Phenolic Derivatives From Medicinal Herbs and Plant Extracts: Anticancer Effects and Synthetic Approaches to Modulate Biological Activity

Abstract Cancer is nowadays one of the most devastating diseases, being a central public health problem as well as a leading cause of death worldwide. In an attempt to fight this illness, great efforts have been carried out to find more potent drugs with fewer side effects. Natural products have been a valuable source for such drugs, whether used as a natural resource or after chemical modifications. Natural phenolic compounds, in particular, have revealed interesting results concerning the inhibition of proliferation of several cancer cell lines, showing potential to be further studied as anticancer agents. In this chapter, we present a literature review on the phenolic compounds from medicinal herbs and plant extracts with anticancer activity published from 2008 until mid-2016. Particular emphasis is given to the principal phenolic compounds of the extracts as well as to the chemical modifications performed and the synthetic approaches followed to modulate the cytotoxic activity of those compounds. From this, the relevant structure–activity relationships are discussed. The mechanisms by which the extracts and the modified compounds exert their cytotoxic activity are also disclosed. Further, the relation on free radical-induced cancer and protection by phenolic derivatives is related. Finally, a critical analysis of the studies and guidelines for future research is reported in the conclusion.