Polyphenol Phytoalexins as the Determinants of Plant Disease Resistance

Polyphenols is a large group of phytochemicals known for diverse roles in plants metabolism, particularly under biotic and abiotic stress environments. These secondary metabolites may provide the biochemical shield to the sessile plants, against different classes of plant pathogens. Some of these polyphenols are accumulated in plants upon the infestation of pathogens. The defense molecules synthesized in plants in response to a particular plant pathogen are referred to as, phytoalexins. Although the phytoalexins are a group of chemically heterogeneous group of compounds, but out of them, the polyphenolic phytoalexins are of particular interest. The present chapter highlights the antimicrobial/antipathogenic nature of these polyphenol phytoalexins against a number of phytopathosystems. Since the considerable details of their biosynthetic pathway and associated enzymes have been worked out, the expression of these polyphenol phytoalexins may be altered as per the requirement to engineer future crops with better plant disease resistance. Further, an attempt has also been made to discuss their role in human health, since many of them have been known to possess bioactive properties. This chapter is intended to review their chemical groups and subgroups, role in providing disease resistance in plants, biosynthesis and its regulation, role in protection against mycotoxins and in promoting human health, and an attempt has also been made to discuss the possibility to use them as food preservatives.