Polyphenols and Antioxidant Capacity in Fruits and Vegetables Common in the Croatian Diet

The objective of this study was to determine the polyphenol content (total phenols, flavonoids, nonflavonoids, anthocyanins) and antioxidant capacity in selected fruits (apple, ‘Idared’; apricot, ‘Madjarska najbolja’; blueberry, ‘Bluecrop’; mandarin, ‘Kuno’; orange, unknown; sour cherry, ‘Marasca’; strawberry, ‘Maya’ and peach, ‘Redhaven’) and vegetables (broccoli, ‘Belstar’ -flower and steam; cauliflower, ‘Favola’; kale, ‘Melissa’ and leek-leaf and root -unknown) commonly consumed in the Croatian diet. Total phenols, flavonoids and nonflavonoids were measured calorimetrically by using the Folin-Ciocalteu reagent with gallic acid as the standard; anthocyanins were determined using bisulphite bleaching method using cyanidin-3-diglucoside as standard, whereas antioxidant capacity was measured using DPPH method. The highest total polyphenols were observed in sour cherry as 2560 mg GAE/kg fresh weight (FW), followed by blueberry, orange, mandarin, strawberry, apple, apricot, and peach. Among vegetables the highest concentration of total polyphenols was determined in kale (1039 mg GAE/kg FW) followed by broccoli flower, broccoli steam, leek leaf, leek root and cauliflower. In all investigated fruits, as well as vegetables, total flavonoids were predominant polyphenols. Total nonflavonoids were present in low concentration especially in leek leaf, broccoli flower and leek root. The highest antioxidant capacity in fruit and vegetables was determined in samples with higher concentration of flavonoids. In selected fruits, there was a distinct correlation between total phenols or flavonoids and antioxidant capacity, while in vegetable the correlation was not observed