Fluorinated analogues of L-ornithine are powerful inhibitors of ornithine decarboxylase and cell growth of Leishmania infantum promastigotes.

Fluorinated analogues of L-ornithine have been tested on growth and ornithine decarboxylase arising from L.infantum cytosolic extracts. EC50 values estimated from dose/response curves were 38 microM, 2.62 microM and 4.64 microM for alpha-DFMO, delta-MFMO and delta-MFMOme respectively. Also the inhibition produced by all three compounds was effectively reverted by exogenous putrescine, pointing towards the inhibition of L.infantum ODC. ODC from logarithmic phase cytosolic extracts was physicochemically and kinetically characterized, showing a long half-life (more than 24 h) and a km value for L-ornithine of 98 microM. Finally, the inhibitory effect of fluorinated analogues of L-ornithine was analysed on L.infantum ODC showing a time-dependent irreversible behavior, with Ki values estimated on 125 microM, T1/2 3.5 min for alpha-DFMO; 13.3 microM, T1/2 1.8 min for delta-MFMO and 4.3 microM, T1/2 4 min for delta-MFMOme.

Putrescine uptake inhibition by aromatic diamidines in Leishmania infantum promastigotes.

The effect of a series of aromatic diamidines has been tested on Leishmania infantum promastigotes in both culture growth and putrescine uptake. The EC50 values calculated by means of dose-response curves were 45, 80, 165, 259 and 600 microM for 4', 6-diamidino-2-phenylindole (DAPI), dibromo propamidine, pentamidine 2-hydroxy stilbamidine and stilbamidine, respectively, although no inhibitory effects on cell growth were found at 1 mM propamidine, phenamidine and amicarbalide. When these compounds were kinetically analysed for putrescine uptake using Lineweaver-Burk plots, the Ki values reached were: DAPI, 15 microM; pentamidine, 3 microM; dibromo propamidine, 7 microM; 2-hydroxy stilbamidine, 21 microM; stilbamidine, 20 microM; propamidine, 25 microM; and phenamidine, 95 microM. Amicarbalide, however, was not able to reduce putrescine uptake to a significant extent, even at the highest concentration studied of 1 mM.

Pharmacokinetics of triclabendazole in rabbits.

1. Pharmacokinetic profiles of triclabendazole (TCBZ) following intravenous (i.v.) and oral administration of the drug in rabbits were carried out. 2. In normal rabbits, TCBZ was metabolized rapidly to its sulphoxide (TCBZ-SO) and sulphone (TCBZ-SO2) derivatives following administration, with undetectable concentrations of unchanged TCBZ in the plasma of the treated animals at any time (detection limit, 10 ng/ml). 3. The disposition kinetics of this drug in rabbits can be described by a two-compartment open model. 4. Mean peak concentrations in plasma of TCBZ-SO and TCBZ-SO2 of 12.41 micrograms/ml and 9.5 micrograms/ml occurred 7.5 and 9.5 hr after oral administration, respectively. 5. Both metabolites were eliminated slowly from plasma with elimination half-lives of 16.86 hr for the sulphoxide and 13 hr for the sulphone. 6. The area under the plasma concentration versus time curve (AUC) was 240 mg hr/l for the sulphoxide, higher than that found for the sulphone, 185 g hr/l.

Aromatic diamidines are reversible inhibitors of porcine kidney diamine oxidase.

The inhibitory ability of aromatic diamidines has been studied on porcine kidney diamine oxidase. The reversibility of drug-protein interactions has been tested by means of exhaustive dialysis experiments, showing in all cases a reversible binding pattern. Ki values obtained by means of Lineweaver-Burk plots were: stilbamidine 12 microM, 2-OH-stilbamide 8.5 microM, phenamidine 4 microM, propamidine 8 microM, dibromopropamidine 4.9 microM and amicarbalide 12 microM.

Selective inhibition of mammalian diamine oxidase by aquatic biotoxins.

The inhibitory activity of saxitoxin and tetrodotoxin on diamine oxidase and S-adenosyl-l-methionine decarboxylase from mammalian sources have been analysed. Unlike tetrodotoxin, saxitoxin was a reversible non-competitive inhibitor of pig kidney diamine oxidase with an estimated K(i) of 140 mum. S-Adenosyl-l-methionine decarboxylase from a highly purified source was not affected by the concentrations tested of either biotoxin. A possible analytical application of this finding is discussed.

Determination of luxabendazole in biological fluids by high-performance liquid chromatography.

Luxabendazole, a new benzimidazole, is a highly potent broad-spectrum anthelmintic. A high-performance liquid chromatographic method has been developed for its determination in serum and urine samples. In order to optimize the clean-up of samples we compared two procedures: C18 Sep-Pak cartridges and ultrafiltration through a cellulose membrane with a 30,000 relative molecular mass cut-off. In order to obtain the most suitable mobile phase, we studied the influence of pH and acetonitrile content on the capacity factor (k'). Chromatographic separation and quantification were performed on a reversed-phase column packed with 5-microns Nucleosil C18. The mobile phase was acetonitrile-0.05 M phosphate buffer (pH 7.0), (40:60, v/v). The column effluent was monitored by ultraviolet-visible spectrophotometry at 290 nm. The method shows good recovery, precision and accuracy. The lower limit of detection for luxabendazole is 15 ng/ml in serum samples and 25 ng/ml in urine samples.

Reversed-phase ion-pair high-performance liquid chromatographic determination of triclabendazole metabolites in serum and urine.

An ion-pair high-performance liquid chromatographic method was developed for measuring the concentrations of triclabendazole metabolites (sulphoxide and sulphone) in plasma and urine samples. The diluted biological fluids are ultrafiltered before chromatography through a 30,000 relative molecular mass cut-off filter and then injected into a C18 column. They are then isocratically eluted with a mobile phase consisting of 0.05 M phosphate buffer (pH 7.0)-acetonitrile (55:45, v/v) with addition of 1.0 mmol/l sodium decanesulphonate and monitored by ultraviolet-visible spectrophotometry at 312 nm. Recoveries over the range 0.01-9.0 micrograms/ml for triclabendazole sulphoxide and sulphone are, respectively, 91.7% and 91.6% in serum and 90.3% and 90.2% in urine. For both metabolites, the limit of detection is 10 ng/ml in both urine and serum.

Inhibition of diamine oxidase from porcine kidney by pentamidine and other aminoguanidine compounds.

1. Three bisguanidine compounds (those of pentamidine, streptidine and phenformin) were compared for their in vitro inhibitory capacity on diamine oxidase activity (EC 1.4.3.6), the first enzyme of putrescine degradation. 2. Pentamidine was the most potent inhibitor, and phenformine the weaker. Two and a half micromoles of pentamidine was enough to reduce the enzyme activity by 50%, while streptidine and phenformin produced the same effect at concentrations greater than 0.90 and 4 mM, respectively. 3. Pentamidine, streptidine and phenformin appeared to be non-competitive inhibitors, and the Ki values calculated by a Dixon plot were 3 microM, 0.95 mM and 4 mM, respectively.