Class does chemical prospecting in semester-sized bites

From left, instructor John Berry, junior Joey Sager, sophomore Yanerys Ramos and Professor Eloy Rodriguez examine plants for medicinal properties in a lab in the Biotechnology Building. Charles Harrington/University Photography

By Roger Segelken

The scientific experiments were real, designed by the undergraduate students themselves and performed, in many cases, for the first time anywhere. The experimental materials were authentic, gathered from rain forests in South America and Africa, where exotic diseases and the medicinal plants that cure them thrive side by side. And the experiments' results would be published in a technical journal and reported at a poster session, as befits cutting-edge science.

Only the time frame was unrealistic. Students in BioG 442, Microbial Assays in Chemical Prospecting, had one semester to complete experiments that can take years in the laboratories of pharmaceutical companies.

Of course some students had a significant head start for the class, which teaches laboratory methods for determining effects of natural chemicals on disease organisms. George C. Hunter, for example, spent the previous summer in a Yekuana Indian village in the Venezuelan rain forest, eating the same indigenous foods he was studying, through a Cornell-based program in ethnobotany field work. The senior's field work showed him that the Yekuana children's diet kept them remarkably healthy, and the microbial assay class was his chance to discover why.

Tiffani Rogers, a senior, also had rain forest experience on her resume. Her field work took her up close and personal with 35 species of ants -- including some of the world's most aggressive -- and she used the laboratory class to explore the chemistry behind myrmecophyte relationships, the mutually beneficial relationships some ants have with plants.

Taught by Eloy Rodriguez, the university's Perkins Professor of Environmental Studies and a researcher known for explaining why primates use medicinal plants, and by John P. Berry, a recent Ph.D. graduate of Cornell who studies African mountain gorillas and the plants they seek, BioG 442 is a hands-on class from day one. Students learn the techniques of chemical prospecting by performing them, extracting compounds from their plant and animal samples and analyzing them with thin layer chromatography and other techniques. They learn and promptly try a virtual arsenal of assays -- including disc diffusion, minimum inhibitory concentration, vinegar eel motility and protease inhibitor assays -- to test natural materials for antibacterial, antifungal and antiparasitic activity.

And they pay special attention because any of the newly learned techniques could be the key to success in the experiments they are designing. Some of the projects take on a particular urgency. Lori Dolinger , a junior, examines microbiological activity in the Ugandan herbal preparations used to treat AIDS symptoms. Sophomore Linda Good-man tackles antimicrobial and antiparasitic activity in plants of South America, where malaria is making a horrific comeback.

Some of the lab techniques don't work the first time, no matter how diligently applied, or even the 15th time. Scientific experimentation on the biomedical frontier is like that, the students are discovering. As the Dec. 3 poster session approached, some results remained maddeningly allusive. "Don't worry," Berry told his students. "Report what you have found."

In the main conference room of Cornell's Biotechnology Building, the scene resembled poster sessions convened by distinguished scientists, although these investigators are younger and frequently better dressed. The task of cramming all the hard-won information onto posters was tougher than battling Amazon mosquitoes, the students agreed, and they nervously endured the scrutiny of learned scientists and "celebrity judges" who perused their work.

An announcement by Professor Rodri-guez broke the tension with two pieces of good news: The fieldwork sites for upcoming expeditions in chemical prospecting had been selected, and students in this laboratory course have an inside track on the coveted, all-expenses-paid research opportunities. Furthermore, the first issue of the world's only journal of undergraduate research in chemical prospecting, Emanations from the Rain Forest, is going to press, Rodriguez said, waving a printer's proof copy. And the best of the studies conduced in BioG 442 will be reported in the second issue.

Then the poster-judging resumed. After the examinations, the results were announced. Yanerys Ramos, a sophomore, was a runner-up with her project, "Medicinal Use of Lobelia wollastonii by Gorilla gorilla beringei." So was junior Jennifer Louis-Jacques for "Chemical Analysis of the Uropygial Gland Secretions from 3 Neotropical Bird Species." And the winner was ... Stephen deSouza, a junior, with "Investigation of the Chemical Defenses Against Insect Herbivory in Young and Mature Leaves."

In one Cornell semester, deSouza's experiments had shown that insects are more likely to eat mature leaves, compared with younger ones, and he made a start at determining the chemistry involved. He had failed to detect any antimicrobial or anti-protease properties of the plants, he admitted, and he couldn't be sure the phenolic chemicals he found really were repelling the insects.

That next step will require further experiments. DeSouza can't wait to get started.