engleski

Electrochemical determination of total polyphenolic content and antioxidant activity of plants Immortalle, St. John's Wort, Yarrow and Chamomile

Polyphenols are versatile molecules that are characterized by many positive effects that help offset chronic diseases, such as cardiovascular diseases and cancer. Also, they are known for their antioxidant activity so many people consume large amounts of teas and other pharmaceutical supplements that are rich in polyphenols. Although a lot of research is done regarding polyphenols, in recent years some plants are becoming more popular because of their potential positive effects on human health [1, 2]. In this research, we wanted to give insight into the electrochemical properties of plants Immortelle, St. John's wort, common Yarrow and Chamomile. Not a lot of research was done on these plants, but it is known that they are rich in polyphenolic compounds. Total polyphenols were extracted using supercritical CO2 and residues in form of an oil were obtained. Samples were diluted in ethanol and electrochemical measurement was performed using the voltammetry of immobilized microfilm on glassy carbon electrode (GCE). Additionally, Folin-Ciocalteu method and HPLC analysis were performed. Standards that were used in this research were gallic and caffeic acid. For all samples, different voltammograms were obtained, i.e. neto peak signals were at different potentials. Also, best results for all tested samples were obtained at the lowest frequency of 10 Hz which suggests that oxidation reaction of all polyphenols in tested samples is a slow process. Other optimal experimental conditions were: pH 2.5, pulse amplitude of 50 mV and step potential of 2 mV. Immortelle showed the most complexed oxidation mechanism because three oxidation peaks were obtained at potentials Ep, 1 = 0.491 V, Ep, 2 = 0.674 V and Ep, 3 = 0.927 V. Responses for St. John’s wort and Yarrow were very similar and oxidation signals were obtained at E = 0.720 V and E = 0.795 V, respectively. Electrochemical oxidation of Chamomile showed only one broad peak at E = 1.07 V. Electrochemical measurements provided information about oxidation mechanism of dominant phenolic compounds in samples, but also about their antioxidant properties. Additional experiments are needed to determine specific compounds in these samples. [1] D. Del Rio, L. G. Costa, M. E. J. Lean, A. Crozier, Nutr. Metab. Cardiovasc. Dis. 20 (2010) 1-6. [2] G. Chiva-Blancha, F.Visioli, J. Berry Res. 2 (2012) 63–71.

total polyphenols ; voltammetry ; antioxidant activity

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