1-O-Acetyl-6beta-O-Isobutyrylbritannilactone
1-O-Acetyl-6beta-O-Isobutyrylbritannilactone (compound 5), a sesquiterpene lactone, can be isolated from the flowers of Inula britannica. 1-O-Acetyl-6beta-O-Isobutyrylbritannilactone shows significant cytotoxicity to tumor cells[1].