Madagascar Periwinkle (Catharanthus roseus) also known as the Rosy Periwinkle, an important medicinal plant. In Madagascar and South Africa it has been used to treat diabetes, indigestion and constipation. It is the source of the alkaloids vinblastine and vincristine. These chemicals have been developed into highly effective chemotherapy treatments for various cancers including Hodgkins lymphoma, lymphatic leukemia, testicular cancer, and childhood leukemia.