Falcarindiol and dichloromethane fraction are bioactive components in Oplopanax elatus: Colorectal cancer chemoprevention via induction of apoptosis and G2/M cell cycle arrest mediated by cyclin A upregulation.

Oplopanax elatus (Nakai) Nakai has a long history of use as an ethnomedicine by the people living in eastern Asia. However, its bioactive constituents and cancer chemopreventive mechanisms are largely unknown. The aim of this study was to prepare O. elatus extracts, fractions, and single compounds and to investigate the herb's antiproliferative effects on colon cancer cells and the involved mechanisms of action. Two polyyne compounds were isolated from O. elatus, falcarindiol and oplopandiol. Based on our HPLC analysis, falcarindiol and oplopandiol are major constituents in the dichloromethane (CH2Cl2) fraction. For the HCT-116 cell line, the dichloromethane fraction showed significant effects. Furthermore, the IC50 for falcarindiol and oplopandiol was 1.7 μM and 15.5 μM, respectively. In the mechanistic study, after treatment with 5 μg/ml for 48 h, dichloromethane fraction induced cancer cell apoptosis by 36.5% (p < 0.01% vs. control of 3.9%). Under the same treatment condition, dichloromethane fraction caused cell cycle arrest at the G2/M phase by 32.6% (p < 0.01% vs. control of 23.4%), supported by upregulation of key cell cycle regulator cyclin A to 21.6% (p < 0.01% vs. control of 8.6%). Similar trends were observed by using cell line HT-29. Data from this study filled the gap between phytochemical components and the cancer chemoprevention of O. elatus. The dichloromethane fraction is a bioactive fraction, and falcarindiol is identified as an active constituent. The mechanisms involved in cancer chemoprevention by O. elatus were apoptosis induction and G2/M cell cycle arrest mediated by a key cell cycle regulator cyclin A.