Chapter 6 - Biologically Active Isothiocyanates: Protecting Plants and Healing Humans

Abstract Organic isothiocyanates (ITCs) are a very important group of biologically active compounds. They do not occur as a free form in nature, but they are liberated from glucosinolates in plant tissues by enzymatic degradation. In this group are compounds with very different structural features, ranging from the simplest methyl isothiocyanate, contained in the caper plant, to the structurally complex welwitindolinone isothiocyanate, which comes from the broth of a blue-green algae, which has a bridge ring system and numerous stereogenic centers including quaternary carbons and many heteroatoms. A key feature of all these compounds is the role of the isothiocyanate function on their biological activity. Over the past several years, numerous comprehensive reviews have been published on the biological activities of natural ITCs in general, and sulforaphane (SFN), a constituent of broccoli that is considered to be one of the most important antitumor compounds, in particular. However, with the discovery of important new therapeutic applications, this field continues to evolve and remains an active area of research. In fact, the vast majority of the reviews focus on ITC biological activities and omits other important aspects as synthesis and structure-activity relationship. The aim of this paper is to fill this gap by describing all the natural biologically active ITCs known to date and covering aspects related to the mechanism of action and biological activities of these compounds, with a particular emphasis on the methodologies developed for their synthesis. In the case of chiral derivatives, we will describe the procedures developed for their asymmetric synthesis as well as the studies related to the influence of the chirality on activity. Finally, based on the exceptional biological activity of SFN, we will also highlight the concepts of functional and epigenetic foods and discuss the importance of diet for human health.