Triterpenoids with antiproliferative activities from the twigs and leaves of Melaleuca linariifolia

One new pentacyclic triterpenoid, urs-12,16-dien-3-one (1), together with twelve known pentacyclic triterpenoids (2‒13), were isolated from the twigs and leaves of Melaleuca linariifolia. Their structures were characterized by their 1D- and 2 D-NMR spectra analysis and mass spectra studies. Furthermore, all isolated compounds were tested the inhibitory effect on proliferation of six human cancer cell lines in vitro, including NCI-H441, NCI-H460, A549, SKOV3, hela, and caki-1 cells. Among them, compounds 3, 5, 7, 9, 12, and 13 exhibited moderate antiproliferative activities with IC50 values ranging from 3.85 to 33.31 μM.