Influence of irrigation on the chemical compounds in leaves in vegetative and reproductive stage and bracts of globe artichoke (Cynara cardunculus var. scolymus L.)

Artichokes contain antioxidant compounds, principally phenols which are beneficial for health. The content of these active principles can depend on irrigation, genotype and stage of plant's development. This study was aimed at determining the concentration of cynarin and chlorogenic acid, both in leaves in vegetative and reproductive stage and in central and outer bracts of inflorescences. The selected genotypes were 'Oro Verde FCA' (OV), 'Guri FCA' (GU) and 'Gauchito FCA' (GA), all of them produced on the Faculty of Agricultural Sciences, Rosario's National University (UNR). The plants were treated with 194 mm of irrigation by dripping from June to November and the controls did not receive irrigation. The extracts were prepared with 5 leaves from the middle layer of 4 plants in vegetative and reproductive conditions and with bracts of primary heads stored in freezer (-80°C) until the preparation of extracts. Measurements were made at the Mass Spectrometry Laboratory of Scientific and Technology Center (CCT-CONICET Rosario, Argentina). Extracts were analyzed by HPLC using UV spectroscopy (330 nm) and electrospray MS as detectors. The content of cynarin in plants leaves with irrigation was 3052 mg kg-1 for GA in vegetative state and 4257 mg kg-1 in reproductive state, while in the control the content of cynarin was 1873 and 1599 mg kg-1 in each stage. In OV, cynarin was detected in reproductive stage with irrigation (734 mg kg-1) and without irrigation (482 mg kg-1). In the central bracts, the highest content of cynarin was found in irrigated plots of OV and GA, whereas in the outer bracts the same behavior was observed but in GU and GA. The highest content of chlorogenic acid was observed in leaves of irrigated plants in the reproductive stage, with 3445 mg kg-1 in OV, 1447 mg kg-1 in GU and 1079 mg kg-1 in GA. Chlorogenic acid was only detected in the central bracts of irrigated plants, showing the highest concentration in the early cultivars (GA 3405 and OV 1218 mg kg-1). This study demonstrates that irrigation allows to increase the content of active principles in leaves and inflorescences of artichoke crops in which both leaves and inflorescences are harvested.