Isolation, Characterization And Biological Activity Of Collagen Extracted From The Channel Catfish Skin

Collagen is an abundant protein in animal tissues and constitutesapproximately30%of total animal protein. Due to its unique chemical features,collagen has been utilised in various fields of industry, such as leathers, beauty,cosmetics, biomedical, pharmaceutical applications, food. Acid soluble collagen（ASC） and pepsin soluble collagen （PSC） from the skin of channel catfish（Ictalurus punctaus） were isolated. The isolated protein was confirmed as collagenby different physico-chemical techniques and detected biological activity.The yield of acid-soluble collagen （ASC） and pepsin-soluble collagen （PSC）from the channel catfish skin was optimized by statistical analysis using responsesurface methodology. The optimal conditions to obtain the highest acid-solublecollagen yield of channel catfish skin were pH2.3, liquid-solid ratio （w/v）1:60,extraction time46h, and the actual experimental collagen yield was46.28%.Theoptimal conditions to obtain the highest pepsin-soluble collagen yield of channelcatfish skin were pepsin amount50U/g, pH1.8, liquid-solid ratio（w/v）1:50,extraction time17h, and the actual experimental collagen yield was52.01%, withthe accumulated yield of76.65%.Acid-soluble and pepsin-soluble collagens （ASC and PSC）were extracted fromthe skin of channel catfish and partially characterized.α1and α2chains of ASC withmolecular weight of120and110kDa, respectively. Both α1andα2chains of PSChad slightly lower molecular weight, compared with those of ASC. A great amountof β chain can be observed in the pattern of all these collagens. Collagens from theskin had glycine as the major amino acid. Relatively high contents of alanine,proline, hydroxyproline and glutamic acid were observed. However, very lowcontents of cysteine and tyrosine were observed. The ASC, PSC from the channelcatfish skin have maximum absorptions near220nm, with little or no absorbancenear280nm. The amide A band of ASC and PSC were found at3310and3320cm^-1,which shows that there were NH groups involved in hydrogen bonds. The amide Bband positions of ASC and PSC were both observed at2930cm^-1. Regions ofamides I, II and III for ASC and PSC were1650cm^-1（amide I）;1560cm^-1（amideII）; and1240cm^-1（amide III）, exhibiting peaks in same wave numbers. Thus, both ASC and PSC showed a same secondary structure. The ASC and PSC showedtransitional curves with maximum temperatures （Tmax） of35.01℃,34.50℃,respectively. Compared with the collagens from some marine species, the Tds ofcollagens from channel catfish skin were higher than those of collagens fromwalleye pollock and brownstripe red snapper. The CD curves of ASC and PSCshowed a rotatory maximum at221nm, a minimum at198nm which wascharacteristic of the triple helical conformation of the protein. On the basis ofexperiments, the collagens from the skin of channel catfish were found to be type Icollagen.The properties of moisture retention and moisture adsorption of collagen wereevaluated by controlling the relative humidity of the desiccators. The resultsshowed that at a time period of12h, the moisture adsorption of ASC and PSCunder relative humidity of43%and81%achieves20.85%,32.83%and22.44%,28.89%respectively. A time period of84h, the moisture retention of ASC and PSCunder relative humidity of43%and81%achieves55.73%,82.07%and51.03%,83%respectively. Channel catfish skin collagen was hydrolyzed to obtainantioxidant peptides and assessed for scavenging effects on·OH and DPPH·. Theresults showed that collagen peptide had a certain capacity to scavenge·OH andDPPH·, and the efficiency of scavenging was increased with the concentrations.When the collagen peptide concentration achieved0.5mg/mL, the scavengingpercentage of·OH reached87.69%, and when the concentration of collagen peptidewas100mg/mL, the clearance rate of DPPH· was55.22%. It was proved collagen isof good moisture adsorption, moisture retention and antioxidant activity.Effects of collagen peptide on chronic ultraviolet radiation-induced skinphotoaging in hairless mice were studied in this chapter. Protective effects on miceskin damaged by exposing to ultraviolet B were studied. Collagen peptide couldincrease the activities of SOD, GSH-PX and the content of hydroxyproline, whiledecrease the content of MDA, which alleviated the oxidant press UV-induced.