Inhibition of carbonic anhydrase isoforms I, II, IV, VII and XII with carboxylates and sulfonamides incorporating phthalimide/phthalic anhydride scaffolds.

We report a panel of carboxylates and sulfonamides incorporating phthalic anhydride and phthalimide moieties in their structure and their interaction with the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). They were synthesized from substituted anthranilic acids and trimellitic anhydride chloride, followed by reaction with primary amines and were tested for the inhibition of five physiologically relevant CA isoforms, the human (h) hCA I, II, IV, VII and XII, some of which are involved in serious pathologies (CA II, IV and XII in glaucoma; CA VII in epilepsy; CA XII in some solid tumors). The carboxylic acids were generally poor inhibitors of isoforms hCA I, II and IV but were highly effective, low nanomolar inhibitors of hCA VII and XII. The sulfonamides inhibited all isoforms significantly, and some of them were sub-nanomolar hCA VII inhibitors, although their isoform selectivity was lower compared to the carboxylates. This study proves that carboxylic acids incorporating a phthalic anhydride/phthalimide based scaffold may lead to isoform-selective inhibitors by applying the tail approach, mostly used up until now for obtaining sulfonamide, sulfamide and sulfamate CA inhibitors.

Kinetics of action of a two-stage pro-inhibitor of serine ß-lactamases.

ß-Lactamase inhibitors are important in medicine in the protection of ß-lactam antibiotics from ß-lactamase-catalyzed destruction. The most effective inhibitors of serine ß-lactamases covalently modify the enzyme active site. We have recently studied O-acyl and O-phosphyl hydroxamates as a new class of such inhibitors. In this paper, we describe our studies of the N-acyl derivatives of a cyclic O-acyl hydroxamic acid, 3H-benzo[d][1,2]oxazine-1,4-dione, and, in particular, the N-tert-butoxycarbonyl derivative. This compound is not a ß-lactamase inhibitor itself but undergoes spontaneous hydrolysis in aqueous solution, yielding an O-phthaloyl hydroxamic acid, which is a ß-lactamase inhibitor. This compound spontaneously, but reversibly, cyclizes in solution to form phthalic anhydride, which is also a ß-lactamase inhibitor. Both inhibitors react to form the same transiently stable phthaloyl-enzyme complex. Thus, we have a two-step cascade, beginning with a pro-inhibitor, in which each step leads to a different inhibitor, presumably with different enzyme specificities. The kinetics of these transformations have been elucidated in detail. The phthaloyl derivatives, where the free carboxylate is important for facile reaction with the enzyme, represent a new lead for serine ß-lactamase inhibitors. Analogues can be conveniently constructed in situ by reaction of nucleophiles with phthalic anhydrides and then screened for activity. Active hits may then become new leads.

Synthesis of water-dispersible zinc oxide quantum dots with antibacterial activity and low cytotoxicity for cell labeling.

Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

Intrinsically fluorescent and highly functionalized polymer nanoparticles as probes for the detection of zinc and pyrophosphate ions in rabbit serum samples.

Intrinsically fluorescent polymer nanoparticles (F-PNPs) were synthetized from 2-hydroxy-5-methylisophthalaldehyde and melamine by solvothermal method. F-PNPs can emit strong yellow green fluorescence at 542 nm without the conjugation to any external fluorescent agent and surface modification. Owing to the abundant amino and hydroxyl groups on their surface, the F-PNPs possess multiple binding sites, good biocompatibility and excellent water-solubility. Addition of Zn2+ to the F-PNPs solution resulted in a blue shift (Δλ=40 nm) with obvious enhancement in the fluorescence intensity at 502 nm; while there was negligible change in the presence of other metal ions. The subsequent treatment with pyrophosphate (PPi) can cause fluorescence recovery of F-PNPs by pulling the Zn2+ out of the coordination cavity of F-PNPs-Zn2+ nanocomposites. No interference was observed from other anions and nucleotides, making the F-PNPs-Zn2+ ensembles highly sensitive and selective nanoprobes for PPi. The detection limit is 2.75 × 10-8 M/L and 7.63 × 10-8 M/L for Zn2+ and PPi, respectively. The proposed nanoprobes were then used for detecting the recovery of Zn2+ and PPi in rabbit serum samples, which were found to be 99.4-104.2% and 98.6-104.7%, respectively. The present strategy for the fabrication of nanoparticles may offer a new sight for the preparation of polymer nanostructures. The F-FNPs based probes can provide an accurate method for the detection of Zn2+ and PPi in serum samples.

Carbonic anhydrase activators. Part 24. High affinity isozymes I, II and IV activators, derivatives of 4-(4-chlorophenylsulfonylureido-amino acyl)ethyl-1H-imidazole.

N-1-Tritylsulfenyl histamine was synthesized by reaction of histamine (Hst) with tetrabromophthalic anhydride followed by protection of its imidazole moiety with tritylsulfenyl chloride. After hydrazinolysis, it afforded a key intermediate which was derivatized at the aminoethyl group in order to obtain new types of activators of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). Reaction of the key intermediate with 4-chlorophenylsulfonylureido amino acids (cpu-AA) in the presence of carbodiimides afforded, after deprotection of the imidazolic nitrogen atom, a series of compounds with the general formula cpu-AA-Hst (cpu, 4-ClC(6)H(4)SO(2)NHCO). Some structurally related dipeptide derivatives with the general formula cpu-AA1-AA2-Hst (AA, AA1 and AA2 represent amino acyl moieties) were also prepared by a strategy similar to that applied for the amino acyl compounds mentioned above. The new derivatives proved to be efficient activators of three CA isozymes. Best activity was detected against hCA I and bCA IV, for which some of the new compounds showed affinities in the 1-10 nM range (h, human; b, bovine isozymes). hCA II, on the other hand, was less prone to activation by the new derivatives, which possessed affinities around 20-50 nM for this isozyme. This new class of CA activators might lead to the development of drugs/diagnostic agents for CA deficiency syndrome, a genetic disease of bone, brain and kidneys.

Catalyst optimization strategy: selective oxidation of o-xylene to phthalic anhydride.

The oxidation of o-xylene and/or naphthalene to phthalic anhydride is one of the important industrial processes based on catalytic selective oxidation reactions. Vanadia--titania catalysts have been used in the industrial phthalic anyhdride process for the last 50 years. The operation parameters like the temperature range of operation, reactor inlet pressures, contact times, o-xylene loadings, etc. were constantly improved during this period of continuous process optimization so as to optimize catalyst performance and increase its life time. However, a fundamental understanding of the mutual interaction of the rather complex reaction network and the catalyst formulation is still missing. Recently, a detailed study of by-product formation as function of process conditions allowed us to develop a novel, improved reaction scheme for the catalytic oxidation of o-xylene. Based on this understanding, a detailed investigation was conducted for the first time of the by-product formation under varying operation conditions and as a function of the active mass variation exploiting high-throughput, as well as bench scales reactors. This high-throughput testing allowed us to relate reaction kinetics to novel catalyst formulations.

Synthesis of demethylated nidulol via an intramolecular Michael reaction.

An expeditious synthesis of 5,7-dihydroxy-6-methylphthalide from open-chain precursors is described. The key intermediates, synthons 3 and 4, were readily obtained from accessible materials and were further transformed to a common precursor, a five-membered lactone derivative, via an intramolecular Michael addition. Lactone 2 was aromatised to the phthalide system under basic conditions. The process thus constitutes a formal synthesis of the phthalide framework.

Synthesis of new N-analogous corollosporine derivatives with antibacterial activity by laccase-catalyzed amination.

Corollosporine isolated from the marine fungus Corollospora maritima and N-analogous corollosporines are antimicrobial substances. Owing to the basic structure of the N-analogous corollosporines, they have become an attractive target for laccase-catalyzed derivatisation. In this regard we report on the straightforward laccase-catalyzed amination of dihydroxylated arenes with N-analogous corollosporines. In biological assays the obtained amination products are more active than the parent compounds.

Synthesis and antimicrobial activity of N-analogous corollosporines.

Corollosporine is an antimicrobial metabolite, which was isolated from the marine fungus Corollospora maritima. Owing to its basic 4-hydroxyphthalic acid anhydride structure, it has become an attractive target for a structure/activity relationship modelling of derived compounds with potential antibiotic activity. In this regard we report on the straightforward synthesis of hetero analogous corollosporines, which were easily prepared by a three-step reaction sequence, taking advantage of a novel multicomponent reaction (AAD-reaction) and a subsequent aromatization/Grignard reaction protocol. Furthermore, the obtained products were tested in several biological assays to evaluate their antimicrobial activity.

[Determining the occupational risk of skin diseases at the chemical plant "G. Genov" in Ruse]. / Opredeliane na profesionalniia risk ot zaboliavaniia na kozhata v niakoi proizvodstva na SKhK "G. Genov"--Ruse.

A study is performed on workers from some productions of a Chemical Plant--H-acid, phthalic anhydride, ferrum-oxidate dyes and lacquers, in view of estimating the occupational risk of skin diseases. It is established that the highest occupational risk of skin diseases to which workers are exposed is in the production "H-acid"--25.8%, followed by "Phthalic anhydride"--13.2% and "Ferrum-oxidate dyes"--13%. The epicutaneous test shows positivation of the samples with phthalic-anhydride in 20% of the examined. In those engaged in the production of ferrum-oxidate dyes positive tests are observed in 23.2% of the examined; the highest relative part is taken by the potassium--56.2% and the sodium-bichromate--37.5%. The study of immunoglobulin A, M and G in workers from the lacqueur shop proved the irritating effect of the noxae, and established statistical significant higher values of immunoglobulin "A". The study of some functional investigations--pH and alkaline resistance of the skin give no significant deviations, save single cases. The authors consider the necessity of technological improvement of the production processes in the production "H-acid" where the workers are exposed to the highest occupational risk of skin diseases.

Synthesis of corollosporine, an antibacterial metabolite of the marine fungus Corollospora maritima.

Corollosporine [(+/-)-3-hexyl-3,7-dihydroxy-1(3H)-isobenzofuran-1-one], an antibacterial metabolite of the marine fungus, Corollospora maritima, was synthesized by four different routes from 3-hydroxyphthalic anhydride or 2-methoxybenzoic acid as the starting material to verify its proposed structure.

Gas transfer and blood compatibility of fluorinated polyimide membranes.

Fluorinated polyimide derived from 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and bis[4-(4-aminophenoxy) phenyl]sulfone (APPS) was synthesized to develop a novel membrane oxygenator combining excellent gas transfer and blood compatibility. The asymmetric gas exchange membranes of 6FDA-APPS made by a dry/wet process consisted of an ultrathin and defect-free skin layer supported by a porous substructure. O2 transfer through the 6FDA-APPS membrane was extremely augmented as compared with that of the presently available membrane, poly(dimethylsiloxane), and the previously reported 6FDA-DDS membrane. Since CO2 transfer through the 6FDA-APPS membrane increased with a decrease in CO2 pressure according to dual-mode transport theory, CO2 from the membrane was selectively removed at low CO2 pressure. For the evaluation of in vitro blood compatibility, the platelet adhesion and the plasma protein adsorption on the surface of the 6FDA-APPS membrane were observed by using scanning electron microscopy and the amounts of platelet and plasma protein were determined by an amino acid analyzer. The results indicated that the fluorinated polyimide membranes showed excellent blood compatibility.