Anti-inflammatory activities of isopimara-8(9),15-diene diterpenoids and mode of action of kaempulchraols B–D from Kaempferia pulchra rhizomes

Kaempulchraols B–D (2–4), isopimara-8(9),15-diene diterpenoids isolated from Kaempferia pulchra rhizomes collected in Myanmar, were identified as potent NF-κB inhibitors. These compounds were also effective as NO inhibitory agents, with IC₅₀ values of 47.69, 44.97, and 38.17 μM, respectively, without showing any cytotoxicity against LPS-induced RAW264.7 cells. Investigations of the mechanisms of action of 2–4 revealed that they inhibit the NF-κB-mediated transactivation of a luciferase reporter gene, IL-6 production, and COX-2 expression, with an effective dose of 25 μM. Thus, isopimarane diterpenoids are suggested to be potent inhibitors of NF-κB pathways and could be further explored as potential anti-inflammatory lead compounds.