Research On Preparation, Separation, Purification Of Low Molecular Weight Corn Peptides And Its Physiological Activity

Free radicals are the dissociative molecules, atoms or ions with unpaired electron, having an active chemical property. They are constantly produced and constantly scavenged in organism. Under the physiological condition, the concentration of free radicals, occupying the state of equilibrium, is very low. Not only do they not damage the organism, but also have some special physiological functions. Under the pathological condition, free radicals generated by physical factor and xenobiotics directly or indirectly cannot be scavenged in time, or the equilibrium of producing and scavenging endogenous free radicals is broken, then the body are injured by free radicals. The main free radicals in organism are oxygen free radicals as well as derivants, including superoxide anion radical(O2-), hydroxyl radical(·OH), hydrogen peroxide(H2O2), singlet oxygen(1O2) and the product of lipid peroxidation, if the materials mentioned above were accumulated in vivo or not scavenged in time, they will do harm to the organism greatly. Testified by generous circumstances, lots of diseases relate to oxygen free radicals and derivants. In the course of cancerous development, free radicals are generated and participated in every stage, otherwise free radicals are also participated in course of cancerous treatment, therefore, it is regarded that the relationship between free radicals and cnacer is very intimate; There is a theory which recognize oxygen free radicals have tremendous effect to aging of organism; Other research indicates that oxygen free radical also have some effect to apoptosis, presuming that active oxygen free radicals may be the media or transmitte during the apoptosis. In addition, oxygen free radicals cause other diseases, such as diabetes mellitus, autoimmune disease and so on.Because of the damage by free radicals, it is extremely necessary to scavenge oxygen free radical as well as derivants. On the normal circumstance, it is a dynamic equilibrium for producing and cleanning free radical, because there are some enzymes in organism which can scavenge some free radicals, such as superoxide dismutase (SOD), peroxydase, glutathione peroxidase and so on. Contrarily, on the abnormal circumstance, such as sickness, the dynamic equilibrium will be broken by the augment of oxygen free radicals, or the descent of enzymic activity, and then cause the injury to the organism. In this condition, it is necessary to supply the exogenous oxygen free radical scaverger keeping this dynamic equilibrium. So it is important for screening and inverstigating the antioxidants, which we know frequently are vitamin E, vitamin C and glutathione (SGH) etc. Recently, more and more researches pay close attention to natural antioxidants, represented by tea polyphenols, tanshinone, schizadrin etc. The extracts of ginkgo leaf, which are testified, also have the antioxidative ability. Corn peptides (CP) is a kind of bioactive peptides prepared form corn gluten meal (CGM). First, we prepared the zein form CGM using ethanol precipitation. Then the zein is hydrolyzed by a type of alkaline protease, which has a wide substrate specificity, at 50℃and pH 8.0. The degree of hydrolysis(DH) was controlled to be 25%. After via a series of separation using molecular sieve, the hydrolysate were freeze-dried and the CP was obtained. This bioactive peptides, the CP from corn protein display a wide-ranging antioxidative properties and capability, when CP's concentration is 20 mg/ml, the inhibition ratio to pyrogallic acid autoxidation reach to 44.4%, having a strong ability to scavage superoxide anion; when CP is 2 mg/ml, the clearance rate to hydroxyl radical is 48.63%; the CP also can inhibit the degree of lipid peroxidation when concentration is 10 mg/ml; As a wide-ranging antioxidant, CP can scavage DPPH radical when 10 mg/ml, the clearance rate is 74.36%; the reduce power of CP is 0.824 when 0.039 mg/ml, therefore, the CP can be regarded as one kind of extensive antioxidant.We also examined the CP's positive function to anti-fatigue and alcoholic liver disease. The results indicate that the CP can extend the swimming time of rats, degrade the content of blood urea, increase the content of hepatic glycogen and cut down the content of blood lactic acid. At the same time, the CP can relieve the alcoholic liver disease by increasing the level of GSH and depressed the level of MDA and TG in liver. Both of them have a close relationship with the antioxidative ability of CP.In addition, by tracking the antioxidation of different fractions of CP and using different separation method, we further separate and purificate the CP under 3000 dal, trying to find a single peptide, having more antioxidative ability, from CP and determine the primary structure. Separation method mainly include amylaceum gel and ion exchange. Detecting the antioxidation is the scavenging ability of DPPH. The fraction we separate now have three peaks by HPLC.On the basis of above content, we not only prepare one kind of extensive antioxidant-corn peptides, but also confirm CP can relieve fatigue and the alcoholic liver disease. All above will provid rationale and practice for the exploitation and application of corn peptides.