Camptotheca acuminata is a member of the family Nyssaceae (tupelo family) and is native only to China and Tibet, where it is known as xi shu ("happy tree"). Its primary anti-cancer ingredient is a quinoline alkaloid called camptothecin, which in turn has been modified to create a host of other anti-cancer drugs, including irinotecan, topotecan, 9-aminocamptothecin, and CPT-11. Camptothecin and these analogs are being investigated to treat a wide variety of cancers, but the compounds are quite toxic, and only topotecan (Hycamtin®) and irinotecan HCl (Camptosar®) have met with FDA approval; Hycamtin® has been approved for ovarian cancer theray, and Camptosar® is approved for metastatic colorectal cancers.

Western researchers (Dr. Monroe E. Wall of the USDA and Jonathon Hartwell of the National Cancer Institute) first discovered Camptotheca's anticancer properties in 1958. In 1966, after Wall joined the Research Triangle Institute, he and other researchers isolated camptothecin. A camptothecin analog (camptothecin sodium) was tested on gastrointestinal cancer patients in the early 70's, but the clinical trials were discontinued because the patients suffered severe side effects. Researchers continued to investigate camptothecin to develop drugs with fewer side effects, and their work began to bear fruit in the late 80's. In China, camptothecin has been used to treat leukemia and cancers (carcinomas) of the stomach and liver.