Application of histochemical staining in detecting lignin structural units

As the most abundant aromatic renewable polymer in nature, lignin has been widely utilized in various fields such as industry, agriculture, medicine, and environmental protection, making it an important biomass resource. The characterization of lignin's structural units and their distribution in the cell wall is crucial for its isolation. Histochemical staining, a traditional method for detecting lignin, can rapidly and visually analyze important information such as the ratio of lignin structural units and their distribution in the cell wall. This paper provides a review of the color and fluorescent reactions in lignin histochemical staining. The staining mechanisms of each reaction and their applications in lignin detection are elucidated separately. In particular, in-depth discussions are conducted on the synergistic application of staining reactions with instrumental analytical methods. The paper concludes with an overview of the challenges and prospects for future developments in this research field.