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Finding the needle in a chemical haystack

July 25, 2003

Imagine you're standing in the middle of a crowded square, and you've been asked to find one particular person. But all you know is that he or she speaks a specific dialect. A similar situation is faced by chemists hunting for pharmacologically useful ingredients in natural plant extracts. Out of the several hundred substances in the complex mixture, they have to find the one responsible for the therapeutic action. The traditional way is to classify and seperate similar compounds in groups of decreasing size, rather like subdividing languages into local dialects. Each individual element is finally isolated and identified. As talking to the different methods, the compound reveals its identity through repeated separation and analysis.

Researchers in the Fraunhofer Life Sciences Alliance have developed a technique to speed up and systematize this chemical discovery process. It uses three combined analysis techniques, and goes by the abbreviation HPLC-NMR-MS. "In the HPLC or high-performance liquid chromatography stage, the complex mixture is separated as far as possible," explains Dr. Alfred Preiss of the Fraunhofer Institute for Toxicology and Experimental Medicine ITEM in Hanover. The resulting fractions, usually containing numerous very similar compounds, are then analyzed using mass (MS) and nuclear magnetic resonance (NMR) spectroscopy. MS reveals the mass of the molecules and its fragments. NMR measurements give a picture of the molecular structure, i.e. the bonds between atoms or groups of atoms. Each method supplies a different but complementary set of data. Known chemical compounds can be identified by their distinctive signatures, which are recorded in standard databases. For unknown substances software may suggest approximate identities.

"This is precisely the advantage of our threefold method," emphasizes Dr. Preiss. "It allows us to even identify unrecorded substances." The scientists have already demonstrated the powers of their method in several projects. In collaboration with Schwabe in Karlsruhe, a manufacturer of herbal medicines, they have investigated natural extracts and identified previously unknown compounds. The method can also be used in other areas besides drug research. In environmental monitoring for instance, screening samples lead to a catalogue of pollutants in soil, groundwater, or even a haystack. Such tests are an important aspect of toxicological studies to assess risks to human health and the environment.

Fraunhofer-Gesellschaft