'Hunting for a needle in a haystack'. This is the analogy used by scientists at the Fraunhofer Life Sciences Alliance to describe the task faced by chemists hunting for pharmacologically useful ingredients in natural plant extracts.
Out of the several hundred substances in the complex mixture, scientists have to find the one responsible for the therapeutic action. The traditional way is to classify and separate similar compounds in groups of decreasing size. Each individual element is finally isolated and identified and the compound eventually reveals its identity through repeated separation and analysis.
Researchers in the Alliance now claim to have developed a technique to speed up and systematize this chemical discovery process. It uses three combined analysis techniques, and is referred to by the abbreviation HPLC-NMR-MS.
"In the HPLC or high-performance liquid chromatography stage, the complex mixture is separated as far as possible," explained 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 - 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 the software may suggest approximate identities.
"This is precisely the advantage of our threefold method," emphasized Preiss. "It allows us to even identify unrecorded substances."
Preiss says the team has already demonstrated the powers of its method in several projects, citing a collaboration with Schwabe in Karlsruhe, a manufacturer of herbal medicines, where they have investigated natural extracts and identified previously unknown compounds.
The method can also be used in other areas besides drug research, adds Preiss. In environmental monitoring for instance, screening samples lead to a catalogue of pollutants in soil, groundwater, or even a haystack. Such tests, they add, are an important aspect of toxicological studies to assess risks to human health and the environment.
For further information contact Dr Alfred Preiss.