Antioxidant Flavonoid Glycosides

In this thesis the chemical composition of heartsease (Viola tricolor L.) was studied to support the evidence-based determination of its biological activities. Henceforth, a proper sample preparationmethodwas developed, yielding a fraction rich on polar constituents (characteristic of the traditionally applied aqueous extract), which was further separated by conventional Sephadex LH-20 column chromatography. HPLC-UV analysis of the fractions suggested that the two main flavonoid components had been successfully isolated. They were definitly identified by LC-MS and NMR studies as violanthin (6-C-glucosyl-8-C-rhamnosyl apigenin) and rutin (3O-rhamnoglucosyl quercetin) (1). Furthermore, sixteen of the minor flavonoid components (C-glycosides, O-glycosides and C,O-glycosides) were tentatively identified by nanoLC-MS (2). Although violanthin could not be quantified in the lack of a commercially available reference molecule, rutin was quantitatively determined by HPLC with UV detection ((0.42± 0.01)%). The antioxidant capacities (electron-donor and hydrogen donor activities) of the fractions were determined by the TEAC and DPPH assays, respectively. In respect to their antioxidant properties, the highest electron-donor capacity was measured with rutin, and a fraction enriched on flavonoids exhibited the highest hydrogen donor activity (1). Garden pansies (V. x wittrockiana Gams.) are plants of complex hybrid origin. In this thesis, beside a comparative HPLC study, the anthocyanidin and flavonoid contents as well as the antioxidant capacities of garden pansies of different petal color and heartsease were compared.The anthocyanidin and flavonoid contents of the samples were quantified by spectroscopic methods registered in the European Pharmacopoeia 5.0. While the highest anthocyanidin content was measured in the violet flower sample, the white and yellow pansy samples showed the highest flavonoid content. The antioxidant capacity of the samples was determined by the TEAC assay. The heartsease and pansy samples were observed to be as good antioxidants as the well-known ginkgo leaf. In addition, significant correlation was found between the flavonoid content and the antioxidant capacity of the samples (3). (1) V. Vukics, A. Kery, G. K. Bonn, and A. Guttman. Major flavonoid components of heartsease (Viola tricolor L.) and their antioxidant activities. Anal. Bioanal. Chem., 390:1917–1925, 2008. (2) V. Vukics, T. Ringer, A. Kery, G. K. Bonn, and A. Guttman. Analysis of heartsease (Viola tricolor L.) flavonoid glycosides bymicro-liquid chromatography coupled to multistage mass spectrometry. J. Chromatogr. A, 1206:11–20, 2008. (3) V. Vukics, A. Kery, and A. Guttman. Analysis of polar antioxidants in heartsease (Viola tricolor L.) and garden pansy (Viola x wittrockiana Gams.). J. Chrom. Sci., 46:823–827, 2008.