The Sennoside Constituents of Rhei Rhizoma and Sennae Folium as Inhibitors of Serum Monoamine Oxidase

Four (in total) compounds with inhibitory effects on the activity of bovine serum monoamine oxidase were isolated from the methanol-water extracts of Rhei Rhizoma (Daiou) and Sennae Folium (Senna), and identified as sennosides A, B, E and F. Among them, sennosides A and B were obtained from both Rhei Rhizoma and Sennae Folium, while sennosides E and F were detected only in the former. The 50% inhibitory concentrations of the four sennosides were 17, 9, 24 and 13 μM, respectively, and the type of inihibition by sennosides A and B with respect to allylamine as the substrate was non-competitive.