Bioactive Compounds and Macroelements of Chicory Plants (Cichorium intybus L.) after Hydroponic Forcing in Different Nutrient Solutions Lovro Sinkovič 1* , Janez Hribar 2 , Lea Demšar 2 , Rajko Vidrih 2 , Marijan Nečemer 3 , Peter Kump 3 , and Dragan Žnidarčič 4 1 Crop and Seed Science Department, Agricultural Institute of Slovenia, Hacquetova ulica 17, SI-1000 Ljubljana, Slovenia 2 Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia 3 Department of Low and Medium Energy Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia 4 Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia *Corresponding author: lovro.sinkovic@gmail.com Received June 7, 2016 / Revised December 30, 2016 / Accepted January 2, 2017  Korean Society for Horticultural Science and Springer 2017 Abstract. The aim of this study was to measure the bioactive compounds and elemental composition in the leaves of different chicory (Cichoruim intybus L.) cultivars after hydroponic forcing. Five chicory cultivars were studied: three red coloured cultivars: ‘Treviso’, ‘Verona’, and ‘Anivip’; one red-spotted cultivar ‘Castelfranco’; and one green cultivar ‘Monivip’. Developing chicory roots were forced in three different nutrient solutions enriched in nitrogen (+N), enriched in potassium (+N/K), or enriched in phosphorus (+N/P/K) to obtain new vegetative apical buds called chicons, or ‘Belgian endive’. Each of the nutrient solutions was used at three concentrations: 1%, 2%, and 3%. Fifty leaf samples (5 cultivars × 10 nutrient solutions) were used for analyses. Total phenolic content, antioxidant potential, and total flavonoid content were determined using spectrophotometric methods at the appropriate wavelengths, and multi-elemental analysis (P, S, Cl, K, Ca, Fe, Zn, Mn, Rb, Br, and Sr) was conducted using energy dispersive X-ray fluorescence spectroscopy. The highest total phenolic and total flavonoid contents of the chicons were observed with the nutrient solution enriched in K, followed by the solution enriched in N, and P. The highest antioxidant potential was observed with the nutrient solution enriched in N. Multi-element analysis detected the major macroelements (> 1 gkg -1 dry weight) as K, P, Ca, Cl, and S. The nutrient solutions enriched in K and P generally showed the highest contents of these two macro- elements in the chicons. Linear discriminant analysis for 19 parameters derived from 43 samples of five cultivars of chicons showed good discrimination between cultivars and nutrient solutions used for hydroponic forcing. Additional key words: antioxidant activity, elements; phenolics, vegetables, X-ray fluorescence Hortic. Environ. Biotechnol. DOI 10.1007/s13580-017-0178-1 ISSN (print) : 2211-3452 ISSN (online) : 2211-3460 Research Report Introduction Cichoruim intybus L. (Asteraceae) is commercially known as chicory, and represents an important industrial and agri- cultural crop in Mediterranean countries (Poli et al., 2002). Chicory consists of many cultivars with a wide pallet of colours and is produced by several methods (Innocenti et al., 2005). One of the most important methods of chicory pro- duction is the forcing of its developed roots in darkness to obtain new, etiolated, vegetative apical buds, known as chicons or ‘Belgian endive’ (Vanstreels et al., 2002). In recent years, chicons have gained increasing commercial interest due to their unique shape and culinary features that are produced by the post-harvest forcing. Forcing conditions are designed to improve the nutritional and aesthetic quality of the product, as well as to increase the market value (Nicoletto and Pimpini, 2009). The hydroponic forcing practice for chicons is divided into vegetative growth of the chicory roots in the field and post-harvest growth in the dark on a nutrient solution to develop fresh leaves (De Rijck and Schrevens, 1998, Tan and Corey, 1990). An abundance of research has shown that fresh leafy vegetables constitute important food crops due to their con- tribution of minerals and biologically active compounds, including phenolics and flavonoids (Lin and Tang, 2007, Nicoletto and Pimpini, 2009, Faller and Fialho, 2010). Due to its chemical composition of bitter compounds, chicon has been said to “purify” the liver, “regulate” the gall bladder,