A relation between the kinetic parameters of the antiradical activity of aryl and hetarylhydrazones and their electronic structure is revealed in the form of the correlation between the reaction rate constants, bond energies of the reaction centers and the antioxidants ionization potentials. The relations obtained can be used to predict the antiradical activity in a series of hydrazones.

Kinetic parameters of the antiradical activity of derivatives of hydrazones of 4-hydroxy-3,5-di- tert -butyl-benzaldehyde are determined photocolorimetrically in their reactions with a stable diphenylpicrylhydrazyl radical, and by chemiluminescence from the capture of peroxide radicals upon the initiated oxidation of ethylbenzene. It is found that during inhibited oxidation, the reactive centers (N-H and O-H) in hetaryl- and acylhydrazone molecules operate in parallel. Regularities of the compounds’ inhibiting effect are studied in heterogeneous systems upon the initiated oxidation of ethylbenzene in emulsion, and in a water-lipid model of the oxidation of phosphatidylcholine dispersion. It is established that hydrazone derivatives are antioxidants of combined action in heterophase processes of the oxidation of unsaturated substrates, displaying properties of hydroperoxide deactivators in addition to their antiradical activity.

Antioxidant effect of 2-methyl-1,3-benzoxazol-6-ol in radical chain oxidation of organic compounds with molecular oxygen was studied. Antiradical activity in the reaction with stable diphenylpicrylhydrazyl radical was examined by photocolorimetry. The kinetic parameters of the reaction of 2-methyl-1,3-benzoxazol-6-ol with peroxy radicals of different natures were determined by volumetric and chemiluminescence methods. A relation was found between the antioxidant activity and electronic structure parameters calculated by quantum-chemical methods. Factors responsible for differences in chemiluminescence in the oxidation of organic substances with different polarities in the presence of the title compound were analyzed.

Initiated oxidation of tridecane in chlorobenzene solution with molecular oxygen in the presence of a series of phenol derivatives was studied by chemiluminescence and gas-volumetric methods. The kinetic parameters of the antiradical and antioxidant activity of the compounds were determined.

The antiradical activity (ARA) of fresh squeezed juices and those reconstituted from concentrate was examined in reactions with diphenylpicrylhydrazyl (DPPH). Fresh squeezed juices contain a higher amount of phenolic substances and exhibit stronger ARA. The maximum ARA among the studied fruit juices was observed for orange and grapefruit juices. The ability to discolor aqueous EtOH solutions of DPPH can be used as a test for primary quantitative evaluation of the ARA of fruit juices.

The antiradical activity of natural and concentrate-recovered juices was examined in reactions with diphenylpicrylhydrazyl (DPPH). Natural juices contain a higher amount of phenolic substances and exhibit stronger antiradical effect. The maximum antiradical activity among the fruit juices studied was observed for the orange and grapefruit juices. The ability to produce discoloration of DPPH aqueous ethanol solutions can be used as a test for primary quantitative evaluation of the antiradical activity of fruit juices.

Conditions for improving the extraction of substances with antioxidant properties from bearberry (Arctostaphylos Adams) leaves have been studied. It is established that the natural antioxidants are most completely extracted by maceration in a constant electric field (U = 35 V, I = 250 mA) for 2 h at 303 K with stirring. The optimum extractant is 1% aqueous acetic acid with added surfactant (Tween-80, 8.8 × 10− 4 M). This extract increases the stability (storage time) of sunflower oil more than four times. The proposed method of electroextraction increases the yield of extracted substances with antioxidant properties and decreases the yield of ballast substances without complicating the procedure and increasing the consumption of materials.

The extraction of phenolic antioxidants from solid plant raw materials (bark and roots) under the action of an electric current was studied. A relationship between the amount and antioxidant activity of extracted phenolic compounds with the particle size and the procedure of grinding plant raw material was found. The most complete extraction of phenols was reached in experiments with ground samples. The resulting extracts from the bark of arrowwood (Viburnum opulus L.) and the root of burnet (Sanguisorba officinalis L.) were superior to the extracts obtained by circulation extraction in a Soxhlet extractor in terms of the antioxidant activity, and they increased the stability of sunflower oil to oxidation by a factor of 2–3.

Conditions of intensification of the extraction of substances with antioxidant properties from the leaves of bearberry (Arctostaphylos Adans) have been studied. It is established that the nature antioxidants are most completely extracted by maceration in a constant electric field (U = 35 V,I = 250 mA) for 2 h at 303 K with stirring. The optimum extractant is 1% aqueous solution of acetic acid with additives of surfactant (Twin-80, 8.8 × 10-4 M). This extract increases the stability (storage time) of sunflower oil more then four times. The proposed method of electroextraction increases the yield of extracted substances with antioxidant properties at a reduced yield of ballast substances without complicating the procedure and increasing the consumption of materials.

The effects of ultrasound ( f = 60 kHz) on the quantity of biologically active substances extracted from bearberry leaves into a water:ethanol (1:1) mixture were studied, along with their antioxidant properties. The optimal conditions for extract preparation were identified: the raw material:extractant ratio and the duration of ultrasound exposure. Positive and negative aspects of the ultrasound extraction of antioxidants are discussed. The antioxidant activity of the extract prepared in optimum conditions was greater than that of a bearberry leaf extract prepared without ultrasound, increasing the resistance of sunflower oil to oxidation by factors of 2–2.2.

We have studied the effect of ultrasound (frequency f = 60 kHz) on the yield of biologically active substances extracted with water - ethanol mixture (1:1) from bearberry leaves (Arctostaphylos adans) and on the antioxidant activity of extracts. Optimum extraction conditions (material - solvent ratio, duration of ultrasonic treatment) are established. Advantages and disadvantages of the process of ultrasonic extraction of antioxidants are pointed out. The bearberry leaves extract obtained under optimum ultrasonic treatment conditions exhibits antioxidant activity exceeding that of the extract obtained without application of ultrasound and increases the stability of sunflower oil to oxidation by a factor of 2 - 2.2.

The gasometric method of iron-initiated oxidation of egg yolk lipoproteins has been employed for analysis of antioxidant activity. The optimal conditions of oxidation providing reproducible results on the kinetics process have been chosen. The antioxidant concentration required for 50% decrease of oxygen consumption is proposed as the parameter characterizing antioxidant activity of the compounds studied. The influence of different factors on effectiveness of inhibition of lipid peroxidation by phenolic antioxidants was analyzed.

Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.

Antioxidant properties of aminophenols in initiated oxidation of Nujol were studied by a chemiluminescence procedure.

The kinetics and mechanism of reaction of arylhydrazones with molecular oxygen were studied by gas volumetry. The reaction rate was studied in relation to the structure of arylhydrazone and kind of the solvent. The inhibiting power of the compounds toward initiated oxidation of ethylbenzene was evaluated, and the most effective compounds were found, judging from the ratio of the rate constants of the reactions with molecular oxygen and with peroxy radicals arising in the course of ethylbenzene oxidation.

In a study of the reactivity of sterically protected phenols in the reaction with ethylbenzene peroxy radicals as a function of their molecular structure and as compared with unprotected phenols, we have established the major characteristic features of the structure–antioxidant activity relation for phenols of different structures.

A study was made of the chemiluminescence in the course of initiated oxidation of sunflower oil with a luminescence activator in the presence of natural phenols. The kinetic parameters \({{k_2 } \mathord{\left/ {\vphantom {{k_2 } {\sqrt {k_1 } }}} \right. \kern-\nulldelimiterspace} {\sqrt {k_1 } }}\) were determined, which take into account the appearance of chemiluminescence and characterize the antioxidative activity of the phenols.