1.23 – Lignans (Neolignans) and Allyl/Propenyl Phenols: Biogenesis, Structural Biology, and Biological/Human Health Considerations

This comprehensive, extensively illustrated, critical review chapter addresses the biochemical pathways to two major plant metabolic classes, namely, the rather ubiquitous allyl/propenyl phenols and lignans, which are the subclasses of phenylpropanoids (C6C3). These substances are considered to have diverse physiological/ecological roles within plants, including defense against microbes and insects, as antioxidants, and also as pollinator attractants. Comprehensive analysis of their structural diversity in extant plant groups provides much needed insight into their evolution. In addition, what is known of their biosynthetic pathways is extensively discussed, including the genes/proteins known to be responsible for each biochemical step, their enzymatic kinetic behaviors, three-dimensional structures, and postulated chemical mechanisms. Lastly, many are historically important natural products, and their current and potential human uses in spices, medicines, nutrition, and other fields are broadly reviewed. The text is supported by more than 50 illustrations and schemes including more than 300 compounds, and about 550 key references are presented to the reader.