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

A 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 5.57 10⁵ 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 (¹H NMR and ¹³C 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-β-d-Glcp, 1,3,4-α-d-Glcp, 1,4-α-d-Manp, 1,6-α-d-Manp, 1,3-α-d-Galp and 1,6-β-d-Galp. The thermogravimetry analysis (TGA) and the differential scanning calorimetry (DSC) were used and showed that PLP1 has good thermal stability under 229 °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.