engleski

Voltammetric characterization of carotenoids in aqueous media

Carotenoids are responsible for the coloration of many plants and fruits. They possess potential membrane antioxidant activity due to their reactivity with singlet oxygen and oxygen free radicals which can prevent oxidative damage and offer protection against various diseases. So far, electrochemical investigations of carotenoids have been performed in non-aqueous media [1] with the notable exception of some studies in micelle systems [2] and as self-assembled monolayers (SAM) in aqueous phase [3]. Such conditions are closer to the natural carotenoid surrounding in the living cell and offer the opportunity to ascertain the effect of different factors e.g. pH, ion content etc. Because of that, development of novel methods for characterization of carotenoids in aqueous phase could lead to better understanding of processes in living cells and their functions. This work presents the electrochemical oxidation of the naturally occurring pigments β-carotene and astaxanthin on a paraffin impregnated graphite electrode (PIGE) using square-wave voltammetry (SWV) in 0.1 M HClO4 aqueous electrolyte. Voltammetry of microparticles (VIM) was used in a wide range of potential scan rates as this method allows determination of electroactive compounds in crystalline state. The results revealed that the oxidation of both compounds is a chemically controlled irreversible process. Oxidation peak for β-carotene was obtained at E = 0.853±0.033 V (see Fig. 1) and for astaxanthin at E = 1.111±0.029 V (see Fig. 2). It should be noted that responses for β-carotene were obtained in a mixture of β-carotene and sepiolite, electroinactive phyllosilicate clay, in ratio 1:1.

carotenoids, aqueous media, voltammetry of microparticles

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