Program

Sea cucumber peptide powder (SCPP) is high in nutrition and digestible, and is commonly used in the products development with high quality and value in the form of nutrition compatibility as basic material powder. However, during processing and storage the peptide powder has metamorphosing phenomenon such as moisture absorption, sticky, getting agglomeration, and off-flavor forming, resulting in loss of functionality and lowered quality. Thus, in the present study, moisture absorption characteristic of SCPP was investigated with aid of low field nuclear magnetic resonance (LF-NMR), and the effect of hygroscopicity on peptide chemical structure, morphology and composition of volatile components were analyzed with flourier transformation infrared spectroscopy (FT-IR spectroscopy), scanning electron microscopy (SEM) and the full two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOF-MS). Sum of T₂ relaxation peak area (A_2t) was 13106.02 ± 10.72 and 27932.03 ± 789.64 when 1 g SCPP was exposed at 25°C/75% RH for 0 h and 28 h. The increase of A_2t could be attributed to absorbed water. In addition, the adsorbed water mainly existed in the form of bound water with T₂ relaxation time less than 1 ms. The results of GC×GC-TOF-MS suggest that there were 21 major volatile components in the original SCPP, including 8 alcohols, 1 ketone, 5 aldehydes, 6 alkanes and 1 ester. However, after SCPP was exposed at 25°C/75% RH for 28 h, 8 alcohols, 1 ketone, 4 aldehydes, 8 alkanes were detected. Moreover, the content of some volatile components changed significantly. The results attained in this study can provide a reference for the processing and storage of the SCPP.

Sea cucumbers(stichopus japonicus) have been consumed and used in traditional medicine for centuries. The aquaculture of sea cucumber has been rising rapidly in Asia in recent decades. However, sea cucumber ovum (SCO) is often discarded during industrial processing, causing waste and environmental pollution. Most notably, the SCO is a valuable raw material to produce protein hydrolysates for calcium-chelating peptides owing to its high protein content, availability and low cost. In this study, a novel peptide from SCO tryptic hydrolysates, containing specific amino acids associated with calcium binding, was obtained and identified by UPLC-QTOF-MS/MS with Mascot analysis, and synthesized by solid-phase peptide synthesis method using Fmoc-protected amino acids. The possible mechanism of calcium binding to the sea cucumber ovum peptide (SCOP) was elucidated using analytical techniques such as ultraviolet-visible spectroscopy, energy-dispersive X-ray spectroscope, scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and isothermal titration calorimetry. The formation of sea cucumber ovum peptide-calcium (SCOP-Ca) complexes was confirmed by ultraviolet-visible spectroscopy and energy-dispersive X-ray spectroscope. The scanning electron microscopy, and dynamic light scattering revealed that the SCOP bind with calcium ions to form compact nanoparticles. Further, the formation of the compact nanoparticles was attributed to peptide folding primarily via the interaction of calcium ions with carboxyl oxygen and amino nitrogen atoms in the SCOP. Therefore, this study identifies SCO as a good source of peptides with potential applications as functional ingredients in the management of calcium deficiencies.

The efficacy of the controlled Maillard reaction with alginate oligosaccharide (AO) in a dry state was examined for development of an anti-inflammatory compound from fish myofibrillar protein (Mf).
Lyophilized Mf and its digested peptides by pepsin-trypsin (Mf-P) were mixed with AO (half of the total protein weight) and incubated under controlled temperature/humidity conditions for covalently introduction of AO through the Maillard reaction (referred to as Mf-AO and Mf-P-AO). After digestion of Mf-AO with pepsin-trypsin (dMf-AO), the two kinds of AO introduced peptides (dMf-AO and Mf-P-AO) were subjected to anti-inflammatory assay using lipopolysaccharide (LPS)-stimulated murine macrophage (RAW 264.7 cells) and inflammation model animals.
The results were as follows: (1) dMf-AO and Mf-P-AO markedly suppressed the secretion of inflammatory mediators (nitric oxide, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6)), and the suppressive effect was enhanced with the progress of the AO conjugation. Concurrently, (2) dMf-AO suppressed the LPS-induced gene and protein expression of inducible nitric oxide synthase, TNF-a, IL-6, and cyclooxygenase (COX)-2, while COX-1 expression was unaffected. Furthermore, (3) oral administration of Mf-AO and dMf-AO inhibited exacerbation of carrageenan-induced paw edema in mice. (4) Acidic peptide fractions of dMf-AO and Mf-P-AO (around pI=2), fractionated by isoelectrophoresis, showed strong suppressive effect on the secretion of the inflammatory mediators in RAW 264.7 cells. These results indicate that AO-conjugation using the controlled Maillard reaction is a useful approach for enhancing the anti-inflammatory activity of salmon Mf as a nutraceutical food.

Selenoneine is a novel selenium containing compound discovered in the blood of bluefin tuna. Since selenoneine has strong antioxidant activity and detoxification ability of methyl mercury, it is expected to be used for functional foods as antioxidant and selenium supplements. This study characterized its biological activities against hypertension and skin melanism.
Inhibition of angiotensin converting enzyme (ACE) and tyrosinase was assayed in the presence of selenoneine. Melanin generation was measured in mice melanoma cells and human melanoma cells.
Selenoneine inhibited activities of ACE and tyrosinase. The Km values of ACE were 1.396 ± 0.103 mM with selenoneine and 0.724 ± 0.051 mM without selenoneine. Lineweaver-Burk plots for inhibition of ACE activities by selenoneine indicated a competitive inhibition. Melanin generation was also inhibited by selenoneine in enzyme activity assay and bioassay with human cultured keratinocytes. On the other hand, selenite and ergothioneine (thiol-analog of selenoneine) did not inhibit these enzyme activities and melanin generation.
ACE and tyrosinase are metalloenzymes. ACE has a zinc ion and tyrosinase has two copper ions in their active centers. Since seelenoneine inhibited metalloenzymes, selenol group in selenoneine may interact with metal ions situated active sites. Therefore, selenoneine has a novel biological functions in metalloenzyme inhibition, relating to prevention of hyper-tension by ACE inhibition and reduction of melanin production by tyrosinase inhibition.

Selenoneine, 2-selenyl-Nα,Nα,Nα-trimethyl-L-histidine, is a strong antioxidant found in the tissues of tuna and other fish that can mediate the prevention of autoxidation of heme proteins, such as hemoglobin and myoglobin. We measured concentrations of selenoneine, total selenium, and total mercury in the red muscles of tuna species. Red muscles of yellowfin tuna contained the high levels of selenium at 5.6–21.2 mg/kg, and almost all selenium in tuna muscles was identified to be selenoneine by HPLC-ICP-MS analysis. We developed selenium-rich surimi products from the red muscles of yellowfin tuna. The surimi product contained selenoneine at 0.28 mg Se/kg. We also concentrated and purified selenoneine from the waste water and guts of the surimi processing of fish. After filtration of the boiling water by reverse osmosis membrane and column chromatography with cation exchange and Sepabeads resins, selenoneine was purified by reverse-phase HPLC. The tuna surimi products and the purified selenoneine concentrate can be applied to be the selenium-rich functional food and feed to enhance selenium-mediated antioxidant functions.

[Objective] Many researches have been done on health functional properties of red algae-derived substances, such as flavonoids and steroids. In this study, polysaccharides were extracted from red algae (Chondrus verrucosus) and the anti-allergic activities were investigated.

[Materials and Methods] (1) Purification of polysaccharides: The specimens were collected on the coast of Kesennuma, Miyagi, Japan in May, 2016. Polysaccharide was extracted with 3 volumes of 0.17 N hydrochloric acid and was further purified by anion-exchange column chromatography with a sodium chloride concentration linear gradient of 0 to 2 M.
(2) The anti-allergic activities: Hyaluronidase inhibitory activity, and mast cell degranulation release effect on rat basophilic leukemia (RBL-2H3) cultured cell line by the antigen and A23187 (calcium Ionophore) stimulation were investigated.
(3) The percentages of surface molecules: The Muse® Human CD4 T Cell Assay, and human Lymphocyte CD69 Assay were performed using the Muse® Cell Analyzer.

[Results and Discussion] The polysaccharide was fractionated into the three major fractions which were eluted at around 0.69 M, 0.96 M and 1.69 M NaCl, respectively. The sulfate group content in the 0.69 M (34.5%) and 0.96 M (42.0%) fractions were higher than in the 1.69 M (12.5%) fraction. Each fraction showed the ability to inhibit cell proliferation and changed the ratio of CD4 T cells, and CD69 expression. For release inhibition of β-hexosaminidase, the 0.69 M (59.1%) and 0.96 M (62.9%) fractions showed higher degranulation inhibiting activity than the 1.69M (49.8%) fraction. From these results, it was inferred that the polysaccharides derived from the red algae C. verrucosus have the ability to suppress allergies.

Astaxanthin is a valuable food component because of its antioxidative properties. This compound is mainly produced by algae and commonly found in seafood products such as crustaceans and salmon. Due to its highly unsaturated structure, astaxanthin can be prone to degradation under certain conditions. This study was conducted to evaluate the effects of incorporating ergothioneine-rich mushroom extract (ME) in astaxanthin-rich fish muscle, using liposomes as an in vitro cell model. ME containing ergothioneine was added into the liposome suspension, and its effects on astaxanthin and lipid stability were evaluated. Liposomes of different variations, with or without astaxanthin or ergothioneine, were prepared and subjected to different conditions in the presence or absence of radical initiators (AAPH or AMVN) at different temperatures (25°C and 37°C). Lipid hydroperoxides (HPO), astaxanthin, and ergothioneine were quantitatively measured. Results showed that HPO formation in all the treatments without the presence of radical initiators at 25°C, did not significantly increase even after 17 days. The addition of radical initiators significantly accelerated the HPO formation. The antioxidative effects of ME against AMVN-induced HPO formation was not apparent, however the presence of ergothioneine in ME significantly controlled HPO formation by AAPH. There was a significant decrease in the astaxanthin content in all treatments during storage, and this was accelerated by the addition of AAPH or AMVN. However, the addition of ME significantly delayed astaxanthin degradation by AAPH, and retained at least 20% more astaxanthin than the treatment with no ME. Ergothioneine content in the treatment with AAPH at increased temperature (37°C) slightly decreased to 85% after 24 hours. Nonetheless, ergothioneine remained stable in other storage conditions. Results of this study illustrate the feasibility of protecting astaxanthin against degradation and controlling lipid oxidation in the model system through the antioxidative action of ergothioneine from mushroom extracts.