Environmental pollution is one of the world's biggest problems, and plant waste is one of its causes. For this reason, we have tried in this work to take advantage of this waste and benefit from it instead of being one of the pollutants. Seven dry waste from different plants (bitter orange peels, pomegranate peels, bitter orange leaves, Ziziphus leaves, albizia leaves, waste of black tea, and zahidi date palm fibers) were tested as cheap source of melatonin )MLT), which is a very important indoleamine compound. Throughout the current study, this hormone was extracted from these plants’ waste (which are considered as environmental pollutants) by applying different modified methods, whereby melatonin was identified and quantified by the HPLC-fluorescence system at The National Center for Drug Control and Researches (NCD). The results indicated the presence of different concentrations of melatonin in this waste. Bitter orange peels are a rich source of this hormone (868.868 µg melatonin /gm dried peel) in comparison to the other tested waste, followed by the waste of black tea (164.333 µg melatonin /gm waste). The results also showed the presence of trace concentrations of melatonin in Ziziphus leaves and Zahid date palms’ fibers. This work provides a cheap source of MLT, it is a recycling method for plant waste.
