Abstract: High performance liquid chromatography (HPLC) and high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) were used to analyze the anthocyanins in four different blueberry varieties. The antioxidant capacity of 13 anthocyanins was determined in vitro using the oxygen radical absorbance capacity (ORAC) assay, and the molecular structure parameters, active hydroxyl bond dissociation energy (BDE), ionization potential (IP) and semi-quinone free radical spin density distribution were calculated by using density functional theory (DFT) at the M062-x/6-311++G** level. Furthermore, the difference in the antioxidant activity of anthocyanins was evaluated among blueberry varieties. The results showed that the antioxidant capacity of anthocyanidin galactosides was higher than that of arabinoglycosides and glucosides originating from the same anthocyanindins. The antioxidant capacity of petunia-3-O-galactoside was found to be the strongest among the 13 anthocyanins, with BDE, IP and spin density of semi-quinone radical of only 251.21 kJ/mol, 484.51?kJ/mol, and 0.032 78, respectively. The theoretical calculation of antioxidant capacity was consistent with the results of antioxidant assay in vitro. In addition, the relationship between anthocyanin content in blueberry fruit and antioxidant capacity was analyzed. This study indicated that the DFT method provides a theoretical basis for studies on the antioxidant activity of blueberry anthocyanins.

Key words: blueberry; anthocyanin; density functional theory; antioxidant