Analysis of the distribution and persistence of organophosphorus pesticides malathion and diazinon in herbal plants

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.