Planta Med 2011; 77 - PA29
DOI: 10.1055/s-0031-1282225

Study of electrooxidation mechanisms and antioxidant properties of flavonols and flavonolignans

J Ulrichova 1, M Zatloukalova 1, V Kren 2, J Vacek 1
  • 1Institute of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
  • 2Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague

Flavonoids are a large group of naturally occurring polyphenolic compounds that are distributed in vascular plants. A wide range of the biological activities are attributed to flavonoids' antioxidant abilities. Flavonoids are benzo-γ-pyrone derivatives that can be divided into several groups according to their structural differences. Here we focused on quercetin, silybin and their derivatives which belong to the group of flavonols and flavonolignans, respectively.

We described basic aspects of electrooxidation of flavonols and flavonolignans at a pyrolytic graphite electrode using cyclic and square wave voltammetry. Flavonols (quercetin, rutin and isoquercitrin) and flavonolignans (silybin, 2,3-dehydrosilybin, 7-O-methylsilybin, 20-O-methylsilybin and isosilybin), were studied in an adsorbed state using ex situ (adsorptive transfer – AdT) voltammetric methods. Under the given conditions, flavonols and flavonolignans are subject to a multistep oxidation. The potential of the oxidation of hydroxy groups and other substituents corresponds with antioxidant properties of studied polyphenols.

Using ex situ voltammetry, the following order in antioxidant capacities was proposed: flavonols >>2,3-dehydrosilybin > silybin and its derivatives. The results provide a solid basis for further study of both the antioxidant and prooxidant parameters of polyphenolic compounds using voltammetric methods and extend our knowledge of their electrooxidation mechanisms.

Acknowledgement: This work was supported by the Czech Science Foundation (Grant Projects No. P503/11/P312 and P301/11/0767), by the Ministry of Education, Youth and Sports (MSM 6198959216).