Diterpene Glycosides from the Seeds of Pharbitis nil

Six new ent-kaurane diterpene glycosides, pharbosides A-F (1-6), and a new ent-gibbane diterpene glycoside, pharboside G (7), together with three known ent-kaurane diterpenoids, 7beta,16beta,17-trihydroxy-ent-kauran-6alpha,19-olide (8), 6beta,7beta,16alpha,17-tetrahydroxy-ent-kauranoic acid (9), and 6beta,7beta,16beta,17-tetrahydroxy-ent-kauranoic acid (10), were isolated from an ethanolic extract of the seeds of Pharbitis nil. The structures of the new compounds were determined by spectroscopic methods including 1D and 2D NMR analysis. The absolute configurations of the compounds were clarified by CD spectroscopic studies. Full NMR data assignments of the three known compounds (8-10) are reported. The isolated compounds were evaluated for their cytotoxic activities against four human cancer cell lines.