Abstract: Selenium is an essential trace element for human body, but it can easily cause poisoning because of its low safety threshold. Previous studies have demonstrated that selenized polysaccharides and nano-selenium have higher safety and biological activity, and so they are ideal selenium supplements. In this study, selenized polysaccharides (Se-SLPC) and nano-selenium-polysaccharide (SLPC-SeNPs) were prepared from the polysaccharides of Suillellus luridus (SLPC), the physicochemical and structural properties of the raw and selenized polysaccharides were compared, and the surface morphology and stability of SLPC-SeNPs were determined. Additionally, the antioxidant activities of both selenium-rich polysaccharides were evaluated. The results showed that the selenium content of Se-SLPC was 1.62 mg/g, whose polysaccharide moiety was composed of mannose, glucose, and galactose and had an average molecular mass of 8.2 kDa. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the substitution reaction took place at the C4 position and at the glycosidic linkage position C3. The SLPC-SeNPs have a particle size of 55.46 nm and a uniform spherical surface, which can be stably maintained at 4 ℃ for at least 80 d. In addition, both Se-SLPC and SLPC-SeNPs had significantly higher antioxidant activity than SLPC. This study can provide data support for the development of safe and efficient selenium supplements.

Key words: Suillellus luridus; selenium-enriched polysaccharides; selenium nanoparticles; antioxidant activity