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Seven new polyhydroxylated oleanane-type triterpene saponins, arenarosides A-G ( 1 - 7 ), together with four known compounds, were isolated from an ethanol extract of the aerial parts of the Vietnamese plant Polycarpaea arenaria . The chemical structures of the newly isolated oleanane saponins were elucidated on the basis of spectroscopic and spectrometric analysis, especially 2D NMR and HRMS. Biological evaluation revealed that 3 , 4 , 6 , and 7 showed moderate activities against four human cancer cell lines (A549, HTC116, PC3, and RT112) with IC 50 values of 6.0-9.9 μM, and 3 , 4 , 5 , and 7 also displayed promising antiangiogenesis effects with IC 50 values <5 μM in the test system used. Among the isolates, arenaroside D ( 4 ) exhibited the most potent inhibitory effects, not only in cancer cell proliferation but also in angiogenic activities. Preliminary SAR studies revealed that the presence of an acetyl group at C-22 in oleanane-type triterpene saponins increases these bioactivities.