Different fractions of sea buckthorn fruits were investigated for antioxidant activity and its relationship to different phytonutrients. Capacity to scavenge radicals of the crude extract, like the phenolic and ascorbate extracts, decreased significantly with increased maturation. The changes were strongly correlated with the content of total phenolics and ascorbic acid. Antioxidant capacity of the lipophilic extract increased significantly and corresponded to the increase in total carotenoids. The phenolic fractions made a major contribution to the total antioxidant capacity due to the high content of total phenolics. The lipophilic fractions were most effective if the comparison was based on the ratio between antioxidant capacity and content of antioxidants. The crude extract of fruits showed the highest inhibitory effect in both 2,2-azobis(2,4-dimethylvaleronitrile) (AMVN) and ascorbate-iron induced lipid peroxidations. The aqueous and ascorbate-free extracts showed higher inhibition in the AMVN assay, but lower inhibition in ascorbate-iron induced peroxidation, than the lipophilic extract.

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Plant breeding in black chokeberry (Aronia melanocarpa) is based mainly on seedlings derived from domesticated Russian plants. Previous studies have, however, demonstrated very low levels of phenotypic variation within this gene pool. The present investigation was undertaken in order to study the genetic structure in native populations growing in North America. Random amplified polymorphic DNA (RAPD) marker variation was analysed in eight populations (three or five mother plants/population and five seedlings/mother plant) and compared with the variation in four cultivars and 15 seedlings derived from a Russian plantation. The four cultivars and all the Russian seedlings turned out to have identical RAPD profiles. In the native plant material, there were two types of mother plants: diploid plants that produced very heterogeneous offspring and tetraploid plants that produced homogeneous offspring. Partitioning of variability based on Shannon's diversity index attributed approx. 22% of the variation to the among-population level in diploids, compared to approx. 55% in the tetraploids. However, the diploid populations and the tetraploid populations did not differ significantly in within-population variation. These results prompted a second set of RAPD analyses, which were carried out on offspring obtained through open pollination of the initially examined material when growing in an experimental field. The analyses showed that tetraploid plants produced tetraploid offspring that, with few exceptions, were identical, indicating apomixis, whereas offspring of diploid plants were diploid or triploid, and highly heterogeneous, indicating outcrossing. Presumably, the tetraploid form of Aronia is an allopolyploid, with A. melanocarpa as one of the parents.