Diterpenoids from Saliva plebeia R. Br. and Their Antioxidant and Anti-Inflammatory Activities

A new skeleton of diterpenoid, 1,2,3,4,4α,9,10,10α-octahydro-(4α-hydroxyymethyl) -1,1-dimethyl-9-(1-methylethyl)-(2S,3S,4αR,9R,10αS)-2,3,5,7-phenanthrenetertrol, named plebeianiol A (1), along with four known diterpenoids (2–5), were isolated from Salvia plebeia R. Br. Their structures were determined on the basis of spectral analysis. In the bioactivity tests, compounds 1, 2 and 5 showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities with IC50 values of 20.0–29.6 µM. In addition, these three compounds had significant inhibitory effects on reactive oxygen species (ROS) production in lipopolysaccharide (LPS)-induced macrophages. Compounds 1–3 inhibited nitric oxide (NO) production in LPS-induced macrophages with IC50 values of 18.0–23.6 µM. These results showed that compounds 1, 2 had significant antioxidant and anti-inflammatory activities and might provide basis for the treatment of diseases associated with oxidative lesions and inflammation.