Cytotoxic Activities of Naturally Occurring Oleanane‑, Ursane‑, and Lupane‑type Triterpenes on HepG2 and AGS Cells

Background: It is well known that the naturally occurring modified triterpenes in plants have a wide diversity of chemical structures and biological functions. The lupane‑, oleanane‑, and ursane‑type triterpenes are the three major members of natural triterpenes with a wide range of biological properties. A systematic approach is necessary to review their structures and biological activities according to the backbones and the different substituents. Objective: Thirty lupane‑(L1‑7), oleanane‑(O1‑14), and ursane‑type (U1‑9) triterpenes with structural diversity were examined to evaluate their cytotoxic activities against two cancer cell lines, human hepatocellular carcinoma (HepG2) and AGS cells. Materials and Methods: They were isolated from Hedera helix, Juglans sinensis, and Pulsatilla koreana using a series of column chromatography methods and were treated to evaluate their cytotoxic activities against HepG2 and AGS human gastric adenocarcinoma cell. Further, two triterpenes showing the most potent activities were subjected to the apoptotic screening assay using flow cytometry. Results: The polar groups, such as an oxo group at C‑1, a free hydroxyl at C‑2, C‑3, or C‑23, and a carboxylic moiety at C‑28, as well as the type of backbone, explicitly increased the cytotoxic activity on two cancer cells. O5 and U5 showed significantly the potent cytotoxic activity in comparison to other glycosidic triterpenes. In annexin‑V/propidium iodide (PI) staining assay, the percentage of late apoptosis (annexin‑V+/PI+) 12 and 24 h after treatment with O5 and U5 at 25 μM increased from 14.5% to 93.1% and from 46.4% to 49.1%, respectively, in AGS cells. The cytotoxicity induced by O5 showed a significant difference compared to U5 for 12 and 24 h. Conclusion: In the study, we can suggest the potent moieties which influence their cytotoxic activities against two cancer cells. The polar groups at C‑1, C‑2, C‑3, C‑23, and C‑28 and the linkage of sugar moieties influenced the different cytotoxic activities.