Cultivar and seasonal variation in bioactive compounds of highbush blueberry fruits (Vaccinium corymbosum L.)

Seasonal and cultivar variations of the phenolic, thiol, and ascorbate compound contents as well as the antioxidative enzyme activity in six cultivars of highbush blueberry were investigated. Berries of the ‘Earlyblue’, ‘Patriot’, ‘Bluecrop’, ‘Duke’, ‘Darrow’ and ‘Lateblue’ cultivars were sampled in 2005 and 2006. Chlorogenic acid, (-)-epicatechins, and ascorbate contents and CAT activity were found to be at the lowest degree affected by growing season conditions. ‘Seasonal effect’ had, however, a huge impact on the GR activity, as well as L-cysteine and glutathione content, suggesting that the glutathione system was highly influenced through growing factors in blueberry fruit. Berries of ‘Earlyblue’ were the richest source of antioxidants, at the same time revealing their quite stable quantity over the examined years. The second highest in bioactive stability was ‘Duke’, classified as medium with respect to antioxidant content.