[Development of a novel method for UPLC-QTOF-MS analysis of anti-schistosomiasis heterocyclic compounds].

OBJECTIVE: To develop an ultra-performance liquid chromatography/quadrupole-time of flight mass spectrometry (UPLC-QTOF-MS) method for the determination of an oxadiazole-2-oxide heterocyclic compound F-2015-14. METHODS: Mouse plasma and liver homogenate specimens were extracted with ethyl acetate and chromatographed on a Waters CORTECS column (C18, 1.6 µm, 2.1 mm × 150 mm) by using a mobile phase of 10% acetonitrile-0.1% formic acid with by a volume fractionation by gradient elution. Then, UPLC-QTOF-MS was performed to determine F-2015-14 in mouse plasma and liver homogenate specimens. RESULTS: The linearity of F-2015-14 in plasma ranged from 12.5 to 250 mg/mL with a correlation coefficient of 0.990 and a detection limit of 8.8 mg/mL. F-2015-14 in liver homogenates ranged from 12.5 to 250 mg/mL. The linearity was good with a correlation coefficient of 0.992 and a limit of detection of 5.6 mg/mL. If the concentration of plasma and liver homogenate specimens was 12.5 mg/mL, the accuracy and the matrix effect were 80% to 120%, and the inter-day and intra-day precision was within 20%. If the concentrations of plasma and liver homogenate specimens were 100 mg/mL and 200 mg/mL, the accuracy and the matrix effect were 85% to 115%, and the inter-day and intra-day precision was within 15%. CONCLUSIONS: The UPLC-QTOF-MS established in this study has a high sensitivity and good reproducibility for the determination of F-2015-14, which provides bases for the development of novel anti-schistosomiasis drugs.

In vivo schistosomicidal activity of 7-epiclusianone and its quantification in the plasma of healthy and Schistosoma mansoni infected mice using UPLC-MS/MS.

BACKGROUND: The tetraprenylated benzophenone 7-epiclusianone (7-epi) is a substance isolated from the fruits of Garcinia brasiliensis and in vitro studies have demonstrated that 7-epi is effective against Schistosoma mansoni adult worms. HYPOTHESIS/PURPOSE: Here we report the in vivo evaluation of 7-epi and its pharmacokinetic in healthy and Schistosoma mansoni infected mice. STUDY DESIGN AND METHODS: In this work, we assayed the schistosomicidal activity of 7-epi at the dose of 100 mg/kg and 300 mg/kg body weight/day in S. mansoni experimentally infected mice. Besides, two groups of animals were treated and a detailed analysis of plasma samples was performed by liquid chromatography coupled to mass spectrometry (LC-MS/MS). RESULTS: The worm burden showed a reduction in the infected mice after treatment with 300 mg/kg for five days (p < .05). And we found an increase of AUC0-∞ (20846 vs. 32438 ng.h/ml) and a decrease of total apparent clearance (0.006 vs. 0.004 l/h/kg) of 7- epi in the infected group compared to the healthy group. Consequently, the half-life increased (1.73 vs. 6.11 h) and Cmax was reduced (5427.5 vs. 3321.0 ng/ml) in the infected group compared to the healthy group. In addition, histopathological investigations were performed analysing liver samples from healthy and infected mice. CONCLUSION: The results showed significant schistosomicidal in vivo activity at 300 mg/kg. In addition, livers from S. mansoni infected mice showed a greater number of egg granulomas and the changes in the pharmacokinetic parameters in this group could be associated with the pathology of the murine experimental schistosomiasis.

High-performance liquid chromatographic method for determination of 2-difluoromethyl-DL-ornithine in plasma and cerebrospinal fluid.

A simple, sensitive, selective and reproducible method based on anion-exchange liquid chromatography with post-column derivatisation was developed for the determination of eflornithine (2-difluoromethyl-DL-ornithine; DFMO) in human plasma and cerebrospinal fluid. The 1-alkylthio-2-alkyl-isoindoles fluorescent derivative of the drug was separated from the internal standard (MDL 77246A) on an anion-exchange column (PRP-X300, 250x2.1 mm, 7-microm particle size: Hamilton, USA), with retention times of 6.9 and 10.7 min, respectively. Fluorescence detection was set at 430/340 nm (emission/excitation wavelength). The elution solvent consisted of a solution of 30 mM potassium dihydrogen phosphate buffer (pH 2.2) and acetonitrile (50:50, v/v), running through the column at a flow-rate of 0.3 ml/min. The chromatographic analysis was operated at 37 degrees C. Sample preparation for either plasma or CSF (100 microl) was done by single-step protein precipitation with 20% trichloroacetic acid after incubation at 4 degrees C for 1 h. Calibration curves for plasma (100, 200, 400, 600, 800 and 1200 nmol/100 microl, and 10, 20, 40, 80, 120 and 160 nmol/100 microl for the high and low concentration range curves, respectively) and CSF (1, 2, 4, 8, 16, 32 nmol/100 microl) were all linear with correlation coefficients better than 0.999. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) at high concentration range was below 15%, whereas at low concentration range was below 20% (% coefficient of variations: %C.V.) Good accuracy was observed for both the intra-day or inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +/-15 and +/-20% at high and low concentration range, respectively. The limit of quantification was accepted as 0.1 nmol using 100-microl samples. The mean recovery for DFMO and the internal standard were greater than 95%. The method was free from interference from commonly used drugs including antimalarials and antihelminthics. The method appears to be robust and has been applied to a pharmacokinetic study of DFMO in patients with African trypanosomiasis following oral doses of Ornidyl (Aventis Pharma, Frankfurt, Germany) at 500 mg/kg body weight (125 mg q.i.d.) for 14 days.

Do hemoglobin and hemocyanin impair schistosoma killing by no?

Nitric oxide (NO) possesses antiparasitic effects on both Protozoa and Metazoa in definitive and intermediate hosts as well as in vectors. Here, we postulate that hemoglobin and hemocyanin may impair Schistosoma killing by NO in the definitive and intermediate hosts. Interestingly, hemoglobin, myoglobin, and neuroglobin may protect Plasmodium and Trypanosoma from the antiparasitic effects of NO.

Determination of a chemopreventive agent, Oltipraz, in rat plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the determination of a chemopreventive agent, Oltipraz, in rat plasma and urine. The sample preparation was simple; 2 volumes of acetonitrile were added to deproteinize the biological sample. A 50-microl aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase, acetonitrile : 0.5 mM ammonium acetate (55: 45, v/v for rat plasma and 45 : 55, v/v for rat urine), was run at a flow-rate of 1.5 ml/min. The column effluent was monitored using an ultraviolet detector set at 305 nm. The retention times for Oltipraz in rat plasma and urine were approximately 5.8 and 8.6 min, respectively. The detection limits of Oltipraz in rat plasma and urine were 20 and 50 ng/ml, respectively. The coefficients of variation of the assay (within-day and between-day) were generally low (below 4.65%) in concentration ranges from 0.02 (0.05) to 10 microg/ml for rat plasma and urine. No interference from endogenous substances was found.

Stability, blood partition and protein binding of an antifibrotic agent, oltipraz.

The stability, blood partition and factors influencing the binding of oltipraz to 4% human serum albumin (HSA) were evaluated. Oltipraz was relatively stable in various pH (1-12) solutions for up to 48-h incubation, however, it was unstable in pH 13 solution and rat plasma and urine. Oltipraz reached an equilibrium fast (within 30 s mixing manually) between plasma and blood cells o f rabbit blood and the plasma-to-blood cells concentration ratios were independent of initial blood concentrations of oltipraz, 1 and 5 microg/ml; the ratios ranged from 0.908 to 1.004. The binding of oltipraz to 4% HSA was independent of oltipraz concentrations ranging from 1 to 100 microg/ml using an equilibrium dialysis technique: the mean value was 95.0%. However, the binding of oltipraz was dependent on HSA concentrations (the low concentrations, 3, 2, 1 and 0.5% of HSA caused an increase in the unbound fraction of oltipraz by 1.32, 1.98, 3.44 and 5.31 times, respectively, compared with the mean value from 4-6% HSA), incubation temperature (the unbound fractions at 37 degrees C and 22 degrees C increased 1.89 and 1.73 times, respectively, than that at 4 degrees C) and the buffer pHs (the unbound fractions were 6.36, 6.51, 5.60 and 4.63% for buffer pHs of 5.8, 6.4, 7.4 and 8.0, respectively).

A simple kinetic spectrophotometric method for the determination of oxamniquine in formulations and spiked biological fluids.

A simple and sensitive kinetic method for the determination of oxamniquine in pharmaceutical preparations and biological fluids was developed. The procedure is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 20 min. The absorbance of the colored manganate ions was measured at 610 nm. Alternatively, the decrease in the absorbance of potassium permanganate after addition of the drug was measured at 525 nm. The absorbance concentration plots in both procedures were rectilinear over the range 0.5-4 microg ml(-1). The concentration of oxamniquine is calculated using the corresponding calibration equation for the fixed-time method. The determination of oxamniquine by fixed-concentration and rate-constant methods was feasible with the calibration equations obtained but the fixed time method had been found to be more applicable. Both procedures were applied to the determination of oxamniquine in formulations. The results obtained were in good agreement with those obtained using the official method. The fixed time method of 20 min was further applied to spiked human urine and plasma, the recoveries (%) were 100.94 +/- 0.57 and 98.07 +/- 0.88 for urine and plasma, respectively, at 610 nm, and 97.51 +/- 1.27 and 95.69 +/- 1.23 for urine and plasma, respectively, at 525 nm.

Fluorimetric determination of oxamniquine in biological fluids.

A highly sensitive and specific fluorimetric method was developed for the determination of oxamniquine in biological fluids (urine and plasma). The proposed method is based on the reduction of oxamniquine using zinc/calcium chloride to obtain its nitroso derivative. The latter is then allowed to react with 2-cyanoacetamide to get a highly fluorescent product. The different experimental parameters affecting the intensity of the fluorescence were carefully studied and incorporated into the procedure. Under the described conditions, the method is applicable over the concentration range of 0.08-0.88 microgram/ml with a minimum detectability (S/N = 2) of 8 ng/ml. The percentage recoveries from spiked urine and plasma were 99.75 +/- 1.58 and 97.46 +/- 0.44%, respectively.

Pharmacokinetics of oxamniquine in rabbit and rat.

The pharmacokinetics of the schistosomicidal agent oxamniquine (6-hydroxmethyl-2-isopropylaminomethyl-7-nitro-1,2,3,4-tetra hydroquinoline) were studied in 8 (4 male, 4 female) New Zealand White rabbits and 5 female Wistar rats, following intravenous administration (15 mg/kg). The pharmacokinetic parameters (mean +/- SD) in the rabbit and rat, respectively, were as follows: plasma clearance, 65.5 +/- 33 and 17.2 +/- 5.7 ml/min/kg; steady-state volume of distribution, 7.9 +/- 4.5 and 2.1 +/- 0.5 l/kg; terminal elimination half-life, 1.8 +/- 0.3 and 1.8 +/- 0.9 h. Oxamniquine appeared to be widely distributed in both species, although significantly higher in the rabbit. Similarly, plasma clearance was significantly higher in the rabbit. Using reported estimates of liver blood flow and fractions excreted unchanged in urine of the rabbit and rat, calculations based on blood clearances indicated that oxamniquine has a low hepatic extraction ratio (0.2) in the rat and an intermediate hepatic extraction ratio (0.6) in the rabbit. From separate experiments, however, hepatic extraction appeared to be low in the rabbit, suggesting that oxamniquine disposition is probably broadly similar in both rabbit and rat.

Selective determination, in plasma, of artemether and its major metabolite, dihydroartemisinin, by high-performance liquid chromatography with ultraviolet detection.

A sensitive and selective reversed-phase high-performance liquid chromatographic method for the determination of artemether and its major metabolite dihydroartemisinin in plasma has been developed. It involves extraction of plasma with dichloromethane, solid-phase separation of the two analytes and acid decomposition prior to chromatography on a C18 Spherisorb column with a mobile phase of acetonitrile-water (50:50, v/v). Run time is 30 min. The assay satisfies all of the criteria required for use in clinical pharmacokinetic studies.

The apparent absorption kinetics of Ro 15-5458, a schistosomicidal drug.

The absorption kinetics of Ro 15-5458, a new antischistosomal drug, was studied in rabbits following the administration of a single 50 mg/kg oral dose as an aqueous suspension in 25% glycerol-1% cremophor EL. Ro 15-5458 was absorbed from the gastrointestinal tract rapidly with a lag time of about 6 min and declined without a plateau with a half-life of about 6 h. There was variable extent of drug appearance in plasma after oral administration. Maximum plasma levels ranged from 500 to 1200 ng/ml (1.3-3.1 microM). The plasma concentration-time profile of Ro 15-5458 after a single oral dose appears to follow a one-compartment pharmacokinetic model with zero-order absorption, first-order elimination.

Oltipraz: administration with food increases its anti-schistosomal activity.

In a previous study it was demonstrated that the concentration of oltipraz in the plasma of human volunteers was significantly elevated when administered with food. In this study we attempted to determine if this food-induced increase was associated with an increase in the drug's anti-schistosomal activity. The drug was administered with and without food to two groups of patients infected with Schistosoma mansoni. The concentration of oltipraz in the plasma of these patients was measured at varying intervals after dosing. Results indicate that the food-induced increase in the bioavailability of oltipraz in patients with S. mansoni produces a significant increase in the drug's anti-schistosomal activity.

Plasma determination of 3-methylclonazepam by capillary gas chromatography.

A capillary gas-liquid chromatographic method for the determination of 3-methylclonazepam in plasma was developed. This method involved a single extraction by butyl acetate followed by analysis of the organic extract on a CP-Sil 5 glass capillary column with detection by electron capture. The detection limit was about 0.1 ng/ml, and the inter- and intra-assay precision did not exceed 8% for the concentration range 0.1-6.0 ng/ml. Specificity towards some of the possible metabolites in human plasma was demonstrated. This method was used for the measurement of the pharmacokinetic parameters of 3-methylclonazepam in healthy volunteers after a single intravenous administration of 1 mg, and oral administrations of 1 and 4 mg.

Diet-controlled blood levels of oltipraz in healthy male subjects.

The bioavailability of the new antischistosomal agent, oltipraz, was examined under three different dietary conditions in seven healthy males. Oltipraz tablets (500 mg) were administered in single doses (25 mg/kg) under fasting conditions, with a low fat meal (less than 5% fat) and a high fat meal (24% fat). The extent and rate of oltipraz bioavailability were significantly increased by concurrent administration of the drug with food, as demonstrated by the increase in the plasma peak concentration, the area under the plasma concentration vs. time curve and the absorption rate constant. The plasma peak concentration was also reached earlier. Oltipraz plasma concentrations, following its administration under fasting conditions, were almost negligible. The likely mechanisms underlining oltipraz-food interaction are discussed.

Effect of cysteine on oltipraz blood levels in green monkeys (Cercopithecus aethiops).

Oral coadministration of oltipraz, an antischistosomal compound, with cysteine to green monkeys (Cercopithecus aethiops) led to a marked increase in both the extent and rate of oltipraz bioavailability. The drug blood levels were monitored using a single extraction gas-liquid chromatographic assay. When 6 healthy adult animals were given oltipraz together with cysteine in a crossover study, peak serum concentrations, areas under the curve and absorption rate constants of oltipraz were on average 7 times greater than when the drug was administered alone. Oltipraz peak serum concentrations were reached 1 h earlier as a result of cysteine administration (2 h after dosing). At present, the mechanisms responsible for the effect(s) of cysteine on oltipraz bioavailability have not been identified. The marked increase in oltipraz bioavailability produced by coadministration of cysteine, irrespective of the exact mechanisms involved, may have significant clinical implications with regard to the treatment of schistosomiasis. Our results also indicate that oltipraz blood levels seem to be influenced by some sex-related factors. Male monkeys had higher oltipraz blood levels than females. These sex-induced differences were more evident in oltipraz-cysteine-treated monkeys.