Abstract: Hazelnuts contain a variety of bioactive components, but the contents of bioactive components in hazelnuts vary depending on the variety and part. In the present study, eight cold-resistant varieties of flat European hazelnut were tested for the contents of bioactive components such as total polyphenols, total flavonoids, tannins and proanthocyanidins in shell, skin and kernel. The antioxidant activities of total polyphenols from hazelnut skin were determined. The results indicated that contents of bioactive components in skin were significantly higher than in shell and kernel (P < 0.05). Among the 8 varieties, the seed coat of the variety 7# had the highest contents of total phenolics and proanthocyanidins (185.76 and 77.28 mg/g, respectively), while the highest contents of total flavonoids and tannins (29.96 and 39.10 mg/g, respectively) were found in the seed coat of the variety 6#. Moreover, total phenolics were significantly more abundant than three other bioactives in hazelnut skin (P < 0.05). The antioxidant activity of seed coat polyphenols from 7# was better than that of any other variety. The percentage of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of total phenols from the skin of 7# was 87.70%, the ferric reducing power was 0.450, the percentage of superoxide anion radical scavenging activity was 53.1%, and the percentage of lipid peroxidation inhibition was 82.0%. The scavenging capacity against superoxide anion and DPPH radicals, the lipid peroxidation inhibition capacity, and the ferric reducing power of total phenolics from hazelnut skin were all positively correlated with total phenolics content with correlation coefficients of 0.843, 0.793, 0.695 and 0.620, respectively.

Key words: flat European hazelnut, active components, antioxidant properties