**1.1 Drug repositioning**

Drug repositioning or repurposing is an interesting way to reuse old drugs for new indications; For example, chloroquine, an old antimalarial drug, showed promising results for treating COVID-19, interfering with multidrug resistance (MDR) in several types of cancer, and chemo-sensitizing human leukemic cells. There is a great economic impact of drug repurposing on drug discovery for the treatment of many skin infectious diseases, neurological disorders, cancers, and orphan diseases [1]. In this aspect, the liver research laboratory (FAB-Lab, Faculty of Pharmacy, Mansoura University, Mansoura, and Egypt) has utilized several approaches for not only optimizing and enhancing the therapeutic effect of the commonly available natural products but also recognizing novel applications for them so that one therapeutic agent could be used for the treatment of several or complex conditions adopting different strategies for drug repositioning [2–12].
