11β 13 dihydrolactucopicrin

All reagents used were of the highest commercially available purity. Parthenolide and costunolide were acquired from Sigma-Aldrich (SML0417, P0667) (Gillingham, UK). Lactucin, lactucopicrin, 11β-13-dihydroLactucin and 11β-13-dihydrolactucopicrin were acquired from Extrasynthese (3809, 3813, 3810, 3811) (Genay Cedex, France).

Brussels/witloof chicory juice was handmade by the homogenization of 2700 g of fresh Brussels/witloof chicory (Hebei Vilof Agritech Co., Ltd., Beijing, China) in 1800 mL of water while using a juice making machine (HAIPAN, Model BL-6A, Zhongshan, China). Lactucin, 11β,13-dihydroLactucin, lactucopicrin, and 11β,13-dihydrolactucopicrin were purchased from Extrasynthese (Lyon-Nord, France). Methanol was used to prepare stock solutions of standard SLs. Working standard solutions were prepared daily by dilution in methanol. Sulfatase (type H-1 from Helix pomatia, containing β-glucuronidase), β-glucuronidase (EC 3.2.1.31, type IX A from E. coli), d-saccharic acid 1,4-lactone (a glucuronidase inhibitor), santonin, and brain heart infusion broth were from Sigma–Aldrich (St. Louis, MO, USA). The cellulase enzyme (from Aspergillus niger) was from Solarbio (Beijing, China).