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Uptake, Accumulation and Metabolism of Chemicals of Emerging Concern in Vegetables

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Uptake, Accumulation and Metabolism of Chemicals of Emerging Concern in Vegetables UPTAKE, ACCUMULATION AND METABOLISM OF CHEMICALS OF EMERGING CONCERN IN VEGETABLES By YA-HUI CHUANG A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Crop and Soil Sciences – Environmental Toxicology – Doctor of Philosophy 2017 ABSTRACT UPTAKE, ACCUMULATION AND METABOLISM OF CHEMICALS OF EMERGING CONCERN IN VEGETABLES By YA-HUI CHUANG Pharmaceuticals have been most commonly used as medicine to treat human and animal diseases, and as animal feed supplements to promote growth. These applications have rendered the ubiquitous presence of pharmaceuticals in animal excretions and their discharges from wastewater treatment plants (WWTPs). Land application of animal manures and biosolids from WWTPs and crop irrigation with reclaimed water result in the dissemination of these pharmaceuticals in agricultural soils and waters. Crops and vegetables could take up pharmaceuticals from soil and water, leading to the accumulation of trace-level pharmaceuticals in fresh produce. The pharmaceutical concentrations in crops and vegetables are much lower than the dosage for effective therapy. However, the impacts of long-term consumption of pharmaceutical-tainted crops/vegetables to human and animal health remain nearly unknown. Currently, the mechanism of plant uptake of pharmaceuticals from soil and water is not clear, which impedes the development of effective measures to mitigate contamination of food crops by pharmaceuticals. We hypothesize that water flow is the primary carrier for pharmaceuticals to enter plants, and plant physiological characteristics, pharmaceutical physicochemical properties as well as plant-pharmaceutical interactions (e.g., sorption affinity) collectively influence pharmaceutical accumulation and transport in plants. In this work, a sensitive and effective extraction method was first developed to quantify the uptake of thirteen pharmaceuticals by lettuce (Lactuca sativa) from water. The results indicated that small-sized pharmaceuticals with molecular weight (MW) < 300 g mol−1 could enter lettuce, and those pharmaceuticals with low affinity to lettuce roots such as caffeine and carbamazepine could substantially transport to shoots. A strong positive linear relation was observed between their mass accumulation in shoots and the amount of transpiration water. Lamotrigine and trimethoprim are also small-sized pharmaceuticals; however, their relatively strong affinity to lettuce roots mitigated the amount of transfer to shoots. Large-sized pharmaceuticals (MW > 400 g mol−1) such as lincomycin, monensin sodium, oxytetracycline and tylosin were primarily accumulated in lettuce roots with limited amount to transfer to shoots. The results of mass balance showed that acetaminophen, β-estradiol, carbadox, estrone, and triclosan were readily metabolized in lettuce with ≥ 90% loss during 144-h exposure period. A workflow for identification of non-targeted metabolites was developed using liquid chromatography coupled to hybrid triple quadrupole-linear ion trap mass spectrometer, and this method was applied to investigate the metabolism of caffeine in lettuce. The results revealed that caffeine underwent metabolism in lettuce with > 50% loss during 144-h exposure period. The major metabolism reaction was demethylation forming the products of losing one, two or three methyl functional groups, and these products accounted for 20% of the initial dosage of caffeine. Caffeine also underwent oxidation and hydroxylation reactions in lettuce. Overall, this study sheds new light to uptake pathways and transport characteristics of pharmaceuticals in vegetables (e.g. lettuce). The mechanistic insights obtained could help form a framework for exposure modelling of diverse pharmaceutical compounds, and facilitate the development of scientifically informed management strategies to mitigate pharmaceutical accumulation in agricultural food produce. This dissertation is dedicated to my supportive parents, Shuang-Jung Chuang and Su-Mei Peng, and parents-in-law, Shao-Chih Liu and Sung-Ying Chung, my love, Cheng-Hua Liu, and our precious daughter, Emma Liu. I love you all! iv ACKNOWLEDGEMENTS This dissertation would not have been possible without the inspiration, help, and support of a number of wonderful individuals. I would like to take the opportunity to thank several of them. First and foremost, I would like to express my deepest gratitude and appreciation to my major advisor, Professor Hui Li, for his guidance, support, and encouragement as well as providing me an excellent research environment throughout my Ph.D. program . Without his professional advice and endless patience, this dissertation would not have been completed or written. I would also like to sincerely thank Professor Stephen A. Boyd, Professor Ray Hammerschmidt and Professor Wei Zhang for kindly serving on my academic committee and generously offering their time, help, and valuable advice through extensive discussions around my work. Many thanks to all members of our research group, current and past, for their ideas, assistance, and friendship: Dr. Yingjie Zhang, Dr. J. Brett Sallach, Dr. Zeyou Chen, and Dr. Yuanbo Li as well as Cheng-Hua Liu, Mark Bezdek, Feng Gao, Sangho Jeon, Gemini D. Bhalsod, Geoffrey Rhodes, Yike Shen, Jianzhou He, and all the visiting scholars I have worked with. Last but not least, I would like to express my profound gratitude to not only my parents: Shuang-Jung Chuang and Su-Mei Peng but also my parents-in-law: Shao-Chih Liu and Sung-Ying Chung for their love and great support. My greatest appreciation is to my husband Cheng-Hua Liu for his love, support, collaboration, and advice as well as staying with me in every moment of my graduate study, and to our beloved daughter Emma Liu for being such a good and lovely girl always cheering daddy and mommy up. It is gratefully acknowledged that the work was financially supported in part by Agriculture and Food Research Initiative Competitive Grant 2016-67017-24514 from USDA National Institute of Food and Agriculture, and MSU AgBioResearch Project GREEEN. v TABLE OF CONTENTS LIST OF TABLES ....................................................................................................................... ix LIST OF FIGURES ..................................................................................................................... xi LIST OF SCHEME.................................................................................................................... xiii CHAPTER I LITERATURE REVIEW, RESEARCH HYPOTHESES AND OBJECTIVES ......................................................................................................................................................... 1 LITERATURE REVIEW ............................................................................................................... 2 Pharmaceutical Production ............................................................................................................ 2 Pharmaceutical Release to the Environment .................................................................................. 2 Analytical Methods for Pharmaceutical Residues in Vegetables ................................................... 4 Mechanism of Plant Uptake of Pharmaceuticals ............................................................................ 6 Pharmaceutical Metabolism in Plants ............................................................................................ 9 RESEARCH OBJECTIVES AND HYPOTHESES ..................................................................... 10 REFERENCES ............................................................................................................................. 12 CHAPTER II COMPARISON OF ACCELERATED SOLVENT EXTRACTION AND QUICK, EASY, CHEAP, EFFECTIVE, RUGGED AND SAFE METHOD FOR EXTRACTION AND DETERMINATION OF PHARMACEUTICALS IN VEGETABLES ....................................................................................................................................................... 21 ABSTRACT .................................................................................................................................. 22 INTRODUCTION ........................................................................................................................ 23 MATERIALS AND METHODS .................................................................................................. 26 Chemicals and Materials .............................................................................................................. 26 Preparation of Vegetable Samples................................................................................................ 29 Extraction and Cleanup ................................................................................................................ 29 LC-MS/MS Analysis ...................................................................................................................... 31 Method Validation ........................................................................................................................ 31 Method Application to Analyze Pharmaceuticals in Vegetables .................................................. 32 RESULTS AND DISCUSSION ................................................................................................... 33 LC-MS/MS Analysis .....................................................................................................................
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