Abstract: Polysaccharides (NHP) extracted from Nymphaea hybrid by ultrasonic-assisted hot water extraction were degraded with a combination of ascorbic acid and H2O2 into three low-molecular-mass polysaccharides (DNHP-1, DNHP-2 and DNHP-3). The structural, rheological, functional and antioxidant properties of the polysaccharides were studied. The results showed that although the monosaccharide types of NHP kept unchanged after degradation, the molar percentages of galacturonic acid and mannose decreased and the molar percentage of rhamnose increased. Fourier transform infrared (FTIR) spectroscopic analysis revealed that the primary structures of the polysaccharides were not affected after degradation. Congo red test showed that none of the four polysaccharides had triple helix structures. Rheological analysis demonstrated that DNHP solutions displayed lower apparent viscosity than NHP solution at the same concentration, while the elasticity of DNHP was improved compared with that of NHP. DNHP had better water-holding capacity and weaker oil-holding and emulsifying capacity. Furthermore, DNHP-2 collected after 60 minutes of degradation had stronger antioxidant activity in terms of scavenging capacity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, 2,2’-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical cation and hydroxyl radicals. The results of this study may provide a theoretical basis for the application of N. hybrid polysaccharides in foods, cosmetics and medicines.

Key words: Nymphaea hybrid; polysaccharide; degradation; low-molecular-mass polysaccharide; antioxidant activity