Purification and identification of Se-containing antioxidative peptides from enzymatic hydrolysates of Se-enriched brown rice protein

As a further study of Se-containing proteins (Se-Pro) derived from Se-enriched brown rice (Se-BR), this paper aimed to purify and identify Se-containing antioxidative peptides (Se-antioxi-Peps) from Se-Pro hydrolysates. The total Se content in Se-BR was 6.26 μg/g DW, and selenocystine, Se-methylselenocysteine, and selenomethionine were identified as the main organic Se species by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Se-Pro was extracted and hydrolyzed by four types of proteases, and Alcalase was chosen as the optimum enzyme according to the degree of hydrolysis (DH). The hydrolysate with 17.08% DH possessing the highest DPPH radical scavenging activity was separated into five fractions (F1 to F5). Fractions F3 to F5, which had high antioxidative activities, were further separated. Sub-fractions F3-3, F4-2, and F5-1 were chosen to evaluate antioxidative activities and analyze Se species. The Se-antioxi-Pep with the sequence SeMet-Pro-Ser was identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.