Structural characterization, antioxidant and antimicrobial activities of polysaccharide from Akebia trifoliata (Thunb.) Koidz stem

Polysaccharides have a variety of beneficial pharmacological impact on human health. Akebia trifoliata (Thunb.) Koidz. has promising development prospects as a food resource with medicinal value. The aim of this study was to investigate the structural characterization, antioxidant, and antibacterial properties of A. trifoliata (Thunb.) Koidz polysaccharides (ATKPs). ATKP-II was purified from ATKP by DEAE-cellulose column with NaCl solution as eluent. ATKP and ATKP-II structures were characterized by high performance gel permeation chromatography, gas chromatography, ultraviolet-visible, Fourier transform infrared spectroscopy, thermogravimetry analysis and scanning electron microscopy. ATKP and ATKP-II were primarily composed of rhamnose, arabinose, xylose, mannose, glucose, and galactose in a molar percent of 1.6: 22.1: 3.6: 6.3: 55.7: 10.7, and 0.5: 22.1: 3.7: 10.2: 42.1: 21.4, respectively. Their structure may contain β-D-glucopyranose. The thermogravimetry analysis showed that ATKP and ATKP-II have good thermal stability at 230 °C and 200 °C, respectively. ATKP had the best antioxidant activities for 2, 2-diphenyl-1-picrylhydrazyl, hydroxyl, and superoxide free radical scavenging activities in vitro, and reducing ability than that of the purified polysaccharides. Moreover, ATKP was demonstrated an appreciable in vitro antibacterial activity, against Staphylococcus aureus, Bacillus subtilis, Salmonella, Penicillium italicum, Rhizopus and Aspergillus niger, but showed no activity against Escherichia coli and Saccharomycetes. These results demonstrated that ATKP displayed excellent antioxidant and antibacterial activities. This study provides a basis for the development and utilization in ATKP.