Since ancient times, humanity has used herbal remedies to heal itself and traditional medicine still represents the predominant health care system in many parts of the world. Indeed, the use of natural products and their synthetic derivatives is central to the discovery of new drugs, especially antibacterial and anticancer agents. However, herbal medicine research suffers from some important weaknesses. Despite hundreds of preclinical studies, evidence in humans is scanty, due to the paucity of clinical trials evaluating the efficacy of natural products. Poor oral bioavailability is another major issue as phytochemicals are metabolized and eliminated by gut enzymes and efflux mechanisms, similar to xenobiotics. Furthermore, natural does not always mean safe. The safety of herbal products is rarely investigated as well as the phytochemical-drug interactions with possible variations in therapeutic efficacy for some drugs with a narrow therapeutic index. The combination of natural products with conventional drugs, particularly anticancer and antimicrobial drugs, represents another therapeutic approach able to (chemo)sensitize chemoresistant cancer cells and pathogens. Finally, the rationale for the use of natural products is based on their multitarget action mechanism of particular interest in the treatment of disorders with multistage pathogenesis.

In this very wide context, we invite investigators to submit both original research and review articles that explore all these aspects.