Antioxidant activity and chemical composition of <i>Cichorium spinosum</i> L. in relation to nitrogen rate

In the present study, the effect of nitrogen (N) application rate on phenolic compounds content and antioxidant activity of Cichorium spinosum L. leaves was examined. Seeds were sown in seed trays containing peat and young seedlings were transplanted in 2-L plastic pots containing soil. Four nitrogen rates were applied, namely: a) control (no added N), b) 200 mg L-1 of total N, c) 400 mg L-1 of total N, and d) 600 mg L-1 of total N. Plants were harvested when rosettes reached marketable size. The results showed that the most abundant phenolic compounds of leaves extracts were chlorogenic acid, chicoric acid and kaempferol-3-O-glucuronide, while increasing nitrogen rates resulted in a significant decrease of the main phenolic compounds content. Similarly, the application of 600 mg L-1 of total nitrogen resulted in significant decrease of antioxidant potency of leaf extracts comparing to control, regardless of the performed assay, whereas for all the assays except for DPPH the application of 200 mg L-1 showed the best antioxidant properties. In conclusion, although the application of high nitrogen rates is tempting in order to achieve higher yields, rates higher than 200 mg L-1 are not recommended for C. spinosum cultivation, since a significant decrease of the bioactive compounds is observed that could compromise the quality of the final product. © 2021 International Society for Horticultural Science. All rights reserved.