superoxide production and oxidative stress and enhances the susceptibility of Saccharomyces cerevisiae, Candida albicans, and C.?glabrata cells to cycloheximide, 5-fluorocytosine, and azole antimycotic drugs. Here, we demonstrate the antifungal activity of CTBT against 14 tested filamentous fungi. CTBT prevented spore germination and mycelial proliferation of Aspergillus niger and the pathogenic Aspergillus fumigatus. The action of CTBT is fungicidal. CTBT increased the formation of reactive oxygen species in fungal mycelium as detected by 2',7'-dichlorodihydrofluorescein diacetate and reduced the radial growth of colonies in a dose-dependent manner. Co-application of CTBT and itraconazole led to complete inhibition of fungal growth at dosages lower than the chemicals alone. Antifungal and chemosensitizing activities of CTBT in filamentous fungi may be useful in combination treatments of infections caused by drug-resistant fungal pathogens.     

Isoindolo[2,1-c]benzo[1,2,4]triazines: a new ring system with antiproliferative activity

A series of isoindolo-benzo-triazines of type 4 was obtained by diazotization of 2-(2-aminoaryl)-1-cyanoisoindoles 3a-j. All the synthesized derivatives were screened by the National Cancer Institute (NCI, Bethesda, USA), for in vitro antitumor activity against a 3-human cancer cell line panel consisting of MCF7 (breast), NCI-H460 (lung), and SF-268 (CNS). Derivatives 4a, f, i, j were selected to be evaluated in the full panel of about 50 human tumor cell lines derived from nine human cancer cell types and showed antiproliferative activity generally in the micromolar range. The most sensitive cell lines were: MOLT-4 and SR of the leukemia subpanel, A549/ATCC and EKVX of the nonsmall cell lung subpanel, COLO-205 of the colon cancer subpanel, LOX IMVI of the Melanoma subpanel, OVCAR-8 of the ovarian cancer subpanel, and MCF7, BT-549 of the breast cancer subpanel.     

Synthesis of new pyrazolo[5,1-c][1,2,4] benzotriazines, pyrazolo[5,1-c]pyrido[4,3-e][1,2,4] triazines and their open analogues as cytotoxic agents in normoxic and hypoxic conditions

The synthesis and antitumor activity in normoxic and hypoxic conditions of a series of pyrazolo[5,1-c][1,2,4]benzotriazine and its related analogues are reported. All compounds were tested on human colorectal adenocarcinoma cell line HCT-8 and for compounds 15 and 20, which show to have selective cytotoxicity in hypoxic and in normoxic conditions respectively, ROS production, cell cycle, and DNA fragmentation were measured. This preliminary study encouraged us to consider 15 and 20 as interesting leads for further optimization.     

Propolis protects human spermatozoa from DNA damage caused by benzo[a]pyrene and exogenous reactive oxygen species

Many environmental, physiological and genetic factors have been implicated in defective sperm function, the most common cause of infertility. In addition, sperm preparation techniques such as centrifugation, used prior to in vitro fertilization, are associated with the generation of reactive oxygen species (ROS) and an increase in the level of DNA damage. Factors that can offer spermatozoa protection are, therefore, of great importance. This study was designed to examine in vitro the effect of a Chilean propolis ethanolic extract on human spermatozoa treated with benzo[a]pyrene and exogenous reactive oxygen species. Our experimental evidence demonstrated that the natural drug under investigation is able to protect genomic DNA by damage induced by benzo[a]pyrene, hydrogen peroxide (H2O2) and hydrogen peroxide in combination with adenosine 5'-diphosphate (ADP) and ferrous sulfate (FeSO4), determining a significant reduction of the intracellular oxidants. An increase in membrane damage, measured by monitoring the formation of thiobarbituric acid-reactive substances (TBARS) and lactic dehydrogenase (LDH) release, was observed only in sperm treated with H2O2, ADP and FeSO4. The propolis extract was shown to possess the capacity to protect sperm membrane from the deleterious action of oxidative attack, reducing TBARS formation and LDH release. In summary, our results evidence that the protective effect exhibited by this natural compound in human spermatozoa is correlated, at least in part, to the antioxidant capacity of its active components, and suggest that propolis may have a role in protection against male infertility.     

Synthesis and cytokinin-like activity of 7-chloro-imidazo[1,2-c]pyrimidines

Some 5-amino substituted 7-chloro-imidazo[1,2-c]pyrimidines and 7-chloro-8-methylthio-imidazo[1,2-c]pyrimidines were synthesized for further information on the role of the purine ring in cytokinin structure/activity relationships. Their cytokinin-like activity was examined using four different tests: expansion of cucumber etiolated cotyledons; formation of chlorophyll in etiolated cotyledons of cucumber; preservation of chlorophyll breakdown in sections of barley leaves; inhibition of root growth in intact wheat seedlings. Compounds with the imidazopyrimidine ring were generally less active than those with the purine ring, with the exception of the pentenylamino derivatives, which showed an activity comparable with that of the control, kinetin.     

Effect of psoralens on Fenton-like reaction generating reactive oxygen species

Psoralens (psoralen, 5-methoxypsoralen, 8-methoxypsoralen, khellin, and visnagin) in 1 mM doses were shown to enhance the generation of reactive oxygen species, such as the hydroxyl radical (HO*), the superoxide anion radical (O2(-)), and singlet oxygen ((1)O(2)), from the system generating chemiluminescence (CL), as well as free radicals in the absence of light. The system that generated CL was made up of CoCl(2) and H(2)O(2). Incubation of psoralens in 0.2 mM doses with the generating system showed that only 8-methoxypsoralen and khellin have antioxidative effects. Antioxidative effects were also observed in the case of visnagin but in low concentration (0.05 mM). High doses of psoralens (1 mM) showed prooxidative effects. Measurements were done using a deoxyribose assay, the CL method, and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide and 2,2,6,6-tetramethylpiperidine combined with electron spin resonance spectroscopy and spectrophotometry methods.     

Substituted 7H-pyrido[4,3-c]carbazoles with potent anti-HIV activity

Several substituted 7H-pyrido[4,3-c]carbazoles were synthesized from the natural product mukonal and tested for inhibition of HIV replication in H9 lymphocytes. 5-Methoxy-7-methyl-7H-pyrido[4,3-c]carbazole (7) had an EC50 value of 0.0054 microgram/mL and the highest therapeutic index (TI = 503) in the series.     

Pyrazolo[4,3-e][1,2,4]triazine sulfonamides as carbonic anhydrase inhibitors with antitumor activity

A series of sildenafil analogues and aniline substituted pyrazolo[4,3-e][1,2,4]triazine sulfonamides were prepared and evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors and for their anticancer activity against two human breast cancer cell lines (MCF-7, MDA-MB-231). The new compounds were ineffective as CA I inhibitors, poorly inhibited CA II, but were more effective against the tumor-associated isoforms CA IX and XII, with some compounds acting as low nanomolar inhibitors. Evaluation of the cytotoxicity by using an MTT assay, the inhibition of [³H]thymidine incorporation into DNA as well as collagen synthesis inhibition, demonstrated that these sulfonamides exhibit cytotoxic effects on breast cancer cell lines ex vivo.     

Pyridazine derivatives and related compounds. Part 13: Synthesis and antimicrobial activity of some pyridazino[3',4':3,4]pyrazolo[5,1-c]-1,2,4-triazines

A general method for the preparation of substituted pyridazinopyrazolotriazines is reported. 3-Aminopyrazolo[3,4-d]pyridazine was diazotized and coupled with active methylene reagents to afford the tricyclic pyridazino[3',4':3,4]pyrazolo[5,1-c]-1,2,4-triazines with substituents such as methyl, phenyl, ethoxycarbonyl, acetyl or benzoyl, depending on the methylene reagent used. In addition several condensation reactions with hydrazines gave the corresponding acid hydrazide and/or hydrazones. Reactions of 3 with aromatic aldehydes afforded hydrazones. The products were screened for their antimicrobial activity against five microorganisms.     

Synthesis and antihypertensive activity of novel 3-benzyl-2-substituted-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-ones

A series of 3-benzyl-2-substituted-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-ones have been synthesized by the cyclocondensation of 3-amino-2-benzylamino-3H-quinazolin-4-one with a variety of one-carbon donors. The starting material 3-amino-2-benzylamino-3H-quinazolin-4-one was synthesized from methyl anthranilate by a novel innovative route. The title compounds were evaluated for their in vivo antihypertensive activity using spontaneously hypertensive rats (SHR). While all the test compounds exhibited significant antihypertensive activity, 3-benzyl-2-methyl-3H-[1,2,4]triazolo[5,1-b] quinazolin-9-one exhibited antihypertensive activity more than the reference standard prazocin.     

Identification of antitumour activity of novel derivatives of 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-dione and 8-aryl-4-imino-2,3,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3(6H)-one

The series of 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-diones (11-20) and 8-aryl-4-imino-2,3,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3(6H)-ones (21-25) were designed and their in vitro cytotoxic activities against human LS180, HeLa, T47D, A549 and RPMI 8226 carcinoma cells are presented. In the crystalline state molecule 12 exists as the predominant tautomeric 3-oxo form, whereas the second possible 3-hydroxy tautomer is not observed. Compound 19 revealed a strong affection to LS180 cancer cells at lower tested concentration (37.9 microM) and simultaneously was found to be non-toxic towards the normal cell line investigated--GMK cells. Furthermore, this compound was proved to possess the efficiency for DNA strand breakage of the examined cancer cell lines. However, imidazotriazin-3,4-dione 20 was able to cause significant viability decreases in human RPMI 8226 peripheral blood myeloma cells. Compound 22 has exhibited remarkable inhibitory effects against LS180 and A549 carcinoma cells, whereas 24 revealed the highest growth inhibition against A549 cell line. Simultaneously, at lower tested concentration these compounds were proved to be completely non-toxic for GMK cells. Moreover, cytotoxic and antibacterial properties of starting, tautomeric 1-aryl-2-hydrazonoimidazolidines (1-6 and 8-9) are presented. Six of them (1-2, 4-6 and 9) proved active as antimicrobials. All these compounds revealed MIC values in the range of 15.0-78.6 microM. Their activities were compared to those of ampicillin and chloramphenicol.     

Novel tetrahydropyrido[3,2-c]pyrroles as 5-HT(7) antagonists

The synthesis and SAR for a novel series of tetrahydropyrido[3,2-c]pyrroles is described. Optimization of the pendant aryl ring lead to high binding affinity at the 5-HT₇ receptor when small lipophilic groups were placed in the para position. Modification of the N-benzyl group and secondary amine were not well tolerated. A representative set of compounds was shown to be functional antagonists of the 5-HT₇ receptor.     

Synthesis and anticonvulsant activity evaluation of 6-substituted-[1,2,4]triazolo[3,4-a](tetrazolo[5,1-a])phthalazine derivatives

With the aim of finding new anticonvulsant drugs, new 6-substituted-[1,2,4]triazolo[3,4-a] (tetrazolo[5,1-a]) phthalazine derivatives (1–34) have been designed and synthesized. All the compounds were evaluated for their anticonvulsant activities using the maximal electroshock test (MES). Most of the synthesized compounds exhibited potent anticonvulsant activities in the MES. The most promising compound 14 showed significant anticonvulsant activity in MES test with ED₅₀ value of 9.3 mg/kg. It displayed a wide margin of safety with protective index much higher than the standard drug Carbamazepine. And the potency of compound 14 against seizures induced by Pentylenetetrazole, Isoniazid, Thiosemicarbazide and 3-Mercaptopropionic acid in the chemical-induced seizure tests suggested that compound 14 displayed wide spectrum of activity in several models.     

Potent and selective adenosine A(2A) receptor antagonists: [1,2,4]-triazolo[4,3-c]pyrimidin-3-ones

Antagonism of the adenosine A_2A receptor affords a possible treatment of Parkinson’s disease. In the course of investigating pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine A_2A antagonists, we prepared [1,2,4]-triazolo[4,3-c]pyrimidin-3-ones with potent and selective (vs A₁) A_2A antagonist activity. Structure-activity relationships are described for this series.     

Discovery of anti-cancer activity for benzo[1,2,4]triazin-7-ones: Very strong correlation to pleurotin and thioredoxin reductase inhibition

The thioredoxin (Trx)–thioredoxin reductase (TrxR) system plays a key role in maintaining the cellular redox balance with Trx being over-expressed in a number of cancers. Inhibition of TrxR is an important strategy for anti-cancer drug discovery. The natural product pleurotin is a well-known irreversible inhibitor of TrxR. The cytotoxicity data for benzo[1,2,4]triazin-7-ones showed very strong correlation (Pearson correlation coefficients ∼0.8) to pleurotin using National Cancer Institute COMPARE analysis. A new 3-CF₃ substituted benzo[1,2,4]triazin-7-one gave submicromolar inhibition of TrxR, although the parent compound 1,3-diphenylbenzo[1,2,4]triazin-7-one was more cytotoxic against cancer cell lines. Benzo[1,2,4]triazin-7-ones exhibited different types of reversible inhibition of TrxR, and cyclic voltammetry showed characteristic quasi-reversible redox processes. Cell viability studies indicated strong dependence of cytotoxicity on substitution at the 6-position of the 1,3-diphenylbenzo[1,2,4]triazin-7-one ring.     

Synthesis of Certain Acyclic Nucleoside Analogs of 1,2,4-Triazolo[3,4-f][1,2,4]triazine and Pyrimido[5,4-d]pyrimidine

Abstract

Synthesis of 2-penten-1-yl (8a) and ganciclovir analog (8b) of 1,2,4-triazolo[3,4-f][1,2,4]triazine was accomplished by the ring annulation of the corresponding hydrazides (6a and 6b), which in turn was obtained by the dehydrative coupling of 4 with 5a or 5b. Base catalysed ring expansion of N9-alkylpurine-6-carbonitriles (10a 10c 10e) provided the acyclic analogs of 4-aminopyrimido-[5,4-d]pyrimidines (13a 13d 13e). Debenzylation of 13e afforded the ganciclovir analog (13f) of 4-amino-8-(β-D-ribofuranosylamino)-pyrimido[5,4-d]pyrimidine. However, compound 10b did not undergo the expected rearrangement but resulted in the formation of the methyl formimidate derivative (12).     

Synthesis of chiral pyrazolo[4,3-e][1,2,4]triazine sulfonamides with tyrosinase and urease inhibitory activity

A new series of sulfonamide derivatives of pyrazolo[4,3-e][1,2,4]triazine with chiral amino group has been synthesized and characterized. The compounds were tested for their tyrosinase and urease inhibitory activity. Evaluation of prepared derivatives demonstrated that compounds (8b) and (8j) are most potent mushroom tyrosinase inhibitors whereas all of the obtained compounds showed higher urease inhibitory activity than the standard thiourea. The compounds (8a), (8f) and (8i) exhibited excellent enzyme inhibitory activity with IC₅₀ 0.037, 0.044 and 0.042?μM, respectively, while IC₅₀ of thiourea is 20.9?μM.     

Benzo[a]yrenedione/benzo[a]pyrenediol oxidation-reduction couples and the generation of reactive reduced molecular oxygen.

The ability of the isomeric quinone metabolites of benzo[a]pyrene, benzo[a]pyrene-6,12-dione, benzo[a]pyrene-1,6-dione, and benzo[a]pyrene-3,6-dione to undergo reversible, univalent oxidation-reduction cycles involving the corresponding benzo[a]pyrenediols and intermediate semiquinone radicals has been characterized. Under anaerobic conditions, all three benzo[a]pyrenediones are easily reduced to benzo[a]pyrenediols, even by mild biological agents such as NAD(P)H, cysteamine, and glutathione. The benzo[a]pyrenediols, in turn, are very rapidly autoxidized to the benzo[a]pyrenediones when exposed to air. Substantial amounts of hydrogen peroxide are produced during these autoxidations, and other reactive reduced oxygen species, such as the superoxide and hydroxyl radicals, are probably formed transiently as well. The benzo[a]pyrenediol-benzo[a]pyrenedione interconversions proceed by one-electron steps; the corresponsing semiquinone radicals can be monitored by electron spin resonance spectroscopy as inter mediates during these reactions carried out at high pH. Benzo[a]pyrenediones induce DNA strand scission when incubated with bacteriophage T7 DNA. This damage is modified by conditions which indicate that reduced oxygen species propagate the free-radical reactions responsible for the strand scission. Benzo[a]pyrenediones are electron-acceptor substrates for NADH dehydrogenase from Clostridium kluyveri. Catalytic amounds of these benzo[a]pyrene metabolites, together with this respiratory enzyme function as cyclic oxidation-reduction couples which link NADH and molecular oxygen in the continuous production of hydrogen peroxide. These data, together with preliminary results with cells in culture, indicate that benzo[a]pyrenediones are potentially harmful metabolites of benzo[a]pyrene, acting by processes which lead to their regeneration rather than depletion; nucleic acid and call damage is probably produced by the reactive reduced oxygen species resulting from such regenerative oxidation-reduction cycles.     

Synthesis and anticonvulsant activity of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines

A series of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline derivatives was synthesized using 6-hydroxy-3,4-dihydro-1H-quinolin-2-one as a starting material. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES test) and the subcutaneous (s.c.) pentylenetetrazol test (scMet test), and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). MES and scMet tests show that 7-(4-fluorobenzyloxy)-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4l was found to be the most potent with ED50 value of 11.8 and 6.7 mg kg(-1) and protective index (PI = TD50/ED50) value of 4.6 and 8.1, respectively.