| As a porphyrin pigment protein,C-phycocyanin(C-PC)is an important functional active ingredient in Spirulina.It has broad application prospects in the fields of natural pigments,natural medicines,and biochemical reagents.However,it is susceptible to discoloration and instability in storage environment,and there are few reports of changes in the functional activity of C-PC when discoloration and instability occurs.This study explored the effects of different environmental factors on the optical characteristcs and biological activity of Spirulina platensis C-PC,comprehensively evaluated its stability,and made reference to its application conditions and in-depth basic research.The main results are as follows:Environmental factors such as p H,temperature,light and protein denaturants all have significant effects on the optical characteristcs of C-PC.Under the conditions of p H10,temperature(?70 ?),and guanidine hydrochloride(?1 mol/L),ethanol(?50%,V/V),SDS(?1%,W/V),C-PC pigment retention rate and fluorescence intensity decreased by more than40%.The increase of light intensity and time could make the optical properties of C-PC decrease and the red and blue band light sources have the greatest influence on it.Results have shown that the change in optical characteristics of C-PC is less than 15.12% under p H6-7,temperature4-30 ?,and dark conditions,which can maintain a relatively stable range.Based on the experimental basis in Chapter two,the ability of C-PC to scavenge DPPH and ABTS free radicals was evaluated under the previousfactors.With the increase of temperature,the scavenging ability of C-PC firstly increased and then decreased,and its antioxidant activity was significantly correlated with color(pigment retention rate,blueness value b*)and fluorescence intensity(F.I).However,in the evaluation of p H factors,its antioxidant activity was significantly correlated with b*,but not significantly correlated with F.I.It showed that only when the temperature rises causes fading,it can also lead to the weakening of F.I.and antioxidant activity.Under the denaturing effect of protein denaturants SDS,urea and guanidine hydrochloride,C-PC still has antioxidant activity within a certain range,and the ABTS scavenging activity is even 7.07% higher than the untreated sample in the SDS 0.01-0.05%(W/V)complete denaturation range.Evaluation of the antioxidant activity of C-PC during simulated gastrointestinal digestion found that the free radical scavenging ability of the experimental group was higher than that of the undigested control group,and the increase in antioxidant activity of the intestinal digestion stage was higher than that of gastric digestion stage.This demonstrated the availability of C-PC as an antioxidant.The results showed that the color change of C-PC has a correlation with antioxidant activity within a certain range,and its overall antioxidant activity also comes from apoproteins.The anti-tumor activity of C-PC was investigated under the fading factor.C-PC can significantly inhibit the proliferation of A549 and Hep G2 tumor cells(p<0.05),but after treatment with fading factors,it has no antitumor activity under extreme p H2 conditions and high temperatures of80 ? and 100 ?,and Caspase-3 apoptotic enzyme activity evaluation also showed consistent results.Analysis of the secondary structure of C-PC showed that the content of the main chain ?-helical structure decreased at p H2 and 80 ? and changed to the structure of random coil structure,which provided a basis for the change of antitumor activity.The results of this study indicate that high temperature and extremely acidic p H conditionsdestroy the optical properties and biological activity of C-PC,and there is an apoprotein structure influence mechanism.This study provides a research basis for its application and a reference for in-depth structure-effect relationship research. |
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