# Antioxidant Properties of Selenium Nanoparticles Synthesized Using Tea and Herb Water Extracts
## 3 Results and Discussion  
### HPLC Analysis ad UV-Vis Spectroscopy of Used Plant Extracts  
Chromatographic analysis of polyphenols and ascorbic acid in all tested infusions was performed in HILIC mode and its results are presented in Table 1. Ascorbic acid was included in the research because it is often used as a selenium reducer in the chemical synthesis of SeNPs [18]. Its presence in extracts can significantly affect the course of the synthesis reaction, as well as the properties of the obtained selenium nanoparticles. Catechins (flavan-3-ols) are the dominant polyphenic compounds present in tea leaves and their infusions. These compounds were detected in high amounts in both green and black tea. However, green tea infusion seems to be a better source of catechins. According to the literature, total catechins decreases in amount with increasing fermentation from green to oolong and black tea, which can also be seen in our results [27]. The levels of epigallocatechin-3-gallate (EGCG) ranged from 1.69 to 90.1 mg L\({}^{-1}\), making it the major polyphenic constituent of green tea. Antioxidant and health-promoting effects of EGCG have been widely described in the literature. It was reported that EGCG acts as an angiogenesis inhibitor by modulating protease activity during endothelial morphogenesis and thus inhibits the growth of cancer [28]. It should be mentioned that, in addition to the catechins designated by us, tea infusions also contain other compounds from this group, e.g., epigallocatechin, epicatechin gallate, gallocatechin, and gallocatechin gallate. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**Herbal Extracts**} & \multicolumn{2}{c}{_Camelia sinensis_ Extracts} \\ \cline{2-5}  & **Chamomile** & **Mint** & **Black Tea** & **Green Tea** \\ \hline \multicolumn{5}{c}{Polyphenylonic acids} \\ \hline Gallic & 0.150 \(\pm\) 0.006  & 4.76 \(\pm\) 0.183  & 2.45 \(\pm\) 0.110  \\ Caffeic & 0.101 \(\pm\) 0.005  & 0.265 \(\pm\) 0.013  & \(\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\textMS spectra confirmed their presence in the infusions, but their quantitative analysis was not performed. In general, the content of polyphenols in tea leaves varies with climate, season, horticultural practices, and leaf age [29]. Rutin (quercetin-3-rutinoside) was found in the studied tea extracts at the highest level, but its concentration in herbal infusions was below the limit of detection. On the other hand, luteolin was detected only in chamomile and mint infusions. The presence of luteolin, rutin, and chlorogenic acid in chamomile infusion was also reported in our previous work [30]. Mint was described in the literature as a good source of luteolin and caffe acid, which was also confirmed by our results [31]. All of the studied extracts were good sources of polyphenolic acids. p-Hydroxybenzoic acid (pHBA) was present in all studied infusions in high concentrations and caffeic acid was detected only in herbal infusions. In plants, caffeic acid is formed from p-coumaric acid and then transformed into ferulic acid [32]. In the case of our infusions, p-coumaric acid was present in all samples, with a significantly higher concentration in teas. The concentrations of ferulic acid in all studied samples were below the limit of detection. The high quantity of polyphenolic compounds is crucial from the point of view of selenium nanoparticles synthesis, as they are responsible for the reduction of selenium salt and also can stabilize obtained SeNPs. However, the presence of other compounds in plant extracts can affect the efficiency of the nanoparticle synthesis. Ascorbic acid is an example of such a compound due to its reductive properties. Its concentration in all studied infusions was increasing in the order: mint < chamomile < green tea < black tea (Table 1).