Abstract: Total phenolic content (TPC), total flavonoid content (TFC) and total proanthocyanin content (TAC) were determined in blueberry flowers, tender stems, tender leaves and old leaves. Antioxidant activities of acidified methanol extracts from different parts of blueberry were evaluated by ferric reducing antioxidant power (FRAP) and hydrolxyl, DPPH and ABTS+ free radicals scavenging capacity assays. Results indicated that tender leaves contained the highest level of TPC (43.77 mg gallic acid/g md), which was increased by 3.45, 1.42 and 1.12 folds as compared to flowers, tender stems and old leaves, respectively. Old leaves contained the highest levels of TFC (68.01 mg rutin/g md) and TAC (23.29 mg catechinic acid/g md), which were 2.57 and 4.61, 1.79 and 1.23, and 1.03 and 1.98 folds higher than those in flowers, tender stems, and tender leaves, respectively. The FRAP activity of the extract from old leaves was the highest, followed by tender stems, flowers, and tender leaves. The hydroxyl radical scavenging activity was in the following order: tender stems > tender leaves > flowers > old leaves. Both the DPPH radical scavenging capability and total antioxidant capacity (TAC) were in the following order: tender stems > tender leaves > old leaves > flowers > VC. In summary, the DPPH radical scavenging was the strongest of the antioxidant activities for all the blueberry extracts, followed by TAC, and their antioxidant activities were the weakest in terms of hydroxyl radical scavenging capacity and FRAP activity.

Key words: blueberry, flavonoids, phenolics, antioxidant activity