# Antioxidant Properties of Selenium Nanoparticles Synthesized Using Tea and Herb Water Extracts
## 3 Results and Discussion
### Antioxidant Activity of Obtained SeNPs  
Selenium nanoparticles are also gaining great popularity due to their antioxidant properties. Many studies proved that SeNPs possess higher antioxidant activity than the plant extract, which was used for their synthesis [46; 47]. Thus, the ability of the synthesized selenium nanoparticles to neutralize hydroxyl radicals was determined. This is a very important aspect as OH- radicals are the major members of the reactive oxygen species (ROS). In a living organism, ROS can contribute to oxidative stress, i.e., an imbalance between the systemic production of ROS and the ability of cells to instantly detoxify the reactive intermediates or to restore the resultant impairment [48]. Increased oxidative stress is associated with metabolic risk factors and may contribute to the development of several diseases [49]. Nanoparticle antioxidants, called \"nanoantioxidants\" constitute a new wave of antioxidant therapies for the prevention and treatment of diseases involving oxidative stress. Showing strong and persistent interactions with biomolecules, they would be more effective against free radical induced damage [50]. The obtained results confirmed the high antioxidant activities of SeNPs, which are presented in Table 3.  
In each case, the SeNPs showed a higher ability to scavenge hydroxyl radicals than the extracts that were used for their synthesis. In the case of selenium nanoparticles synthesized using Lipton Yellow Label (black tea), the highest antioxidant capacity was shown by nanoparticles obtained after mixing the reagents in a 1:1 ratio (97.3 \(\pm\) 3.21%). Increasing the concentration of any of the used reagents resulted in a decrease in their activity. The same relationship was observed for Lipton Green Tea Classic. However, the determined maximum ability to neutralize OH radicals was in this case close to 100% and significantly higher than that determined for black tea. Herbal infusions showed significantly lower antioxidant capacity compared to tea extracts. However, some of the SeNPs obtained with their participation showed the OH radical scavenging capacity significantly above 90%. With the use of mint and chamomile extracts, no clear trend was observed between the increase in the concentration of reagents used for synthesis and the antioxidant capacity of the obtained SeNPs. In the case of chamomile, the highest antioxidant capacity was exhibited by nanoparticles obtained with a fourfold excess of tea extract to selenium (99.10 \(\pm\) 4.10%). In the case of mint, SeNPs obtained with a four-fold excess of any of the reagents showed similar values of antioxidant capacity and these values were close to 100% (99.9 \(\pm\) 3.70% for the excess of the extract and 99.95 \(\pm\) 2.20 for excess of selenium salt). \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{2}{c}{**FC Method [mg GA/L]**} & **OH: Assay [\%]** \\ \hline Black tea extract & 597.1 \(\pm\) 7.23 \({}^{\text{a}}\) & 65.6 \(\pm\) 2.71 \({}^{\text{a}}\) \\ \hline \multicolumn{3}{c}{SeNPs synthesized with black tea extract} \\ \hline Selenium/infusion ratio & & \\ \hline  
}}\) & 79.6 For all of the analyzed samples, the Folin-Ciocalteu (FC) method was also applied. This method, based on a single electron transfer and very often called the total phenolic content (TPC), is an indirect measurement in terms of antioxidant activity. It measures the reductive capacity of an antioxidant. It is assumed that the antioxidant activity is equal to the reducing capacity of a given sample and there is a direct correlation between antioxidant activity and TPC value [51]. However, it should be remembered that FC reagent is not specific only for phenolic compounds; some other compounds also react with it to give elevated apparent phenolic contents in plant-derived food and biological samples [52]. The total content of polyphenols in the extracts used for SeNPs synthesis increases in the following order: chamomile < mint < black tea < green tea (Table 2).