Euphorane C, an unusual C17-norabietane diterpenoid from Euphorbia dracunculoides induces cell cycle arrest and apoptosis in human leukemia K562 cells

Abstract

Four new polycyclic diterpenoids euphoranes A − D (1–4), together with 12 known terpenoids (5–16) were isolated from the whole plants of Euphorbia dracunculoides. Compound 2 represents the first example of aromatic 15,16,17-trinorabietane diterpenoid in Euphorbia species, and euphorane C (3) is an unusual 17-norabietane diterpenoid. The absolute configurations of 1, 2, and 4 were determined by single crystal X-ray diffraction, while that of 3 was established with the aid of ECD and 1D NMR quantum chemical calculation. Moreover, the absolute stereochemistry of 11 was demonstrated for the first time by crystallographic data. Compounds 1–16 were screened for antiproliferative activities against five human cancer cell lines, and 3 showed significant cytotoxicity against the human leukemia K562 cells with IC50 value of 3.59 μM. Preliminary mechanistic investigation revealed that 3 could induce cell cycle arrest at G0/G1 phase and apoptosis in K562 cells.

Keywords

• Euphorbia dracunculoides
• Cytotoxicity
• Apoptosis
• Abietane diterpenoid
• Norabietane