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Effects of dietary phytochemicals on residual pesticide concentrations in honey bees – a metabolomics approach

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

  • Hamidreza Ardalani
Honey bees are important pollinators that are subject to various stressors, such as decline in floral resources, parasites, and pesticides exposure. Stresses encountered by honey bees in the form of environmental chemicals and toxins influence organisms and systems across the agriculture spectrum. Hence, exposure to pesticides is an increasing global concern for honey bee conservation. When honey bees forage across the landscape, they are very vulnerable to exposure to a wide range of agricultural chemicals such as pesticides, phytochemicals and chemical fertilizers. Honey bees often are expose to a broad range of pesticides including insecticides, fungicides, acaricides, and herbicides, therefore residual concentrations of pesticides frequently accumulate in their body. Honey bees rely on their detoxification system to alleviate the negative effects of these agrochemicals. The pollen and nectar that honey bees gather from plants constitute a rich source of protein and carbohydrates as well as a diversity of phytochemicals, of which some exert biological effects on honey bees. However, only a few studies in literature demonstrate effects of plant secondary metabolites in the honey bees’ detoxification system. Hence, it was essential to elucidate the effects of phytochemicals on residual pesticide concentrations in honey bees.
The aim of this PhD study was to implement mass spectrometry-based analysis to illuminate the impact of plant secondary metabolites on residual pesticide concentration and on the metabolic changes in honey bees. Accordingly, the first experiment was designed to test the effect of dietary quercetin (a well-known immune booster in honey bees) on the residual concentration of the exposed insecticide imidacloprid, the fungicide tebuconazole, and the acaricide tau-fluvalinate in honey bees. The results showed that dietary quercetin reduced the concentration of imidacloprid absorbed in honey bees.
In the second experiment, untargeted mass spectrometry-based metabolomics was exploited to uncover the plant secondary metabolites which enhance the metabolism of pesticides in honey bees. After feeding honey bees with pollen and nectar from four attractive plants, and exposing to above-mentioned pesticides, an LC-QqQ-MS/MS was used to make an absolute quantification of residual pesticides in honey bees. Subsequently, the phytochemical profile of pollen and nectar diets were examined with the use of an LC-Orbitrap-MS/MS. Multivariate statistics as well as metabolomics data analysis tools were implemented to elucidate the phytochemicals which altered the concentration of pesticides in honey bees. The results suggested two promising flavonoids, datiscin and kaempferol-3-O-β glucopyranosyl-7-O-α-rhamnopyranoside, which may alleviate the concentration of exposed imidacloprid in honey bees.
In the third assay, the metabolome of honey bees fed various diets and exposed to the three mentioned pesticides were analyzed via an LC-Orbitrap-MS/MS and GC-TOF-MS to reveal the metabolic changes of honey bees in response to their phytochemical diet and exposure to pesticides. Extensive metabolic changes of honey bees were seen in the presence and absence of tebuconazole and fluvalinate while exposure to imidacloprid did not change the metabolic pathway of honey bees. It was also found that diets change the metabolome of honey bees.
This study gave more insight into the impacts of plant secondary metabolites on residual pesticide concentrations in honey bees. Two flavonoids were suggested to reduce the concentration of exposed imidacloprid in honey bees. Elucidating the metabolic pathway of honey bees exposed to the mentioned pesticides provide a better understanding of the mechanisms which honey bees utilize to alleviate the effects of agrochemicals.
ForlagAarhus Universitet
Antal sider101
ISBN (Trykt)978-87-93148-85-7
StatusUdgivet - feb. 2021

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