The occurrence of tricin and its derivatives in plants

Our understanding of the structure and biosynthetic pathway of lignin, a phenylpropanoid heteropolymer, continues to evolve, especially with the discovery of new lignin monomers/structural moieties such as monolignol acetate, hydroxycinnamyl aldehyde/alcohol, and p-hydroxybenzoate in the past decades. Recently, tricin has been reported as a component incorporated into monocot lignin. As a flavonoid compound widely distributed in herbaceous plants, tricin has been extensively studied due to its biological significance in plant growth as well as its potential for pharmaceutical importance. Tricin is biosynthesized as a constituent of plant secondary metabolites through a combination of phenylpropanoid and polyketide pathways. Tricin occurs in plants in either free or conjugated forms such as tricin-glycosides, tricinlignans, and tricin-lignan-glycosides. The emergence of tricin covalently incorporated with lignin biopolymer implies the possible association of lignification and tricin biosynthesis. This review summarizes the occurrence of tricin and its derivatives in plants. In addition, synthesis, potential application, and characterization of tricin are discussed.