An efficient one-pot, three-component synthesis of indeno[1,2-b]quinoline-9,11(6H,10H)-dione, acridine-1,8(2H,5H)-dione and quinoline-3-carbonitrile derivatives from enaminones

An efficient one-pot, three-component method for the preparation of indeno[1,2-b]quinoline-9,11(6H,10H)-dione, acridine-1,8(2H,5H)-dione and various multi-substituted quinoline-3-carbonitrile derivatives has been developed through the Michael addition to enaminones, which was achieved by both microwave irradiation and conventional heating.

Flow injection chemiluminescence determination of isoniazid using the lucigenin–periodate system

A weak chemiluminescence (CL) signal was observed during the mixing of isoniazid with lucigenin in alkaline aqueous solution. The CL signal was enhanced more than 100 times in the presence of potassium periodate. This CL system was developed for the determination of isoniazid using a flow injection mode. The CL intensity is proportional to the concentration of isoniazid in the range 0.005-1.0 mg/L. The limit of detection is 0.0034 mg/L and the relative standard deviation is 2.0% for 0.2 mg/L isoniazid solution in 11 repeated measurements. The method was applied to the determination of isoniazid in pharmaceutical preparations and satisfactory results were obtained.

Targeted delivery of plasmid DNA into the nucleus of cells via nuclear localization signal peptide conjugated to DNA intercalating bis- and trisacridines

Efficient nuclear targeting via nonviral delivery of DNA is still an unmet challenge in gene therapy. We have synthesized a novel 9-aminoacridine amino acid monomer that conveniently allows multiple acridines to be incorporated into peptide conjugates. In particular we have prepared bis- and trisacridine conjugates of nuclear localization signal peptide (NLS) ((Acr)2-NLS and (Acr)3-NLS) and studied these as functional transporters for the nuclear delivery of DNA. We show that these conjugates can enhance transfection efficacy as well as nuclear localization of plasmid DNA by more than 50-fold when combined with polyethylenimine at an N:P ratio of 2-3. These conjugates have high reversible affinity for double stranded DNA by intercalation and the technique provides a simple means of associating NLS with DNA of any sequence and at any ratio.

Trisubstituted Acridines as G-quadruplex Telomere Targeting Agents. Effects of Extensions of the 3,6- and 9-Side Chains on Quadruplex Binding, Telomerase Activity, and Cell Proliferation

The synthesis is reported of a group of 3,6,9-trisubstituted acridine compounds as telomeric quadruplex-stabilizing ligands with systematic variations at the 3-, 6-, and 9-positions. A new microwave-assisted methodology has been developed for trisubstituted acridine synthesis. Structure-activity relationships are reported using surface plasmon resonance and a fluorescence melting assay to examine quadruplex binding, together with a telomerase inhibition assay. These reveal relationships between G-quadruplex stabilization and telomerase inhibition and optimal 3,6- and 9-substituent side-chain lengths for maximal activity. Qualitative molecular modeling using molecular dynamics simulations has been undertaken on four quadruplex-DNA complexes. Long-term exposure of MCF7 cancer cells to a subset of the most active compounds, at doses lower than the IC(50) values, showed that one compound produced a marked decrease in population growth, accompanied by senescence, which is consistent with telomere targeting by this agent.

Synthesis of acridine-nuclear localization signal (NLS) conjugates and evaluation of their impact on lipoplex and polyplex-based transfection

We report on the synthesis of various acridine (Acr)-spacer-nuclear localization signal (NLS) peptide conjugates and explore whether their use as NLS-labeling agent of plasmidic DNA could improve gene nuclear import and expression into cells when mediated by synthetic DNA complexes. As the conditions of successful use of the NLS properties to enhance gene transfer are not clear, and with the aim of detecting and defining the requirements of NLS-enhanced transfection, we investigated gene delivery and expression into various cell lines with various DNA complexes (lipoplexes or polyplexes) that were formulated for various N/P ratios from various preformed Acr-spacer-NLS/DNA complexes (1:1, 5:1 and 10:1 molar ratio). For the in vitro transfection assays, the lipoplexes and polyplexes were formulated from the preformed Acr-spacer-NLS/DNA complexes and dioctadecylamidoglycylspermine (DOGS)/dioleylphosphatidylethanolamine (DOPE) 1:1 mol and branched polyethyleneimine (PEI) 25 kDa, respectively, which are very efficient in vitro gene transfer systems. We show by fluorescence experiments that part of the acridine-NLS-conjugates remains intercalated within the plasmid for most of the N/P lipoplexes and polyplexes investigated. We show that, as several other studies performed with NLS-conjugates that are not covalently linked to DNA, the expression of the transgene is in most cases not improved upon complexation of plasmidic DNA with NLS-intercalating conjugates prior to its formulation as lipoplexes or polyplexes.

Spectrophotometric determination of the dissociation constants of crown ethers with grafted acridone unit in methanol based on Benesi-Hildebrand evaluation

As potential chromo- and fluorophores for optical sensors a number of acridone grafted crown ethers containing NO2 group(s) and/or Br or Cl atom(s) in the aromatic rings (compounds) were studied by spectrophotometric method. In the first step of this work the acid-base and complexing properties of these compounds as well as those of the acridone, thioacridone and 4,5-dinitroacridone were investigated. Compounds proved to be very week acids and therefore the conventional spectrophotometric method based on the measurement of the ratio of the protonated/deprotonated forms of the compounds was not applicable for the determination of the dissociation constants (pKa values). Thus, a new spectrophotometric approach was elaborated for the pKa determination of these compounds, which is based on spectrophotometric titration in methanol with strong base and the titration results were evaluated by the Benesi-Hildebrand method. (In the studies with TEAOH, TMAOH and LiOMe, the complex formation between the ionophores and the cations of the bases could be excluded.) As it was expected, the experimentally determined pKa values depended on the nature of the substituents of the acridone moiety and pKa values ranged between 12.6 and 14.9. The lower pKa value of thioacridone compared to the acridone can be explained by the larger size of the sulfur atom. The outstandingly larger pKa value for 4,5-dinitroacridone can be attributed to the formation of intramolecular hydrogen-bonds between the ortho-position nitro group and the NH proton. As a trend, the strong electron withdrawing nitro substituents decreased considerably the pKa values of compounds and compared to that of the halogen (Cl and Br) atoms (for example compounds and) of weaker withdrawing effect.

Synthesis and antitumor activity of 5-(9-acridinylamino)anisidine derivatives

A series of 5-(9-acridinylamino)anisidines were synthesized by condensing methoxy-substituted 1,3-phenylenediamines (10 and 11) with 9-chloroacridine derivatives to form 5-(9-acridinylamino)-m-anisidines (AMAs, 14a-e) and 5-(9-acridinylamino)-o-anisidines (AOAs, 15a-e). 5-(9-Acridinylamino)-p-anisidines (APAs, 17a-e) were synthesized by reacting 2-methoxy-5-nitroaniline (12) with 9-anilinoacridines, followed by reduction. The cytotoxic inhibition of growth of various human tumor cells in culture, inhibitory effects against topoisomerase II, and DNA interaction of these agents were studied. The structure-activity relationship studies revealed the following degree of potency: AOAs > AMAs > APAs. They also revealed that the newly synthesized derivatives bearing CONH(2)NH(2)NMe(2) and Me substituents at C4 and C5 positions of the acridine chromophore (i.e., AMA 14e, AOA 15e, and APA 17e) exhibited significant cytotoxicity against human tumor cell growth in vitro. AOA (15e) was the most potent among these derivatives, which resulted in 60% suppression of tumor volume at a dose of 20 mg/kg (Q2D x 9), intravenous injection on day 26 in nude mice bearing human breast carcinoma MX-1 xenografts.

Reactive oxygen species in spermatozoa: methods for monitoring and significance for the origins of genetic disease and infertility

Human spermatozoa generate low levels of reactive oxygen species in order to stimulate key events, such as tyrosine phosphorylation, associated with sperm capacitation. However, if the generation of these potentially pernicious oxygen metabolites becomes elevated for any reason, spermatozoa possess a limited capacity to protect themselves from oxidative stress. As a consequence, exposure of human spermatozoa to intrinsically- or extrinsically- generated reactive oxygen intermediates can result in a state of oxidative stress characterized by peroxidative damage to the sperm plasma membrane and DNA damage to the mitochondrial and nuclear genomes. Oxidative stress in the male germ line is associated with poor fertilization rates, impaired embryonic development, high levels of abortion and increased morbidity in the offspring, including childhood cancer. In this review, we consider the possible origins of oxidative damage to human spermatozoa and reflect on the important contribution such stress might make to the origins of genetic disease in our species.

A Computational Study of Carbocations from Oxidized Metabolites of Dibenzo[a,h]acridine and Their Fluorinated and Methylated Derivatives

In a model computational study aimed at understanding structure-reactivity relationships and substituent effects on carbocation stability in aza-polycyclic aromatic hydrocarbons, the epoxides, diol epoxides, and the dihydrodiols of dibenzo[a,h]acridine (DB[a,h]ACR) were studied by density functional theory at the B3LYP/6-31G level. Bay region carbocations were formed via the O-protonated epoxides in barrierless processes. Relative carbocation stabilities were determined in the gas phase and in water as solvent (polarized continuum model method). Charge delocalization modes in the resulting carbocations were deduced by gauge-independent atomic orbitals (GIAO) NMR (based on Delta delta13C values) and via the natural population analysis (NPA)-derived changes in charges. Although the solvent decreases the exothermicity of the epoxide ring-opening reactions due to greater stabilization of the reactants, relative reactivity trends remain the same. Whereas fluorine substitution at ring positions bearing significant positive charge leads to carbocation stabilization by fluorine p-pi back-bonding, fluorine substitution at a ring position that presented negative charge density in the unsubstituted compound leads to inductive destabilization. Methylated derivatives exhibit less sensitivity to substituent effects as compared to the fluorinated analogues. A bay region methyl group produces structural distortion, and this deviation from planarity destabilizes the epoxide, favoring ring opening. Relative energies, changes in NPA charges, and GIAO NMR data in the resulting "benzylic" carbocations are examined collectively and discussed, taking into account the available biological activity data on these compounds.

An aminoacridine derivative for radionuclide therapy: DNA binding properties studied in a novel cell-free in vitro assay

Radiolabelled DNA-binding compounds can be used to increase the efficiency of radionuclide cancer therapy of disseminated disease. In this work, the aminoacridine compound N-[3-(acridine-9-ylamino)-propyl]-3-iodobenzamide (A3) labelled with the Auger-emitting nuclide 125I using Chloramine-T was studied. Optimal labelling conditions of 125I-A3 were investigated and the interaction with DNA was studied using a novel cell-free in vitro assay with naked human genomic DNA in agarose plugs. This novel assay showed to be simple and reliable. The results verify that 125I-A3 specifically binds DNA with low dissociation and is potent in causing double-strand breaks, yielding 1.0-1.4 breaks per decay. In conclusion, 125I-A3 is a most suitable DNA-binding compound for future therapeutic studies of Auger-electron emitters like 125I.

N-Aryl-9-amino-Substituted Acridizinium Derivatives as Fluorescent “Light-Up” Probes for DNA and Protein Detection

[reaction: see text] N-Arylamino-substituted acridizinium (benzo[b]quinolizinium) derivatives are almost nonfluorescent in water or organic solvents; however, upon addition of calf thymus DNA or bovine serum albumin the fluorescence intensity increases by a factor of 10 to 50. Thus, these dyes exhibit ideal properties to be used as DNA- and protein-sensitive "light-up probes".

Selective Oxygenation of 4,4‘-Dimethylbiphenyl with Molecular Oxygen, Catalyzed by 9-Phenyl-10-methylacridinium Ion via Photoinduced Electron Transfer

Photooxygenation of 4,4'-dimethybiphenyl with oxygen occurs efficiently in the presence of 9-phenyl-10-methylacridinium perchlorate (AcrPh(+)ClO(4)(-)) under visible light irradiation in O(2)-saturated chloroform (CHCl(3)) to yield 4-(4'-methylphenyl)benzaldehyde as a main oxygenated product. Prolonged photoirradiation afforded the further oxygenated product, 4,4'-diformylbiphenyl. The reactive radical intermediates involved in the photocatalytic cycle have successfully been detected by laser flash photolysis and electron spin resonance (ESR) measurements. The photocatalytic mechanism for the oxygenation of 4,4'-dimethybiphenyl via photoinduced electron transfer from 4,4'-dimethybiphenyl to the singlet excited state of AcrPh(+) is clarified based on the dependence of quantum yields on concentrations of substrates and the detected radical intermediates.

Induction of unique structural changes in guanine-rich DNA regions by the triazoloacridone C-1305, a topoisomerase II inhibitor with antitumor activities

We recently reported that the antitumor triazoloacridone, compound C-1305, is a topoisomerase II poison with unusual properties. In this study we characterize the DNA interactions of C-1305 in vitro, in comparison with other topoisomerase II inhibitors. Our results show that C-1305 binds to DNA by intercalation and possesses higher affinity for GC- than AT-DNA as revealed by surface plasmon resonance studies. Chemical probing with DEPC indicated that C-1305 induces structural perturbations in DNA regions with three adjacent guanine residues. Importantly, this effect was highly specific for C-1305 since none of the other 22 DNA interacting drugs tested was able to induce similar structural changes in DNA. Compound C-1305 induced stronger structural changes in guanine triplets at higher pH which suggested that protonation/deprotonation of the drug is important for this drug-specific effect. Molecular modeling analysis predicts that the zwitterionic form of C-1305 intercalates within the guanine triplet, resulting in widening of both DNA grooves and aligning of the triazole ring with the N7 atoms of guanines. Our results show that C-1305 binds to DNA and induces very specific and unusual structural changes in guanine triplets which likely plays an important role in the cytotoxic and antitumor activity of this unique compound.

Novel Bifunctional Acridine−Acridinium Conjugates: Synthesis and Study of Their Chromophore-Selective Electron-Transfer and DNA-Binding Properties

Novel bifunctional conjugates 1-3, with varying polymethylene spacer groups, were synthesized, and their DNA interactions have been investigated by various biophysical techniques. The absorption spectra of these systems showed bands in the regions of 300-375 and 375-475 nm, corresponding to acridine and acridinium chromophores, respectively. When compared to 1 (Phi(f) = 0.25), bifunctional derivatives 2 and 3 exhibited quantitative fluorescence yields (Phi(f) = 0.91 and 0.98) and long lifetimes (tau = 38.9 and 33.2 ns). The significant quenching of fluorescence and lifetimes observed in the case of 1 is attributed to intramolecular electron transfer from the excited state of the acridine chromophore to the acridinium moiety. DNA-binding studies through spectroscopic investigations, viscosity, and thermal denaturation temperature measurements indicate that these systems interact with DNA preferentially through intercalation of the acridinium chromophore and exhibit significant DNA association constants (K(DNA) = 10(5)-10(7) M(-1)). Compound 1 exhibits chromophore-selective electron-transfer reactions and DNA binding, wherein only the acridinium moiety of 1 interacts with DNA, whereas optical properties of the acridine chromophore remain unperturbed. Among bifunctional derivatives 2 and 3, the former undergoes DNA mono-intercalation, whereas the latter exhibits bis-intercalation; however both of them interact through mono-intercalation at higher ionic strength. Results of these investigations demonstrate that these novel water-soluble systems, which exhibit quantitative fluorescence yields, chromophore-selective electron transfer, and DNA intercalation, can have potential use as probes in biological applications.

Pivotal role of NOX‐2‐containing NADPH oxidase in early ischemic preconditioning

Reactive oxygen species (ROS)-mediated signaling is implicated in early ischemic preconditioning (PC). A NOX-2-containing NADPH oxidase is a recognized major source of ROS in cardiac myocytes, whose activity is augmented by preconditioning mimetics, such as angiotensin II. We hypothesized that this oxidase is an essential source of ROS in PC. Hearts from wild-type (WT) and NOX-2 knockout (KO) mice were Langendorff perfused and subjected to 35 min ischemia/reperfusion with or without preceding PC or drug treatment. Infarct size was measured by triphenyl tetrazolium chloride staining, and NADPH oxidase activity by lucigenin chemiluminescence. PC significantly attenuated infarct size in WT (26+/-2% vs. control, 38+/-2%, P<0.05) yet was ineffective in KO hearts (33+/-3% vs. control, 34+/-3%). Concomitantly, PC significantly increased NADPH oxidase activity in WT (+41+/-13%; P<0.05), but not in KO (-5+/-18%, P=NS). The ROS scavenger MPG (N-2-mercaptopropionyl glycine, 300 micromol/L) abrogated PC in WT (39+/-2% vs. control, 33+/-1%). CCPA (2-chloro N6 cyclopentyl adenosine, 200 nmol/L), a putative ROS-independent PC trigger, significantly attenuated infarct size in WT, MPG-treated WT and KO hearts (24+/-2, 23+/-1, and 20+/-3%, respectively, P<0.05). Furthermore, CCPA did not augment NADPH oxidase activity over control (+22+/-11%, P=NS). Inhibition of protein kinase C (PKC) with chelerythrine (CHE, 2 micromol/L) completely abrogated both PC (38+/-2% vs. CHE alone, 35+/-2%) and associated increases in oxidase activity (+3+/-10%, P=NS). PKC-dependent activation of a NOX-2-containing NADPH oxidase is pivotally involved in early ischemic PC. However, adenosine receptor activation can trigger a ROS and NOX-2 independent PC pathway.

DNA minor groove adducts formed by a platinum-acridine conjugate inhibit association of tata-binding protein with its cognate sequence

PT-ACRAMTU ([PtCl(en)(ACRAMTU-S)](NO(3))(2), en = ethane-1,2-diamine, ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea) is a cytotoxic platinum-acridine conjugate previously shown to form adducts with the N3 endocyclic nitrogen of adenine in the DNA minor groove. This unusual observation and our prior determination of the pronounced 5'-TA/TA base-step affinity of the drug have prompted us to investigate effects of these adducts on DNA minor groove binding proteins. Here, we used electrophoretic mobility shift assays to study the recognition of a PT-ACRAMTU-modified TATA box sequence by TATA-binding protein (TBP). The frequency of PT-ACRAMTU adducts in the minor groove of the TATA box was varied by selective elimination of potential major groove and minor groove binding sites in a 24-bp probe sequence through incorporation of deaza nucleobases. The most dramatic effect on TBP binding was observed in a duplex substituted with 7-deaza-G and 7-deaza-A, which reduced binding by as much as 73% compared to an unplatinated duplex. In contrast, elimination of A-N3 binding sites had no significant effect on TBP binding, suggesting that minor groove adducts of PT-ACRAMTU are the cause of inhibition. This notion was further corroborated by efficient platinum-mediated photo-cross-linking of the drug-modified DNA to TBP. PT-ACRAMTU appears to be the first platinum-based drug capable of targeting DNA sequences critical for transcription initiation. The biological consequences of PT-ACRAMTU's minor groove adducts are discussed.

Cancer preventive agents, Part 2: Synthesis and evaluation of 2-phenyl-4-quinolone and 9-oxo-9,10-dihydroacridine derivatives as novel antitumor promoters

2-Phenyl-4-quinolone and 9-oxo-9,10-dihydroacridine derivatives were synthesized and screened as potential antitumor promoters by examining the ability of the compounds to inhibit Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Interestingly, compounds 14, 15, and 17 showed similar inhibitory effects (89-92%, 66-69%, and 24-29% at 1000, 500, and 100 mol ratio to TPA, respectively) against EBV-EA with potencies comparable to those of glycyrrhetic acid, a known natural antitumor-promoter.

Photoreactive threading agent that specifically binds to abasic sites in DNA

We report the synthesis and study of a photoreactive nitrobenzamide containing acridine that specifically interacts at abasic site in DNA by threading intercalation and introduces under irradiation a lesion on the opposite strand at the unpaired pyrimidine.

Fluorescence of acridinic dyes in anionic surfactant solution

The interaction of the cationic dyes acridine, 9-aminoacridine (9AA), and proflavine, with sodium dodecyl sulfate (SDS) was studied by electronic absorption, steady-state and time-resolved fluorescence spectroscopies. The dyes interact with SDS in the pre-micellar region leading in two cases to dimerization in dye-surfactant aggregates, but with distinct molecular arrangements. For proflavine, the observed red shift of the electronic absorption band indicates the presence of J-aggregate, which are nonfluorescent. In the case of 9AA, the aggregates were characterized as nonspecific (neither J- nor H-type is spectroscopically observed). The time-resolved emission spectra gives evidences of the presence of weakly bound dimers by the recovery of three defined decay times by global analysis: dye monomer (tau1 = 16.4 ns), dimer (tau2 = 7.1 ns), and a faster component (tau3 = 2.1 ns) ascribed to intracluster energy migration between monomer and dimer. Acridine has a weak interaction with SDS forming only an ion pair without further self-aggregation of the dye.

Characterization of the bisintercalative DNA binding mode of a bifunctional platinum-acridine agent

The DNA interactions of PT-BIS(ACRAMTU) ([Pt(en)(ACRAMTU)2](NO3)4; ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea, en = ethylenediamine), a bifunctional platinum-acridine conjugate, have been studied in native and synthetic double-stranded DNAs and model duplexes using various biophysical techniques. These include ethidium-DNA fluorescence quenching and thermal melting experiments, circular dichroism (CD) spectroscopy and plasmid unwinding assays. In addition, the binding mode was studied in a short octamer by NMR spectroscopy in conjunction with molecular modeling. In alternating copolymers, PT-BIS(ACRAMTU) shows a distinct preference for poly(dA-dT)2, which is approximately 3-fold higher than that of ACRAMTU. In the ligand-oligomer complex, d(GCTATAGC)2.PT-BIS(ACRAMTU) (complex I*), PT-BIS(ACRAMTU) increases the thermal stability of the B-form host duplex by DeltaT(m) > 30 K (CD and UV melting experiments). The agent unwinds pSP73 plasmid DNA by 44(+/-2) degrees per bound molecule, indicating bisintercalative binding. A 2-D NMR study unequivocally demonstrates that PT-BIS(ACRAMTU)'s chromophores deeply bisintercalate into the 5'-TA/TA base pair steps in I*, while the platinum linker lies in the minor groove. An AMBER model reflecting the NMR results shows that bracketing of the central AT base pairs in a classical nearest neighbor excluded fashion is feasible. PT-BIS(ACRAMTU) inhibits DNA hydrolysis by BstZ17 I at the enzyme's restriction site, GTA downward arrowTAC. Possible consequences for other relevant DNA-protein interactions, such as those involved in TATA-box-mediated transcription initiation and the utility of the platinum-intercalator technology for the design of sequence-specific agents are discussed.

Position-specific incorporation of a highly photodurable and blue-laser excitable fluorescent amino acid into proteins for fluorescence sensing

A new fluorescent amino acid, L-2-acridonylalanine, was incorporated into proteins at specific positions using 4-base codon/anticodon strategy. The efficiency of the incorporation was high enough to obtain enough quantities of the mutants. The acridonyl group was highly fluorescent when it was excited at the wavelengths of blue-lasers and was highly photodurable compared with conventional fluorophores often used for biological analyses. The fluorescence intensity was sensitive to small changes in the polarity of the environment. When the nonnatural amino acid was incorporated into specific positions of streptavidin, the mutant protein worked as a fluorescent sensor to biotin. Similarly, when the amino acid was incorporated into camel single-chain antibody, the mutant protein sensitively responded to the antigen molecule. The high incorporation efficiency, the high photodurability, the excitability with blue-lasers, and high sensitivity to the environment make the acridonylalanine as the promising fluorescent amino acid for sensing small molecules when incorporated into specific positions of various antibodies, receptors, and enzymes.

Determination of Catechin in Aqueous Solution by Chemiluminescence Method

A method to determine catechin in aqueous solution by measuring chemiluminescence intensities using a stopped flow system has been studied. The lucigenin-hydrogen peroxide chemiluminescence reaction was chosen for the determination of catechin. Fe(II) ion was added to the chemiluminescence system to increase the sensitivity. The chemiluminescence intensity from the lucigenin system was increased by the addition of catechin. Effects of flow rates of reagent and sample and concentrations of lucigenin, hydrogen peroxide, Fe(II) ion and KOH were investigated. The calibration curve for catechin was linear over the range from 1.0x10(-6) to 1.0x10(-3) M and the detection limit was 3.0x10(-7) M under the optimal experimental conditions.

Synthesis and biological activity of novel acridinylidene and benzylidene thiazolidinediones

A novel set of acridinylidene thiazolidinediones and benzylidene thiazolidinediones was synthesized by nucleophilic addition of cyanoacrylates. Some of these compounds were evaluated for their glucose lowering capability and their effects on the triglyceride level in alloxan diabetic mice.

2,7-Dihydro-3H-pyridazino[5,4,3-kl]acridin-3-one derivatives, novel type of cytotoxic agents active on multidrug-resistant cell lines. Synthesis and biological evaluation

We have earlier postulated that the presence of a pyridazone ring fused with an anthracenedione moiety resulted in the analog's ability to overcome multidrug resistance of tumor cells [J. Med. Chem.1999, 42, 3494]. High cytotoxic activity of obtained anthrapyridazones [Bioorg. Med. Chem.2003, 11, 561] toward the resistant cell lines, prompted us to synthesize the similarly modified acridine compounds. A series of pyridazinoacridin-3-one derivatives (2b-h) were prepared from the reaction of 9-oxo-9,10-dihydroacridine-1-carboxylate with POCl(3), followed by addition of the appropriate (alkylamino)alkylhydrazines. In vitro cytotoxic activity toward sensitive and resistant leukemia cell lines: L1210, K562, K562/DX, HL-60, HL-60/VINC, and HL-60/DX, with various type of multidrug resistance (MDR and MRP) was determined. The compounds studied exhibited in comparison to the reference cytostatics (DX, MIT) desirable very low resistance indexes (RI). Variations have been observed depending upon the substituent and the type of drug exporting pump. The cytotoxic activities of examined compounds, as well as of model anthrapyridazone derivative PDZ, were lower than those of reference drugs (DX, MIT) due to their diminished affinity to DNA.

INHIBITION OF HUMAN CYP1A2 OXIDATION OF 5,6-DIMETHYL-XANTHENONE-4-ACETIC ACID BY ACRIDINES: A MOLECULAR MODELLING STUDY

1. The aim of the present study was to investigate the structural requirements for the inhibition of 6-methyl-hydroxylation of the antitumour agent 5,6-dimethyl-xanthenone-4-acetic acid (DMXAA) by acridine analogues and use a CYP1A2 homology model to provide some insight into this interaction. 2. Concentrations causing 50% inhibition (IC50) of the 6-methylhydroxylation of DMXAA were determined in human liver microsomes in the presence of various acridines. Some of the acridines were also tested for their ability to inhibit the CYP1A2-mediated 7-ethoxyresorufin O-de-ethylation. The molecular modelling studies of human CYP1A2 used the crystal structure of rabbit CYP2C5 as a template based on protein sequence homology and an interactive docking procedure using a dynamic hydrogen bond feature. 3. The in vitro IC50 studies for the inhibition of 6-methylhydroxylation of DMXAA indicated: (i) the importance of the position of the carboxamide side-chain on the acridine nucleus (and, to a lesser extent, its composition); (ii) the addition of hydroxyl groups to the 5-, 6- and 7-position of the acridine nucleus diminished the inhibitory potency; and (iii) amsacrine (acridine nucleus with methansulphonanilide side-chain at the 9-position) had no significant inhibitory effect. Similar structural trends were observed for the inhibition of O-de-ethylation of 7-ethoxyresorufin by acridines, supporting the involvement of CYP1A2 in DMXAA 6-methyl hydroxylation. 4. The molecular modelling studies indicated: (i) both DMXAA and N-[2-(dimethylamino)-ethyl]acridine-4-carboxamide (DACA) form two hydrogen bonds plus putative pi-pi stacking interactions with the CYP1A2-binding domain, typical of CYP1A2 substrates and inhibitors; (ii) the DMXAA 6-methyl group is 4.0 A from the central iron atom of the heme moiety and ideal for oxidation; (iii) the known oxidation sites for DACA are orientated away from the heme iron, supporting the non-involvement of CYP1A2; and (iv) amsacrine did not fit the putative CYP1A2 site owing to the steric hindrance of the bulky methanesulphonanilide side-chain. 5. These results suggest that docking studies with this homology model may be useful in the design of further acridine anticancer agents, in particular to identify agents that do not interact either as substrates or inhibitors with the CYP1A2-binding domain.