Isolation, Identification, and Antitumor Activities of Glucosinolates and Isothiocyanates in Chinese Cabbage Seeds

Isothiocyanates (ITCs), which are derivatives of glucosinolates (GSLs) from Brassica plants, have been investigated as anticancer agents. An extensively studied anticancer ITC is sulforaphane, which is found in low amounts in Chinese cabbage. We aim to investigate the types and content of GSLs (precursors of ITCs with anticancer activity) in Chinese cabbage seeds. GSLs from Chinese cabbage seeds were isolated and purified using acidic Al₂O₃ column chromatography and preparative HPLC. GSL and ITC profiles were further identified using UHPLC-Q-TOF-MS. The antitumor activities of ITC (produced by exogenous enzymatic hydrolysis of GSLs) were evaluated in vitro. Seventeen GSLs and seven ITCs were identified, and the dominant GSLs were gluconapin, glucobrassicanapin, and progoitrin in Chinese cabbage seeds. High-purity gluconapin (>99%) was purified. The ITCs showed synergistic-, dose-, and time-dependent effects on the inhibition of HepG2 cells, and the key ITCs were 3-butenyl ITC, sulforaphane, and 2-phenylethyl ITC. The corresponding parent GSLs were gluconapin, glucoraphanin, and gluconasturtiin, respectively. 3-Butenyl ITC could significantly induce HepG2 cell proliferation (IC50 = 89.44 μg/mL) and apoptosis (p < 0.05). Our results suggested that Chinese cabbage seed could be a valuable source of natural antitumor ingredients.