Herbs and herbal extracts are rich sources of biologically active compounds widely used in production of drugs, nutrition supplements, flavoring agents, repellents and cosmetics. Such complex samples usually contain tens or even hundreds of compounds possessing different physicochemical properties and multiple biological effects. One of the major group of compounds presented in herbs are polyphenolic compounds including both phenolic acids and flavonoidic natural antioxidants. For the separation and determination of the content of (poly)phenolic compounds in herb samples, several methods have been developed in this work. The liquid chromatographic methods based either on uni-dimensional reversed-phase separations employing columns packed with porous shell particles coupled to mass spectrometry, or based on combinations of liquid chromatography with capillary electrophoresis in multidimensional system were optimized to achieve high peak capacities for detailed characterization of the samples. In both systems, various silica-based stationary phases have been tested, including octyl, octadecyl, phenyl, phenyl hexyl, pentafluoro phenyl and polyethylene glycol chemically bonded functional groups together with optimized gradients of organic solvents and mobile phase additives. On-line liquid chromatography-micellar electrokinetic capillary chromatography experimental setup has been developed with the transfer of the fractions between both techniques via flow-gating microfluidic interface. Methods based on radical scavenging activity of the antioxidants (DPPH and ABTS) and methods based on ferric reducing antioxidant power (FRAP) were used for determination of the antioxidant capacities of selected seven species of herbs (i.e. elderberry, chamomile, linden, melissa, mint, nettle, sage). The polyphenolic profiles of the herb samples determined using developed separation methods and their antioxidant capacities, expressed as the Trolox equivalent antioxidant capacities (TEAC), show good correlation.

Complex characterization of herbs using high peak capacity liquid phase separations and the correlation with the antioxidant capacity

246th National Meeting (2013)

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