Besides sennoside A, sennosides B, C, E and F were isolated from rhubarbs. Sennosides E and F are new compounds and have comparable purgative activity to other sennosides. Sennosides E and F are stereoisomer mutually, and they are oxalates of sennosides A and B, respectively. Although sennoside A was able to be isomerized to sennoside B irreversibly, the plant contained more of the former.
