Manel Araoud

Multiresidue analysis of pesticides in fruits and vegetables by gas chromatography-mass spectrometry

A multiresidue method was assessed for the determination of several pesticides (organochlorine, organophosphorus, pyrethroids, triazole, amidine) using gas chromatography/mass spectrometry. The extraction of pesticides was carried out by liquid-liquid extraction (LLE) and solid-phase extraction (SPE) using two types of columns (CN and C18). The extracts were cleaned by the addition of florisil, the pesticides were separated by capillary column gas chromatography and detected by mass spectrometry in the electron impact mode. The extraction using C18 column provided the best results for most of the analyzed pesticides. The majority of pesticides recoveries from the four fruits and vegetables (apples, pears, tomatoes and pepper) were greater than 60%. Linearity and precision were satisfactory. The estimated limits of detection and limits of quantification ranged from 0.01 to 0.1 mg/kg and from 0.02 to 0.3 mg/kg, respectively. The proposed procedure was found to be useful for the multiresidue analyses of pesticides in agricultural products for routine monitoring programs.

Paraoxonase 1 Correlates with Butyrylcholinesterase and Gamma Glutamyl Transferase in Workers Chronically Exposed to Pesticides

Paraoxonase 1 Correlates with Butyrylcholinesterase and Gamma Glutamyl Transferase in Workers Chronically Exposed to Pesticides: Manel Araoud, et al. Laboratory of Biochemistry 05/UR/09‐09, Faculty of Medicine of Monastir, Tunisia

Development of an automated method for the determination of human paraoxonase1 activity

Abstract Background: Human plasma paraoxonase1 (PON1) is an esterase catalyzing the hydrolysis of organophosphorus pesticides and other xenobiotics. The aims of this study were to develop a rapid method to determinate PON1 activity, evaluate some interference, and study the influence of storage temperature on PON1 activity assay. Methods: Measurement of PON1 activity was performed for 369 samples by measuring the hydrolysis of paraoxon using a spectrophotometric method adapted on konelab 30 ⃞. Results: The developed method facilitates the determination of PON1 activity at the rate of more than 200 samples per hour, and it is linear between 2 and 900 IU/L. Intra and inter-assay imprecision coefficients of variation were 2% and 5% respectively. PON1 activity in serum was correlated with those in heparinized plasma (r = 0.994, p < 0.001) and in plasma/EDTA (r = 0.962, p < 0.001). The mean inhibition of the PON1 activity was, by EDTA/K3, 41 ± 10 %. There was not significant PON1 activity variation after 40 days of storage at -20°C or at +4 ⃞ C. There were no substantial interferences from haemoglobin, jaundice and hyperlipidemia. Conclusion: The developed method is reliable, reproducible, and suitable. It can also be performed on heparinized plasma for the determination of PON1 activity. Hence, it may be useful for assaying PON1 activity in several intoxications such as organophosphorus, sarin, and soman nerve agents.

Lower paraoxonase 1 activity in Tunisian bipolar I patients.

BackgroundThe purpose of this study was to investigate the variations of paraoxonase activity and lipid profile in bipolar I patients, and the association of this activity with the sociodemographic, clinical and therapeutic characteristics of this population.Patients and methodsOur study included 66 patients with bipolar I disorder and 64 controls aged 37.9 ± 12.6 and 36.3 ± 18.2 years, respectively. Paraoxonase activity was determined by kinetic methods; high-density lipoprotein cholesterol (c-HDL), low-density lipoprotein cholesterol (c-LDL), triglycerides and total cholesterol were determined by enzymatic methods; apolipoprotein (Apo)A1, ApoB and lipoprotein (a) (Lp(a)) were determined by immunoturbidimetry using Konelab 30 equipment (Thermo Scientific).ResultsCompared with controls, patients had a significantly lower paraoxonase activity and ApoA1 level, and significantly higher total cholesterol, c-LDL and Lp(a) level and ApoB/ApoA1 ratio. Furthermore, paraoxonase activity was significantly correlated with c-HDL values (r = 0.5612; P < 0.001). The lowest paraoxonase activity was noted in relation to age and body mass index (BMI). Moreover, it was associated with gender but not with smoking and alcohol consumption status. In patients, there was no significant change in paraoxonase activity in relation to illness episodes, whereas the lowest values of this activity were seen in manic patients. In contrast, paraoxonase activity was significantly associated with treatment. Indeed, patients taking lithium had the lowest levels.ConclusionsBipolar patients had a significant decrease in paraoxonase activity and perturbations in their lipid profile that contribute to increased risk of cardiovascular diseases. Decrease in this activity was significantly associated with treatment with lithium but not with sociodemographic and clinical characteristics. Therefore, such patients require specific care, particularly with regard to their lipid profile.

Toxic effects of methamidophos on paraoxonase 1 activity and on rat kidney and liver and ameliorating effects of alpha‐tocopherol

The role of alpha‐tocopherol on nephrotoxicity and hepatotoxicity induced by methamidophos (MT) was investigated in wistar rats. Animals were given via gavage, for four weeks, a low dose of MT (MT1), a high dose of MT (MT2), vitamin E (200 mg/kg of bw) or both MT2 plus vitamin E (Vit E) and control group was given distillate water. MT treatment resulted in a significant decrease in the body weight of MT2‐treated group. Moreover, MT‐treated groups had significantly lower butyrylcholinesterase (p < 0.01) and paraoxonase 1 (PON1) activities compared with the control group (p < 0.05). However, MT2‐treated group had significantly higher alkaline phosphatase activity compared with untreated rats (p < 0.05). Both MT‐treated groups had significantly higher urea (p < 0.01) and uric acid levels (p < 0.05) compared with the control group. However, significant low uric acid level (p < 0.05) was noted in MT2 plus vit E‐treated rats compared with MT2‐treated group. Histopathological changes in organ tissues were observed in both MT‐treated groups and MT2 plus vit E‐treated rats. However, the damage was reduced in MT2 plus vit E‐treated rats. Therefore, this study deduces that alpha‐tocopherol administration may ameliorate the adverse effects of subacute exposure to MT on rat liver and kidney and this antioxidant can protect PON1 from oxidative stress induced by this organophosphorus pesticide.

Adverse effects of pesticides on biochemical and haematological parameters in Tunisian agricultural workers.

Biomonitoring of effects in agricultural workers is necessary to assess the individual risk of handling pesticides. In this study, biochemical and haematological parameters were measured to evaluate the effects of exposure to these compounds in agricultural workers. The study was carried out in 110 workers and 97 control subjects. Several haematological and biochemical parameters were analysed. Assessment of haematological parameters revealed that the mean cell volume and haematocrit levels were significantly lower in workers than in controls (P=0.002 and 0.013, respectively), while mean corpuscular haemoglobin concentrations were higher in workers (P<0.001). There was also a significant inhibition of butyrylcholinesterase activity in workers compared with that in controls (P<0.001). Assessment of biochemical parameters further showed significantly higher activities of transferases, lactate dehydrogenase (P<0.001), alkaline phosphatase (ALP) (P=0.006) and creatine kinase (CK) (P<0.015), as well as higher levels of proteins (P<0.001), creatinine (P=0.001) and urea (P=0.001) in workers compared with controls, along with significantly higher uric acid levels (P=0.012). Furthermore, the number of years exposed to pesticides predicted higher activities of alanine aminotransferase, CK, ALP, as well as uric acid levels. Overall, chronic exposure to pesticides appeared to affect several biochemical parameters. These biomarkers seem to be indicative of adverse effects of pesticides in agricultural workers, confirming their use for routine monitoring of effects.

Simple analytical method for determination of pesticide residues in human serum by liquid chromatography tandem mass spectrometry.

The aim of this study was to develop an analytical method for the determination of residues of organophosphorus and carbamate pesticides which are widely used in Tunisia. This method involves a liquid-liquid extraction procedure followed by liquid chromatography tandem mass spectrometry (LC/MS/MS) for the identification and quantification of compounds. Ionization of molecules was performed by the electrospray mode. Multiple reactions monitoring (MRM) was the acquisition mode used for the monitoring of two MS/MS transitions for each compound. The average recoveries obtained, at three different fortification levels, ranged between 65% and 106% for most of the pesticides studied, except for methamidophos (lower than 25%).The linearity of the method was in the range of 5 to 50 μ g/L with a correlation coefficient from 0.995 to 0.999, depending on the analyte. The estimated limit of detection and limit of quantification were 2 μ g/L and 5 μ g/L, respectively. The precision of the analytical procedure was satisfactory and the coefficients of variation, evaluated at three concentration levels were lower than 15% for most pesticides studied. The application of the method was investigated in a population of agricultural workers chronically exposed to various pesticides some of which, such as carbofuran, carbendazim, methomyl and pirimicarb, were detected in some serum samples.

Étude de l’activité de la cholinestérase plasmatique au cours des atteintes hépatiques

Plasma cholinesterase activity (ChE) may vary in some pathological circumstances. We studied the changes in activity of this enzyme according to the type of liver injury, to assess the interest of this parameter in the diagnosis of liver diseases. Our study was performed on 102 patients with different liver diseases and 53 healthy controls. The ChE activity was lower in patients compared to control group (p < 0.0001), and more pronounced in cirrhotic patients compared to those suffering from hepatitis. Elevated activities of AST, ALT, GGT and ALP and bilirubinemia, and decreased albuminemia were noted in patients compared to controls (p < 0.001). Hypoalbuminemia was significantly important in cirrhotic patients compared to those suffering from cholestasis or hepatitis. A correlation between ChE and bilirubin, albumin and serum protein was found in patients with cirrhosis or those with chronic hepatitis. A significantly lower activity of ChE was found in patients with hepatic insufficiency (HI). In case of suspicion of HI, the prescription of ChE activity could guide or confirm the diagnosis of the impairment.

Signes cliniques et variations de l’activité de la cholinestérase plasmatique chez des travailleurs agricoles exposés aux pesticides

L’objectif de cette etude est de contribuer a l’evaluation et l’appreciation des risques reels lies a l’exposition chronique aux pesticides, a partir des variations de l’activite de la cholinesterase plasmatique (PChE), et des manifestations cliniques susceptibles d’etre dues a l’exposition professionnelle aux pesticides. L’etude a concerne 110 travailleurs agricoles et 97 individus temoins, vivant dans le Sahel tunisien. Chaque individu a beneficie d’un examen clinique, afin de rechercher des symptomes fonctionnels en relation avec une intoxication chronique aux pesticides. La determination de l’activite de la PChE a ete realisee par une methode cinetique adaptee sur konelab 30 (Thermo Clinical Labsystems™). Les signes neurologiques sont les plus frequemment retrouves chez les travailleurs, suivis des atteintes osteomusculaires et des signes dermatologiques. Une association significative a ete retrouvee entre les signes neurologiques mentionnes par les travailleurs et l’exposition a des organophosphores (OP) et/ou des carbamates (CB) (p = 0,013). L’activite moyenne de la PChE est significativement plus basse chez les travailleurs par rapport aux temoins (p < 0,001). Elle est diminuee chez les travailleurs exposes a des melanges de pesticides OP-CB par rapport a ceux n’ayant utilises que des OP (p = 0,030) ou des CB (p = 0,031). Une association significative a ete notee entre la diminution de la PChE et l’exposition aux OP et/ou CB (p < 0,001). La variation de la PChE est egalement liee a la duree d’epandage et l’anciennete d’exposition. Ainsi, l’activite de la PChE constitue un important biomarqueur d’effet de l’exposition aux pesticides. Cependant, l’interpretation de l’activite de cette enzyme chez les travailleurs doit prendre en consideration certains facteurs, notamment la nature des pesticides utilises ainsi que la duree et l’anciennete de l’exposition.