Flavonoid constituents and their contribution to antioxidant activity in cultivars and hybrids of rabbiteye blueberry (Vaccinium ashei Reade)

Fruit from 42 blueberry (Vaccinium spp.) cultivars, including 36 rabbiteye cultivars (Vaccinium ashei Reade), three V. ashei hybrid derivatives, and three northern highbush (Vaccinium corymbosum L.) standards were evaluated for antioxidant capacity, individual flavonoid content, and the contribution of each identified phenolic compound to total antioxidant activity. Considerable variation was found in flavonoid content, antioxidant activity, and their contribution to total antioxidant activity among cultivars. Among 42 blueberry cultivars, the rabbiteye ‘Early May’ contained the highest amount of chlorogenic acid, myricetin 3-arabinoside, quercetin derivatives, and delphinidin-, cyanidin-, petunidin-, and malvidin-basis anthocyanins. ‘Early May’ cultivar also had the highest antioxidant activity (88.2 μmol TE/g fw). ‘Owen’, ‘Bluegem’, ‘Clara’, Climax’, and ‘Centurion’ were among the other rabbiteye cultivars that also had high levels of flavonoids and antioxidant activities. In contrast, the pink-fruited V. ashei hybrid, ‘Pink Lemonade’, had the lowest content of flavonoids and lowest antioxidant activity. The mean flavonoid content and antioxidant activity of rabbiteye cultivars was higher than those among northern highbush and V. ashei hybrids. The antioxidant activity of V. ashei hybrid derivatives was derived mainly from chlorogenic acid, myricetin, and quercetin, which contributed 62.5% of total antioxidant activity, whereas anthocyanins (malvidin, petunidin, delphinidin, and cyanidin) were the main contributors to the antioxidant activity of rabbiteye cultivars (76.2%) and northern highbush standards (76.8%). Blueberry cultivars identified to have high phenolic content and high antioxidant activity could be used as parents for future blueberry breeding programmes to develop new blueberry cultivars with higher antioxidant activity and further improve human health.