## 4 Discussion
### Gamma Irradiation Effect on Antiradical Capacity  
Previous studies of plant products established a relationship between the content of phytochemicals in the samples and the antioxidant properties which they exhibit. In this study, a significant correlation was also established between the data on the total phenolic and flavonoid content and the antiradical activity exhibited by the tested non-irradiated and irradiated samples of peeled and shell chestnut seeds. This indicates that the major contribution to the antioxidant activity of horse chestnut has its polyphenic content. The experimental results from the current study show that the radical scavenging activity of both kinds of horse chestnut samples (pealed and shell seeds) differs and also the irradiation effect on them, obtained by both EPR and spectrophotometric measurements. Other researchers also reported a higher amount of phenolic substances in _A. hippocastanum_ seed shell extract, and which exhibited higher DPPH radical-scavenging activity than peeled seed extract [8; 9]. The generation of free radicals is one of the main effects of gamma irradiation because of the high energy ionizing rays releasing electrons from molecules. These radiation induced free radicals could cause structural and chemical changes on the irradiated samples. Furthermore, irradiation effects are strongly dependent on the chemical structure of the sample, the amount of compounds having antioxidant properties and their activity (i.e., polyphenic compounds), and on the applied dose of high-energy radiation [33]. On the other hand, antioxidant molecules found in plant extracts could scavenge the gamma-generated radicals and, in the course of the process, they become exhausted. The combination of these factors will influence the gamma radiation behavior, the changes of composition, and the biological activity of the _A. hippocastanum_ seeds. In this relation, a slight decrease in the TEAC values in peeled seeds was found after irradiation (see Sections 3.1.3 and 3.2.1). As mentioned, the polyphenic composition is mainly responsible for the antiradical ability of plant products. Although the amount of some of the individual polyphenic components increased according to the HPLC analysis after gamma processing of PS, a decrease in total phenolics was observed. The reduction of total phenolics and flavonoids was most noticeable for samples irradiated by 10 kGy. Probably, this is the reason for the observed greatest decrease in FRSA after irradiation of PS at this dose. The significant decreases in concentration of quercetin, which is a strong free radical scavenger [34], and also in caffeic and ferulic acids are probably responsible for reduced scavenging activity at 10 kGy for irradiated peeled chestnut seeds. On the other hand, gamma generated free radicals from the degradation of cellulose and starch in chestnut seeds could be reducing the antioxidant activity, since the phenolic compounds can take part in the process of free radicals inactivation. The positive effect of gamma irradiation on antiradical activity of chestnut shell seeds was established in our study, most pronounced in the 5 kGy irradiated samples. This result is in agreement with the observed increase in both the total phenolic and flavonoid content of SS. Probably, the reasons are complex for enhanced free radical scavenging activity after gamma treatment. It is known that the radiation induced free radicals could lead to the breakage of some glycosidic bonds in the polyphenic constituents, resulting in the formation of more compounds having antioxidant ability. The various phenolic derivatives possess different contributions to antioxidant activity [34]. In the case of irradiated shell chestnut seeds, probably the presence of p-cumaric acid, caffeic acid, and morin (see Section 3.3) are responsible for enhanced FRSA compared to non-irradiated samples (these compounds were not available in non-irradiated SS).