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Li Y.,Ocean University of China | Li W.,Qingdao University | Zhang G.,Ocean University of China | Lu X.,All China Federation of Supply and Marketing Co operatives | And 4 more authors.
International Journal of Biological Macromolecules

Two different degradases from Alteromonas sp. A321for polysaccharides from Enteromorpha prolifera (DPE-L and DPE-P) were purified to homogeneity. The molecular weights of purified DPE-L and DPE-P were 75.2 and 102.5kDa, respectively, and their internal sequences were analysed by LC-MS-MS. The enzymes exhibited an optimum temperature of 30-40°C (DPE-L) and 35-45°C (DPE-P), an optimum pH of 7.0 (DPE-L) and 6.0 (DPE-P). DPE-P was highly stable in the presence of EDTA and 1,10-phenanthroline while DPE-L was inhibited by 1,10-phenanthroline. The Km values of DPE-L and DPE-P were 2.93mg/ml and 0.31mg/ml and the Vmax values were 6.11μmol/min/ml and 2.88μmol/min/ml, respectively. Results of HPLC and ESI-MS analyses showed that enzymatic products were: Rha1(SO3H)1, Rha1(SO3H)1Gluc1, Rha2(SO3H)2Gluc1, and Rha3(SO3H)3Gluc1Xyl1 by DPE-L, and Glu2, Glu3, plus Glu4 by DPE-P, respectively. Thus DPE-L and DPE-P can be used to produce oligosaccharides which potentially revealed more of structure of polysaccharides from E. prolifera. © 2016 Published by Elsevier B.V.. Source

Zhang D.,China Agricultural University | Liu Y.,Jimei University | Chu L.,All China Federation of Supply and Marketing Co operatives | Wei Y.,Chinese National Research Institute of Food and Fermentation Industries | And 4 more authors.
Journal of Physical Chemistry A

Various radical-scavenging activities (RSA) assessment assays are based on discrete mechanisms and on using different radical sources. Few studies have analyzed the structural significance of flavonoids in their peroxyl radical activities in the oxygen radical absorbance capacity (ORAC) assay. In this study, the RSA of 13 flavonoids in two ORAC assays with different probes (fluorescein and pyrogallol red) were investigated. Neither O-H bond dissociation enthalpy nor ionization potential values of flavonoids correlated with ORAC values. The proton affinity (PA) and electron transfer enthalpy (ETE) values, which were obtained via the sequential proton-loss electron-transfer mechanism, were significantly associated with the ORACpyrogallol Red and ORACfluorescein assays, respectively. Thus, PA represented the kinetic aspect of RSA, whereas ETE reflected the RSA extent. The PA values and the most acidic sites of flavonoids were affected by intramolecular electronic interactions, H-bonding, 3-hydroxyl group in the C ring, and conjugation systems. The stability of the deprotonated flavonoid determined the ETE value. Apart from the PA and ETE values in the first oxidation step of flavonoids, the PA and ETE values in the second oxidation step also affected the ORAC values of flavonoids. © 2013 American Chemical Society. Source

Zheng X.,All China Federation of Supply and Marketing Co operatives | Zhu F.,All China Federation of Supply and Marketing Co operatives | Wu M.,All China Federation of Supply and Marketing Co operatives | Yan X.,All China Federation of Supply and Marketing Co operatives | And 2 more authors.
Journal of the Science of Food and Agriculture

BACKGROUND: Carotenoid content analysis in wolfberry processed products has mainly focused on the determination of zeaxanthin or zeaxanthin dipalmitate, which cannot indicate the total carotenoid content (TCC) in wolfberries. RESULTS: We have exploited an effective approach for rapid extraction of carotenoid from wolfberry juice and determined TCC using UV-visible spectrophotometry. Several solvent mixtures, adsorption wavelengths of carotenoid extracts and extraction procedures were investigated. The optimal solvent mixture with broad spectrum polarity was hexane-ethanol-acetone (2:1:1) and optimal wavelength was 456 nm. There was no significant difference of TCC in wolfberry juice between direct extraction and saponification extraction. CONCLUSION: The developed method for assessment of TCC has been successfully employed in quality evaluation of wolfberry juice under different processing conditions. This measurement approach has inherent advantages (simplicity, rapidity, effectiveness) that make it appropriate for obtaining on-site information of TCC in wolfberry juice during processing. © 2014 Society of Chemical Industry. Source

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