N-tert-butoxycarbonyl-methylenedioxymethamphetamine, an methylenedioxymethamphetamine derivative, exhibits rewarding and reinforcing effects by increasing dopamine levels.

An N-protected methylenedioxymethamphetamine (MDMA), N-tert-butoxycarbonyl-3,4-methylenedioxymethamphetamine (t-BOC-3,4-MDMA), contains tert-butoxycarbonyl and can remain undetected in the illicit drug market. It is a new type of precursor substance that is not a chemical intermediate and can be converted into a controlled substance, MDMA, by deprotection of the N-tert-butoxycarbonyl group. Categorization of this chemical into a precursor or psychotropic substance is an issue because it is an unprecedented precursor that could have misuse potential. Although MDMA causes rewarding and reinforcing effect through dopaminergic transmission, the misuse potential of t-BOC-3,4-MDMA has not yet been characterized. Here, we aim to evaluate the misuse potential of t-BOC-3,4-MDMA. The response to the drug at a dose of 5 mg/kg was determined by a climbing test, and its rewarding and reinforcing properties were assessed through conditioned place preference and self-administration tests. In the conditioned place preference test, intraperitoneal administration of t-BOC-3,4-MDMA (5 mg/kg) significantly altered place preference in mice. In the self-administration models, t-BOC-3,4-MDMA induced drug-taking behavior at the dose of 0.5 mg/kg/infusion (intravenous) during 2 hr sessions under fixed-ratio schedules in mice. In addition, microdialysis experiments verified that t-BOC-3,4-MDMA impacted the dopamine levels of the brain (striatum) of rats. These experimental results indicate that t-BOC-3,4-MDMA has a potential for misuse. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Discriminative stimulus and reinforcing effects of diclazepam in rodents.

Diclazepam, a designer benzodiazepine, is a lesser-known novel anxiolytic substance and a structural analog of diazepam. Although several case studies have reported the adverse effects of diclazepam, their potential impacts remain unknown. Therefore, this study aimed to determine the effects of diclazepam in rodents using drug discrimination, locomotor activity, self-administration (SA), and conditioned place preference (CPP) tests. Sprague-Dawley rats (male, 8 weeks old, weighing 220-450 g, n = 12 per group) and C57BL/6 mice (male, 7 weeks old, weighing 20-25 g, n = 7-8 per group) were administered alprazolam, morphine, and diclazepam. Diclazepam fully elicited alprazolam-appropriate dose-dependent lever responses (>80 %) similar to those of alprazolam. In rats administered 0.5 mg/kg of morphine, a partial substitution (80 %-20 %) was observed. Mice receiving intraperitoneal injections of diclazepam (0.05, 0.2, and 2 mg/kg) showed decreased locomotor activity. In the SA experiment, mice that self-administered intravenous diclazepam (2 µg/kg/infusion) showed significantly higher infusion and active lever responses compared to the vehicle group. No statistically significant rewarding effects of diclazepam at the doses of 0.2 and 2 mg/kg evaluated using the CPP paradigm were found. In conclusion, diclazepam has reinforcing effects and shares the interoceptive effects of alprazolam. Therefore, legal restrictions on the use of diclazepam should be carefully considered.

New in vitro multiple cardiac ion channel screening system for preclinical Torsades de Pointes risk prediction under the Comprehensive in vitro Proarrhythmia Assay concepta.

Cardiotoxicity, particularly drug-induced Torsades de Pointes (TdP), is a concern in drug safety assessment. The recent establishment of human induced pluripotent stem cell-derived cardiomyocytes (human iPSC-CMs) has become an attractive human-based platform for predicting cardiotoxicity. Moreover, electrophysiological assessment of multiple cardiac ion channel blocks is emerging as an important parameter to recapitulate proarrhythmic cardiotoxicity. Therefore, we aimed to establish a novel in vitro multiple cardiac ion channel screening-based method using human iPSC-CMs to predict the drug-induced arrhythmogenic risk. To explain the cellular mechanisms underlying the cardiotoxicity of three representative TdP high- (sotalol), intermediate- (chlorpromazine), and low-risk (mexiletine) drugs, and their effects on the cardiac action potential (AP) waveform and voltage-gated ion channels were explored using human iPSC-CMs. In a proof-of-principle experiment, we investigated the effects of cardioactive channel inhibitors on the electrophysiological profile of human iPSC-CMs before evaluating the cardiotoxicity of these drugs. In human iPSC-CMs, sotalol prolonged the AP duration and reduced the total amplitude (TA) via selective inhibition of IKr and INa currents, which are associated with an increased risk of ventricular tachycardia TdP. In contrast, chlorpromazine did not affect the TA; however, it slightly increased AP duration via balanced inhibition of IKr and ICa currents. Moreover, mexiletine did not affect the TA, yet slightly reduced the AP duration via dominant inhibition of ICa currents, which are associated with a decreased risk of ventricular tachycardia TdP. Based on these results, we suggest that human iPSC-CMs can be extended to other preclinical protocols and can supplement drug safety assessments.

Various extraction methods for detection of bistrifluron residues in Asian pear using high-performance liquid chromatography: application to dissipation patterns under open-field conditions.

The present study was carried out to develop an analytical method for the detection and quantification of bistrifluron, a benzoylphenylurea compound, in pear using high-performance liquid chromatography with UV detection. Samples were extracted using conventional, AOAC and EN quick, easy, cheap, effective, rugged and safe 'QuEChERS' methods. As expected, conventional and EN-QuEChERS methods gave higher recoveries than AOAC. In addition, interference around the analyte retention time was observed in the conventional method. Thus, the EN-QuEChERS method was selected and validated by studying various parameters, including linearity, limit of detection, limit of quantification (LOQ), recovery and precision. Linearity was excellent, with a correlation coefficient of 0.9998. Recovery rates at three spiking levels (0.05, 0.2 and 1 mg/kg) ranged from 73.76 to 98.66%. Intra- and inter-day precisions, expressed as relative standard deviations, were <6%. The LOQ of 0.05 mg/kg was considerably lower than the maximum residue limit (1 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed method was successfully applied to open-field pear samples, in which the target analyte was slowly dissipated (55% decline) over 14 days with a half-life of 10.19 days. Notably, the residue levels throughout the period of sample collection (14 days) were lower than the maximum residue limit, indicating that the residue was not hazardous for consumers. Copyright © 2016 John Wiley & Sons, Ltd.

A combination of solid-phase extraction and dispersive solid-phase extraction effectively reduces the matrix interference in liquid chromatography-ultraviolet detection during pyraclostrobin analysis in perilla leaves.

Perilla leaves contain many interfering substances; thus, it is difficult to protect the analytes during identification and integration. Furthermore, increasing the amount of sample to lower the detection limit worsens the situation. To overcome this problem, we established a new method using a combination of solid-phase extraction and dispersive solid-phase extraction to analyze pyraclostrobin in perilla leaves by liquid chromatography with ultraviolet absorbance detection. The target compound was quantitated by external calibration with a good determination coefficient (R(2) = 0.997). The method was validated (in triplicate) with three fortification levels, and 79.06- 89.10% of the target compound was recovered with a relative standard deviation <4. The limits of detection and quantification were 0.0033 and 0.01 mg/kg, respectively. The method was successfully applied to field samples collected from two different areas at Gwangju and Muan. The decline in the resiudue concentrations was best ascribed to a first-order kinetic model with half-lives of 5.7 and 4.6 days. The variation between the patterns was attributed to humidity.

Dynamic behaviour and residual pattern of thiamethoxam and its metabolite clothianidin in Swiss chard using liquid chromatography-tandem mass spectrometry.

A simultaneous method was developed to analyse thiamethoxam and its metabolite clothianidin in Swiss chard using tandem mass spectrometry (in the positive electrospray ionisation mode using multiple reaction monitoring mode) to estimate the dissipation pattern and the pre-harvest residue limit (PHRL). Thiamethoxam (10%, WG) was sprayed on Swiss chard grown in two different areas under greenhouse conditions at the recommended dose rate of 10 g/20 L water. Samples were collected randomly up to 14 days post-application, extracted using quick, easy, cheap, effective, rugged, safe (QuEChERS) acetate-buffered method and purified via a dispersive solid phase extraction (d-SPE) procedure. Matrix matched calibration showed good linearity with determination coefficients (R(2)) ⩾ 0.998. The limits of detection (LOD) and quantification (LOQ) were 0.007 and 0.02 mg/kg. The method was validated in triplicate at two different spiked concentration levels. Good recoveries (n=3) of 87.48-105.61% with relative standard deviations (RSDs) < 10 were obtained for both analytes. The rate of disappearance of total thiamethoxam residues in/on Swiss chard was best described by first-order kinetics with half-lives of 6.3 and 4.2 days. We predicted from the PHRL curves that if the residues were <19.21 or 26.98 mg/kg at 10 days before harvest, then total thiamethoxam concentrations would be below the maximum residue limits during harvest.

Development of high performance liquid chromatography-ultraviolet detection method for screening mebendazole, clorsulon, diaveridine, and tolfenamic acid in animal-based food samples.

This study focused on the detection and validation of the residues of the four veterinary drugs, mebendazole, clorsulon, diaveridine, and tolfenamic acid, using high performance liquid chromatography (HPLC) and an ultraviolet (UV) detector. Utilizing C18 column as a stationary phase and applying appropriate mobile phases to each analysis according to the properties of the analytes, target compounds in food samples were successfully detected and separated within 15-50 min. Additionally, in order to optimize detection, liquid-liquid extraction (LLE) and purification steps were established to minimize the endogenous peaks and their interferences. The method was validated through testing of linearity, accuracy, precision, the limit of detection (LOD) and the limit of quantification (LOQ). The LOQ levels of the four drugs were lower than the maximum residual limit, and the coefficient of determination (R(2) ) was over 0.99. The recovery results ranged from 82.3-105.2%, 79.3-83.3%, 79.4-86.0%, and 81.7-88.5% with relative standard deviations lower than 20% for mebendazole, clorsulon, diaveridine, and tolfenamic acid, respectively, corresponding to the CODEX guideline. This proposed method reduces costs and enables easier application in rural or remote areas where testing facilities or instruments often are unavailable.

Determination of PDE-5 inhibitors and appetite suppressants in adulterated dietary supplements using LC/PDA and LC/MS.

There have been a number of reports of dietary supplements contaminated with illegal adulterants that threaten consumers' health because of their adverse pharmacological effects. In the present study, a convenient and economic method was developed to detect illegal pharmaceutics, such as PDE-5 inhibitor and appetite suppressants, using liquid chromatography (LC)/photodiode array (PDA) for screening and LC/mass spectrometry (MS) for successive confirmation. Target peaks were identified by comparison of their chromatographic retention times and PDA spectra with those of synthetic standards and finally confirmed by LC/MS. As a result, tadalafil, a PDE-5 inhibitor, and N-desmethylsibutramine, a derivative of sibutramine, were detected in various dietary supplements at concentrations of 13.5-21.9 mg and 3.0 mg per single dose, respectively. The present study will contribute to the development of an analytical method enabling rapid screening of a variety of health foods, and the result suggests that consumers should be aware of serious health risks related to these illegal compounds.

Simultaneous determination of orysastrobin and its isomers in rice using HPLC-UV and LC-MS/MS.

Orysastrobin is a new strobilurin-type fungicide to control leaf and panicle blast and sheath blight in rice. An analytical method was developed to determine the residues of orysastrobin and its two isomers, the main metabolite F001 and the major impurity F033, in hulled rice by the use of high-performance liquid chromatography with ultraviolet photometry (HPLC-UV) and liquid chromatography with tandem mass spectrometry (LC-MS/MS). All compounds were extracted with acetone from hulled rice samples. The extract was diluted with saline water, and an extraction step using dichloromethane/n-hexane partition was used to recover analytes from the aqueous phase. An n-hexane/acetonitrile partition and Florisil column chromatography were employed to further remove interfering coextractives prior to instrumental analysis. An octadecylsilyl column was successfully applied to identify orysastrobin and its isomers in sample extracts. Net recovery rates of orysastrobin, F001, and F033 from fortified samples ranged from 80.6 to 114.8% using HPLC-UV and LC-MS/MS. Relative standard deviations for the analytical methods were all <20%, and the quantification limits of the method were in the 0.002-0.02 mg/kg range. The proposed methods were reproducible and sufficiently accurate to evaluate the terminal residue of orysastrobin and its isomers in rice.

Determination of Oxyclozanide in Beef and Milk using High-Performance Liquid Chromatography System with UV Detector.

This study was developed and validated for the determination of oxyclozanide residue concentrations in beef and commercial milk, using high-performance liquid chromatography system. Oxyclozanide was successfully separated on a reverse phase column (Xbridge-C(18), 4.6×250 mm, 5 µm) with a mobile phase composed of acetonitrile and 0.1% phosphoric acid (60:40, v/v%). This analytical procedure involved a deproteinization process using acetonitrile for beef and 2% formic acid in acetonitrile for commercial milk, dehydration by adding sodium sulfate to the liquid analytical sample, and a defatting process using n-hexane; after these steps, the extract was exposed to a stream of nitrogen dryness. The final extracted sample was dissolved in the mobile phase and filtered using a 0.45 µm syringe filter. This method had good selectivity and recovery (70.70±7.90-110.79±14.95%) from the matrices. The LOQs ranged from 9.7 to 9.8 µg/kg for beef and commercial milk. The recoveries met the standards set by the CODEX guideline.

Development and validation of a liquid chromatography method with electrospray ionization tandem mass spectrometry for the determination of brotizolam residues in beef and commercial whole milk.

In this work, a liquid chromatography-tandem mass spectrometric detection technique was developed and validated for the determination of brotizolam residues in beef muscle and commercial whole milk. This procedure involves the extraction of the analyte from the samples via liquid-solid extraction, and caffeine was used as an internal standard. The analyte was successfully separated on an XTerra-C(18) column, with a mobile phase composed of 0.01% formic acid in acetonitrile and 1 mm ammonium formate-0.01% formic acid in water. The one-step extraction method evidenced good selectivity, precision (RSD = 9.87-26.47%), and the recovery of the extractable analyte was 92.61-115.98% in the matrices. The limits of quantification ranged between 0.4 and 0.5 µg/kg. The developed method is simple since it requires no additional cleanup procedures.

Simultaneous determination of three acidic herbicide residues in food crops using HPLC and confirmation via LC-MS/MS.

2,4-D, dicamba and 4-CPA with auxin-like activity have been intensively used in agriculture, for the control of unwanted broadleaf weeds. An analytical method involving HPLC coupled with UVD was developed for the simultaneous analysis of these three analytes in Chinese cabbage, apple and pepper fruits (representative non-fatty samples) and brown rice and soybean (representative fatty samples) using liquid-liquid partitioning and column cleanup procedures. The residues were confirmed via tandem mass spectrometry (MS/MS) in ion electrospray ionization (ESI) mode. The standard curves were linear over the range of the tested concentrations (0.25-10 microg/mL), as shown by a marked linearity in excess of 0.9999 (r(2) ). The average recoveries (mean, n = 3) ranged from 94.30 to 102.63 in Chinese cabbage, from 94.76 to 108.47 in apple, from 97.52 to 102.27 in pepper, from 76.19 to 101.90 in brown rice, and from 74.60 to 107.39 in soybean. The relative standard deviations (RSDs) were <9% in all tested matrices. The limits of detection and quantitation were 0.006 and 0.02 mg/kg, respectively. Samples purchased from local markets were analyzed to evaluate the applicability of the methods developed herein. The concentration of the 2,4-D residue was measured at 0.102 mg/kg in the soybean sample; however, this level is exactly the same MRL set by the Korea Food and Drug Administration. This developed method deserves full and complete consideration, as it clearly displays the sensitivity, accuracy and precision required for residue analysis of 2,4-D, dicamba and 4-CPA in food crops.