Interactions between ascorbic acid and water soluble polysaccharide from the seeds of Plantago asiatica L.: Effects on polysaccharide physicochemical properties and stability

Abstract

Viscous polysaccharide is one kind of main bioactive components in Plantago asiatica L. seeds. This study aims to investigate effects of various monosaccharides, disaccharides, especially ascorbic acid (VC), on apparent viscosity and physicochemical properties of crude water soluble polysaccharide from the seeds of P. asiatica L. (PLWEP-C), as well as its stability and degradation mechanism. Results showed that small molecules such as glucose, sucrose, maltose, and lactose had little effects on apparent viscosity of PLWEP-C, while VC could significantly reduce the viscosity. There was no obvious change in FT-IR spectra and monosaccharide composition of PLWEP-C after VC addition. Hydroxyl radicals were probably involved in the degradation of polysaccharide induced by VC, which was confirmed by glucose inhibition test. SEM observation showed that PLWEP-C was mainly in lamellar and filamentous appearance, and no great change was generated by VC. The solution stability of PLWEP-C can only be kept well, when VC was at low concentration and low temperature. In conclusion, VC could significantly reduce the viscosity of polysaccharide from the seeds of P. asiatica L., which was probably attributed to the reduction of molecular weight. Hydroxyl radicals participation were probably one of main reasons in the degradation process.