Stephen F. Austin State University

Plants are the primary source for many FDA approved drugs for cancers and some fatal infectious diseases. Dr. Shiyou Li and his research team at Stephen F. Austin State University have targeted native plants while most scientists focus their investigations on exotic plants, particularly those in tropical forests.

Researchers at SFA's National Center for Pharmaceutical Crops have recently isolated 25 new compounds from Red Buckeye, a small tree species common in the southeastern United States. One of these new compounds shows promising anti-tumor activities in 60 cell line tests conducted cooperatively at the National Cancer Institute.

Cancer is the biggest killer for Americans under the age of 85, Li said. Of 140 anti-cancer drugs available in western countries and Japan, most are either natural products or developed based on natural product leads.

"Plants are the obvious choice for further research, not only because they have an almost infinite variety of novel organic molecules, but also many compounds are structurally complex and difficult to synthesize," Li said. "Plants will undoubtedly continue to provide many of the new structures which will be used as templates for the construction of novel compounds with enhanced bioactivity by combinational synthetic techniques."

Texas is home to approximately 5,100 vascular plant species representing 203 families and 1,328 genera, which encompasses approximately 28 percent of the entire flora of North America.

Some Texas plants or related species in other countries have been used for cancer treatment in folk medicine, Li said. However, most of the native plants in Texas have never been systematically investigated for their chemical constituents and anti-cancer activity. Therefore, their potential medicinal value has been ignored by modern medicine, Li said.

According to Li, native plants were selected as research materials because they are readily available, easy to access, and can be easily developed as high-value crops.

"In addition to providing new bioactive agents, we believe that native plants could be a new source to secure valuable pharmaceuticals that currently rely on uncertain foreign supplies," he said. "Plants in our backyards could save our lives."

Red Buckeye has never been investigated for its medicinal qualities. In Europe and China, its sibling species have been used as astringent to treat diarrhea and hemorrhoids, as a stomachic and analgesic in the treatment of distention, for chest and abdominal pain, and in the treatment of malaria.

Recently, SFA researchers isolated more than 40 compounds, including 25 new ones, from the plant. These major new compounds, known as triterpenoid saponins, were initially tested in vitro by NCI for their activity against three cell lines of human lung cancer, human breast cancer, and human central nervous system cancer. Five similar compounds were selected by NCI for further in vitro tests and showed promising anti-tumor activity against 60 cell lines from nine different human cancers including leukemia, non-small cell lung, colon, central nervous system, melanoma, ovarian, renal, prostate, and breast, Li said.

A recent independent investigation showed one of these new anti- tumor agents, unlike existing drugs, does not damage normal liver cells but can effectively control the liver cancer cells at least in vitro tests.

A research paper describing the new structures and activity data will be published in an upcoming issue of Phytochemistry, a leading international journal of the Phytochemical Society of Europe and the Phytochemical Society of North America.

Li recognized Dr. Zhizhen Zhang, a research scientist at SFA, who was responsible for the isolation and structural determination of the new compounds.

"I really appreciate the support of U.S. Sen. Kay Bailey Hutchison and Congressman Louie Gohmert who secured federal funds for our research," Dr. Scott Beasley, dean of the Arthur Temple College of Forestry and Agriculture said.

The National Center for Pharmaceutical Crops at SFA is committed to discovering novel anti-cancer and antiviral drugs and to the development of new pharmaceutical crops for the production of pharmaceuticals, Li said.

The Center is one of the few medicinal plant research centers in the U.S. and the only one in Texas. Since 1993, SFA researchers have conducted extensive studies on the plant biology and crop development of Camptotheca. Funded by CDC, USDA, and other sources, SFA researchers have conducted pioneering research in identifying bioactive agents from native plants in Texas. To date, more than 1,000 species of vascular plants representing 138 families found in Texas have been collected and screened for the identification of antiviral and anti-cancer agents. Over 550 pure compounds, including 92 new compounds, have been isolated from 19 species.

Recently, SFA discovered a native plant as a new source of shikimic acid. A shortage of shikimic acid is the main reason for the global shortage of "Tamiflu," the drug for avian flu. Current natural resources in East Texas alone would produce a sufficient quantity of shikimic acid to meet the global Tamiflu demand.

Research at the Center has received strong support from SFA administrators and the local community.

According to Dr. Li, in the last three years, approximately $1 million has been awarded by CDC, USDA, and the Department of Education for anti-cancer and antiviral drug discovery from plants with the effort of Sen. Kay Bailey Hutchison.