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 (IC(50) > 100 μM), 8 exhibited potent inhibitory effects on NO production (IC(50) of 14.8 μM), with the others showing weak anti-inflammatory activity (IC(50) > 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.