Antioxidant activity of protein hydrolysates and purified peptides from Zizyphus jujuba fruits

In recent years, there has been a considerable interest in bioactive peptides derived from food proteins which might have beneficial effects on human health. Zizyphus jujuba is a medicinal plant with well-demonstrated biological functions for which various bioactive compounds except antioxidant peptides have been reported. Therefore, the aim of this study was to determine the antioxidant activity of Z. jujuba-derived protein hydrolysates and the purified peptides. Based upon this study, it was revealed that the hydrolysates prepared from Z. jujuba fruit possessed antioxidant effects. Among the prepared hydrolysates, trypsin hydrolysate with the highest antioxidant activity was fractionated using reverse-phase high-performance liquid chromatography (RP-HPLC). The most potent antioxidant peptides, named fractions F3 and F6, identified as VGQHTR (MW: 678.36 +/- 0.3 Da) and GWLK (MW: 482.27 +/- 0.3 Da), respectively, using tandem mass spectrometry. This study demonstrated that the derived hydrolysates and the purified peptides from Z. jujuba proteins can prevent oxidative reactions and might be underutilised for food preservation and medicinal purposes. However, more detailed studies are required to explore their antioxidant abilities in vivo. (C) 2012 Elsevier Ltd. All rights reserved.