Pyromeconic acid and its glucosidic derivatives from leaves of Erigeron annuus, and the siderophile activity of pyromeconic acid

3'-O-Caffeylerigeroside (pyromeconic acid 3-O-beta-D-glucoside 3'-O-caffeyl ester) was obtained from the leaves of Erigeron annuus as a new pyromeconic acid derivative, and its structure was elucidated. Together with the gamma-pyrone derivative, pyromeconic acid (3-hydroxy-4H-pyran-4-one) and its beta-glucoside (erigeroside) were also isolated from the aerial parts of E. annuus. The siderophile activity of pyromeconic acid was also studied.