Natural NO inhibitors from the leaves of Callicarpa kwangtungensis: Structures, activities, and interactions with iNOS

Abstract A phytochemical investigation to obtain new NO inhibitors resulted in the isolation of a new diterpenoid with a rare 9,10- seco -abietane skeleton ( 1 ) and twelve known terpenoids ( 2 – 13 ) from Callicarpa kwangtungensis . Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configuration of compound 1 was established by comparison of the calculated and experimental electronic circular dichroism (ECD) spectra. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these terpenoids were evaluated, and all of the compounds showed inhibitory effects. The following molecular docking studies showed interactions of the bioactive compounds with the iNOS protein.