Structural characterization, antioxidant and antibacterial activities of a novel polysaccharide from Periploca laevigata root barks

novel water-soluble polysaccharide named PLP1 was successfully isolated from root barks of Periploca laevigata by hot water extraction and further purified by DEAE-sepharose chromatography. PLP1 has a relative molar mass of 5.57 10(5) g/mol determined by Ultra-high performance liquid chromatography (UHPLC). The PLP1 structure was investigated by chemical and instrumental analysis including gas chromatography mass spectrometry (GC-MS), methylation analysis, Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic spectroscopy (H-1 NMR and C-13 NMR). Results showed that PLP1 was mainly composed of glucose, galactose, mannose and glucuronic acid in a molar percent of 62.9, 19.4, 11.8 and 5.9, respectively. The backbone of PLP1 was composed of 1,3-beta-D-Glcp, 1,3,4-alpha-D-Glcp, 1,4-alpha-D-Manp,1,6-alpha-D-Manp,1,3-alpha-D Galp and 1,6-beta-D-Galp. The thermogravimetry analysis (TGA) and the differential scanning calorimetry (DSC) were used and showed that PLP1 has good thermal stability under 229 degrees C. Moreover, the purified polysaccharide demonstrated an appreciable in vitro antioxidant potential and high antibacterial activity against several Gram ( + ) and Gram ( - ) strains. These finding suggested that PLP1 might be suitable for use as functional foods and as potential therapeutic agents.