Physico‐chemical properties, antioxidant activity, and ACE inhibitory activity of protein hydrolysates from wild jujube seed

Abstract

Wild jujube seed protein (WJSP) as one kind of functional food material has attracted much attention due to its highly nutritive and medicinal value in anti‐inflammatory and improving immunomodulatory ability. However, owing to its large molecular weight and complex structure, biological activities of WJSP were greatly limited and cannot be fully utilized by the human body. Therefore, how to improve the bioavailability of WJSP and develop promising WJSP nutritious materials is a great challenge. In this work, wild jujube seed protein hydrolysates (WJSPHs) were prepared from WJSP via enzymatic hydrolysis method, and their physico‐chemical properties, antioxidant activity, and angiotensin converting enzyme (ACE) inhibitory activity in vitro have been investigated for the first time. SDS–PAGE electrophoresis and size–exclusion chromatographic results indicate that WJSPHs have lower molecular weight distribution (< 5,000 Da) than WJSP. Circular dichroism (CD) spectroscopy and Fourier transform infrared spectroscopy (FTIR) results illustrated that random coil is the main secondary structure of WJSPHs. Antioxidant experiments indicate that WJSPHs exhibit high radicals‐scavenging ability of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radicals (94.60%), 2,2′‐azinobis‐(3‐ethylbenzthiazoline‐6‐sulfonate) (ABTS+) radicals (90.84%), superoxide radicals (44.77%), and hydroxyl radicals (47.77%). In vitro, WJSPHs can significantly decrease the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), and increase the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px) in HepG2 cells. Moreover, ACE activity was found that can be significantly inhibited by WJSPHs (73.02%). Therefore, all previously mentioned results suggest that WJSPHs may be a promising antioxidant food to prevent oxidative‐related diseases in future. Practical Application This study shows that WJSPHs exhibit high antioxidant activity and ACE inhibitory activity in vitro, which provide potential application value as antioxidant peptides to prevent oxidative‐related diseases.

Identification and Functional Validation of Two Novel Antioxidant Peptides in Saffron

“…From Figure 4 N,O, compared with the model group, MDA decreased by 4-fold at a 0.08 concentration mg/mL of DGGSDYLGK ( p < 0.001), and decreased by 1.6-fold at a 0.08 concentration of VDPYFNK ( p < 0.05). The MDA and GSH-Px contents of the two peptides at a concentration of 0.02 mg/mL were significantly higher than the reported antioxidant peptides of wild jujube seed [ 32 ]. Taken together, these results suggested that the DGGSDYLGK and VDPYFNK could protect HepG2 cells against H 2 O 2 -stimulated oxidative damage by enhancing the activities of antioxidant enzymes and reducing the MDA content.…”

“…Peptide groups included H 2 O 2 (IC 50 ) and different concentrations of peptides mixed in the DMEM. After that, the SOD, CAT, MDA, and GSH-Px were detected according to different assay kits (Sangong Biotech, Shanghai, China) [ 31 , 32 ].…”

Structural properties of Kudzu protein enzymatic hydrolysate and its repair effect on HepG2 cells damaged by H2O2 oxidation

“…30 The rubber plate was configured according to the instructions, and then analysis was conducted following a previously published method. 31 The molecular weight distribution of KPH was determined using size exclusion chromatography coupled with high-performance liquid chromatography (SEC-HPLC). A Shodex OHpak SB-803 HQ GPC column was used for the elution of analytes using acetonitrile–water–trifluoroacetic acid (20 : 80 : 0.2, v/v/v) as the mobile phase.…”

“…Cell viability was determined using the Cell Counting Kit-8 (CCK-8) assay according to the method of Han et al 31 with minor modifications. Briefly, HepG2 cells were inoculated in 96-well plates (8 × 10 3 cells per well in 100 μL) and cultured at 37 °C for 24 h. Then, the cells were incubated with various concentrations of KP and KPH for another 24 h. After treatment, HepG2 cells were treated with a certain amount of CCK-8, absorbance at 450 nm was recorded, and cell viability was calculated as the percentage relative to the negative control (cells cultured with medium only).…”

“…The quenching ability of ROS was tested using the DCFH-DA method. 31 HepG2 cells were first treated with 1.5 mM H 2 O 2 for 1.5 h and then incubated in a medium containing KP or KPH for 24 h. ROS levels were determined as described. The results are expressed as the percentage of ROS levels relative to the negative control.…”