# Antioxidant Properties of Selenium Nanoparticles Synthesized Using Tea and Herb Water Extracts
###### Abstract  
Selenium nanoparticles (SeNPs) are the object of great interest due to their potential to be used in many areas of industry and medicine. Work is still underway on their synthesis methods; however, green methodologies are becoming more and more popular. In this study, aqueous extracts of black and green tea as well as infusions of popular herbs such as chamomile and mint were used in the synthesis of SeNPs serving as the Se(IV) reducers to its nano form. The influence of the reagents concentration ratios on the properties of the obtained nanoparticles were examined. SeNPs showed a greater ability to neutralize hydroxyl radicals compared to tea extracts. It has been proven that in the infusion of selenium-containing tea, the formation of SeNPs occurs.  
selenium; nanoparticles; green synthesis; tea and herb infusions +
Footnote †: journal: Medical  
saponins, carbohydrates, proteins, tannins, and steroids as natural reducers and/or stabilizers. The mechanism of their action in the synthesis of NPs is complex. According to [PERSON] [19], when selenium salt dissociates, cations are saturated to form hydroxyl complexes. After that, crystallite growth of metal with oxygen species starts to originate. At this stage of the NPs synthesis, heating is playing a key role in providing energy to the reaction system. The process continues until activation of the capping agent from the plant extract, which eventually stops the growth of high-energy atomic growth planes. The result of this process is formation of NPs. Reducing agents from plant extract are electron donors to the metals ions and convert them to the nanoparticles. From this point of view, secondary plant metabolites are very important in green SeNPs synthesis; they act as selenium reductors, but also prevent the aggregation of NPs and promotes production of smaller particles. The use of green synthesis was used to obtain many metallic nanoparticles, including AgNPs [20], ZnO NPs [21; 22], or PdNPs [23].  
Green synthesis of selenium nanoparticles is also described in the literature. Generally, selenium precursor (most often Na\({}_{2}\)SeO\({}_{3}\)) is mixed with the plant extract solution at different ratios and stirred for different periods, sometimes with heating. During this process, the colour of the reaction media changes to red, indicating the formation of Se nanoparticles. In the synthesis of SeNPs, the main goal is their formation with minimum particle size and maximum stability as a smaller size can guarantee more powerful antioxidant activities [24].  
In the present study, the potential of water extracts of popular black (Lipton Yellow label) and green tea (Lipton Green Tea Classic) as well as chamomile (_Matricaria recuitta_) and mint (_Mentha_), commonly used to make herbal infusions, were compared in the biosynthesis of SeNPs. The dependence of the ratio of reagents on the properties of the obtained SeNPs has been investigated. The content of polyphenolic compounds, which can potentially act as selenium reducing reagents, was measured using liquid chromatography operating in HILIC mode. The antioxidant activity of extracts themselves, as well as obtained nanoparticles, were determined using a hydroxyl radical scavenging assay. The reductive properties were evaluated by the Folin-Ciocalteu method. An attempt has been made to link the properties of the obtained SeNPs with the ratios of the reagents used for the synthesis.