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I Ujváry

Publications and source records attributed to I Ujváry.

10 recordsLinked to original sources
PubMed2001

Synthesis of 3-(12-hydroxy-p-carboranyl)propionic acid, a hydrophobic, N-terminal tyrosine-mimetic for peptides.

A new, p-carborane containing analog of tyrosine, namely 3-[1-hydroxy-1,12-dicarba-closo-dodecaboran(12)-12-yl]propionic acid was prepared from p-carborane in five steps involving hydroxypropylation of O-protected 1-hydroxy-p-carborane as the key transformation. The simple tyrosine mimetic can function as a hydrophobic surrogate for an N-terminal tyrosine residue in insect and mammalian neuropeptides to enhance the lipophilicity, and therefore, the cuticle and/or tissue permeability properties of mimetic analogs.

Animals↗
PubMed1999

Antimicrobial activity of o-carboranylalanine.

Functionalized polyhedral carboranes, including amino acid analogs, have unique physicochemical properties and are used as experimental anticancer agents. However, our current knowledge on their effect in nonmammalian biological systems is limited. We investigated the activity spectrum in vitro of o-carboranylalanine (o-Cba), considered to be a highly lipophilic analog of phenylalanine, against representative plant pathogenic bacteria and fungi of various taxonomic position. The antibacterial effect of o-Cba against some species was comparable to that of the widely used agricultural antibiotic, streptomycin. The sensitivity of individual bacterial species to o-Cba within the same genus varied to a greater extent than the average sensitivity of various genera. In general, this carborane-containing amino acid was more toxic to Gram positive bacteria (Bacillus, Corynebacterium, Curtobacterium, Micrococcus, Rhodococcus, and Staphylococcus) than to Gram negative ones (Agrobacterium, Erwinia, Escherichia, Pseudomonas, Rhizobium, and Xanthomonas). Compared to the commercial fungicide, prochloraz, o-Cba was weakly toxic against various fungi (Zygo- and Ascomycota). It was also inferior to the commercial fungicide metalaxyl in inhibiting the vegetative growth of oomyceteous plant pathogens (Pythium irregulare, Phytophthora cryptogea and Plasmopara halstedii). Against the asexual spores of P. halstedii, o-Cba, however, was over a thousandfold more active than tridemorph, a selective zoospore inhibitor fungicide. For all taxonomic groups, the observed antimicrobial effect of o-Cba could be diminished with histidine, but not with phenylalanine. In studies on healthy and mildew-infected sunflower and tobacco plants o-Cba showed neither fungicidal nor phytotoxic effects at 500 ppm. This is the first report on the biological activity spectrum of a carborane-containing amino acid.

Anti-Bacterial Agents↗
PubMed1999

Effects of veratridine and its derivatives on the Na-conducting channels in Helix neurons.

Effects of veratrum alkaloids were studied on the Na-channels of the land snail Helix pomatia. It was found that veratridine and its analogues depolarize the membrane due to the increased Na-permeability. The inactivation was shifted right along the voltage axis and the recovery from the inactivation was faster after veratridine treatment. After alkaloid treatment the selectivity of the Na-channel decreased, however, the selectivity sequence was not altered. The activation curve was not shifted. Veratridine derivatives, which appeared to be more effective on insects, had almost no effect on the Na-current.

Action Potentials↗
PubMed1997

Hydroxy juvenile hormones: new putative juvenile hormones biosynthesized by locust corpora allata in vitro.

The in vitro production of sesquiterpenoids was investigated by using corpora allata (CA) of the African locust Locusta migratoria migratorioides. Labeled products from unstimulated biosynthesis were extracted, purified by normal phase HPLC, and derivatized to determine the functional groups present. An extra hydroxyl group was detected in each of two juvenile hormone (JH) biosynthetic products. One compound, NP-8, was found to co-migrate with a chemically-synthesized (Z)-hydroxymethyl isomer, 12'-OH JH-III, but not with the (E)-hydroxymethyl isomer, 12-OH JH III. Mass spectral analyses further supported the identity of the synthetic material with that biosynthesized by the corpora allata. A second compound was identified as the 8'-OH JH-III based on spectroscopic analyses. 12'-OH JH-III exhibited morphogenetic activity when tested on the heterospecific Tenebrio test. These data suggest that 12'-OH JH-III and 8'-OH JH-III are additional biosynthetically-produced and biologically-active juvenile hormones, and constitute the first known members of the class of hydroxy juvenile hormones (HJHs).

Animals↗
PubMed1997

Partial synthesis of 3-O-vanilloylveracevine, an insecticidal alkaloid from Schoenocaulon officinale.

3-O-Vanilloylveracevine has been synthesized for the first time in 70% overall yield by conversion of veracevine into its 3-O-(4-benzyloxy-3-methoxybenzoate) followed by catalytic hydrogenation. The insecticidal activity of the semisynthetic substance against three pest species is inferior to that of cevadine and veratridine, the major components of the insecticidal sabadilla alkaloid mixture.

Animals↗
PubMed1996

Projuvenoids: synthesis and biological evaluation of sulfenylated, sulfinylated, and sulfonylated carbamates.

Applying the proinsecticide principle developed earlier for neurotoxic carbamate insecticides, a series of new N-sulfenylated, N-sulfinylated, and N-sulfonylated derivatives of fenoxycarb were synthesized and evaluated for juvenile hormone mimicking activity. Laboratory evaluations of the compounds using Pieris brassicae and Sitophilus oryzae, as well as field experiments using Bemisia tabaci, showed that several symmetrical biscarbamates with either a sulfenyl or sulfinyl bridge possessed higher activity than the parent carbamate. From the unsymmetrical compounds containing biologically inert derivatizing moieties, one of the sulfenylated biscarbamates also showed improved activity against P. brassicae. The changes in the biological activity of the sulfur-containing derivatives compared to that of the parent compound are attributed to the modified physicochemical characteristics, i.e., increased lipophilicity facilitating penetration, transport, as well as protection of the compound from metabolism.

Animals↗
PubMed1992

In vivo and in vitro biosynthesis and metabolism of methyl farnesoate, juvenile hormone III, and juvenile hormone III acid in the mosquito Aedes aegypti.

Biosynthesis and metabolism of juvenile hormone (JH) III in vivo and in vitro were studied in female Aedes aegypti (L.). [12-3H]Methyl farnesoate was used to follow the synthesis and [12-3H]-(10R)-JH III to study metabolism. The rate of biosynthesis of [12-3H]JH III in vivo after adult eclosion increased from 9 fmol/h per female at 1 h to 22 fmol/h per female at day 6. The rate of biosynthesis by exposed corpora allata (CA) in vitro was 23 fmol/h per CA during the 1st d after adult eclosion, then dropped to 4.8 fmol/h per CA on day 3, then increased again to a constant level of synthesis (12 fmol/h per CA) at days 4-6. Immediately after blood feeding, the rate of synthesis of [12-3H]JH III in vivo and in vitro increased to 27 fmol/h per female and to 23 fmol/h per CA, respectively. The rate of synthesis then decreased in vivo to 12 fmol/h per female at 4 h and in vitro to 6 fmol/h per CA 10 h after the blood meal. After this decrease, the rate of synthesis of [12-3H]JH III increased again reaching a peak of 25 fmol/h per female at 48-96 h in vivo and 12 fmol/h per CA at 72 h in vitro. These results indicated that the CA of sugar-fed and blood-fed female A. aegypti synthesized JH III in vivo and in vitro from [12-3H]methyl farnesoate. When [12-3H]-(10R)-JH III metabolism was followed in vivo in female A. aegypti, the ratio between JH III diol acid:JH III acid:JH III diol was 17:4:1, indicating that JH III was first hydrolyzed by JH III esterase to the acid form, then hydrated to the diol acid by JH III epoxide hydrase. Females treated with [12-3H]JH III acid converted 46% of the JH III acid in 60 min to the diol acid. These results indicated that the enzyme epoxide hydrase acted on JH III acid 17 times faster than JH III.

Aedes↗
PubMed1990

Binding proteins for methyl farnesoate in lobster tissues: detection by photoaffinity labeling.

Methyl farnesoate (MF) is secreted by the mandibular organs of crustaceans, but its physiological role and biochemical distribution are only partially known. Characterization of specific MF binding proteins (MFBP) in homogenates of tissues of the American lobster, Homarus americanus, was achieved by photoaffinity labeling with tritium-labeled farnesyl diazomethyl ketone (3H-FDK). The tissues selected include epidermis, tail muscle, central nervous system, eyestalk, hemolymph, hepatopancreas, ovaries, testes, and Y-organ. Both high-speed pellets and supernatants were tested. Competing ligands employed to verify specificity of light-induced covalent modification included MF, methoprene, and unlabeled FDK. A 40-kDa band was labeled strongly in the hemolymph; the labeling was displaced in the presence of a 100-fold excess of unlabeled MF. Although many other tissues had proteins which labeled with 3H-FDK, none of these showed competition by MF. This MFBP is thus functionally analogous to the hemolymph JH-binding proteins of insects.

Affinity Labels↗
PubMed1986

A rapid method for the evaluation of nerve conduction blocking compounds.

A simple and easily accessible cockroach nerve preparation is described. Afferent potentials elicited by electric stimulation of the cercus showed remarkable stability, providing a fairly adequate background for pharmacological experimentation. Type I and type II pyrethroids were tested on the nerve preparation, and the results were compared with toxicity data obtained on the same species. Blockade of nerve conduction showed positive correlation (r = 0.804) with lethal effects. The preparation would be useful for determining neuronal point of attack of test compounds and the study of pyrethroids.

Animals↗