The scientific activity of Prof. A. Zarrelli is demonstrated by over 190 papers published in peer reviewed international scientific journals (of which in at least half of them he is the reference author or the last author) and over 80 communications at national and international conferences. This research activity explores topics of interest as follows: I) The study of the transformations of xenobiotics (drugs, widely used molecules, etc.) with the use of sterilizing agents used in urban wastewater treatment plants, or transformations induced by abiotic environmental factors (e.g., light and water) on emerging pollutants. II) The synthesis and chemical characterization of modified bioactive natural molecules with promising pharmacological activities (antiviral, anticarcinogenic, and neuroprotective). III) The qualitative and quantitative analysis of secondary metabolites in natural extracts. I) The study of the transformations of xenobiotics (drugs, widely used molecules, etc.) with the use of sterilizing agents used in urban wastewater treatment plants, or transformations induced by abiotic environmental factors (e.g., light and water) on emerging pollutants.