Antioxidant studies of citric acid and citrus fruits towards paraquat by cyclic voltammetry: An antidote of paraquat poisoning

Voltammetric parameters are studied to confirm the antioxidant activity of citric acid towards reduced form of methyl viologen dication (1, 1'-dimethyl-4, 4'-bipyridinium, MV ²⁺, also known as paraquat). In this study the kinetics of the reaction of citric acid with reduced form of methyl viologen is also reported. Out of two oxidative peaks (i.e. MV^o to MV^+˖ and MV^+˖ to MV⁺²) the first peak is almost removed after interaction with citric acid. Shifting in second cathodic peak potential is also obvious and possibility of citric acid to scavenge or making adduct with paraquat is identified. Some real samples (fruit juices) as a rich source of citric acid are also studied. This study presents a simple, relevant and fast voltammetric method by which quick quantitation and monitoring of antioxidant/ scavenging activity of food, herbs and other spices towards paraquat poisoning is possible. It may constitute a new wave of treatment or therapy for the disease caused by paraquat.

An antidote for imazalil-induced genotoxicity in vitro: the lichen, Dermatocarpon intestiniforme (Körber) Hasse

Imazalil (IMA), a commonly used fungicide in both agricultural and clinical domains, is suspected to produce serious toxic effects in vertebrates. In recent years, a number of studies have suggested that lichens might be easily accessible sources of natural drugs that could be used as a possible food supplement. Extensive research is being performed to explore the importance of lichen species, which are known to contain a variety of pharmacological active compounds. In this context, the antigenotoxic effect of aqueous Dermatocarpon intestiniforme (Körber) Hasse. extract (DIE) was studied against the genotoxic damage induced by IMA on cultured human lymphocytes (n = 6) using chromosomal aberration (CA) and micronucleus (MN) as cytogenetic endpoints. Human peripheral lymphocytes were treated in vitro with varying concentrations of DIE (0, 25, 50 and 100 μg/ml), tested in combination with IMA (336 μg/ml). DIE alone were not genotoxic and when combined with IMA treatment, it reduced the frequency of CAs and the rate of MNs. A clear dose-dependent decrease in the genotoxic damage of IMA was observed, suggesting a genoprotective role of DIE. The results of the present study suggest that this plant extract per se does not have a genotoxic potential, but can alleviate the genotoxicity of IMA on cultured human lymphocytes. In conclusion our findings may have an important application for the protection of cultured human lymphocyte from the genetic damage and side effects induced by medical and agricultural chemicals hazardous for people.

FT-IR and XRD analysis of natural Na-bentonite and Cu(II)-loaded Na-bentonite

Na-bentonite has been studied extensively because of its strong adsorption capacity and complexation ability. In this work, surface area, total pore volume, mean pore diameter, TG, DTA, FT-IR and XRD were carried out in order to reveal the characteristics of natural Na-bentonite. XRD and FT-IR of natural Na-bentonite (China) and Cu-loaded Na-bentonite as a function of Na-bentonite dosage and temperature using batch technique were characterized in detail, respectively.

Conformational and configurational analysis of an N,N carbonyl dipyrrinone-derived oximate and nitrone by NMR and quantum chemical calculations

The geometries and relative energies of new N,N carbonyl dipyrrinone-derived oxime molecules (E/Z-s-cis 4a and E/Z-s-cis 4b) have been investigated. The calculated energies, molecular geometries, and (1) H/(13) C NMR chemical shifts agree with experimental data, and the results are presented herein. The E-s-cis conformations of 4a and 4b and the Z-s-cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti-orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments.

A rapid high-pressure liquid chromatographic procedure for determination of flumazenil in plasma

INTRODUCTION

Flumazenil antagonizes the effects of benzodiazepines at gamma-aminobutyric acid (GABA) type A receptors in the central nervous system. Flumazenil has been reported to provoke panic attacks in patients with panic disorder (PD) but not in healthy controls. A rapid high-pressure liquid chromatographic (HPLC) method was developed for determination of flumazenil in plasma samples from PD patients receiving flumazenil and the results obtained with that assay are reported here.

METHODS

Samples from 37 PD subjects receiving 2 mg of flumazenil intravenously were analyzed. Extraction under basic conditions was followed by an HPLC assay with UV detection (250 nm). Lamotrigine was used as intermal standard and a standard curve was constructed for each assay run. Flumazenil concentrations were measured in all the subjects in samples collected at 2 and 4 min after the drug administration and in some subjects, measurements were also done in samples collected at 7.5, 15, 30, 45, and 60 min.

RESULTS

The procedure was reproducible and linear (from 2.5 to 1000 ng/ml). At 2 and 4 min after flumazenil administration, the concentrations did not differ significantly between panicking and nonpanicking subjects, indicating that the pharmacokinetics of the drug is not the major determinant of the responses. There was a steep decline in the plasma concentration-time profile during the first 4 min, reflecting an extensive and rapid distribution after which the decline was slower.

DISCUSSION

The method described here is rapid, replicable, and convenient for the determination of flumazenil in plasma.

Liquid chromatographic analysis of physostigmine salicylate and its degradation products

A simple stability-indicating HPLC assay has been developed for physostigmine salicylate, capable of following its degradation. A 250 x 5 mm i.d. column packed with 10 microm Bondapak C18 was used, with a mobile phase of acetonitrile - ammonium acetate (pH 6.0; 0.1 M) (50:50, v/v) and flow rate 1.2 ml x min(-1). All peaks are eluted in <10 min and the method has good precision. The optimum wavelength for detection of degradation products is 305 nm. Application of the assay for a commercial preparation of physostigmine salicylate for injection is presented.

pKa of 4MP and chemical equivalence in formulations of free base and salts of 4MP

Fomepizole (4-Methylpyrazole, 4MP) is used as an antidote for ethylene glycol and methanol poisoning. In France it is administered intravenously as the sulfate or hydrochloride salt formulation and in the United States, as the free base formulation. Since its pKa was unknown, it was unknown if the free base, hydrochloride and sulfate salt formulations of 4MP are chemically equivalent, and if 4MP is in chemically equivalent forms in blood when these base and salt formulations are administered intravenously. Using UV spectrophotometry, the pKa of 4MP was determined to be 2.91 +/- 0.05 (n = 7) at a low concentration of 0.006 M in formate buffers of various pH, and 3.00 +/- 0.16 (n = 7) when high concentration of 4MP (0.06 M) was titrated with HCl at 25 degrees C. The hydrochloride salt formulation (pH 6.64) was ionically and hence chemically equivalent to the free base formulation (pH 7.02), while the sulfate salt formulation, due to its lower pH of 2.33, showed presence of some ionized 4MP indicating chemical inequivalence. In order to determine chemical equivalence upon intravenous administration, these formulations were diluted with phosphate buffer (pH 7.4) with identical ionic strength and buffer capacity as blood. In spite of chemical inequivalence of the sulfate salt formulation, 4MP free base was observed from all three formulations when diluted with physiological buffer suggesting chemical equivalence under physiological conditions due to the strong buffering action of blood.

[Intrahepatic glutathione and oxidative stress in liver transplantation in the pig]

OBJECT

To determine the loss of endogenous GSH from livers cold-stored and reperfused, using a model of liver transplantation in the pig.

MATERIAL AND METHODS

Four female Yorkshire pigs weighing 19 to 40 kg received a liver allograft. Donor livers were cold-stored in the UW solution. Mean cold ischemic time was 6.5 hours. Malondialdehyde (MDA) levels were used as an index of oxidative stress. MDA plasma levels were measured following recipient laparotomy (H0), immediately (H1), and 90 minutes after liver reperfusion (H2). MDA and GSH levels in liver were measured following donor laparotomy (T0), at the end of cold ischemic period (T1), and at 90 minutes following liver reperfusion (T2).

RESULTS

Three animals survived. MDA liver levels decreased of 44% between T0 and T1, then increased to 92% at T2. In contrast, in plasma, graft reperfusion was associated with an increase of MDA to 140% of the baseline values which reached 188% at H2. Intrahepatic GSH levels decreased of 49% at T1, then to 72% at T2.

CONCLUSION

our study suggests that in liver transplantation: (1) Hepatic GSH is depleted to 49% during cold-storage, and an additional 23% is lost after reperfusion; (2) GSH contained in the UW solution does not prevent the loss of hepatocellular glutathione during preservation and reperfusion; (3) after short periods of cold ichemia, endogenous hepatic GSH may protect against oxydative stress in the transplanted liver.

Endotracheal flumazenil: a new route of administration for benzodiazepine antagonism

The purpose of this study was to determine if flumazenil is absorbed from broncho-pulmonary tissue after intratracheal administration and whether therapeutically significant plasma concentrations can be obtained. Six elective surgical patients received a dose of 1.0 mg flumazenil in 10 mL saline intratracheally during general anesthesia. Blood samples were drawn for 6 hours after administration and plasma concentrations were determined by gas chromatography-mass spectrometry (GC-MS). An average peak plasma flumazenil concentration of 65.9 +/- 43.1 ng/mL was attained within 1 minute after administration. No patients reported chest discomfort or dyspnea upon awakening and there were no other side effects noted. Administration of flumazenil via an endotracheal tube results in rapid attainment of therapeutic blood levels.

Fluorescent estimation of H2O2-induced changes in cell viability and cellular nonprotein thiol level of dissociated rat thymocytes

We have developed a procedure to simultaneously estimate cell viability and the cellular level of nonprotein thiol (presumably glutathione) using two fluorescent dyes, 5-chloromethylfluorescein (5CMF) and ethidium, and rat thymocytes. Diethylmaleate and N-ethylmaleimide reduced, respectively, the intensity of 5CMF fluorescence to 0.23 and 0.1, relative to the control. Incubation with buthionine sulfoximine, an inhibitor of glutathione synthesis, decreased the intensity of 5CMF fluorescence to 0.61. Results indicate that 5CMF fluorescence can be attenuated by agents that decrease the level of cellular nonprotein thiols, suggesting that 5CMF fluorescence is utilized for estimating the level of cellular glutathione. Hydrogen peroxide (10 microM to 3 mM) reduced the intensity of 5CMF fluorescence in a dose-dependent manner and increased the number of thymocytes stained with ethidium (presumably dead cells or cells with compromised membranes) at concentrations of 300 microM or greater. Reduction of cellular glutathione level seems to precede cell death in which oxidative stress is involved.

Modulation of cisplatin chronotoxicity related to reduced glutathione in mice

Intracellular reduced glutathione (GSH) concentrations were measured according to the tissue sampling-time along the 24 h scale in male B6D2F1 mice. A significant circadian rhythm in GSH content was statistically validated in liver, jejunum, colon and bone-marrow (P < or = 0.02) but not in kidney. Tissue GSH concentration increased in the dark-activity span and decreased in the light-rest span of mice. The minimum and maximum of tissue GSH content corresponded respectively to the maximum and minimum of cisplatin (CDDP) toxicity. The role of GSH rhythms with regard to CDDP toxicity was investigated, using a specific inhibitor of GSH biosynthesis, buthionine sulfoximine (BSO). Its effects were assessed on both tissue GSH levels and CDDP toxicity at three circadian times. BSO resulted in a 10-fold decrease of the 24 h-mean GSH in kidney. However a moderate GSH decrease characterized liver (-23%) and jejunum (-30%). BSO pretreatment largely enhanced CDDP toxicity which varied according to a circadian rhythm. Although BSO partly and/or totally abolished the tissue GSH rhythms, it did not modify those in CDDP toxicity. We conclude that GSH have an important influence on CDDP toxicity but not in the circadian mechanism of such platinum chronotoxicity.

Measurement of the oxime HI-6 after peripheral administration in tandem with neurotransmitter levels in striatal dialysates: effects of soman intoxication

In the present study, the technique of microdialysis combined with tandem high-performance liquid chromatography was used to determine the striatal levels of HI-6 and neurotransmitters following peripheral administration of HI-6 (50 mg/kg i.m.) in conscious, freely moving rats. The results were compared with those obtained in animals given soman (135 micrograms/kg i.p.) 1 min before HI-6 (50 mg/kg i.m.). Principal component analysis was used to study the effects of the different treatments on neurotransmitters and signs of poisoning. In all animals given HI-6, maximum levels of HI-6 appeared in the second 20-min fraction after administration of HI-6, then gradually declined, reaching the lower limits of detection after 3 hr. There was a correlation between severity of poisoning and neurochemical changes observed; dopamine and GABA levels increased as the severity of signs of poisoning increased. These results clearly demonstrate that HI-6 can penetrate into the brain of control and soman-intoxicated animals. Tandem measurement of dopamine electrochemically and HI-6 by UV detection provides a simple method for obtaining data on HI-6 penetration into the brain in neurochemical studies of soman poisoning and its treatment.

Experience with an homogeneous immunoassay for paracetamol (acetaminophen)

The performance of an homogeneous enzyme immunoassay (EMIT) for paracetamol (acetaminophen) as configured for the aca series of discretionary analysers (Du Pont de Nemours) was evaluated. The method as initially formulated by the manufacturers gave unacceptable performance which was improved upon, by reagent reformulation and improved kit manufacture procedures, by the manufacturer. The method was fast, precise and free from interference from a range of metabolites, drugs and endogenous physiological compounds. There was good correlation between this method and an enzymatic method for paracetamol (acetaminophen).