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 (IC50: 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.
Keywords: Glochidion puberum; apoptosis; endoplasmic reticulum stress; structural elucidation; triterpenoid.