Glochodpurnoid B from Glochidion puberum Induces Endoplasmic Reticulum Stress-Mediated Apoptosis in Colorectal Cancer Cells

Glochidpurnoids A and B (1 and 2), two new coumaroyl or feruloyl oleananes, along with 17 known triterpenoids (3–19) were obtained from the stems and twigs of Glochidion puberum. Their structures were elucidated by extensive spectroscopic data analyses, chemical methods, and single crystal X-ray diffraction. All compounds were screened for cytotoxicity against the colorectal cancer cell line HCT-116, and 2, 3, 5, 6, 11, and 17 showed remarkable inhibitory activities (IC(50): 0.80–2.99 μM), being more active than the positive control 5-fluorouracil (5-FU). The mechanistic study of 2, the most potent compound, showed that it could induce endoplasmic reticulum (ER) stress-mediated apoptosis and improve the sensitivity of HCT-116 cells to 5-FU.