[Research advances in the preparation and structural characterization of depolymerized oligosaccharides from...

Polysaccharides derived from traditional Chinese medicine （TCM） have attracted widespread attention due to their excellent bioactivities， such as immunomodulatory， anti-inflammatory， and anti-tumor effects. However， these polysaccharides exhibit inherent characteristics including large molecular weights， complex monosaccharide compositions， and diverse branched structures. These features result in low bioavailability and difficulties in unraveling their structure-activity relationships （SARs）， thereby imposing significant limitations on their practical applications. In contrast， oligosaccharides possess distinct advantages： they have low molecular weights， relatively simple structures， and are easy to purify and characterize structurally. Owing to these properties， oligosaccharides serve as ideal models for deciphering the SARs of TCM polysaccharides. Consequently， the preparation， separation and purification， and structural characterization of TCM oligosaccharides have become the core research focuses in this field.This paper firstly reviews various degradation strategies from the perspective of degradation approaches. These strategies include chemical hydrolysis， oxidative degradation， enzymatic hydrolysis， and assisted degradation methods. For each method， a comparative analysis of their degradation mechanisms， product distribution characteristics， and applicable scopes is conducted. Meanwhile， it elaborates on the modification effects of different methods on the degree of polymerization （DP）， anomeric configuration， and branched structure of oligosaccharides， as well as their potential regulatory roles in the bioactivities of oligosaccharides. Subsequently， this paper carries out a systematic review on the chromatographic techniques commonly used for the separation and purification of degraded oligosaccharides， including gel filtration chromatography （GFC）， ion-exchange chromatography （IEC）， hydrophilic interaction chromatography （HILIC）， and porous graphitized carbon chromatography （PGC）. For each chromatographic technique， this paper provides a detailed account of its separation principle， applicable scenarios， and specific applications in the separation of degraded oligosaccharides. Finally， regarding the oligosaccharide structural characterization techniques-such as monosaccharide composition analysis， methylation analysis， and nuclear magnetic resonance （NMR） spectroscopy-the paper clarifies the complementarity between different techniques and their respective limitations.In summary， this paper focuses on the application of combined strategies-such as chemical hydrolysis， enzymatic hydrolysis， and physicochemical hybrid methods-in the preparation of degraded oligosaccharides derived from TCM， as well as the roles and key points of separation techniques and characterization techniques in structural elucidation. Looking ahead， the preparation， separation and purification， and structural analysis of TCM oligosaccharides require the further establishment of standardized protocols. Additionally， the integrated application of artificial intelligence and multi-omics technologies should be actively promoted in this research field. It is believed that with the continuous in-depth exploration of degraded oligosaccharides， their SARs will become increasingly explicit. It is anticipated that progress in the purification and structural elucidation of TCM-degraded oligosaccharides， together with the convergence of artificial intelligence and multi-omics approaches， will bring clarity to their structure-activity relationships. This will， in turn， enable their more precise and impactful application in functional food design and pharmaceutical development.