Diversity of phenolic antioxidant content and radical scavenging capacity in the USDA apple germplasm core collection

Regular consumption of fruit and vegetables containing naturally occurring antioxidants has been recommended to intervene in the onset and development of lifestyle diseases, such as cancer and cardiovascular diseases. While apples have long been recognized as beneficial to human health, data on antioxidant content and radical scavenging activity, and particularly on the extent of biodiversity in the germplasm pool has been sparse. We examined juice and fruit tissues from 321 species, selections, and cultivars considered representative of the genetic diversity in the Malus germplasm collection from the USDA Plant Genetic Resources Unit, grown at Geneva, NY and Excelsior MN. This core collection was found to be very diverse in total phenolics (TP) and 2,2' azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) antioxidant capacity. TP ranged from 14 to 7181 mg/L, gallic acid equivalents. MN grown apples were slightly higher than the same cultivars grown in NY. Maximum species TP content varied considerably: M. asiatica = 376, M. baccata rockii = 4606, M. brevipes = 640, M. floribunda = 1454, M. hartwigii = 620; M. mandshurica = 416, M. micromalus, = 3437, M. platycarpa = 1804, M. pumila = 1534, M. sieversii = 731, M. sikkimensis = 7181, M. sylvestris =1108, M. toringoides = 3873, M. transitoria = 2465, M. yunnanensis var. veitchii = 2802 mg/L. Cultivars contained the lowest TP levels ranging from 15 'Gingergold' to 241 'Cox's Orange' mg/L. Crabapple cultivars varied from 212 for 'Dolgo' to 2360 mg/L for 'Prairie Fire. Juice yield varied from 25 to 71 ml/100 g fruit, the highest derived from the largest fruit.