Infrared Spectroscopic Technologies for the Quality Control of Herbal Medicines

The properties of herbal medicines are related to certain classes of compounds such as alkaloids, flavonoids, essential oils, and others. During the last four decades, near-infrared (NIR) spectroscopy (800–2500 nm; 12.500–4.000/cm) has become one of the most attractive and widely used methods for analysis rather than traditionally applied separation methods (including liquid chromatography and electrophoresis) for the following reasons: NIR spectroscopy is a noninvasive analytical tool allowing a fast and simultaneous qualitative and quantitative characterization of herbal medicines and their constituents. Infrared imaging techniques are becoming more and more attractive to understand the function and the biochemical composition of plant tissue. In this contribution, the principle, technique, and methodology are described, followed by a discussion of quantitative and qualitative application possibilities. Finally, some hints to helpful regulatory issues are summarized.