Bioactive Diterpenoids from the Stems of Euphorbia royleana

Two ingenane- ( 1 and 2 ), two ent -atisane- ( 3 and 4 ), two ent -kaurane- ( 5 and 6 ), two ent -abietane- ( 7 and 8 ), and one ent -isopimarane-type ( 9 ) diterpenoid and 12 known analogues have been isolated from the methanolic extract of the stems of Euphorbia royleana . Their structures, including absolute configurations, were determined by extensive spectroscopic methods and ECD data analysis. The nitric oxide inhibitory activities of those diterpenoids were examined biologically in lipopolysaccharide-stimulated BV-2 cells, with compounds 1, 2, 5 – 7, 10, and 12 having IC 50 values lower than 40 μM. Molecular docking was used to investigated the possible mechanism of compounds 1, 2, 5 – 7, 10, and 12 .