Identification and quantification of valuable plant substances by IR and Raman spectroscopy

This review presents various infrared and Raman spectroscopic methods applied to the analysis of valuable plant substances or quality parameters in horticultural and agricultural crops. In most cases, vibrational measurements can be performed directly on plant tissues as well as on fractions isolated from the plant material by hydro-distillation or solvent extraction. Generally, both spectroscopy techniques allow to obtain spectra which present some characteristic key bands of individual components. These bands provide information about the chemical composition, including both primary and secondary metabolites, of the investigated samples. Furthermore, based on such markers related to individual plant substances, spectroscopic analyses in principle allow the discrimination of different species, and even chemotypes among the same species. Combination of vibrational spectroscopy and hierarchical cluster analysis provides a fast, easy and reliable method for chemotaxonomy characterization. In most presented cases, determination of main plant components applying the PLS algorithm results in comparatively high R2 and low SECV values. The ability to rapidly monitor various plant components makes it possible to efficiently select high-quality single plants from wild populations as well as progenies of crossing experiments. Furthermore, the vibrational spectroscopy methods can also be used by the processing industry in order to perform fast quality checks of incoming raw materials as well as continuous controlling of the production.