Physicochemical Properties and Antioxidant Activities of Different Se-proteins from Selenium-enriched Rice

Objective:Different kinds of Se-proteins from selenium-enriched rice were used as raw materials to analyze their physicochemical properties and antioxidant activities. Methods: Water-soluble proteins (WSP), salt-soluble proteins (SSP), ethanol-soluble proteins (ESP) and alkali-soluble proteins (ASP) were prepared by Osborne classification method. The protein content and selenium content of Se-proteins, as well as the molecular weight distribution of Se-proteins were determined. The characteristic groups were conducted by ultraviolet (UV) spectrum and Fourier transform infrared (FT-IR) spectroscopy. The composition of seleno-amino acids in ASP from selenium-enriched rice was performed by liquid chromatography-mass spectrometry (LC-MS) method. On this basis, the total antioxidant capacity (T-AOC) and DPPH free radical scavenging capacity of Se-proteins were further analyzed. Results: Among all Se-proteins, ASP had maximum protein and selenium contents (P<0.05). Three Se-amino acids in ASP from selenium-enriched rice were identified and determined, including selenocysteine (300.22 ± 6.88 µg/kg) and methylselenocysteine (170.19 ± 2.87 µg/kg), as well as a small quantity of selenomethionine. There were obvious dose-response relationships between three Se-proteins and antioxidant capacity. ASP possessed the highest T-AOC and DPPH radical scavenging capacity among all Se-proteins. Through the correlation analysis between the antioxidant activity and the selenium content of Se-proteins, there were extremely significant positive correlation (P<0.01). Conclusion: ASP as selenium-enriched rice extract could be the most ideal protein to be further purified and studied.