Precise Determination of Selenium Forms and Contents in Selenium-Enriched Rapeseed Seedlings and Flowering Stalks by HPLC-ICP-MS.

Rapeseed (Brassica napus L.) has the ability of selenium (Se) enrichment. Identification of selenides in Se-rich rapeseed products will promote the development and utilization of high value. By optimizing the Se species extraction process (protease type, extraction reagent, enzyme sample ratio, extraction time, etc.) and chromatographic column, an efficient, stable, and accurate method was established for the identification of Se species and content in rapeseed seedlings and flowering stalks, which were cultured by inorganic Se hydroponics. Five Se compounds, including selenocystine (SeCys2), methylselenocysteine (MeSeCys), selenomethionine (SeMet), selenite (SeIV), and selenate (SeVI) were qualitatively and quantitatively identified. Organoselenium was absolutely dominant in both seedlings and flowering stalks among the detected rapeseed varieties, with 64.18-90.20% and 94.38-98.47%, respectively. Further, MeSeCys, a highly active selenide, predominated in rapeseed flowering stalks with a proportion of 56.36-72.93% and a content of 1707.3-5030.3 µg/kg. This study provides a new source of MeSeCys supplementation for human Se fortification.

Egg Yolk Selenopeptides: Preparation, Characterization, and Immunomodulatory Activity.

In this study, egg yolk selenium peptides (Se-EYP) were prepared using double-enzyme hydrolysis combined with a shearing pretreatment. The properties of the selenopeptides formed were then characterized, including their yield, composition, molecular weight distribution, antioxidant activity, in vitro digestion, and immunomodulatory activity. The peptide yield obtained after enzymatic hydrolysis using a combination of alkaline protease and neutral protease was 74.5%, of which 82.6% had a molecular weight <1000 Da. The selenium content of the lyophilized solid product was 4.01 µg/g. Chromatography-mass spectrometry analysis showed that 88.6% of selenium in Se-EYP was in the organic form, of which SeMet accounted for 60.3%, SeCys2 for 21.8%, and MeSeCys for 17.9%. After being exposed to in vitro simulated digestion, Se-EYP still had 65.1% of oligopeptides present, and the in vitro antioxidant activity was enhanced. Moreover, Se-EYP exhibited superior immune detection indices, including immune organ index, level of immune factors in the serum, histopathological changes in the spleen, and selenium content in the liver. Our results suggest that Se-EYP may be used as selenium-enriched ingredients in functional food products.