Yuqian Tang

Antioxidant Mechanism of Betaine without Free Radical Scavenging Ability

Betaine (BET) is a native compound widely studied as an antioxidant in agriculture and human health. However, the antioxidant mechanism of BET remains unclear. In this research, radical scavenging assays showed that BET had little free radical scavenging activity. However, the antioxidant activity of BET was confirmed by cellular antioxidant activity (CAA) and erythrocyte hemolysis assays. The results of quantitative PCR (qPCR) and enzyme activity determination kits showed that the antioxidant activity of BET was not due to the gene expression and activity of antioxidases. High-pressure liquid chromatography (HPLC) assessment of the effect of BET on sulfur-containing amino acid metabolism showed that BET increased the levels of nonenzymatic antioxidants,S-adenosylmethionine (SAM) and methionine (p < 0.05), via the regulation of the methionine-omocysteine cycle. Additionally, the three methyl groups of BET were found to play a key role in its antioxidant activity. The possible reason was that because of the hydrophobicity of the three methyl groups and hydrophilicity of the carboxyl of BET, a tight protective membrane was formed around cells to prevent oxidative stress inducer from inducing ROS generation and cell damage. In conclusion, the antioxidant mechanism of BET was found to enhance nonenzymatic antioxidant defenses via the methionine-homocysteine cycle and form a protective membrane around cells.

Structural Characterization of a Novel Polysaccharide from Lepidium meyenii (Maca) and Analysis of Its Regulatory Function in Macrophage Polarization in Vitro

In our previous study, three novel polysaccharides, named MC-1, MC-2, and MC-3, were separated from the roots of maca (Lepidium meyenii), which is a food source from the Andes region. The structural information and immunomodulatory activity of MC-1 were then investigated. The structure and activity of MC-2 are still unknown. In this study, structural characterization revealed that MC-2 has an average molecular weight of 9.83 kDa and is composed of arabinose (20.9%), mannose (4.5%), glucose (71.9%), and galactose (2.7%). The main linkage types of MC-2 were proven to be (1→5)-α-l-Ara, (1→3)-α-l-Man, (1→)-α-d-Glc, (1→4)-α-d-Glc, (1→6)-α-d-Glc, and (1→6)-β-d-Gal by methylation and NMR analyses. Congo red assay showed that MC-2 possesses a triple-helix conformation. Immunostimulating assays indicated that MC-2 could induce M1 polarization of original macrophages and convert M2 macrophages into M1 phenotype. Although MC-2 could not shift M1 macrophages into M2, it could still inhibit inflammatory reactions induced by lipopolysaccharide. Furthermore, Toll-like receptor 2, tTll-like receptor 4, complement receptor 3, and mannose receptor were confirmed as the membrane receptors for MC-2 on macrophages. These results indicate that MC-2 could potentially be used toward hypoimmunity and tumor therapies.

Physicochemical properties and antioxidant activities of acidic polysaccharides from wampee seeds.

Two novel polysaccharide fractions, named WP1 and WP3, were extracted and purified from wampee [Clausena lansium (Lour.) Skeels] seeds. Their physicochemical properties, in vitro and in vivo antioxidant activities were investigated. Results indicated that both WP1 and WP3 were acidic heteropolysaccharides with uronic acid content of 45.35% and 56.79%, respectively. The molar ratio of rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, arabinose of WP1 was 5.01:1.50:39.53:1:10.76:23.50 while WP3 was 5.76:1.73:27.27:1:4.72:8.77. Furthermore, WP3 not only exhibited stronger in vitro antioxidant activities than WP1, but also more significantly increased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) level in serum of SD rats induced by high-fat diet.

Isolation and identification of a novel anticoagulant peptide from enzymatic hydrolysates of scorpion (Buthus martensii Karsch) protein

An enzymatic hydrolysis approach was proposed for the preparation of bioactive hydrolysate of scorpion Buthus martensii Karsch (BmK) protein. Results showed that the anticoagulant activity of the hydrolysates of BmK protein was closely related to both the enzyme type and the degree of hydrolysis. Alcalase AF showed to be the best enzymes for the hydrolysis. And the hydrolysis degree (DH) was closely related with the anticoagulant activity of the hydrolyzate. At a DH value of 18% with Alcalase AF, the hydrolyzate exhibited the highest activity. The hydrolysate was then separated and purified by consecutive chromatographic procedures, giving a novel anticoagulant peptide consisting of ten amino acids (MW: 1119.8Da) with its sequence of Val-Glu-Pro-Val-Thr-Val-Asn-Pro- His-Glu identified by MALDI-TOF/TOF MS. The negatively charged amino acids and hydrophobic amino acids may contribute to the anticoagulant activity of the prepared peptides. And the Val residue in N-terminal was also critical for the anticoagulant activity of the BmK peptide. Furthermore, the anticoagulant activity kept stable after in vitro digestive simulation. This research provided a promising bioprocessing route for production of anticoagulant peptides using BmK protein as a potentially valuable bioresource.

Secretory expression and characterization of a novel peroxiredoxin for zearalenone detoxification in Saccharomyces cerevisiae.

Zearalenone (ZEN) is a Fusarium mycotoxin, which is considered to be an oestrogenic endocrine disruptor found to cause severe morphological and functional disorders of reproductive organs in livestock. Increasing attention has been paid to the development of an effective strategy for ZEN decontamination. ZEN is oxidized into smaller estrogenic metabolites by a novel peroxiredoxin (Prx) isolated from Acinetobacter sp. SM04. The Prx coding gene was cloned in a secretory vector pYES2-alpha (pYα) with an alpha (α) signal peptide gene inserted into the multiple cloning site of pYES2. The recombinant Prx was secreted from Saccharomyces cerevisiae INVSc1 after inducing with 2% (w/v) galactose for 72 h, and was found to be nearly 20 kDa through 12% SDS-PAGE. The expressed amount of recombinant Prx was 0.24 mg/mL in the extracellular supernatant. Recombinant Prx showed a gradient increase at the beginning of ZEN degradation. The final ZEN degradation amount was 0.43 μg by one unit recombinant Prx after 12 h. Furthermore, the temperature, H(2)O(2) concentration, and pH for highest peroxidase activity of recombinant Prx were 80°C, 20 mM and 9.0, respectively. When compared with other peroxidases, the thermal stability and alkali resistance of recombinant Prx were much better. The results suggest that recombinant Prx is successfully expressed in S. cerevisiae.