Professor Han Quanbin's research team successfully corrects the chemical structure of a natural polysaccharide through oligosaccharide fragments

September 08, 2022

A research team led by Professor Han Quanbin of the Teaching and Research Division established a simple analytical method by which a series of oligosaccharides were then accurately isolated and identified.  Based on these oligosaccharides, the characteristic polysaccharide marker DOP of Dendrobii Officinalis Caulis is corrected from a β-1,4-glucomannan to β-1,4-mannan.  The team went on to find that the glucose actually came from resistant starch residue.  These results provided useful reference for further studies into the chemical structures of natural polysaccharides.

The research findings were published in Food Hydrocolloids, with Dr. Wong Tin-long and Dr. Li Lifeng as co-first authors.  The related techniques have been granted with a US patent.

Qualitative and quantitative analysis of polysaccharides remains a challenge in QC of Chinese medicines

The globally recognized Botanical Drug opens the door to the international market for natural mixtures, like Chinese medicines. At the same time, a higher-level quality standard is set. Polysaccharides, being the majority of water decoction that is the most used preparation form of TCM, show diverse bioactivities and high safety, and also bring difficulties in quality analysis of TCM. Without polysaccharides, the related products will not carry on the full function spectrum of the traditional formula.

Breakthroughs in the development of polysaccharide markers and oligosaccharide markers

Over the past few years, the team led by Professor Han successfully developed polysaccharide markers for Dendrobii Officinalis Caulis and cordyceps, which contributed immensely to the chemical authentication of these valuable Chinese medicines.  The subsequent development of a series of oligosaccharide markers has enabled the qualitative and quantitative analysis of specific polysaccharides in formula products, e.g. Danggui Buxue Tang, like what has been done to small molecules.  

Increasing interest in oligosaccharides in studies of polysaccharide structures

Because of impurity interference and the NMR signal overlapping, it is difficult to accurately characterise the chemical structures of polysaccharides.  This project, by transforming polymers into oligomers with remaining rich structure features, and further to detectable and separable glycosides, realised the accurate identification of the polymer structures.  Furthermore, it is found that the widely reported glucose actually came from resistant starch which is not addressed by the normal de-starch operation.  This finding reveals a need to revisit and improve the conventional analytical methods.

This research project is a collaborative effort by SCM and scientists from Xinxiang Medical University, Nanchang University, Kunming Institute of Botany (Chinese Academy of Sciences), The Chinese University of Hong Kong, with support from the Health and Medical Research Fund and Vincent & Lily Woo Foundation. 

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