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). Hydroxylates germacrene A acid to 6-alpha-hydroxy-germacrne A acid, a precursor of sesquiterpene lactones that spontaneously undergoes a lactonization which yields costunolide (PubMed:21515683). germacra-1(10),4,11(13)-trien-12-oate + O2 + reduced [NADPH--hemoprotein reductase] = (+)-costunolide + 2 H2O + oxidized [NADPH--hemoprotein reductase] Secondary metabolite biosynthesis; terpenoid biosynthesis. Belongs to the cytochrome P450 family.