Chiral flavonoids: Methods of enantioseparation and extraction of polyphenol mixtures

Natural products have many health benefits that gives a potential to use them in prevention and treatment of various diseases, particularly so-called diseases of civilization. Special properties of that products are related to action of biologically active compounds contained in them, e.g., polyphenols. However, natural compounds, as well as synthetic ones, like drugs, may occur in different isomeric forms, among others, as optical isomers. Opposite enantiomers may expose completely different biological activity. Moreover, in some cases they can undergo a conversion processes, e.g., during raw material processing to obtain final product. That all results in the need for the determination of particular enantiomers content. It can be obtained by the use of enantioseparation methods, especially the chiral chromatography. This chapter summarizes the described in literature chromatographic methods for the determination of the enantiomers of flavonoids with one stereogenic center. Methods available for simultaneous determination of enantiomers of few compounds within the group seem to be especially valuable. These compounds often occur in plant material in the presence of each other, so such methods are time- and cost-effective. Additionally chapter contains also a comparison of polyphenols extraction methods from plant material, as well as methods for purification of obtained extracts and final determination of polyphenolic non-chiral compounds contained in them.