An X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy was used to examine the free radical scavenging activity of the following infusions, which were nonirradiated and exposed to UVA: root of Asparagus racemosus and herbs of Mitchella repens, Cnicus benedictus L., Galega officinalis L., and Eupatorium cannabinum L. The plant materials for obstetrics applications were chosen for analysis. The aims of these studies were to compare the free radical scavenging ability of the tested infusions and to determine the influence of UVA irradiation of the plant materials on interactions of these infusions with free radicals. Both the magnitude and kinetics of the interactions of the infusions with the model DPPH free radicals were examined. The ability to quench the free radicals for the examined plant infusions increases in the following order: Asparagus racemosus (root) < Mitchella repens (herb) < Cnicus benedictus L. (herb) < Galega officinalis L. (herb) < Eupatorium cannabinum L. (herb). The analyzed infusions differ in the kinetics of the interactions with free radicals. The fastest interactions with free radicals characterize the infusions of Galega officinalis L. herb and Eupatorium cannabinum L. herb. The infusion of Mitchella repens herb interacts with free radicals in the slowest way. UVA radiation reduces the antioxidant interactions of all tested infusions, especially the infusion of Eupatorium cannabinum L. herb, which should be protected against UVA radiation during storage. The weakest decrease of free radical scavenging activity was observed for the infusion of the root of Asparagus racemosus exposed to UVA radiation. UVA radiation affected the speed of the free radical interactions of the infusions, depending on the type of plant materials. EPR spectroscopy is useful to examine the free radical scavenging activity of plant infusions, which is helpful to find effective antioxidants for applications in obstetrics and their optimal storage conditions.

AB ST R ACT OBJE C T I V E :Soybean extract is a valuable food supplement used for the prevention of cancer and other purposes. The role of free radicals in carcinogenesis has been proven. Studies have also confirmed the effect of storage conditions on the formation of free radicals in natural medicinal products. The study presents an attempt to optimize the storage conditions of soybean extract to prevent the formation of free radicals. A I M O F T H E S T U D Y :The aim of the study was to determine the effect of temperature and UV radiation on the formation of free radicals in soybean extract during storage. M A T E R I A L A N D M E T H O D S :Samples of soybean extract were heated to temperatures of 30, 40 and 50°C. Subsequent samples were exposed to UV radiation (wavelengths 315-400 nm) for 30 and 60 minutes. EPR (electron paramagnetic resonance) spectroscopy was used to analyse the amplitude and linewidth of the EPR signal and to calculate the concentration of free radicals in the samples.

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