Inhibitory Effect of Compounds Isolated from the Aerial Part of Piper bavinum on Nitric Oxide Production

Nitric oxide (NO) is a major product and its production is controlled by nitric oxide synthases (NOSs), which include inducible nitric oxide synthases (iNOS). The overproduction of NO by iNOS regulation has been concerned with the pathology of several inflammatory disorders, including septic shock, tissue damage, and rheumatoid arthritis. NO production induced by lipopolysaccharide (LPS) through iNOS can reflect the degree of inflammation. This study reports the anti-inflammatory activity of isolated compounds from Piper bavinum C.CD. (Piperaceae). Eight secondary metabolites (1-8) have been isolated from the aerial part of P. bavinum. The chemical structures of 1-8 were established mainly by NMR and mass spectra. Compound 5 was isolated from P. bavinum for the first time. The anti-inflammatory activity of the isolated compounds was evaluated against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 cells in vitro. Compound 4 inhibited LPS-induced NO production the most effectively, with an value of 5.2 M, followed by compound 5, which inhibited NO production with an value of 13.5 M. Compound 4 suppressed LPS-induced COX-2 and iNOS expression in a dose-dependent manner at the protein level. The findings suggested that P. bavinum and its constituents may have anti-inflammatory properties.