ABSTRACT: Investigation of the South African plant Urginea
depressa Baker (Asparagaceae Juss.) for antiproliferative activity
against the A2780 ovarian cancer cell line led to the isolation of
the six new homoisoflavonoids urgineanins A−F (1−6), the
two known bufatrienolides 7 and 9, and the new bufatrienolides
urginins B and C (8 and 10). Structures were elucidated based
on analysis of their 1D and 2D NMR spectra, electronic circular
dichroism, and mass spectrometric data. Five of the six new
homoisoflavonoids had good antiproliferative activity against
the A2780 ovarian cancer, A2058 melanoma, and H522-T1
human non-small-cell lung cancer cells, and urgineanin A (1) had submicromolar activity against all three cell lines. The four
bufatrienolides 7−10 had strong antiproliferative activity against the same cell line, with IC50 values of 24.1, 11.2, 111, and
40.6 nM, respectively.