Returning to campus from expeditions in the forests of South and Central America, a team of Cornell University undergraduate science students is applying modern analytical techniques to learn the chemistry behind the nature-based medicinals that work for native peoples -- and which someday may find a place on our druggists' shelves, too.

"We haven't identified these plants with their scientific names yet, so we're labeling them with the Piaroa Indian names -- like tŸŸ dau, their plant to treat inflammation from ant bites, or cuo mariche, for bloody diarrhea," explained Patricia Luckeroth. "One of their plants is prescribed both for lice and dandruff."

The College of Agriculture and Life Sciences junior majoring in botany from San Juan, Puerto Rico, was one of 14 students spending last summer in the Amazon rain forest of Venezuela. Others trekked to the drier but equally intriguing forests of the Mexican Yucatan, where the ancient herbal tradition of the Mayans offers hope for 21st century ills.

Hundreds of miles from any major city, at a former ecotourism resort called Yutaje on a tributary of the Orinoco River, where Cornell's Eloy Rodriguez, the James Perkins Professor of Environmental Studies, hopes to establish a scientific field station, analytical chemistry doesn't come easy. In rain forest-style chemistry, TLC stands for thin-layer chromatography, a low-tech but portable method that gives a rough idea of the compounds student-ethnobotanists are finding in extracts of the plants.

For now, at least, more precise analysis of their promising findings must await the return to the laboratories at Cornell, where state-of-the-art (and energy -hungry) equipment does not rely on electricity from a sputtering gasoline-fueled generator.

The list of plant medicinal uses that the students chronicled from the Piaroas gives some idea of that people's medical priorities -- and also of the perils faced by the student field workers: Skin fungi, diarrhea, snake bites and muscle injuries all have effective, plant-based treatments in the Piaroa tradition. So do ant bites (by the inch-long and aptly named 24-hour ant whose venom inflicts agony for at least a day), asthma, bone fractures and leismanaisis (the disfiguring skin disease that starts with the bite of a mosquito that previously bit an infected mouse).

"My dad said, 'Just be cautious,'" Leslie Esterrich said, recalling her announcement of plans to spend the summer conducting research in the Amazons of Venezuela. Until then, the most adventurous summer vacation for the Vienna, Va., junior in the College of Arts and Sciences had been a pre-med program at the University of Virginia Medical School.

"We learned not to touch things we weren't familiar with and to look before you jump," Luckeroth said of the orientation the students received in Caracas before setting out for Yutaje, where the life lessons continued. Snakes of the Amazon are one thing, she knew already, but even the prettiest caterpillar can bear a painful skin irritant. Her research will now focus on shigas, a weedy legume that grows along river banks where the Piaroa harvest its seeds for bread. Shigas, she said, appears to have antibiotic properties, and if so, that will be news to science: Until now the legume has been little-known in the scientific literature except for its nitrogen-fixing capabilities.

Support for the student study in Venezuela and Mexico was provided by the Minority International Research Training Program of the National Institutes of Health. The students already have reported preliminary findings at a national scientific meeting, sponsored by the Society for the Advancement of Chicanos and Native Americans in the Sciences (SACNAS). Travel funding to the Los Angeles meeting was provided by Cornell's Latin American Studies Program, Mario Einaudi Center for International Studies, College of Agriculture and Life Sciences, SACNAS and the Howard Hughes Foundation through the Cornell College of Arts and Sciences.

For Jesus Verduzco, a sophomore environmental systems technology major from Brownsville, Texas, his research site was not so remote, "only" an hour and a half into the coastal forests from the Yucatan city of Merida. There he collected insects, algae and plants. One plant is of particular interest, Asclepias currasavica, which Indians use to treat "external cancer," he said, noting that Mayans do not distinguish between true cancers and skin lesions that are slow to heal. That plant, too, may have antibacterial properties -- a possibility he plans to explore with additional bioassays at Cornell.

One update that Rodriguez envisions for the palm-thatched field station in the Amazon is a satellite uplink, so that researchers who find an unknown species of plant can transmit digital images for identification by expert taxonomists at Cornell. That way, the plant collectors will know almost instantly whether cuo mariche, for example, is a new-to-science plant and whether they should look for related species in the same area.

Last summer's field experience already is changing the career plans of some students. Esterrich, the animal-physiology student who collected Amazon plants in the Costus family to test for steroid precursors after learning that indigenous women use the plants as contraceptives, now is considering graduate study in tropical medicines and pathology. Or maybe a dual M.D.-Ph.D. program. Maria DeJoseph, a sophomore from central New York who traveled to the Yucatan, wants to pursue a Ph.D. in pharmacology, chemical ecology or ethnobotany.

"The Yucatan trip changed my life," DeJoseph said. "It opened my eyes to a whole new world, culturally as well as scientifically."

With the encouragement of Rodriguez, a pioneer in the field of zoopharmacognosy (the study of natural medicines used by animals), the students are taking ethnobotany (the study of plants used by people) one step further. They are trying to discover how animals' use of medicinal plants is incorporated into human medical tradition. One example is the rinds of citrus plants that capuchin monkeys rub on their fur to control mite and flea infestations.

"Those monkeys are not just playing with their food. That plant really seems to work for them, and maybe we can learn to use it, too," Esterrich said.

The students are not adverse to trying the folk remedies themselves. Verduzco reports success in treating a badly infected insect bite on his arm with a plant used by the Mayans.

And Esterrich learned to chew Costus plant stems for moisture when her canteen ran empty or when nausea relief was needed, and she marveled at the multiple uses of a single plant.

"Only later was I told that the same plant reduces inflammation from insect bites," she said, "if you rub it on your skin."

Now all they have to do is find out why.