Abstract: Chinese wolfberries (Lycium barbarum L.) harvested at different developmental stages were analyzed for their physical and chemical properties. L. barbarum polysaccharides were purified and their structures were analyzed. The molecular mass, monosaccharide composition, sugar chain structure, thermal properties and surface morphology were determined by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR) spectroscopy comprehensive thermal analyzer and scanning electron microscopy (SEM). The HPLC results showed that L. barbarum polysaccharides were small molecules at different growth stages. The analysis of monosaccharide composition by GC-MS showed that L. barbarum polysaccharides were mainly composed of arabinose, rhamnose, glucose, xylose, mannose and galactose. The results of infrared spectroscopy indicated that the structure of the purified L. barbarum polysaccharides, found to be acidic polysaccharids, contained a β-pyran ring. Thermal analysis showed that the thermal characteristics of L. barbarum polysaccharides were both similar and different at different growth stages. The entire changes could be seen as mass losses sequentially caused by moisture release and polysaccharide breakdown. The observation by SEM showed that the structure of L. barbarum polysaccharides was different at different growth stages, and gradually changed from dense and lamellar to loose and peak-shaped and finally completely collapsed.

Key words: Lycium barbarum L. polysaccharides; physical and chemical properties; structural analysis