Use of UPLC-MS/MS for the analysis of abamectin and difenoconazole commercial products in tissues, pollen, and honey of Scaptotrigona postica: evaluation of biochemical biomarkers and neurotransmitters after oral and topical exposure.

• Grant number: 25/27235-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: August 01, 2026
• End date: September 30, 2029
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
• Principal Investigator: Eny Maria Vieira
• Grantee: Rafaela Garcia da Silva
• Host Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Bees play an essential role in maintaining ecological balance, being fundamental for the pollination of agricultural crops and native plants. However, the intensive use of pesticides has compromised the health of bees and their colonies, contributing to population decline and even species extinction. In this context, the present study aims to develop and validate an analytical method based on ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) for the determination of the insecticide abamectin and the fungicide difenoconazole, commercial formulations, in tissue, pollen, and honey samples from the native stingless bee Scaptotrigona postica exposed orally and topically to different concentrations. Sample preparation will be performed using the modified acetate QuEChERS method, followed by UPLC-MS/MS analysis for quantification and confirmation of the compounds, with validation of analytical parameters including linear range, limits of detection (LOD) and quantification (LOQ), accuracy, precision, and recovery. In parallel, toxic effects of pesticide exposure will be assessed through biochemical biomarkers and neurotransmitter analyses, determining the activities of antioxidant and detoxification enzymes such as total antioxidant capacity (ACAP), catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST), in addition to the levels of malondialdehyde (MDA), carbonylated proteins (PC), and DNA strand breaks. Neurotransmitters such as dopamine and serotonin will also be quantified to investigate neurochemical alterations associated with exposure. Additionally, a locomotion track test will be conducted to assess the behavioral performance of exposed bees, analyzing movement patterns through parameters such as velocity, distance traveled, residence time, and path tortuosity, enabling the detection of sublethal and motor effects related to pesticide exposure. Finally, an environmental risk assessment will be carried out by integrating toxicity, biomarker, and behavioral data, including the construction of species sensitivity distribution (SSD) curves from experimentally obtained EC¿¿ values and complementary literature data, allowing the estimation of safe concentration levels (HC¿) and inference of the potential ecological risks of these compounds in tropical ecosystems. The expected results will provide a comprehensive understanding of the physiological, metabolic, and behavioral responses of S. postica to oral and topical exposure to commercial pesticide formulations, contributing to the evaluation of detoxification mechanisms, oxidative stress, sublethal effects on bee health, and the ecological sustainability of colonies in agricultural environments. (AU)