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Introduction. Determination of pesticide residues presence in herbal plants and preparations based on them is an important step in confirming safety at the stage of the quality control of herbal plants. The usage of organophosphate pesticides (OPs) for the purposes of treatment of medicinal plants in the growing process is increasing. Scientific sources provide information on the detection of OPs in herbal plants, including quantities exceeding the allowed percentage limits as it is settled in regulatory documentation. At the same time, the problem of the distribution of particular kinds of OPs in the organs of herbal plants and their persistence remains understudied.Aim. The present research aims to study the distribution in various parts of the herbal plants (marigolds, valerian, and stinging nettle) and the persistence of malathion and diazinon.Materials and methods. Stinging nettle, that grows everywhere, exclusively cultivated marigolds, and valerian were selected as model plants. All of the plants were divided into three equal groups. Young plant shoots were processed twice with "Aliot" products containing 570 g/l of malathion and "Terradox" containing 40 g/kg of diazinon. The first group of plants was processed with pesticides following the manufacturer's instructions. The second group was treated in quantities, that were three times higher than the recommended dosage. The third group (control), was not processed with pesticides. Samples of various parts of growing herbal plants were analyzed at certain time points with the HPLC-MS/MS method according to the developed methodology. In order to study the persistence, we carried out a repeated analysis of dried samples stored without access to sunlight 0.5 years after the first one according to the requirements of the State Pharmacopoeia of the Russian Federation XV.Results and discussion. The authors found malathion and diazinon in all of the analyzed parts of medicinal marigolds, in leaves and roots of nettle dioecious, in deciduous shoots and rhizomes with roots of valerian officinalis. The highest proportion of pesticides was discovered in underground plant organs. When processed according to the instructions, in marigold and nettle roots and in rhizomes with valerian roots 16.7 mg/kg, 4.5 mg/kg, and 1.7 mg/kg of malathion and 19.6 mg/kg, 4.1 mg/kg, and 1.5 mg/kg of diazinon were found, respectively. These quantities exceed the allowed limits. The quantity of pesticides in the flowers of medicinal marigolds does not exceed the permissible values. The research on the persistence of these OPs data demonstrates that malathion and diazinon persist in plant tissues for a long time.Conclusion. As a result of the research quantitative characteristics of the distribution of malathion and diazinon in various parts of medicinal marigolds, medicinal valerian, and dioecious nettle, as well as the rate and the extent of degradation of OPs during six months, were determined.

Quercetin is one of the most promising natural polyphenolic radioprotective compounds. This property is based on its radical-scavenging activity and high antioxidant capacity, in the manifestation of which the products of oxidative degradation of quercetin play a significant role. The formation of specific metabolites during the oxidation of quercetin can determine not only its radioprotective properties, but also toxic manifestations. The purpose of this article is to summarize previously obtained data regarding the reaction pathways of oxidative transformation of quercetin. Materials and methods. We used publicly available scientific publications dedicated to the study of quercetin transformation processes. The method of analysis is descriptive. The discussion of the results. A review of scientific works dedicated to oxygen oxidation, radical-initiated oxidation, electrochemical and enzymatic oxidation is presented, possible transformation products of quercetin and the mechanisms of their formation are given. The most characteristic oxidation pathways of quercetin are determined by the chemical structure of the rings, which exhibit specific reactivity. The influence of the solvent composition on the oxidation products during the autoxidation of quercetin was revealed, while the radical and electrochemical models of oxidation differ in the presence of polymer adducts. Once in a living organism, quercetin can bind free radicals, thereby preventing the harmful effects of radiation, that is, it has the properties of a radioprotector. Conclusions. Quercetin can be considered as a potential radioprotector due to its ability to bind free radicals formed in the biological fluids of living organisms exposed to radiation.

The timely detection of violations of the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction (CWC) requires reliable methods for detecting toxic chemicals that can be used for chemical attacks. The purpose of this investigation is to estimate chromatographic and mass-spectral characteristics of some toxic chemicals recently included into Schedule 1 of the Annex on Chemicals of the CWC, in particular N-(N,N-diethylacetamidino)-methylfluorophosphonate (DEAMP), N-(N,N-diethylacetamidino)-O-methylfluorophosphate (DEAOMP) and N-(N,N-diethylacetamidino)-O-ethylfluorophosphate (DEAOEP) and the improvement of the qualification of the Chemical Analytical Control Laboratory experts taking part in the OPCW Proficiency Tests. Materials and methods. The technique of high efficient liquid chromatography coupled with tandem high resolution mass spectrometry (LC-MS/HRMS) was used during the investigation. The results. The results of optimization of conditions of mass-spectrometric detection, selection of optimal pairs of ion reactions and program of gradient elution during separation of chemicals in reversed-phase liquid chromatography were presented. Presented approach was tested in analysis of model aqueous samples; metrological parameters of detection of compounds were estimated. Conclusion. It was shown during investigation that electrospray ionization mass-spectra of DEAMP, DEAOMP and DEAOEP contain intensive peaks of protonated molecular ions, which after further fragmentation produce characteristic product-ions used for identification and high sensitive detection of parent compounds by LC-MS/HRMS. Limits of detection of DEAMP, DEAOMP and DEAOEP were 1.0 ng/mL, 0.5 ng/mL and 0.5 ng/mL, respectively

Scientific relevance. Deuterated analogues of test substances, when used as internal standards, enable analysts to determine traces of residual pesticides in a medicinal plant raw material by gas or liquid chromatography coupled with mass spectrometry. This prompts the search for an undemanding method for the synthesis of deuterated reference standards, with the ultimate goal of expanding the range of reference standards produced in Russia.Aim. The study aimed to synthesise deuterated reference standards (malathion-D6, chlorophos-D6, dichlorophos-D6, and their precursors) and determine their spectral characteristics using 1Н, 2Н, 13С and 31Р nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry.Materials and methods. The study involved methanol-D4, phosphorus pentasulfide, phosphorus trichloride, maleic acid diethyl ether, triethylamine, hydroquinone, and chloral hydrate. The authors recorded 1H, 2H, 13C, and 31P NMR spectra using a QONE AS400 NMR spectrometer operating at a temperature of 298 °K and respective frequencies of 399.83, 61.38, 100.55, and 161.85 MHz. Mass spectra were obtained using an analytical system comprising an Agilent Infinity 1260 liquid chromatograph equipped with an automatic sample injector and coupled with a Thermo Scientific Orbitrap Fusion Lumos high-resolution mass-selective tandem spectrometer operating in electrospray ionisation mode.Results. The authors used existing methods for the synthesis of organophosphate pesticides as a basis and developed synthesis routes to produce the deuterated analogues malathion-D6, chlorophos-D6, and dichlorophos-D6. The synthesised compounds were identified by NMR spectroscopy and high-resolution mass spectrometry.Conclusions. The synthesised compounds are highly pure and suitable for use as internal standards in the determination of organophosphate pesticides in medicinal plant raw materials. The synthesis methods developed by the authors can be used to produce reference standards in Russia.

A method for the determination of a mustard gas biomarker (an S-hydroxyethylthioethyl adduct with albumin) in blood plasma was optimized with the use of HPLC with tandem mass-spectrometric detection. This method is based on the hydrolysis of this adduct by the proteinase K enzyme with the formation of the following stable tripeptide with cysteine, proline, and phenylalanine: S-HETECys-Pro-Phe. The detection limit of mustard gas in human blood plasma was 2 ng/ml. The approach proposed was tested in the analysis of human blood plasma samples by the standard addition technique and also within the framework of the first official biomedical test carried out by the Organization for the Prohibition of Chemical Weapons (OPCW) in 2016, and it exhibited a good accuracy, reproducibility, and specificity of determination.