Bioactive diterpenoids from Trigonostemon chinensis: Structures, NO inhibitory activities, and interactions with iNOS

A phytochemical investigation to obtain new NO inhibitors led to the isolation of two new (1 and 2) and four known (3–6) diterpenoids from Trigonostemon chinensis. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configurations of new compounds were established by experimental and calculated ECD spectra. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these diterpenoids were evaluated, and all of the compounds showed inhibitory effects. The interactions of bioactive compounds with iNOS protein were also studied by molecular docking.