Seeking secrets from Idaho sagebrush

Tue., March 3, 2015

Bill Roberts Idaho Statesman

A tenacious plant

Sagebrush first showed up in North America about 12 million years ago. The plant you see as you drive along Interstate 84 dates back 350,000 years, said Jennifer Forbey, associate professor of biology at Boise State University.

Sagebrush has a shallow root system to capture water that falls on the earth’s surface, but it also can send a tap root down 15 feet in search of water, said Marcella Fremgen, a graduate student in biology at Boise State.

The plant can develop two sets of leaves. Leaves in the spring and summer help turn the sun’s light into food but are also tempting to critters who dine on sagebrush, such as sage grouse. In winter, sagebrush makes leaves that are more toxic to foragers and help the plant withstand cold desert temperatures.

When animals such as pygmy rabbits or pronghorn antelope munch on sagebrush, the plant sends out a chemical SOS that some nearby plants receive and begin cranking out their own chemicals, making themselves less tasty to predators.

“It’s a great, big chemistry factory out here,” Fremgen said.

Please don’t eat the sagebrush

Sagebrush is fit for a few beasts, but not for man. Sage grouse and pygmy rabbits can eat it, but you shouldn’t, warns Carolyn Dadabay, a College of Idaho researcher.

Sagebrush has strong, toxic chemicals – which is why so few animals eat it – and can be dangerous to people too, she said.

Carolyn Dadabay is a drug prospector.

She’s searching for chemical compounds that will boost the effectiveness of medicines like those used to attack cancer cells in chemotherapy.

She hopes to find them among the millions of sagebrush plants dotting the desert of Southern Idaho. Wild animals are her guide.

“We are the center of sagebrush diversity,” said Dadabay, an associate professor of chemistry at the College of Idaho in Caldwell, where she has taught for the past decade.

Sagebrush, a plant many never give a second thought to as they drive across Southern Idaho, is a powerhouse of chemicals. Each plant carries hundreds of different compounds – some in strong doses – developed over millions of years to help the plants withstand grazing animals, harsh desert conditions and exposure to ultraviolet light from the sun.

“Sagebrush makes the best chemist in the world,” Dadabay said.

She squeezed sagebrush research into her summers and spare time until June, when she was awarded a five-year, $764,000 grant from the Idaho Institutional Development Award Network for Biomedical Research Excellence. The network will distribute $16.5 million in National Institutes of Health money over the next five years in Idaho, said Carolyn Hovde Bohach, a University of Idaho professor of microbiology in the food science school, who oversees the network.

One of the goals is “to study a real problem or try to answer a real-world problem and try to engage students in it,” Bohach said.

Dadabay uses several undergraduate students to help gather sagebrush samples and process them to extract chemical compounds for study.

She and a couple of her students spent a recent afternoon at Bonneville Point, 10 miles east of Boise, snipping samples of sagebrush to take back to the Dadabay’s lab.

All sagebrush isn’t equal. Some varieties have more and different chemical compounds than others.

Pygmy rabbits, sage grouse and pronghorn antelope – which dine on sagebrush regularly – seem to sense chemical differences and stay away from plants with chemicals that may be too strong or that could stay in their systems long enough to harm them.

Wildlife eat different parts of sagebrush. Pygmy rabbits chomp on leaves and stems, said Jennifer Forbey, an associate professor of biology at Boise State University who is working with Dadabay. Sage grouse only eat the leaves, because they can’t break the stems with their beaks. Many critters cannot tolerate the chemicals and leave sagebrush alone.

Bite marks, bird droppings or other evidence that wildlife has fed – or not fed – on a sagebrush plant give Dadabay and her students clues to a bush’s strength of chemicals.

“Sagebrush has gotten to be such a good chemical producer that it now produces chemicals, we think, that actually prevent animals from getting rid of the toxins,” providing a defense against the plants being eaten, Dadabay said.

That could help cancer victims undergoing chemotherapy. As cancer becomes more aggressive, cancer cells develop better ways of rejecting medications. “If we can find the chemicals in sagebrush that prevent animals from spitting the drugs back out, they would also prevent cancer cells from spitting the chemotherapy out,” Dadabay hypothesizes.

In the lab, Dadabay pours super-cold liquid nitrogen on sagebrush leaves to keep them crisp while students grind them up with mortars and pestles. Students put the crushed leaves into a tube along with a solvent. Some of the crushed leaves’ chemicals dissolve into the solvent. The mixture is placed in a drying machine where the solvent is evaporated, leaving the chemical. A tiny bit of solvent is added back to create a concentrated solution that is used for analysis.

Dadabay and her students have found some promising leads that could lead to slowing drugs’ exit from the body.

Dadabay says her work could go well beyond looking for chemicals to keep chemotherapy in the body for longer periods. Researchers might find new antibacterial compounds to fight bacteria that are adapting to existing antibiotics. One relative of the sagebrush in Asia has yielded one of the world’s foremost weapons against malaria, she said.

If Dadabay finds the right chemicals, her work could open the Idaho desert for cost-effective drug prospecting using animals.

“It will be a new way of doing drug discovery,” she said.