New insights into antioxidant activity of Brassica crops.

Antioxidant activity of six Brassica crops-broccoli, cabbage, cauliflower, kale, nabicol and tronchuda cabbage-was measured at four plant stages with DPPH and FRAP assays. Samples taken three months after sowing showed the highest antioxidant activity. Kale crop possessed the highest antioxidant activity at this plant stage and also at the adult plant stage, while cauliflower showed the highest antioxidant activity in sprouts and in leaves taken two months after sowing. Brassica by-products could be used as sources of products with high content of antioxidants. Phenolic content and composition varied, depending on the crop under study and on the plant stage; sprout samples were much higher in hydroxycinnamic acids than the rest of samples. Differences in antioxidant activity of Brassica crops were related to differences in total phenolic content but also to differences in phenolic composition for most samples.