Two New β-Dihydroagarofuran Sesquiterpenes from Celastrus orbiculatus Thunb and Their Anti-Proliferative Activity

Two new β-dihydroagarofuran-type sesquiterpenes (1–2) were isolated and identified from the fruit of Celastrus orbiculatus Thunb, together with seventeen known compounds (3–19). The structures of the isolated new compounds were elucidated based on extensive spectroscopic analyses. The cytotoxic activities of the 19 sesquiterpenes on three cell lines, human acute promyelocytic leukemia HL-60, human leukemic K562, and human colon cancer HCT-116 cells, were evaluated in vitro. Compound 4 exhibited potent cytotoxic activity against HL-60, K562, and HCT116 cell lines with IC(50) values of 3.61 μΜ, 17.13 μΜ and 10.15 μΜ, respectively, and the other compounds displayed moderate activity.