| Jellyfish (Rhopilema esculentum) is one of the most important fishery resource in China, which has the high economic, nutritional and medicinal value. In this paper, collagen without telopeptides was prepared from the umbrella of jellyfish Rhopilema esculentum and the phsicochemical characteristics were studied. The appropriate protease and condition of hydrolysis was selected to produce collagen polypeptides. The antioxidant mechanism of polypeptides was investigated by different tests in vitro. Utilizing cultured B16 melanoma cells, inhibition effects of collagen polypeptides with different molecular weight on melanin biosynthesis and their molecular mechanism were researched from the aspects of antioxidation. Further more, protective effects of collagen and collagen polypeptides on mice skin photoaging induced by UV irradiation were discussed. This paper aimed to broaden the research field of collagen, produce high-valued functional food and medicine from jellyfish and provide a valuable scientific basis for the industrialization development of jellyfish. The main results are as follows:1. The main compositions of jellyfish were determined. Moisture content of fresh jellyfish was above 96%. Contents of crude protein, mucopolysaccharides, fat and ash in dry samples of jellyfish umbrella were 82.5%,1.6%, 0.3% and 15.3%, respectively and contents in jellyfish oral-arm were 79.1%, 1.8%, 0.4% and 17.9%, respectively. Proteins of jellyfish were mainly composed of myofibrillar proteins and alkali-insoluble proteins.2. The studies of the extractions and the biochemical characterizations of collagen from jellyfish umbrella were undertaken. The rates of enzymic extraction were highest among the extraction methods and the rates of extractions by solvent pretreatment and pressure pretreatment were similar. Pepsin-soluble collagen was extracted from jellyfish umbrella and classified as type I collagen. The compositional features of the amino acids were with the highest contents of Gly (300 residues/1000) but with low contents of His, Tyr and Met. Combined with the results of SDS-PAGE, collagen was (α1)3 trimers whileαchain (about 115KDa) resembeledα1 chain of type I collagen of vertebrate. The content of total sugar was 2.8%. The denaturation temperature (Td) and shrinkage temperature (Ts) were 28.8℃and 51.6℃respectively, both lower than those of bovine skin collagen. FTIR investigations showed the existence of helical arrangements of collagen. Furthermore, collagen had the highest solubility at pH3 and the pI was at about 6. No significant changes in solubility were observed in the present of NaCl up to 4% (w/v) and a sharp decrease was found with NaCl above 4% (w/v).3. Jellyfish collagen was hydrolyzed by different protease treatments to obtain antioxidative polypeptides. The collagen hydrolysates by trypsin and properase E exhibited the high drgree of hydrolysis (DH) and hydroxyl radical scavenging activities. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions (including enzyme to substrate ratio, pH and temperature) to prepare protein hydrolysates from jellyfish umbrella collagen. Trypsin was selected to hydrolyze collagen at pH 7.8, 48.8℃, enzyme-to-substrate ratio ([E]/[S]) 3.5%; Properase E was pH9.1, 47.3℃, [E]/[S] 2.8%. The R2 value of radical scavenging activity and DH indicated that the designed models could correctly explain the data variation and significantly represent the actual relationships between the reaction parameters. Double enzymes hydrolysis could improve DH and hydroxyl radical scavenging activities. The optimum parameters of the bienzyme hydrolysis were : pH 9.1, 48.0℃, [E]/[S] 3.5% and 2.8% respectively. Molecular weight (MW) of single enzymic hydrolysis was concentrated to 2,000Da, and that of bienzyme hydrolysis was 700Da. Amino acids compositins of three hydrolysis conditions were similar. They were rich in Gly and Pro and the total hydrophobic amino acids (THAA) contents were above 35%.4. The bienzymic hydrolysates were fractionated into three ranges of molecular weight (JCH1>3,000Da, 1,000Da0.05) which indicated collagen polypeptides had no cytotoxic activity. Collagen polypeptides exerted obvious inhibition on productions of melanin (P<0.05, P<0.01) in concentration dependent manners. Inhibitory activity of JCH2 was higher than JCH1 and JCH2. Afer incubation with JCH2 (100μg/ml) for 48h, melann content was decreased by 38.8%. Compared the other factions, JCH2 showed the highest tyrosinase inhibition (40.5% of control at dose of 50μg/ml). Intracellular GSH levels in B16 melanoma cells were enhanced by JCH2, while GSSG levels were suppressed. Consequently, the GSH/GSSG ratio was increased. It could ensure intracellular reduce capacity. Fourthermore, JCH2 could decrease intracellular levels of cAMP significantly (P<0.01), and then supress the expression of tyrosinase mRNA. The results showed JCH2 was a novel anti-melanogenic peptide from natural resources and exerted actions via its antioxidative properties and copper-chelating ability6. Effects of collagen and collagen polypeptides on chronic ultraviolet radiation-induced skin photoaging in hairless mice were studied in this chapter. Collagen and collagen polypeptides could protect immune system by increasing the indexs of thymus and the indexes of spleen. Collagen and collagen polypeptides coulde increase the activities of SOD, CAT, and GSH-PX (P<0.05) and the content of GSH (P<0.01) while decrease the content of MDA (P<0.05), which alleviated the oxidant press UV-induced. Meanwhile, collagen and collagen polypeptides could recover the abnormal changes of skin collagen, lipid, total ceramide and glycosaminolycan. Fourthremore, histological studies showed collagen and collagen polypeptides could improve the breakdown of dermal interstitial collagen and cross-linking of inter- and intra-collagen molecules, maintain the ratio of type I/III collagen, and ameliorate the order and distribution of elastic fiber. The results showed collagen and collagen polypeptides could relieve the damages of UV treatment, and activities of collagen polypeptides were higher than collagen. Therefore, collagen polypeptides might have a good anti-photoaging action.
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