The LC-MS analysis of the MeOH extract of
the aerial parts of Pergularia tomentosa led to the isolation of
23 compounds, of which the structures were elucidated
unambiguously by NMR spectroscopic data analysis. Three
new doubly linked cardenolides (4, 13, 14) along with several
known cardenolides (1−3, 5, 7, 8, 15−23) and flavonol
glycosides (6, 9−12) were identified. LC-HRESIMS analysis,
in the negative-ionization mode, showed the absence of
flavonoids in a methanol extract of the roots of P. tomentosa.
On the basis of the antiproliferative activity reported for
cardenolides, the isolated compounds were tested for their
ability to decrease the cell viability of five different human cancer cell lines, PC3, HeLa, Calu-1, MCF-7, and U251MG,
exhibiting IC50 values ranging from 0.2 to 8.0 μM. Moreover, an S-phase entry assay was performed to investigate if the
compounds could affect the cell cycle progression of PC3 prostate carcinoma cells. The results obtained demonstrated that the
compounds 4, 7, and 14 at 1 μM considerably reduced the number of cells in the S-phase.