Optimization of Selenium Fortification and Ultrasound-Assisted Extraction of Bioactive Selenium-Polysaccharide Fractions from Germinated Oats (Avena sativa)

Oats are a rich source of bioactive polysaccharides, particularly β-glucan, while selenium is an essential trace element involved in various physiological functions. This study investigated the effects of sodium selenite supplementation during oat germination on selenium accumulation and polysaccharide characteristics, followed by optimization of ultrasound-assisted extraction (UAE). Germination with 150 ppm sodium selenite resulted in a higher extraction yield (10.22%), polysaccharide content (951.04 mg/g extract), and total selenium content in the crude polysaccharide extract (2.91 mg Se/g extract). Response surface methodology identified the optimal UAE conditions as an ultrasonic power of 520 W, an extraction time of 29 min, and a solid-to-liquid ratio of 7.35% (w/v). FTIR analysis indicated changes in the infrared spectral features of the polysaccharide fraction following selenium enrichment, while the major structural characteristics were generally retained. Selenium enrichment in polysaccharide from germinated oats showed no significant cytotoxicity toward RAW264.7 macrophages. Fractionation using DEAE-52 cellulose chromatography revealed that selenium was unevenly distributed among the polysaccharide fractions, with OP150-3 containing the highest selenium content (0.12 mg Se/g polysaccharide) and exhibiting higher antioxidant activity than the corresponding non-enriched fraction. Overall, selenium-enriched germinated oats show potential as a source of selenium-associated bioactive polysaccharides for functional food and nutraceutical applications.