San Antonio Zoo in Texas has a Rare Tree that is Used to Fight Cancer

by Liliana Usvat

Finding effective way to block the forest loss and start the process of forest plantation we are showing the uses of different types of trees for medicine and human health. We try to uncover the lost knowledge about different species of trees and how to plant and where to plant them.


Texas Zoo Tree

A rare tree growing at the San Antonio Zoo is being used by a Texas A&M researcher and professor to help scientists fight cancer.

The tree came to the United States through Chico, Calif., around 1920, says McKnight. Late chemist Monroe Eliot Wall discovered its cancer-fighting properties in the late 1960s. The one in San Antonio is believed to the grandchild of the Chico tree.


The tree is native to China and not otherwise found naturally in the U.S., so the full-time team of horticulturists at the zoo works to keep it thriving.


Since the 1990s, Thomas McKnight has traveled from Texas A&M to the San Antonio Zoo once a year to harvest seeds from the Camptotheca acuminata tree. The seeds look like miniature bananas, only they’re about an inch long.

Derivaties from the tree are used to formulate a second-line cancer drug called camptothecin, which McKnight says is helping fight certain forms of gynecological cancer.Camptothecin is used in combation with other therapies to combat ovarian, cervical, uterine cancer, plus some forms of lung cancer, according to McKnight.”The drug is very toxic out of the tree so it has to be modified,” says McKnight. For a tree that is so valuable to scientists, McKnight says it isn’t remarkable to look at. “The tree is out in the open and not very distinguished from the others,” says McKnight. “It’s not a very pretty tree. The wood doesn’t have much strength.”

Happy Tree

McKnight says the tree doesn’t have a common name, as it is so rare, but to some it is simply called the “happy tree” for brevity.


“It has no redeeming features except that it fights cancer,” McKnight says.

McKnight is not a doctor, so his work is far removed from the clinical groups that are working on the drugs.

The level of the drug in the seeds is very low and McKnight advises against people attempting to ingest the seeds.

Camptotheca acuminata “Happy Tree,”

The plant grows quickly to about 75 feet high and can make a canopy about 40 feet wide! Fortunately, it can be pruned back without damage. It is a deciduous tree in the Tupelo family (Nyssaceae). Its branches are reported to grow only near the top of the tree.

  • Parts of the “Happy Tree” have been used from times of antiquity to the present day in traditional Chinese medicine to provide treatments for ailments as diverse as psoriasis, liver and stomach ailments, and common colds. It is also used to treat leukemia. This latter use led to scientific study to determine if there actually was an anti-cancer compound in C. acuminata. The cancer-fighting properties were first verified in 1958 by Dr. Monroe E. Wall of the USDA and Jonathon Hartwell of the National Cancer Institute in the United States.
  • The active ingredient in the plant was found to be Camptothecin (a pentacyclic quinoline alkaloid). The stem bark, root bark, and seeds can yield trace amounts of Camptothecin, but the highest concentrations may be in the tender young leaves. Camptothecin and its analog compounds can inhibit the nuclear DNA topoisomerase I enzyme and has the effect of interrupting the replication and transcription of cancer cells.
  • Camptothecin is not water-soluble and can be highly toxic, making it difficult to administer as a medicine.
  • The harvesting of C. acuminata for the pharmaceutical industry has decimated the population of the endemic trees in China. The tree may now be considered as “Endangered” by the government of China and export is severely restricted. It is estimated that less than 4,000 of the trees remain in the wild in China.
  • In June 2000, an abstract discussing efforts to grow C. acuminata in Louisiana as a silviculture crop to supply raw materials to the pharmaceutical industry was presented at the U.S. Forest Product Society’s 54th Annual Meeting. It is not known if the plan to commercially cultivate C. acuminata was implemented.
  • One source stated that all the C. acuminata trees in the United States came from the seed of two trees imported by the USDA in the 1900’s

Plant Grow

It grows super-fast in warm, humid areas, such as the American Gulf Coast . It does not like to dry out but with plenty of water and heat and sun, you will have a first-rate shade tree 3 to 5 years.

It is an attractive Chinese native related to the Tupelo family of trees (Nyssa). It is commonly called False tupelo, or Camptotheca acuminata. It is a lovely medium to large tree that is an excellent choice for a fast growing shade tree in warm regions. And it would be a particularly good choice on new lots where a leafy ornamental would be so appreciated. The lush, rich green leaves with deep veining are oval shaped with an elegant taper. They are slightly toothed and emerge with a red blush in spring.

Medicinal Uses in a Nondestructive Manner

The Chinese people have used Xi Shu or Happy Tree  for thousands of years. They use the plant for treating intestionial problems, stomach conditions, and skin diseases. They also use it for soothing sore throats and colds.

Xi Shu – (Camptotheca acuminate) – Xi Shu is also known as Cancer Tree, Happy Tree, Heaven Tree, Dragon Tree, and Tree of Joy. Native to China and Tibet, most American specimens of the plant originate from just two seeds germinated here in the 1930’s. Xi Shu is used in herbal medicine for treating cancer, psoriasis, and diseases of the liver, gallbladder, spleen, and stomach.

Xi Shu is used as a treatment for many kinds of cancers including leukemia. The plant is known to be effective in the treatment of rectum and large intestine cancer. Xi Shu can inhibit cell division and DNA replication which can slow tumor growth. Many other anticancer medications are derived from Xi Shu and two are approved by the U.S. Food and Drug Administration. Topotecan is used to treat ovarian and small lung cancers. Irinotecan is used to treat metastatic colorectal cancer. Xi Shu may prove to be a lifesaver for thousands of cancer patients around the world.

This fast-growing, attractive “Happy Tree” of northern China is currently being grown at Louisiana State University’s (LSU) Agricultural Center’s Experiment Station. The expense of extracting and shipping medicinal Xi Shu compounds from China averages $35,000 per kilogram, but LSU researchers hope to cultivate the tree in Louisiana.

The state’s climate matches northern China’s and 5,000 trees have been grown successfully so far. (LSU researchers see this as a model for a program to research other medicinal plants.) The trees are also being grown in Texas.

Xi Shu wood, bark, leaves, and fruit are all used in herbal remedies. Medicinal compounds are especially concentrated in the young, developing leaves and may actually poison livestock due to the high level of active ingredients.

The herb can be purchased in various forms and is often an ingredient in over-the-counter Chinese medicines.

Over a 12-week period, new growth was collected at different intervals from Camptotheca acuminata trees to determine whether a leaf harvest strategy would be an efficient means for the production of the alkaloid camptothecin. Because camptothecin accumulates in young leaves and because the harvesting of young tissue stimulates axillary bud outgrowth, this strategy increased the harvestable amount of camptothecin from trees in a nondestructive manner.

Blog 65-365


About lilianausvat

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