Analysis of Gamma-Irradiation Effect on Radicals Formation and on Antiradical Capacity of Horse Chestnut (Aesculus hippocastanum L.) Seeds

The irradiation by gamma-rays is a widely used technique for disinfection in the pharmaceutical and cosmetic industries. In view of growing concerns by consumers about this technique, further investigation of the effects of radiation is required. In this work electron paramagnetic resonance (EPR) spectroscopy was applied to study the free radicals in irradiated horse chestnut (Aesculus hippocastanum L.) seeds and to evaluate the free radical scavenging activity (FRSA) using the stable DPPH radical. In order to evaluate the antiradical potential, a spectrophotometric study was also used. The identification and quantification of some individual polyphenol compounds before and after irradiation by 1, 5, and 10 kGy gamma rays of peeled and shell seeds were obtained by high performance liquid chromatography (HPLC). The EPR spectrum recorded on irradiated horse chestnut is a typical signal for irradiated cellulose-contained substances. The results show that the signal is stable, and it can be found in the samples irradiated with a dose of 1 kGy, 45 days after treatment, whereas for samples irradiated by 5 and 10 kGy, it is even found 250 days later. The study showed that free radical scavenging activity increases in shell seeds, while it decreases in peeled seed extracts after irradiation depending on the dosage, which corresponds to the total phenolic content. Shell seed extracts have significantly stronger antiradical activity than that of peeled seeds. Regarding the HPLC analysis, some polyphenolics were degraded and others were formed as a result of irradiation. The irradiation by 5 kGy dosage has a most significant positive effect on the antioxidant potential of shell chestnut seeds.