Cembrane-type diterpenoids from the gum resin of Boswellia carterii and their biological activities.

Eight new cembrane-type diterpenoids, boscartins AH-AK (1-8), along with two known ones (9-10), were isolated from the gum resin of Boswellia carterii. Compounds 1-3 were characteristic of high oxidation assignable to three epoxy groups, while compounds 4-8 were characteristic of two epoxy groups. Spectroscopic examination was used to elucidate their structures. All isolates were evaluated for antiproliferative activity against HCT-116 human colon cancer cells, anti-inflammatory activity against nitric oxide (NO) production, and hepatoprotective activity in vitro. All of them showed weak antiproliferative activity (IC50 > 100 µM), 8 exhibited potent inhibitory effects on NO production (IC50 of 14.8 µM), with the others showing weak anti-inflammatory activity (IC50 > 30 µM), and 1 exhibited more potent hepatoprotective activity than the positive control, bicyclol, at 10 µM against the damage induced by paracetamol in HepG2 cells.