dft study on free radical scavenging activity of new kind of polysaccharide molecule in solution phase

The amanita caesarea polysaccharide is composed of α-d-glucose and α-d-lyxose at a ratio of 2:1. we used a quantum mechanical approach to shed light on the antioxidant ability of this compound in solution phase. calculation of reaction enthalpies for the free radical scavenging by this polysaccharide, and research the lowest energy geometry for all studied molecules were calculated by density functional theory (dft), b3lyp and ub3lyp for close and open shell systems respectively with split-valance 6-31g** basis set using gaussian 2009 software. the analysis of the bond dissociation enthalpy (bde) values and of the radicals to determine the delocalization possibilities clearly shows the importance of the 9-oh group in antioxidant reactivity.