Cytotoxic sesquiterpene lactones from Vernonia bockiana

AIM: To investigate antitumor compounds from Vernonia bockiana. METHODS: The compounds were isolated by column chromatography and preparative HPLC. Their structures were elucidated by 1H and 13C NMR spectroscopic methods and MS experiments. The antitumor activity was evaluated by testing their cytotoxicity against the human promyelomonocyte leukemic cell line HL-60 by the MTT method. RESULTS: Six sesquiterpene lactones, 8-(4-hydroxymethacryloyloxy)-10-hydroxy-13-methoxyhirsutinolide (1), 8-methacryloyloxy-10-hydroxy-13-O-methylhirsutinolide (2), piptocarphin A (3), 8-4-hydroxymethacryloyloxy- 10-hydroxyhisutinolide-13-O-acetate (4), piptocarphin F (5), and 8-acetoxy-10-hydroxy-13-O-methylhirsutinolide (6), and one known inone glycoside, saussureosides B (7), were isolated from the whole plant of V. bockiana. The six sesquiterpene lactones showed cytotoxic activity (IC50 3.87-12.5 molL-1) against the human leukemic cell line HL-60 while the inone glycoside 7 was inactive in the test. CONCLUSION: Compounds 1, 2, 6, and 7 were obtained for the first time from this plant; The sesquiterpene lactones present in V. bockiana were active as antitumor agents against the human leukemic cell line HL-60.