Structural Characterization of a Novel Glucan from Achatina fulica and Its Antioxidant Activity

A novel glucan designated AFPS-IB was purified from Achatina fulica (China white jade snail) by anion-exchange and gel-permeation chromatography. Chemical composition analysis indicated AFPS-IB was composed of glucose, fucose, rhamnose, mannose, and galactose in a molar ratio of 189:2:1:1:2 and with an average molecular weight of 128 kDa. Its structural characteristics were investigated by Fourier transform infrared spectroscopy (FTIR), high performance liquid chromatography (HPLC), gas chromatography mass spectrometry (GC-MS), methylation analysis, nuclear magnetic resonance (NMR) spectroscopy (H-1, C-13, H-H COSY, HSQC, TOCSY, and NOESY), and atomic force microscopy (AFM). The glucan mainly consisted of a backbone of repeating (1 -> 4)-alpha-D-glucose residues with (1 -> 6)-beta-D glucosyl branches at random points on the backbone glucose. Antioxidant studies revealed AFPS-IB showed significant DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, superoxide anion (O-2(-)) scavenging activities and high reduction potential. This study suggested that AFPS-IB could be a new source of dietary antioxidants.