Evaluation of antioxidant peptides generated from Jiuzao (residue after Baijiu distillation) protein hydrolysates and their effect of enhancing healthy value of Chinese Baijiu.

BACKGROUND: Jiuzao is the residue after Bajiu distillation which is usually used as forage for livestock. However, it is not fully utilized yet considering the content of protein remained. The present study aimed to isolate antioxidant peptides from Jiuzao protein hydrolysates, then add these peptides into Baijiu product to enhance the healthy value of Baiju. Meanwhile environmental pollution caused by massive Jiuzao can be mitigated indirectly. RESULTS: Four peptides Ala-Tyr-Ile(Leu) (AYI(L)) and Asp-Arg-Glu-Ile(Leu) (DREI(L)) were identified from Jiuzao protein hydrolysates, the extraction contents of AYI + AYL and DREI + DREL were 896.10 and 110.51 mg kg-1 Jiuzao, respectively. On the one hand, antioxidant activities of these peptides were investigated. For in vitro antioxidant assays, AYI, AYL and DREI exhibited strong capacities in oxygen radical absorbance capacity (ORAC) assay. Furthermore, three levels of four peptides were assessed by 2,2'-azobis(2-methylpropanimidamidine) (AAPH)-induced HepG2 cells model. The results showed that these peptides exerted a degree of antioxidant activities in cells. Meanwhile, selected peptides concentrations according to cell assays remined at effective doses after in vitro digestion. On the other hand, the influence of these four peptides on the characteristic aroma compounds in Baijiu was studied. Most characteristic aroma compounds releases were increased with the addition of peptides. CONCLUSION: In the study, antioxidant activities of peptides were evaluated, the feasibility of utilizing Jiuzao protein hydrolysates to obtain beneficial peptides was also proved. Healthy effect of Baijiu or other food can be increased by adding these functional substances. The findings might contribute to food application and Baijiu industries. © 2019 Society of Chemical Industry.

Structure elucidation and anticancer activity of a heteropolysaccharide from white tea.

White tea, one of the six traditional teas in China, is made only through natural withering and low-temperature drying processes. It demonstrates diverse pharmacological and health-promoting effects, including antioxidant, antiviral, anticancer, and hypolipidemic activities. Despite the significance of polysaccharides in white tea leaves, their fine structure and physiological functions remain unexplored. In this study, the polysaccharide fragment WTP-80a with anticancer activity was isolated and purified from white tea through water extraction, alcohol precipitation, DEAE-52 ion exchange column chromatography, and sephacryl S-200 dextran gel column chromatography. WTP-80a exhibited a molecular weight of 1.14 × 105 Da and consisted of galactose (Gal), arabinose (Ara), rhamnose (Rha), and glucuronic acid (Glc-UA). The main chain skeleton of WTP-80a contained 3,6)-ß-Galp-(1→, 3)-α-Galp-(1→, 5)-α-Araf-(1 â†’ and 3)-α-Glcp-UA-(1→. Branch chains included α-Araf-(1 â†’ and ß-Rhap-(1 â†’ connected to the C3 and C6 positions of →3,6)-ß-Galp-(1→, respectively. In vitro anticancer experiments revealed that WTP-80a effectively hindered the proliferation, colony formation, migration, and invasion of B16F10 cells. Additionally, it induced apoptosis in B16F10 cells by blocking the G2/M phase, increasing active oxygen content, and reducing mitochondrial membrane potential. These findings provide a solid theoretical foundation for the application of white tea polysaccharides as anticancer products.

Extraction, Identification, and In Vitro Anti-Inflammatory Activity of Feruloylated Oligosaccharides from Baijiu Distillers' Grains.

The structure and function of phenoyl oligosaccharides in baijiu distillers' grains (BDGs) have not been identified and investigated yet. This study aimed to elucidate the major phenolic oligosaccharides present in BDGs, optimize their extraction process via a central composite design, and assess their anti-inflammatory properties utilizing the LPS-induced RAW264.7 inflammation model. The main results are as follows: feruloylated oligosaccharides (FOs) were identified as the main phenoyl oligosaccharides in BDGs with a structure of ferulic acid esterified on arabinooligosaccharide xylose. Then, the preparation process of FOs was optimized using the following conditions: pH 5, temperature 55 °C, time 12 h, xylanase addition amount 7 g/L, BDG concentration 120 g/L. Furthermore, the acquired FOs demonstrated notable scavenging activity against DPPH and ABTS free radicals, with Trolox equivalent values of 366.8 ± 10.38 and 0.35 ± 0.01 mM Trolox/mg sample, respectively. However, their efficacy was comparatively lower than that of ferulic acid. Finally, the obtained FOs could effectively inhibit the LPS-induced secretion of TNF-α, IL-6, and IL-1ß and promote the secretion of IL-10 in RAW264.7 cells. Based on the above results, FOs from BDGs were determined to have certain antioxidant and anti-inflammatory activities.

Identification of peptides in Qingke baijiu and evaluation of its angiotensin converting enzyme (ACE) inhibitory activity and stability.

The active peptides in Qingke baijiu fermented from Qingke (highland barley) are rarely reported. This work was designed to accurately identify peptides in Qingke baijiu and evaluate their angiotensin-converting enzyme inhibitory activities in vitro. Four novel peptides, Val-Val-Thr-Gly-Val-Gly-Gly-Gln (VVTGVGGQ), Leu-Pro-Val-Gly-Pro (LPVGP), Leu-Leu-Ser-Pro-Pro (LLSPP), and Phe-Pro-Leu-Gln-Pro-His-Gln-Pro (FPLQPHQP) were identified by Nano-UPLC-MS/MS. Molecular docking showed that LPVGP and FPLQPHQP had a high affinity with ACE (binding energy -8.78, -10.02 kcal mol-1), which matched its in vitro ACE inhibitory activity (IC50 9.05, 5.03 µM). This might be related to their high hydrophobicity. Moreover, three peptides have C-terminal proline, which may contribute to their anti-digestive activity. The content of LPVGP was over 91.23% after digestion, while the content of VVTGVGGQ dropped to 55.47%. Finally, the four peptides have no obvious toxicity to Caco-2 cells. This study clarifies the ACE inhibitory activity and the structure-activity relationship of the four peptides identified in Qingke baijiu.

Optimization of Jiuzao protein hydrolysis conditions and antioxidant activity in vivo of Jiuzao tetrapeptide Asp-Arg-Glu-Leu by elevating the Nrf2/Keap1-p38/PI3K-MafK signaling pathway.

Tetrapeptide Asp-Arg-Glu-Leu (DREL) was isolated from Jiuzao protein hydrolysates (JPHs) by alkaline proteinase (AP) and exhibited antioxidant activity in the HepG2 cell model in the previous study. In this study, the hydrolysis method of Jiuzao protein (JP) was further optimized by using different proteinases under different conditions (i.e., temperature, time, ratio between proteinase and substrate, and pH). Considering the limitation of in vitro assays, the AAPH-induced oxidative stress Sprague-Dawley (SD) rat model was selected to measure the antioxidant capacity of DREL in vivo. Pepsin exhibited the highest hydrolysis degree under the optimum conditions after single factor analysis (SFA) among seven proteinases. The total yield of DREL in Jiuzao was 158.24 mg kg-1Jiuzao under the pepsin's optimum hydrolysis conditions determined by response surface methodology analysis (RSMA). In addition, DREL could activate the Nrf2/Keap1-p38/PI3K-MafK signaling pathway and downstream antioxidant enzymes to improve the antioxidant ability in vivo. DREL also preliminarily exhibited anti-inflammatory activity by inhibiting the secretion of inflammatory cytokines and the mediator through the activation of Nrf2. Of note, the addition of DREL in baijiu brought an inconspicuous change in the taste after sensory evaluation. This study finds out the better proteinase used for JP hydrolysis and verifies the antioxidant capacity of DREL in vivo, which provides a potential approach to apply functional components from Jiuzao for by-product utilization. Meanwhile the antioxidant function of baijiu or other foods can be increased through adding these functional peptides without affecting the original flavor and taste in the future.

Antioxidant mechanism exploration of the tripeptide Val-Asn-Pro generated from Jiuzao and its potential application in baijiu.

Val-Asn-Pro (VNP) was identified from the raw material of baijiu distillation (Jiupei) and exhibit antioxidant activity in vitro. In this study, residue after baijiu distillation (Jiuzao) was used to seek the antioxidant peptide VNP with the methods reported inthe previous study. Its potential antioxidant mechanism in vivo was further assessed. Gene and protein expressions of Nrf2/Keap1-p38MAPK/PI3K-MafK signaling pathway and downstream enzymes (i.e., CAT, GPX1, SOD1, and HO-1) in AAPH-induced oxidative stress Sprague-Dawley (SD) rats were investigated. Influence of VNP on baijiu characteristics was also investigated. Based on the results, VNP was identified with a content of 5.25 mg/g Jiuzao. VNP significantly mitigated excess oxidative stress via activation of Nrf2/Keap1-p38MAPK/PI3K-MafK signaling pathway and activated downstream antioxidant enzymes. Furthermore, VNP showed unconspicuous influence on the flavor and taste of baijiu when added into baijiu and the content remained stable during storage. These results indicated that VNP is a potent antioxidant component isolated from Jiuzao that can be used in baijiu to enhance its antioxidant effect without affecting the main flavor and taste. The utilization of these functional components can also increase the added value of Jiuzao.

Isolation and evaluation of two angiotensin-I-converting enzyme inhibitory peptides from fermented grains (Jiupei) used in Chinese Baijiu production.

In the present study, fermented grains (Jiupei), the raw material for Baijiu distillation, were used to isolate and identify low molecular weight peptides with angiotensin-I-converting enzyme (ACE) inhibitory activities. The methods of peptides extraction from Jiupei are described as follows: ultrasonication, centrifugation and filtration. Peptide purification was performed by ultrafiltration, adsorption on a macroporous resin, gel chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). HPLC with quadrupole-time-of-flight-mass spectrometry/mass spectrometry (HPLC-Q-TOF-MS/MS) was used to identify the peptides, and the ACE inhibitory activities of the peptides were measured. Finally, the optimum peptide extraction and separation parameters were determined to be a liquid/solid (ultrapure water/Jiupei powder) ratio of 15 mL g-1, extraction temperature of 57 °C and ultrasonication time of 33 min. XAD-16 resin was used for the removal of sugars and salts. Under these conditions, the total yield of peptides extracted was 57.682 mg/1 g Jiupei. The peptides identified were Val-Asn-Pro and Tyr-Gly-Asp. Val-Asn-Pro exhibited some ACE inhibitory activity (IC50 = 38.02 µM), while Tyr-Gly-Asp showed higher ACE inhibitory activity (IC50 = 5.21 µM). These results provide an important foundation for the study of peptides in Jiupei and show a reference for the trace of peptides in Baijiu production.