Abstract: In order to study the relationship between the structure and antioxidant activity of scutellarin and its aglycone,the density functional theory (DFT) B3LYP method with 6-311++G**basis set was used to optimize the structure of scutellarin and its aglycone.The properties of the stable geometries have been discussed in detail based on the molecular geometries,the bond dissociation enthalpies (BDE),ionization potential (IP) and the frontier molecular orbitals theory.The results showed that antioxidant properties of scutellarin and its aglycone derived from dehydrogenation capacity of hydroxyl group and the ability of electron abstraction,the C6-OH was the highest active site of scutellarin and its aglycone.On basis of the computed BDE and IP values,scutellarin was less effective antioxidant than its aglycone,which was in good agreement with the experimental results.The antioxidant activity of natural glycoside substances was enhanced after hydrolysis.Moreover,the polarity of the solvent medium has been considered in solution.An H-atom transfer mechanism was the most popular in all environments studied.

Key words: scutellarin, scutellarein, antioxidation activity, DFT