Naphthazarin derivatives: synthesis, cytotoxic mechanism and evaluation of antitumor activity

Patients with type Ib glycogen storage disease (GSD Ib) are susceptible to hypoglycaemic episodes. To determine whether an amylase (alpha-glucosidase) inhibitor, voglibose, can be useful in the control of hypoglycaemia, we tried it in a 14-y-old male with GSD Ib. Oral administration of voglibose prolonged the duration of normoglycaemia and reduced the incidence of hypoglycaemia attacks. These findings indicate that voglibose may be useful for preventing hypoglycaemia in GSD Ib patients.     

Anthracene-1,4,9,10-tetraone derivatives: synthesis and antitumor activity

A series of 2-alkylated anthracene-1,4,9,10-tetraone (ATO) derivatives were synthesized, and their antitumor action in ICR mice bearing S-180 cells and antiproliferative activity against L1210 cells were evaluated. Overall, the introduction of an alkyl group (C1-C8) at C-2 enhanced the antiproliferative activity. Among 2-(1-hydroxyalkyl)- or 2-(1-acetoxyalkyl)-ATO derivatives, four compounds possessing alkyl chain of an intermediate size (C4-C6) gave T/C values of > 300%. Acetylation at 1'-OH failed to cause an enhancement in the antitumor action, in contrast to a remarkable increase in antiproliferative activity. Although there was no direct relationship between antiproliferative activity and antitumor action, the compounds with lower antiproliferative activity tended to show higher antitumor activity. Further study shows that the antiproliferative activity of ATO derivatives may be explained properly neither by redox cycling nor arylating capacity.     

Enhancement of ricin toxin A chain immunotoxin activity: synthesis, ionophoretic ability, and in vitro activity of monensin derivatives

Site-selective toxin delivery was achieved by coupling monoclonal antibody to the A chain subunit of ricin (RTA-IT). The cell-killing potency of RTA-IT can be drastically increased in vitro by using ionophores such as monensin. To reduce the intrinsic toxicity of monensin and to enhance its in vitro and in vivo activity, we synthesized 7 derivatives characterized by different lipophilicities. These derivatives were also analyzed for ionophoretic activity on intact cells, toxicity, and RTA-IT-enhancing activity. Two different RTA-IT were assayed on a human leukemia cell line. A correlation between lipophilicity, ionophoretic activity, and RTA-IT enhancement was observed. The compounds with the highest polar charge showed low intrinsic toxicity, revealed moderate ionophoretic activity, and were able to enhance RTA-IT only at high concentrations, whereas more lipophilic compounds (with a C28 tail or a phenyl group) showed significant ionophoretic activity and good enhancing properties.     

Microbial metabolism of pyridine, quinoline, acridine, and their derivatives under aerobic and anaerobic conditions

Our review of the metabolic pathways of pyridines and aza-arenes showed that biodegradation of heterocyclic aromatic compounds occurs under both aerobic and anaerobic conditions. Depending upon the environmental conditions, different types of bacteria, fungi, and enzymes are involved in the degradation process of these compounds. Our review indicated that different organisms are using different pathways to biotransform a substrate. Our review also showed that the transformation rate of the pyridine derivatives is dependent on the substituents. For example, pyridine carboxylic acids have the highest transformation rate followed by mono-hydroxypyridines, methylpyridines, aminopyridines, and halogenated pyridines. Through the isolation of metabolites, it was possible to demonstrate the mineralization pathway of various heterocyclic aromatic compounds. By using 14C-labeled substrates, it was possible to show that ring fission of a specific heterocyclic compound occurs at a specific position of the ring. Furthermore, many researchers have been able to isolate and characterize the microorganisms or even the enzymes involved in the transformation of these compounds or their derivatives. In studies involving 18O labeling as well as the use of cofactors and coenzymes, it was possible to prove that specific enzymes (e.g., mono- or dioxygenases) are involved in a particular degradation step. By using H2 18O, it could be shown that in certain transformation reactions, the oxygen was derived from water and that therefore these reactions might also occur under anaerobic conditions.     

Lanthanide complexes with β-diketones and coumarin derivates: synthesis,thermal behaviour,optical and pharmacological properties and immobilisation

The paper presents the results of the synthesis of complexes of the type Eu(DBM)₃ and Eu(DBM)₃·Q (DBM-dibenzoylmethane, Q-1,10-phenantroline or 4,7-diphenyl-1,10-phenantroline) and of Tb- and Nd-complexes with the newly-synthesised coumarin derivates 3,3′-[(4-chlorphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one), 3,3′-[(3,5-dimethoxy-4-hydroxy)methylene)bis(4-hydroxy-2H-chromen- 2-one), etc. Elemental and thermogravimetric analysis, IR, UV, NMR and fluorescence spectroscopy and X-ray analysis were applied for characterisation of the complexes. Some peculiarities of the synthetic procedures for both types of complexes were discussed and the influence of the synthetic approach, pH of the reaction medium, temperature of synthesis and drying of the complexes on the composition, stability and optical properties was reported. The immobilisation of the complexes in thin films based on sol-gel produced SiO₂ and on polymethylmethacrylate was studied. The optimal conditions for preparation of the matrices (composition of the starting system, temperature and time of sol aging, etc.) were recommended. The film morphology was evaluated by fluorescence, scanning electron and atomic force microscopy. The interaction of the lanthanide ions with the matrices and the influence of their nature, the effect of the in-situ polymerisation and other factors on photoluminescent excitation and emission spectra and excited state life-times of the complexes were followed. The effect of the second ligand on the photoluminescence properties of the immobilised diketonates was further elucidated. Processes involved in the thermal decomposition of the complexes and microcomposites produced on their base were proposed. Preliminary results on the pharmacological properties of the coumarin complexes reported showed unambiguously higher cytotoxicity of the Nd complex in comparison with that of the respective ligand.     

Synthesis and antitumor evaluation of new thiazolo[5,4-b]quinoline derivatives

A new synthesis of 9-hydroxy- and 9-(alkylamino)thiazolo[5,4-b]quinolines by cyclization of 4-(ethoxycarbonyl)-5-(arylamino)thiazoles and 5-(arylamino)-4-carbamoylthiazoles, respectively, is described. In vitro cytotoxicity of a large number of derivatives of these compounds has been tested against several cell lines. The highest activities observed are associated with the presence of a 2-[[(N,N-diethylamino)ethyl]amino] substituent at C-2 and a fluorine atom at the C-7 position of the tricyclic planar heteroaromatic framework. Three structural features seem to be essential for antitumor activities: a positive charge density at carbon C-7, a side chain at position C-2 or C-9 of the thiazoloquinoline skeleton with two basic nitrogens and a pKa value of 7.5-10 in the most basic center, and a conformational flexibility of this basic side chain. These structural requirements must be simultaneously satisfied in order to ensure a significant antitumor activity.     

Controlled chemical modification of hyaluronic acid: synthesis, applications, and biodegradation of hydrazide derivatives

Controlled modification of the carboxylic acid moieties of hyaluronic acid with mono- and polyfunctional hydrazides leads to biochemical probes, biopolymers with altered physical and chemical properties, tethered drugs for controlled release, and crosslinked hydrogels as biocompatible scaffoldings for tissue engineering. Methods for polyhydrazide synthesis, for prodrug preparation, for hydrogel crosslinking, and for monitoring biodegradation are described.     

Solid phase organic synthesis of polyamine derivatives and initial biological evaluation of their antitumoral activity

The hyperpolarization-activated inward current (If) has been discussed to contribute to arrhythmias in human atrial myocardium. If was found to be increased by beta-adrenergic stimulation. In the present study, we evaluate the modulation of If by carbachol, adenosine and by class Ic, III and IV antiarrhythmic drugs in isolated human atrial myocytes. The whole-cell patch-clamp technique was used to record If in isolated myocytes from 18 human right atrial appendages. A typical time- and voltage-dependent hyperpolarization-activated inward current could be recorded in all cells investigated (n=56). Mean current density recorded at -130 mV was -2.8+/-1.2 pApF(-1). Both adenosine and carbachol were found to directly inhibit If in human atrial myocytes by shifting the activation curves to more negative potentials. Adenosine 10(-5) mol/l shifted the potential of half-maximal activation by -5.9+/-0.4 mV from -99.4+/-0.6 mV to -105.3+/-0.4 mV (n=8; P<0.05), and carbachol 10(-5) mol/l by -5.7+/-0.5 mV from -99.2+/-0.5 mV to -104.9+/-0.6 mV (n=6; P<0.05). The concentration-response curve of adenosine calculated by a Hill function yielded a half-maximal effect of adenosine (EC50) at a concentration of 3.6+/-0.5 micromol/l, a maximal shift of -6.5+/-0.3 mV, and a Hill coefficient (h) of 2.40. We did not observe any effect of flecainide (10(-5) mol/l; n=8), sotalol (10(-5) mol/l; n=6), amiodarone (10(-5) mol/l; n=6) or verapamil (10(-5) mol/l; n=5) on If in human atrial myocytes. However, propafenone (10(-5) mol/l) was found to reversibly reduce If current size (9/13 cells) by shifting the activation curve by -5.2+/-0.4 mV (P<0.05). In human atria adenosine- and muscarinic receptor stimulation might function as endogenous protective mechanisms inhibiting the initiation of ectopic tachycardia by reducing If current size. Propafenone may be more effective in some patients with atrial tachycardias that do not respond to other class Ic, III and IV antiarrhythmic drugs. However, it has yet to be defined whether these agents suppress atrial tachycardias via an inhibition of If in vivo.     

N alpha-alkylated derivatives of 2-phenylhistamines: synthesis and in vitro activity of potent histamine H1-receptor agonists

New potent N alpha-alkylated histamine H1-receptor agonists have been prepared and functionally evaluated for partial agonist potency and selectivity. N alpha-Methyl-2-(3-trifluoromethylphenyl)histamine contracts ileal segments and aortic rings of guinea-pig with a relative potency of 174% (95% confid. lim. 161-188%) and 217% (164-287%), respectively (histamine: 100%) and is the most potent H1 receptor agonist described so far.     

Flavonoid-related modulators of multidrug resistance: synthesis, pharmacological activity, and structure-activity relationships

A series of 28 flavonoid derivatives containing a N-benzylpiperazine chain have been synthesized and tested for their ability to modulate multidrug resistance (MDR) in vitro. At 5 microM, most compounds potentiated doxorubicin cytotoxicity on resistant K562/DOX cells. They were also able to increase the intracellular accumulation of JC-1, a fluorescent molecule recently described as a probe of P-glycoprotein-mediated MDR. This suggests that these compounds act, at least in part, by inhibiting P-glycoprotein activity. As in other studies, lipophilicity was shown to influence MDR-modulating activity but was not the only determinant. Diverse di- and trimethoxy substitutions on N-benzyl were examined and found to affect the activity differently. The most active compounds had a 2,3, 4-trimethoxybenzylpiperazine chain attached to either a flavone or a flavanone moiety (13, 19, 33, and 37) and were found to be more potent than verapamil.     

Aromatase inhibitors: synthesis, biological activity, and binding mode of azole-type compounds

The enantiomers of the potent nonsteroidal inhibitor of aromatase fadrozole hydrochloride 3 have been separated and their absolute configuration determined by X-ray crystallography. On the basis of a molecular modeling comparison of the active enantiomer 4 and one of the most potent steroidal inhibitors reported to date, (19R)-10-thiiranylestr-4-ene-3,17-dione, 7, a model describing the relative binding modes of the azole-type and steroidal inhibitors of aromatase at the active site of the enzyme is proposed. It is suggested that the cyanophenyl moiety present in the most active azole inhibitors partially mimics the steroid backbone of the natural substrate for aromatase, androst-4-ene-3,17-dione, 1. The synthesis and biological testing of novel analogues of 3 used to define the accessible and nonaccessible volumes to ligands in the model of the active site of aromatase are reported.     

New quinoline di-Mannich base compounds with greater antimalarial activity than chloroquine, amodiaquine, or pyronaridine

We have compared the ex vivo antimalarial activity of 12 new quinoline di-Mannich base compounds containing the 7-dichloroquinoline or 7-trifluoromethylquinoline nucleus with amodiaquine, chloroquine, and pyronaridine using the Saimiri-bioassay model. Each compound was administered orally (30 mg/kg of body weight) to three or more noninfected Saimiri sciureus monkeys, and serum samples were collected at various times after drug administration and serially diluted with drug-free (control) serum. In vitro activity against the multidrug-resistant K1 isolate of Plasmodium falciparum was determined in serum samples by measuring the maximum inhibitory dilution at which the treated monkey serum inhibited schizont maturation in vitro. Of the 12 Mannich bases tested, 8 were associated with levels of ex vivo antimalarial activity in serum greater than those of amodiaquine, chloroquine, or pyronaridine 1 to 7 days after drug administration. Further studies were carried out with four of these compounds, and the results showed that the areas under the serum drug concentration-time curves for the four compounds were between 7- and 26-fold greater than that obtained for pyronaridine. Activity against four multidrug-resistant strains of P. falciparum was also much greater in serum samples collected from monkeys after administration of these four compounds than in serum samples collected after administration of pyronaridine or chloroquine. These findings suggest that these four quinoline Mannich base compounds possess a very marked and prolonged antimalarial activity and that further studies should be performed to determine their value as antimalarial drugs.     

Plasmid-mediated mineralization of naphthalene, phenanthrene, and anthracene

The well-characterized plasmid-encoded naphthalene degradation pathway in Pseudomonas putida PpG7(NAH7) was used to investigate the role of the NAH plasmid-encoded pathway in mineralizing phenanthrene and anthracene. Three Pseudomonas strains, designated 5R, DFC49, and DFC50, were recovered from a polynuclear aromatic hydrocarbon-degrading inoculum developed from a manufactured gas plant soil slurry reactor. Plasmids pKA1, pKA2, and pKA3, approximately 100 kb in size, were isolated from these strains and characterized. These plasmids have homologous regions of upper and lower NAH7 plasmid catabolic genes. By conjugation experiments, these plasmids, including NAH7, have been shown to encode the genotype for mineralization of [9-14C]phenanthrene and [U-14C]anthracene, as well as [1-14C]naphthalene. One strain, Pseudomonas fluorescens 5RL, which has the complete lower pathway inactivated by transposon insertion in nahG, accumulated a metabolite from phenanthrene and anthracene degradation. This is the first direct evidence to indicate that the NAH plasmid-encoded catabolic genes are involved in degradation of polynuclear aromatic hydrocarbons other than naphthalene.     

Melanoma affine radiopharmaceuticals I. A comparative study of 131I-labeled quinoline and tyrosine derivatives

We compared two melanoma-specific radioiodine labeled compounds 4-(3-dimethylaminopropylamino)-7-iodoquinoline (I) and L-3-iodo-alpha-methyltyrosine (IV) using three hamster groups. Two groups consisted of hamsters with subcutaneous or subscleral melanotic melanoma, and the third had healthy animals as controls. For the chosen tumor model and in comparison with the quinoline derivative (I), the tyrosine derivative (IV) proved to have some better properties as a melanoma-specific radio-pharmaceutical. This result holds for the first 24 h after administration, thus recommending (IV) for the 123I label. While in that time period (I) did not sufficiently accumulate in the melanoma to compete with the high background activities, especially in the abdominal organs, (IV) had its highest tumor concentration 1 h after administration. The derivative (IV) cleared more slowly from the tumor tissue than from the other organs thus increasing the tumor-to-organ ratio. There was no obvious difference in the biodistribution of (I) and (IV) in relation to the site of the melanoma growth, i.e. eyes and skin. Generally, all three groups of hamsters exhibited similar accumulation and clearance characteristics for each radiopharmaceutical. In contrast to (I), which took part in the formation of the biopolymer melanin, (IV) acted as a reversible inhibitor of the enzyme tyrosine hydroxylase. The affinity to the tyrosine hydroxylase and not the function as a melanin precursor lead to an accumulation of (IV) in the melanoma tissue.     

Cocaine benzoyl thioester: synthesis, kinetics of base hydrolysis, and application to the assay of cocaine esterases

The synthesis and characterization of diastereomers of cocaine benzoyl thioester is described. Allococaine benzoyl thioester and allopseudococaine benzoyl thioester were synthesized by the conjugate addition of p-methoxytolyl thiol to ecgonine methyl ester followed by debenzylation and benzoylation. The absolute structure of the hydrochloride salt of the major ecgonine p-methoxytolyl sulfide formed was determined by single-crystal diffraction analysis and used to establish the addition geometry. When placed in aqueous solution, the cocaine benzoyl thioester diastereomers hydrolyzed to give thioecgonine methyl ester. The rate of cocaine benzoyl thioester hydrolysis was carefully investigated spectrophotometrically by using the Ellman reagent. At neutral pH, the hydrolysis of the diastereomers was found to proceed at detectable rates. Upon increasing pH, the rate of hydrolysis of cocaine benzoyl thioester diastereomers was increased and the reaction was catalyzed by basic buffer species. In addition to defining the kinetics of hydrolysis in aqueous solution, cocaine benzoyl thioester was utilized as a highly efficient method to monitor the activity of cholinesterases and pig liver esterase. Use of cocaine benzoyl thioester represents a rapid and sensitive way to screen for cocaine esterase activity.