Phenolic glycosides as inhibitors of inducible nitric oxide synthase from Populus davidiana in LPS-activated RAW 264.7 murine macrophages.

Nitric oxide (NO) produced in large amounts by inducible nitric oxide synthase (i-NOS) is known to be responsible for the vasodilation and hypotension observed in septic shock and inflammation. Inhibitors of i-NOS, thus, may be useful candidates for the treatment of inflammatory diseases that accompany the overproduction of NO. Two phenolic glycosides, salicortin (1) and salicortin-6'-benzoate (2), were purified as active principles from the extracts of Populus davidiana by activity-guided purification procedures. They showed dose dependent inhibition of NO production in lipopolysaccharide (LPS)-activated RAW 264.7 cells. The IC50 values of salicortin (1) and salicortin-6'-benzoate (2) was 15 microM and over 50 microM, respectively. In immunoblot analysis, salicortin inhibited the expression of i-NOS. These new inhibitors of overproduction of NO may have potentials for the treatment of inflammation.