Inhibitory effect of bisbenzylisoquinoline alkaloids on nitric oxide production in activated macrophages.

Bisbenzylisoquinoline (BBI) alkaloids are anti-inflammatory constituents of plants of the families Menispermaceae and Ranunculaceae, which have been used as folk remedies in Japan and China. Five BBI alkaloids (cepharanthine, chondocurine, cycleanine, isotetrandrine and tetrandrine) were tested for suppressive effect on in vitro nitric oxide (NO) production by lipopolysaccharide-stimulated peritoneal macrophages, which were induced with thioglycollate or bacillus Calmette-Guerin in mice. All these BBI alkaloids significantly suppressed NO production at 5 micrograms/mL. Cepharanthine, isotetrandrine and cycleanine were slightly more inhibitory than tetrandrine and chondocurine. The suppression persisted for at least 48 hr. As NO is one of the critical mediators in inflammation, these results may explain some aspects of the anti-inflammatory mechanisms of BBI compounds.