ANTIOXIDANT PROPERTIES OF LEAVES OF SOME TREES

Abstract

The paper presents the results of studies of antioxidant properties of the leaves of the English oak (Quercus robur), Georgian oak (Quercus iberica), white willow (Salix alba) and common sycamore (Lycium barbarum) leaves. It is shown that all the studied extracts have antioxidant properties. The antioxidant capacity of the investigated extracts is studied on the example of the model reaction of the initiated oxidation of cumene. Azo-di-isobutyronitrile (AIBN) was used as a source of a free radical, and chlorobenzene was used as a solvent. The oxidation of the substances is carried out on a manometric installation with automatic pressure regulation. The total content of antioxidants in the studied extracts was determined by the known method. It is shown that the oxidation of cumene in the presence of all the used extracts takes place in the kinetic curves of oxygen absorption with well-defined induction periods. This indicates the presence of antioxidant substances in the extracts. The measured concentrations of the absorbed oxygen during time t <  were aligned in coordinates using the known method. The obtained data indicate that the mentionned extracts used are slightly inferior to synthetic-classical antioxidants in terms of antioxidant activity. Thus, the reaction rate constant k7 with cumyl peroxide radicals for -naphthol at 333 K is equal to 1,6•105 l/mol.sec, for hydroquinone – 1,2•105, for ionol - 2•105. It was established that, of the studied extracts, the largest number of antioxidants is contained in the extract of Greek oak leaves (1,34•10-4 mol/l in one mg), and the highest antioxidant activity is shown to be in the extract of white willow leaves (1,01•105 mol/l.sec). By comparing the obtained results to the content of antioxidant substances (f.[InH]) and to the antioxidant activity (k7) of the studied extracts, it was confirmed that the antioxidant activity does not depend on the concentration of the inhibitor, i.e. on the content of AO in the reaction mixture. АОА most likely depends on the construction of АО and 〖RO〗_2^. radicals, as well as on the medium of the reaction mixture. Such antioxidant activity of a number of leaves will contribute to their use for the storage of agricultural and food products, which will contribute to the reduction of costs in this process.