Clerodane diterpenoids from Scutellaria formosana with inhibitory effects on NO production and interactions with iNOS protein.

A phytochemical study on Scutellaria formosana afforded five previously undescribed spiro-diterpenoids, scutellapenes A-E. The structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of these compounds were established by the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Scutellapenes B-E possess a spiro-diterpenoid skeleton. All of the compounds showed inhibitory effects on LPS-induced nitric oxide (NO) production in murine microglial BV-2 cells. The further molecular docking studies revealed that these bioactive compounds had strong interactions with the iNOS protein.