Methoxylated flavones: occurrence, importance, biosynthesis

Lipophilic flavones with several methoxyl residues occur in various clades of land plants, from liverworts to core eudicots. Their chemodiversity is mediated by the manifold combinations of oxygenation and methoxylation patterns. In the Lamiaceae, Asteraceae, and Rutaceae, (poly)methoxylated flavones are thought to be produced by secretory tissues and stored externally or in oil cavities. They exhibit an array of bioactivities in vitro and in vivo, and may constitute part of the plants' chemical defense mechanisms and represent promising natural lead molecules for the development of potent antiproliferative, antidiabetic, or anti-inflammatory drugs. The biosynthesis of (poly)methoxylated flavones in sweet basil (Ocimum basilicum L.) has been largely elucidated in the past few years. The knowledge obtained in those studies can be used for enzymatic semi-synthesis of these flavones as well as for further cell biological and physiological studies of basil trichome metabolism. In addition, these findings create an excellent starting point for investigations into (poly)methoxylated flavone metabolism in more and less distantly related taxa, which would shed light on the evolution of this biosynthetic capacity.