Yunhai He

Novel antioxidative peptides from the protein hydrolysate of oysters ( Crassostrea talienwhanensis )

The antioxidative activity of hydrolysate peptides from oysters (Crassostrea talienwhanensis) was investigated. After hydrolysis with subtilisin, the yields of the peptides that were soluble in trichloroacetic acid (TCA-soluble) and the antioxidant activities of the resulting hydrolysate were determined using an orthogonal design and a hydroxyl radical scavenging reaction. The hydrolysate was fractionated using Sephadex G-15 gel filtration chromatography, and the two resulting bioactive peptides were subsequently purified by RP-HPLC with a Kromasil C18 (ODS) column. The amino acid sequences were analyzed by nano-ESI-MS/MS. The critical reaction temperature, pH, hydrolysis time and enzyme-to-substrate (E/S) ratio were determined for the optimum hydrolysis with subtilisin, and the E/S ratio was found to be the most critical reaction condition. The amino acid sequences of the peptides (518 and 440 Da) were proline-valine-methionine-glycine-aspartic acid (PVMGA) and glutamine-histidine-glycine-valine (QHGV), respectively. These two novel peptides exhibited high antioxidative actions based on their hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities.

Structural characterisation of algae Costaria costata fucoidan and its effects on CCl4-induced liver injury

Fucoidan is a well-known natural product that is commonly found in brown algae and shows a variety of activities, including immunomodulation, antioxidation, and the combat of carcinogens. The fucoidan fractions of Costaria costata, a brown algae introduced from Japan and cultured in northern China, were studied. The fucoidan fractions were extracted, separated, and purified using a combinatorial procedure consisting of enzymolysis, ethanol precipitation, and DEAE and size-exclusion chromatographies. The fundamental characteristics of the four enriched fucoidan fractions (F1-F4), such as their sulphate content and monosaccharide composition, were investigated. FTIR and NMR spectroscopy were employed to further elucidate the structural features of the four fractions. It was found that the F1-F4 fractions all showed oxidative activity against hydroxyl radicals. The bioactive effects of the fucoidan fractions on CCl4-induced liver injury suggest their potential use as ingredients for functional foods or pharmaceuticals.

Studies on the hepatoprotective effect of fucoidans from brown algae Kjellmaniella crassifolia

For illustrating the relation of different structural characteristics correlated with the hepatoprotective effect, studies of fucoidan from algae Kjellmaniella crassifolia, a brown alga distributed in north Japan, were carried out. The fucoidan fractions of K. crassifolia were extracted, separated, and purified using a combinatorial procedure consisting of enzymolysis, ethanol precipitation, DEAE and size-exclusion chromatographies. The fundamental characteristics of the four enriched fucoidan fractions (KF1-KF4), including their sulphate content and monosaccharide composition, were investigated. The fucose was the main composition of monosaccharide for KF1-KF4, that of KF4 was up to 91.4%. The Glu-UA was the special composition of monosaccharide. FTIR and NMR spectroscopy were employed to elucidate the structural features of all fractions which further illustrated that fucose was the main monosaccharide. It was found all the four fractions showed antioxidative activity against hydroxyl radical and had the bioactive effects on CCl4-induced liver injury.

Structural characterization and antitumor effects of fucoidans from brown algae Kjellmaniella crassifolia farmed in northern China

Brown alga-derived fucoidan has been proven to have a variety of bioactivities. To explore the antitumor effect of fucoidan, Kjellmaniella crassifolia (farmed in Dalian, China)was enzymatically digested to obtain the crude extract (F), which was further separated into three fractions (F1, F2 and F3). The monosaccharide composition and structural characteristics of the isolated fractions were determined using high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR) and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. F1 is an acetylated galactofucan, and F2 consists of fucose, galactose, mannose and glucuronic acid. F3 has two components, an acetylated galactofucan and a pure sulfated fucan. F, F1 and F2 showed limited cytotoxicity against murine hepatocarcinoma Hca-F cells in vitro. Oral administration of F at a dose of 450 mg/kg d significantly inhibited lump growth in Hca-F-inoculated mice and led to upregulated FAS expression in tumor tissues compared to that of the control. F1 and F2 did not show competitive antineoplastic efficacy, as did the crude extract. Crude fucoidan could be a promising antitumor adjuvant. The origin of its efficacy may be the small molecules, such as phenols that attached to native fucoidan. This theory needs to be further confirmed.

Highly crystalline cellulose from brown seaweed Saccharina japonica : isolation, characterization and microcrystallization

Highly crystalline cellulose was isolated from kelp (Saccharina japonica) and used to prepare microcrystalline cellulose (MCC) via an optimized chemical–mechanical approach. The purity of the cellulose reached 99.9% (dry basis) according to HPLC and FT-IR analysis, with extraction yield reaching 9.9% on a dry kelp basis. The kelp cellulose (KC) had a degree of polymerization (DP) of 695, and featured natively highly crystalline structure with a crystallinity index (CrI) as high as 90.9% according to X-ray powder diffraction analysis. The KC was subjected to successive hydrochloric acid treatment and ball-milling to obtain MCC having a DP of 235 and a CrI of 88.6%. The kelp MCC exhibited comparable quality attributes to commercially available MCC. Polymorphic analysis based on peak deconvolution of the diffractograms revealed that the crystalline region of the kelp cellulose featured one-chain triclinic (Iα) rich polymorph, in contrast to two-chain monoclinic (Iβ) dominant structure found in higher-plant cellulose.Graphical Abstract