BACKGROUND
Breast cancer is a major cause of morbidity, mortality, and medical expenditures among women in Canada. Essiac (Resperin Canada Limited, Waterloo, Ontario, Canada), a blend of at least four herbs (burdock root [Arctium lappa], Indian rhubarb [Rheum palmatum], sheep sorrel [Rumex
Two sesquiterpenoids, mansonone E (ME) and mansonone F (MF) were first isolated from the dried root bark of Ulmus pumila (shironire in Japanese), and their antiproliferative activities on human tumor cells were evaluated in vitro. ME had more potent cytotoxic effects on four tumor cell lines, human