A genus of mostly poisonous, tropical trees and shrubs of the dogbane family (Apocynaceae). Certain species are the source of valuable emetics and cathartics. The species Rauwolfia serpentina (see illus.) has received special attention as the source of tranquilizing drugs. For centuries in India the drug has been used in the treatment of hypertension. It came into use in Western countries because of its effect in reducing blood pressure.Although not a sedative, as that term is usually construed, it often has a quieting influence on the patient. Among the purified alkaloids obtained from R. serpentina, reserpine (Serpasil) is perhaps the one most used as a tranquilizing agent.