Abstract: In this study, anthocyanins were extracted from St. Cloud blueberries and separated by preparative high performance liquid chromatography. Three fractions, named as Ⅰ, Ⅱ and Ⅲ, were obtained and evaluated for their anti-lipid peroxidation activity, reducing power, hydroxyl and DPPH radical scavenging activity, and light and heat stability using in vitro assay systems. The results showed that all the anthocyanin fractions had anti-lipid peroxidation activity, reducing power, hydroxyl and DPPH radical scavenging activity and could be ranked in decreasing order of antioxidant activity as follows: fraction Ⅰ＞ fractionⅡ ＞ fraction Ⅲ. The antioxidant activity of anthocyanins was associated with their concentration and structure. Among the fractions, Ⅲ had the strongest light and heat stability, and I had the weakest light and heat stability. Similarly, the light and heat stability of anthocyanins was also related to their structure. Thus, St. Cloud blueberry anthocyanins can be a source of natural antioxidants and used as food additives.

Key words: St. Cloud blueberry, anthocyanin, antioxidant activity, stability