Some electrochemical methods possibilities and limitations to determe the antioxidant activity of Hippophae rhamnoides L. fruits

The purpose of research is a comparative study of the antioxidant activity of sea buckthorn fruits by electrochemical methods. Tasks: determination in the AOA experiment of samples of sea buckthorn fruits by amperometric and potentiometric methods; study of the quantitative composition of the components that determine the total AOA of sea buckthorn fruits; establishing the dependence of AOA on the ratio of components in fruits; substantiation of the method for determining the AOA of sea buckthorn fruits. The objects of the study were the fruits of sea buckthorn harvested in 2021. The content of individual components with antioxidant activity and antioxidant activity were studied for four varieties of sea buckthorn growing in the Altai Region and the Sverdlovsk Region. The antioxidant activity of sea buckthorn fruits grown in the Sverdlovsk Region is 15-27 % higher than that of fruits grown in the Altai Region. The total AOA of the studied raw materials was measured by two electrochemical methods: the method of inversion potentiometry and the amperometric (reference) method. The determination of the total AOA by the considered methods shows similar results, however, in the case of using an amperometric sensor, the results of determining the AOA may be underestimated, since the technique provides for the preliminary aqueous extraction of substances with AOA, which does not allow taking into account the contribution of carotenoids to the final AOA values. At the same time, the potentiometric method makes it possible to level this shortcoming by registering changes in the potential of the system during the oxidation or reduction of the mediator system K3[Fe(CN)6]/K4[Fe[CN)6], which makes it more universal. Also in the work, correlations were determined between the main components of the composition of sea buckthorn fruits and the value of the total AOA. There is a weak correlation between the content of ascorbic acid, the amount of polyphenolic substances and the total AOA. A strong correlation was noted between the content of procyanidins and total AOA (r = 0.9976).