Yaoguang Chang

Crystalline structure and thermal property characterization of chitin from Antarctic krill (Euphausia superba)

Antarctic krill (Euphausia superba) has been widely studied and extensively recognized as a target for commercial fishing. In this study, Antarctic krill chitin was extracted from defatted Antarctic krill shell, and its crystalline structure and thermal properties were characterized by employing Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry. Results showed that Antarctic krill chitin corresponded to the α-polymorph, and was composed of small, stable, and uniform microcrystals. The degree of N-deacetylation was 11.28 ± 0.86%. The d-spacings of Antarctic krill chitin were 9.78 Å and 4.63 Å at (020) and (110) planes. The crystalline sizes were 6.07 nm and 5.16 nm at (020) and (110) planes, respectively. The activation energy of the polysaccharide chain decomposition was 123.35 kJ/mol and the glass transition (T(g)) of Antarctic krill chitin was 164.96 °C.

A novel glycosaminoglycan-like polysaccharide from abalone Haliotis discus hannai Ino: purification, structure identification and anticoagulant activity.

A novel glycosaminoglycan-like sulfated polysaccharide (AAP) from the pleopods of Haliotis discus hannai Ino was purified by DEAE ion exchange chromatography followed with S-300 HR geltrion chromatography. Chemical composition analysis indicated that AAP was composed of galactosamine, glucuronic acid, fucose, galactose with a ratio of 2.14:2.37:2.94:1, the content of sulfate was 15.5%. The average molecular weight (M(w)) was 56.2 kDa in a TSK G4000 column. Further IR, 1D, 2D NMR spectroscopic analysis of the correlation signals of different sugar units gave a proposal repeating structure, as follows: [chemical structure: see the text] In vitro anticoagulant assay indicated AAP prolonged both the activated partial thromboplastin time (APTT) and thrombin time (TT), with a 22.5 U/mg and 72.0 U/mg compared with standard heparin, respectively. The anticoagulant property of AAP was mainly attributed to powerful potentiation thrombin by anti-thrombin III.

Structural study of fucoidan from sea cucumber Acaudina molpadioides: A fucoidan containing novel tetrafucose repeating unit

Structure of fucoidan from sea cucumber Acaudina molpadioides (Am-FUC) was investigated in this study. Low molecular weight polysaccharide of Am-FUC (Am-LMW) was prepared by enzymatic degradation and assayed by nuclear magnetic resonance. According to the structure of Am-LMW, and referring to previously reported information of Am-FUC oligosaccharides, the structure of Am-FUC was elucidated as [→3-α-l-Fucp-1→3-α-l-Fucp2,4(OSO3(-))-1→3-α-l-Fucp-1→3-α-l-Fucp2(OSO3(-))-1→]n. Compared to other investigated fucoidans, which also consist of tetrafucose repeating units with 1→3-linkages, Am-FUC contains a novel repeating unit distinctive in sulphation pattern.

Enzymatic preparation and structural determination of oligosaccharides derived from sea cucumber (Acaudina molpadioides) fucoidan

Sea cucumber fucoidan is a major bioactive component of sea cucumber. Sea cucumber is widely consumed in East Asian countries as healthy food. Employing the degrading enzyme from the marine bacterium strain Flavobacteriaceae CZ1127, sea cucumber (Acaudina molpadioides) fucoidan oligosaccharides were prepared by enzymatic hydrolysis. The oligosaccharide profile of the hydrolysate was determined by liquid chromatography coupled with mass spectrometry (LC-MS). With the assistance of LC-MS, four major oligosaccharides in the hydrolysate were purified. By using tandem mass spectrometry and nuclear magnetic resonance, delicate structures of the oligosaccharides were verified as α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp, α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp-1→3-α-l-Fucp, α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp-1→3-α-l-Fucp-1→3-α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp and α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp-1→3-α-l-Fucp-1→3-α-l-Fucp-1→3-α-l-Fucp(2,4OSO3(2-))-1→3-α-l-Fucp-1→3-α-l-Fucp.

Structure elucidation of fucoidan composed of a novel tetrafucose repeating unit from sea cucumber Thelenota ananas

Thelenota ananas is one of the most popular edible sea cucumber species consumed in China and some Southeast Asian countries. In this study, the delicate structure of fucoidan from T. ananas (Ta-FUC) was clarified. Oligosaccharides and low molecular weight polysaccharides of Ta-FUC were prepared by enzymatic degradation. Their structures, which retained primary structural features of Ta-FUC, were investigated using tandem mass spectrometry and nuclear magnetic resonance. As a result, Ta-FUC was found to be composed of a novel tetrafucose repeating unit [→3-α-L-Fucp-1→3-α-L-Fucp-1→3-α-L-Fucp2,4(OSO3(-))-1→3-α-L-Fucp2(OSO3(-))-1→]. Meanwhile, it was proven to possess a significant inhibitory effect on superoxide radicals with an IC50 of 17.46±0.14μg/ml. This effect was related to its sulphation pattern.

Isolation and characterization of a sea cucumber fucoidan- utilizing marine bacterium

Aims:  To isolate a fucoidan‐utilizing strain from seawater for sea cucumber fucoidan degradation.

Fucosylated Chondroitin Sulfate from Sea Cucumber in Combination with Rosiglitazone Improved Glucose Metabolism in the Liver of the Insulin-Resistant Mice

This study investigated the effects of a combination of fucosylated chondroitin sulfate (CHS) and rosiglitazone (RSG) on glucose metabolism in the liver of insulin-resistant C57BL/6J mice fed a high-fat high-sucrose diet for 19 weeks. The results showed that the combination (CHS/RSG) synergistically improved body weight gain, liver weight, fasting blood glucose levels, glucose tolerance on an oral glucose tolerance test, serum insulin levels, homeostasis model assessment indexes, and hepatic glycogen content. In liver tissue, CHS/RSG significantly normalized the activities of hexokinase, pyruvate kinase, and glucose-6-phosphatase. In additionally, it increased the mRNA expression of insulin receptors, insulin receptor substrate 2, phosphatidylinositol 3 kinase (PI3K), protein kinase B (PKB), and glycogen synthase, and inhibited glycogen synthase kinase 3β(GSK-3β) mRNA expression in the liver. This suggests that CHS/RSG treatment improves glucose metabolism by modulating metabolic enzymes and strengthening the PI3K/PKB/GSK-3β signal pathway mediated by insulin at the transcriptional level.

Simultaneous determination of dimethylamine, trimethylamine and trimethylamine-n-oxide in aquatic products extracts by ion chromatography with non-suppressed conductivity detection

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-n-oxide (TMAO) in aquatic products. They were separated by means of cation-exchange chromatography using a 3.0 mmol/L methanesulfonic acid solution as eluent and an IonPac CS17 column (250 mm x 4 mm i.d.) as the separation column. Detection limits of dimethylamine, trimethylamine and trimethylamine-n-oxide were 0.06, 0.08 and 0.10 mg/L, respectively. The relative standard deviations (RSDs) of peak area were less than 3.53%. The recoveries were between 93.7% and 104.1%. Unlike traditional methods, this validated method is inexpensive and stable.

Structure and rheological characteristics of fucoidan from sea cucumber Apostichopus japonicus.

Sea cucumber is a traditional health food consumed in East Asia. In this study, fucoidan from sea cucumber Apostichopus japonicus (Aj-FUC) was isolated, and its structure and rheological characteristics were elucidated for the first time. Aj-FUC was a branched polysaccharide mainly composed of a novel repeating unit [α-L-Fucp2(OSO3(-))-1 → 3,(α-L-Fucp-1 → 4-α-L-Fucp-1 →)4-α-L-Fucp2(OSO3(-))-1 → 3-α-L-Fucp2(OSO3(-))], clarified by using a combination of infrared spectroscopy, methylation analysis, enzymatic degradation and nuclear magnetic resonance. In steady shear measurement, Aj-FUC manifested a non-Newtonian shear-thinning behaviour at low shear rate (1-100 S(-1)) while exhibiting a non-Newtonian shear-thickening behaviour at high shear rate (100-1000 S(-1)); salts had limited impact on its flow curve. Comparative study on viscosity and rheological behaviour of Aj-FUC and a linear fucoidan extracted from sea cucumber Acaudina molpadioides suggested that the presence of branch structure might significantly influence the rheological characteristics of fucoidan.

Preparation and thermo-reversible gelling properties of protein isolate from defatted Antarctic krill (Euphausia superba) byproducts

Protein isolate was prepared from defatted Antarctic krill (Euphausia superba) byproducts by 0.1 M NaOH extraction. Maximum yield of krill protein isolate reached 28.66% by precipitation at pH 4.6. Krill protein isolate demonstrated its excellent nutritional values through amino acid composition and in vitro digestibility. Thermal transition of krill protein isolate was determined by differential scanning calorimetry measurement. Extrapolated values of glass transition temperature (Tg) and denaturation temperature (Td) of krill protein isolate were 33.8 °C and 80.3 °C when the heating rate was 2 °C/min. Dispersions of krill protein isolate generated self-supported gels at concentrations above 100 g/L without the addition of salt or other additives. A noticeable enhancement of gel strength was induced through cooling. Gels with krill protein isolate displayed a thermo-reversible behavior under repeating heating/cooling cycles, which was primarily due to the formation and disruption of hydrogen bonds. Network strength of protein gels was strongly dependent on protein concentrations.