Analytical Procedures for Determination of Quercetin and its Glycosides in Plant Material

Quercetin and its glycosides are widely distributed in the plant kingdom and belong to the most abundant of the flavonoid molecules. Besides their important biological roles in plant pigmentation, these flavonols possess anti-cancer and anti-inflammatory properties, which are the consequence of their affinity for proteins and their anti-oxidant properties. The content of quercetin and its glycosides in different plants have been summarized in various papers, although quantitative data are not so reliable due to the wide diversity of extraction and determination procedures. The general analytical strategy involves the isolation from a sample matrix followed by separation, identification and measurement. The recovery step usually involves solvent extraction using a range of solvents. Separation is commonly achieved by high-performance liquid chromatography (HPLC) and capillary electrophoresis. This paper intends to present and discuss the analytical procedures for determination of quercetinaglycone as well as its conjugatesin different plant materials by means of routine and more recently developed separation techniques. Selected applications are included to illustrate the scope and limitations of the various approaches.