Diterpenoid glycosides from the bitter fern Gleichenia quadripartita

Fifteen new diterpenoid glycosides (1a-n, 2) were isolated from an Argentine collection of the bitter fern Gleichenia quadripartita along with the known flavonoid glycoside afzelin. Structure elucidation was accomplished by 1D and 2D NMR spectroscopy and by high-resolution MS analyses. In addition, X-ray crystallographic analysis of a monocrystal of la as well as chemical derivatization of 1h and 1m were performed to confirm their structures.