| Abstract: | We report the isolation of a novel diterpene, designated as `amethane', from Isodon amethystoides (Lamiaceae). The diterpene [amethinol A; systematic name: (4aR,4bR,7R,10aS)‐4b,7‐dihydroxy‐7‐isopropyl‐1,1‐dimethyl‐9‐oxododecahydrobenzo[a]azulene‐4a(2H)‐carboxylic acid], possesses a unique skeleton containing a six/five/seven‐membered tricyclic system. Intermolecular O—H…O close contacts were found to the carboxyl, carbonyl and hydroxy groups, connecting molecules into a two‐dimensional structure. A possible biosynthetic pathway has been proposed. In addition, the compound was evaluated for its biological activities against different disease targets, and was found to significantly attenuate RORγt‐dependent autoimmune responses. |
