Structure-related inhibiting activity of some tobacco cembranoids on the prostaglandin synthesis in vitro

Structure-related inhibitory effects on the prostaglandin synthesis in vitro have been detected among eight diterpenoids of the cembrane class (1-8). The 4,6-diols 1 and 2 are the most active of the cembranoids studied with IC50 values of 0.36 and 0.39 mM, respectively, as compared with an IC50 value of 1.4 for acetylsalicylic acid. Lower activities are found for cembranoids having undergone oxidation of/at the 11,12 double bond (5-8), while the 4-hydroxy-6-oxocembranoids 3 and 4 exhibit effects lower than those of 1 and 2 but higher than those of 5-8.

Effects of the sesquiterpene capsidiol on isolated guinea-pig ileum and trachea, and on prostaglandin synthesis in vitro

The sesquiterpene capsidiol, isolated from elicited, cultured cells of Nicotiana silvestris, inhibits contraction induced by the agonists, histamine, acetylcholine, bradykinin, and barium chloride in the isolated guinea-pig ileum. In addition, capsidiol inhibits contraction induced by histamine and carbachol in the isolated guinea-pig trachea in a nonspecific and noncompetitive but concentration-dependent manner. Capsidiol also inhibits prostaglandin synthesis (cyclooxygenase) in vitro in a concentration dependent manner.