Polyphenolic Compound Variation in Globe Artichoke Cultivars as Affected by Fertilization and Biostimulants Application

Globe artichoke is an ancient herbaceous plant native to the Mediterranean Basin. The edible part of the plant is limited to the fleshy leaves (bracts) and receptacle of a large immature inflorescence (head) that has been shown to be a rich source of bioactive compounds. Nutritional and pharmacological properties of artichoke heads and leaves are attributed mainly to polyphenolic compounds and inulin present at high concentration. In this study, polyphenols were investigated in two artichoke cultivars (Opal and Madrigal) in response to four nitrogen rates and foliar applications of biostimulating products under drip irrigation. Field experiments were carried out over two growing seasons (2015–2016, 2016–2017) in Policoro (MT), Southern Italy, on a deep clay soil in sub-humid climate conditions. Phenolic compounds were isolated and characterized by means of high-performance liquid chromatography with photodiode array detection and electrospray ionization/mass spectrometry (HPLC-DAD-MS/MS) analysis. In both cultivars, caffeoylquinic acids were more abundant when a dose of 100 kg ha(−1) of ammonium nitrate was provided, whereas apigenins were not affected by nitrogen fertilization. Luteolins increased in cv Opal and decreased in cv Madrigal following N fertilization. The application of biostimulants (3 L ha(−1)) favored the accumulation of polyphenols, in particular of caffeoylquinic acids and apigenin, in artichoke heads in both cultivars. The results obtained highlight some positive aspects related to the synergistic effect of nitrogen fertilization and biostimulant foliar application.