Involved in the biosynthesis of germacrene-derived sesquiterpene lactones (PubMed:30468448). Component of the parthenolide biosynthetic pathway; parthenolide and conjugates are promising anti-cancer drugs highly active against colon cancer cells (PubMed:30468448). Catalyzes the conversion of costunolide to parthenolide (PubMed:24704560). (+)-costunolide + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + oxidized [NADPH--hemoprotein reductase] + parthenolide Secondary metabolite biosynthesis; terpenoid biosynthesis. During ovary development, accumulates until the stage 3 and fades out progressively to disappear at stage 6. Belongs to the cytochrome P450 family.