Occurrence and characterization of tricin-lignin

Tricin, a flavonoid, is a noncanonical lignin monomer present in grasses and other monocots, but rarely in dicots. This review explores the latest discovery of biosynthesis, transport, and distribution of tricin in plant cell walls, and discusses the missing gaps in this engaging topic. Tricin biosynthesis in grasses involves the phenylpropanoid and flavonoid pathways, with distinct enzymatic processes leading to tricin incorporation into lignin polymers. Methods for characterizing and quantifying tricin in lignin are also highlighted, including NMR spectroscopy and chromatographic techniques with discussion of challenges associated with its low abundance in plant tissues. The stability of tricin during biomass pretreatment processes is discussed, with findings indicating that acidic and alkaline conditions degrade tricin, while milder pretreatments preserve its structure. These insights underscore the potential of tricin in enhancing the functionality of lignin for sustainable bioprocessing, offering promising applications in pharmaceuticals, nutraceuticals, and biorefinery industries.