科协双语工程论文展播：植物多糖结构解析方法研究进展

Abstract: Plant polysaccharides, a kind of natural macromolecule, are widespread occurrence in plant cells. Many studies have shown that plant polysaccharides have many biological activities such as hypoglycemic, anti-tumor, anti-oxidation, immune regulation, etc. It has become a research hotspot in the fields of food, health care products, medicine and so on. The complex structure of polysaccharides is the key factor affecting its biological activity. Polysaccharides are characterized by large molecular weight, diverse monosaccharide composition, complex glycosidic bond connection mode and complex spatial conformation, which makes the structure analysis of polysaccharides still in the exploratory stage and limits the research and development and application of polysaccharides products. The structure of polysaccharides can be divided into primary, secondary, tertiary and quaternary structures. The primary structure includes molecular weight size and distribution, monosaccharide composition and molar ratio, glycosidic bond connection mode, repeated structural units and branching degree, etc. Secondary, tertiary and quaternary structures are collectively called advanced structures, which are mainly the conformation of polysaccharides. Based on the existing research on structural analysis of plant polysaccharides, in this paper, the primary structure analysis methods of plant polysaccharides, such as phenol-sulfuric acid method, high performance liquid chromatography, gel permeation chromatography, infrared spectroscopy, gas chromatography-mass spectrometry, nuclear magnetic resonance spectroscopy, were introduced firstly. Most of these methods have the advantages of simple operation, accurate results and good reproducibility. The determination methods of total sugar content, monosaccharide composition and proportion, molecular weight size and distribution, glycosidic bond type and connection mode of polysaccharides were described respectively. By summarizing the principles, advantages and disadvantages of these methods, it is found that these analytical methods of primary structure are not only the basis of studying the structural characteristics of polysaccharides, but also one of the important indicators of quality control. The spatial structure of plant polysaccharides is very complex, and its spatial structure will be different with different extraction methods, medicinal materials parts or origins. The study on the spatial structure of polysaccharides can not only explain the structure-activity relationship, but also complete the quality control of polysaccharides. The research methods of polysaccharides advanced structure were introduced, including atomic force microscope, X-ray diffraction, circular dichromatography and so on. Using these structural analysis methods, it can accurately understand the morphology of polysaccharides, obtain the crystal form of matter, and analyze the topological structure of surface molecules. In addition, the orientation and spatial distribution of molecular structure and provide reliable three-dimensional structural information for polysaccharides. At the same time, the method and importance of constructing polysaccharides molecular model were further analyzed. Molecular model is constructed by molecular dynamics simulation, molecular docking, free energy calculation and other methods to simulate the spatial conformation of macromolecules and intermolecular interaction. So as to construct the three-dimensional structure of polysaccharides, and achieve the purpose of structure prediction and mechanism discussion. In addition, the application of structural analysis methods in quality control of plant polysaccharides were reviewed. As a means of component identification and quality control, multi-dimensional fingerprint is one of the important methods to ensure its quality. Multi-dimensional fingerprint technology is a quantitative method based on some structural characteristics of samples. For identifying components and controlling quality, the chromatographic and spectral data which can represent the characteristics of samples by structural analysis methods such as chromatography or spectroscopy. Fingerprint combined with chemometrics is an effective method for the quality control of polysaccharides in traditional Chinese medicine, which is rapid, sensitive and convenient. Combining fingerprint with multivariate analysis, a model of sample identification and discrimination is established, which can be used for product quality evaluation, authenticity identification and variety identification. In this paper, the primary structure, advanced structure and its application in quality control of plant polysaccharides were summarized, and some structural analysis methods of plant polysaccharides were listed. It provides a new idea and certain reference for the study, analysis and quality control of plant polysaccharides, and also lays a foundation for the development and utilization of plant polysaccharides. However, due to the complexity of polysaccharides structure and the limitations of research methods, the research of polysaccharides has lagged behind the study of protein and nucleic acid. At present, most of the researches on the structure of plant polysaccharides focus on the primary structure, and there is no single method to comprehensively analyze the advanced structure of polysaccharides. Because of the complexity of polysaccharides' structure and the polymorphism of its spatial structure, the study on the relationship between polysaccharides higher structure and its activity is not deep enough. Therefore, a single analytical technique is no longer suitable for the analysis of polysaccharides advanced structure, and it is particularly important to find a technical means to characterize the dynamic changes of its advanced structure. To sum up, exploring the advanced structure analysis technology of plant polysaccharides and studying the relationship between structure and biological activity are the key points of future research on polysaccharides. With the development of analytical technology, the structure of polysaccharides can be predicted by computer molecular docking, molecular dynamics simulation and other methods, so as to improve the accuracy of characterization of polysaccharides structure. In addition, the structure-activity relationship can be studied at the level of polysaccharides structure, and new technologies such as 3D can be used to modify the polysaccharides structure and enhance its biological activity. To sum up, the polysaccharides can be widely used in pharmaceutical, biomedical, food and cosmetics industries as a new and high value-added natural product.