Reagents and UHPLC−MS/MS analysis.
Seven STLs were detected in cultivated cardoon leaves: cynaropicrin, cynaratriol, grosheimin, aguerin B, deacylcynaropicrin, 11,13-dihydro-deacylcynaropicrin and 11,13-dihydroxi-8-deoxygrosheimin using santamarine as internal standard (IS). They were obtained following Rial et al. (Rial et al. 2014) and Scavo et al. (Scavoet al. 2019e), while santamarin was synthesized according to Lu and Fischer (Lu & Fischer 1996). Methanol, ethanol, dichloromethane and formic acid were purchased from Fischer Chemicals (Geel, Belgium), ammonium formate was obtained from Sigma-Aldrich (St. Louis, MO, USA) and water for LC−MS/MS analysis was type I obtained from an Ultramatic system from Wasserlab (Barbatáin, Spain). All the solvents were UHPLC-grade. The UHPLC−MS/MS analysis was carried out in accordance to Scavo et al. (Scavo et al. 2019f).