Pitzer in the News 2005-2006 Academic Year

Joint Science Professor Thomas Poon in Atlanta Journal

A higher purpose for sweetgum balls

By MIKE TONER
The Atlanta Journal-Constitution
Published on: 03/30/06

Sweetgum balls — those prickly, prolific seed pods of the sweetgum tree that are the bane of barefoot living throughout the South — may have a redeeming feature after all.

Scientists have discovered that the seeds of the sweet gum are rich in shikimic acid, the starting ingredient for making antiviral drugs to combat bird flu.

For years, homeowners and arborists, who love the stately tree but hate its profusion of spiky fruits, have racked their brains to find some use for the pesky, prickly gumballs, the urban forest's counterpart to the spiny sea urchin.

Some people make holiday wreaths from them. Some paint them and glue them into gumball snowmen. Some people just make mulch of them. And some settle their grudge with the sweet gum with a chain saw.

Now the threat of bird flu offers a glimmer of opportunity, albeit still just a potential one. Researchers at the Claremont Colleges in California told the American Chemical Society meeting in Atlanta on Wednesday that the seeds of the sweet gum tree are surprisingly rich in the amino acid that drug companies need to manufacture the active ingredient in Tamiflu, now being stockpiled throughout the world as a defense against the H5N1 avian flu virus.

"The primary source of shikimic acid is now the seeds of star anise," says Thomas Poon, a chemist at Claremont McKenna, Pitzer and Scripps Colleges.

But Poon says star anise, a licorice-flavored ingredient of Chinese five-spice powder, is in short supply and getting scarcer. Spice merchants report that the price of star anise has risen 30 percent since Swiss pharmaceutical company Hoffman-LaRoche began increasing its production of Tamiflu.

Roche made 55 million doses of the antiviral drug this year, but the company is aiming to produce 400 million doses by 2007. Some of the tightening supply of star anise is a result of drug-related purchases, but some also is due to hoarding in China by people who believe, incorrectly, that the anise seed itself will protect them against bird flu.

Star anise seeds sell for about $1.70 a pound in bulk. Due to the cost of extraction and purification, research quality shikimic acid, the starting material for the synthesis of the antivital agent oseltamivir, fetches about $1,600 a pound — sufficient, after processing, to treat several hundred people.

The Taiwanese government late last year reportedly signed a contract with an unidentified supplier for three tons of shikemic acid, believed to be sufficient to produce enough of the drug for 2.3 million people.

Shikimic acid, ironically, is found in the bark and leaves of nearly all green plants, but only in low concentrations.

"Because large quantities are going to be needed, we decided to see if there was something widely available that might yield useful quantities of shikimic acid," Poon said. "There were a lot of sweetgums growing on our campus, so we decided to try them."

So far, Poon and his students, using a kitchen blender, filtration and distillation to extract shikimic acid, have squeezed the equivalent of about an eighth of an ounce from a pound of sweetgum seeds, only about one-third of the yield drug companies get from a pound of star anise.

"The difference is that sweetgum trees are found in at least 39 states, and each tree bears thousands of seedpods every year," says Poon. "There are a lot of sweetgum seeds out there."

"A lot" understates the potential gumball bounty. The U.S. Forest Service estimates that a single bushel of the spiny husks contains an average 82,500 seeds, or nearly a pound of the stuff.

And once a sweetgum starts reproducing at around 20 years of age, it doesn't quit. Sweetgums can bear seeds — inside those pesky gumballs — until they are 150.

As enthusiastic as he is about the sweetgum tree's potential contribution to world health, Poon has a word of caution for anyone who has visions of a gumball gold mine littering their lawn.

"It's the seeds that are rich in shikimic acid," he says. "And to get the seeds before they disperse, you have to get the husks while they're green. You have to harvest them when they're still hanging on the tree."

(Note: This article also appeared on numerous websites and in various newspapers around the world)