Bingna Cai

Ultrasonic Extraction of Polysaccharides from Laminaria japonica and Their Antioxidative and Glycosidase Inhibitory Activities

In the present study, ultrasonic extraction technique (UET) is used to improve the yield of polysaccharides from Laminaria japonica (LJPs). And their antioxidative as well as glycosidase inhibitory activities are investigated. Box-Behnken design (BBD) combined with response surface methodology (RSM) is applied to optimize ultrasonic extraction for polysaccharides. The optimized conditions are obtained as extraction time at 54 min, ultrasonic power at 1050 W, extraction temperature at 80°C and ratio of material to solvent at 1:50 (g mL−1). Under these optimal ultrasonic extraction conditions, an actual experimental yield (5.75% ± 0.3%) is close to the predicted result (5.67%) with no significant difference (P > 0.05). Vitro antioxidative and glycosidase inhibitory activities tests indicate that the crude polysaccharides (LJP) and two major ethanol precipitated fractions (LJP1 and LJP2) are in a concentration-dependent manner. LJP2 (30%–60% ethanol precipitated polysaccharides) possesses the strongest α-glucosidase inhibitory activity and moderate scavenging activity against hydroxyl radicals (66.09% ± 2.19%, 3.0 mg mL−1). Also, the inhibitory activity against α-glucosidase (59.08% ± 3.79%, 5.0 mg mL−1) is close to that of acarbose (63.99% ± 3.27%, 5.0 mg mL−1). LJP1 (30% ethanol precipitated polysaccharides) exhibits the strongest scavenging activity against hydroxyl radicals (99.80% ± 0.00%, 3.0 mg mL−1) and moderate α-glucosidase inhibitory activity (47.76% ± 1.92%, 5.0 mg mL−1). LJP shows the most remarkable DPPH scavenging activity (66.20% ± 0.11%, 5.0 mg mL−1) but weakest α-glucosidase inhibitory activity (37.77% ± 1.30%, 5.0 mg mL−1). However, all these LJPs exert weak inhibitory effects against α-amylase. These results show that UET is an effective method for extracting bioactive polysaccharides from seaweed materials. LJP1 and LJP2 can be developed as a potential ingredient in hypoglycemic agents or functional food for the management of diabetes. This study provides scientific evidence and advances in the preparation technology and a hypoglycemic activities evaluation method for seaweed polysaccharides, especially glycosidase inhibition in combination with an antioxidative activity evaluation method.

ULTRASONIC-ASSISTED PRODUCTION OF ANTIOXIDATIVE POLYSACCHARIDES FROM Crassostrea hongkongensis

The beneficial effects of oyster extract against various disorders and diseases induced by oxidative stress have aroused great interest. In this article, ultrasonic-assisted enzymolysis was employed to produce polysaccharides of Crassostrea hongkongensis (CHP) and their antioxidant activity was investigated. A single-factor experiment and then a four-factor, three-level Box–Behnken design were first used to optimize ultrasonic extraction for polysaccharides. On the basis of ridge analysis, the optimum conditions are obtained as ultrasonic treatment time of 24 min, power of 876 W, temperature of 49°C, and material–solvent ratio of 1:6 (w/v). It is found that ultrasound pretreatment before protease hydrolysis was a great help to improve CHP yield and purity, especially more favorable with flavorzyme, neutrase, alcalase, and pepsin. Furthermore, the polysaccharide fraction, which was obtained by ultrasonic pretreatment and then alcalase hydrolysis at the conditions of 3000 U/g, 55°C, pH 8.0, for 4 hr, exhibited an obvious scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical (98.48 ± 0.55% and 99.20 ± 0.12%, respectively) and a lenoleic acid peroxidation inhibition effect (85.48 ± 0.65%) at a concentration of 5.0 mg/mL. These results reveal the potential application of CHP in functional food and nutraceuticals.

Immune functional impacts of oyster peptide-based enteral nutrition formula (OPENF) on mice: a pilot study

Oyster peptides were produced from Crassostrea hongkongensis and used as a new protein source for the preparation of an oyster peptide-based enteral nutrition formula (OPENF). Reserpineinduced malabsorption mice and cyclophosphamide-induced immunosuppression mice were used in this study. OPENF powder is light yellow green and has a protein-fat-carbohydrate ratio of 16:9:75 with good solubility in water. A pilot study investigating immune functional impacts of the OPENF on mice show that the OPENF enhanced spleen lymphocyte proliferation and the activity of natural killer (NK) cells in BALB/c mice. Furthermore, OPENF can improve intestinal absorption, increase food utilization ratio, and maintain the normal physiological function of mice. These results suggest that oyster peptides could serve as a new protein source for use in enteral nutrition formula, but more importantly, also indicate that OPENF has an immunostimulating effect in mice.

Kinetic study of alkaline protease 894 for the hydrolysis of the pearl oyster Pinctada martensii

A new enzyme (alkaline protease 894) obtained from the marine extremophile Flavobacterium yellowsea (YS-80-122) has exhibited strong substrate-binding and catalytic activity, even at low temperature, but the characteristics of the hydrolysis with this enzyme are still unclear. The pearl oyster Pinctada martensii was used in this study as the raw material to illustrate the kinetic properties of protease 894. After investigating the intrinsic relationship between the degree of hydrolysis and several factors, including initial reaction pH, temperature, substrate concentration, enzyme concentration, and hydrolysis time, the kinetics model was established. This study showed that the optimal conditions for the enzymatic hydrolysis were an initial reaction pH of 5.0, temperature of 30°C, substrate concentration of 10% (w/v), enzyme concentration of 2 500 U/g, and hydrolysis time of 160 min. The kinetic characteristics of the protease for the hydrolysis of P. martensii were obtained. The inactivation constant was found to be 15.16/min, and the average relative error between the derived kinetics model and the actual measurement was only 3.04%, which indicated a high degree of fitness. Therefore, this study provides a basis for the investigation of the concrete kinetic characteristics of the new protease, which has potential applications in the food industry.

Poster 1024: Accelerated healing of full-thickness cutaneous wound using purified apitoxin from asiatic honey bee (Apis cerana Fabricius).

Background Cutaneous wound healing is a conserved, complex, multi-cellular, multi-molecular process, which is executed and regulated by equally complex signaling networks involving numerous growth factors, cytokines and chemokines. It functions to facilitate barrier restoration following injury-induced loss of skin integrity. Apitoxin, or honey bee venom, has been claimed to be of use in skin wound healing, arthritis, herpes zoster, etc. However, the major allergens in apitoxin such as phospholipase A2 and hyaluronidase, can easily induce life-threatening IgE-mediated allergic reactions in humans. Thus these destructive components should be removed effectively before the apitoxin therapy.

Antiaging activity of low molecular weight peptide from Paphia undulate

Low molecular weight peptide (LMWP) was prepared from clam Paphia undulate and its antiaging effect on D-galactose-induced acute aging in rats, aged Kunming mice, ultraviolet-exposed rats, and thermally injured rats was investigated. P. undulate flesh was homogenized and digested using papain under optimal conditions, then subjected to Sephadex G-25 chromatography to isolate the LMWP. Administration of LMWP significantly reversed D-galactose-induced oxidative stress by increasing the activities of glutathione peroxidase (GPx) and catalase (CAT), and by decreasing the level of malondialdehyde (MDA). This process was accompanied by increased collagen synthesis. The LMWP prevented photoaging and promoted dermis recovery and remission of elastic fiber hyperplasia. Furthermore, treatment with the LMWP helped to regenerate elastic fibers and the collagen network, increased superoxide dismutase (SOD) in the serum and significantly decreased MDA. Thermal scald-induced inflammation and edema were also relieved by the LWMP, while wound healing in skin was promoted. These results suggest that the LMWP from P. undulate could serve as a new antiaging substance in cosmetics.