Structure and antioxidant activity of polysaccharide POJ-U1a extracted by ultrasound from Ophiopogon japonicus

An ultrasonic technique was employed to extract polysaccharides from Ophiopogon japonicus. The ultrasonic extracted polysaccharides (POJ-U) were purified, and POJ-U1a (a homogeneous fraction) was obtained. The structural characteristics of POJ-U1a were investigated by infrared spectra, gas chromatography, high performance liquid chromatography, periodate oxidation. Smith degradation, methylation analysis, gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. The results indicated that the relative molecular weight of POJ-U1a was 4.02 x 10(3) Da. POJ-U1a was an alpha-configuration polysaccharide with a highly branched structure, and consisted of pyranoside and funanside. The backbone of POJ-U1 a consisted of 1,6-alpha-D-glucopyranose and 1,3,6-alpha-D-glucofuranose in the molar ratio of 7:3, while the branched chains were mainly composed of 1,3-alpha-D-glucopyranose and 1-alpha-D-glucopyranose in the molar ratio of 1:3. The branched structure of POJ-U1a was proved intuitively by AFM. Significant antioxidant activity of POJ-U1a has been proved as shown by its DPPH radical scavenging, hydrogen radical scavenging and superoxide anion scavenging activities, which indicated that POJ-U1a showed strong antioxidant activity. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.