Studies On The Acylation And Methylation Modification And Biological Characters Of Anthocyanin From Mulberry

As a kind of natural edible pigment,anthocyanin of mulberry has the physiological functions of anti-oxidation,anti-aging,anti-tumor and anti-inflammatory.However,anthocyanin is easily affected by light,heat,p H,metal ions and other factors.It will be degraded to a certain extent in the process of storage and processing,reducing its biological activity.In order to improve the stability of mulberry anthocyanin and improve its bioavailability,the anthocyanin was purified from fresh mulberry,and its structure was modified by acylation and methylation.The optimal modification conditions were determined.The stability of anthocyanin before and after modification was compared and analyzed,and the antioxidant activity of the modified product was further explored It provides theoretical basis for further processing and utilization.The study results are as follows:Using pyridine as catalyst and succinic acid as acyl donor,acylated anthocyanin was prepared under the condition of heating reaction.The optimized conditions were as follows:the mass ratio of anthocyanin to succinic acid was 1:8.96,the time of acylation was 3h,the temperature of acylation was 50?;using pyridine as catalyst and iodomethane as methyl donor,methylated anthocyanin was prepared under the condition of heating reaction.The optimized conditions were as follows:the mass volume ratio of anthocyanin to iodomethane is 1:1.95,the methylation time is 2.91h,and the methylation temperature is 38.64?.It was proved that acyl group and methyl group were successfully introduced into the modified anthocyanin by UV-Visible Spectrophotometer and Fourier Transform Infrared Spectrometer.The effects of light,temperature,p H and metal ions on the stability of anthocyanin before and after modification were studied.The results showed that the retention rate of un-modified anthocyanins decreased with the increase of temperature and the extension of light time,while the modified anthocyanins showed high stability for light and temperature;the anthocyanins were relatively stable under acid conditions,and were not conducive to anthocyanin preservation when p H was greater than 4;The effects of different metal ions on anthocyanin stability were different.Mn²⁺and Ca²⁺have no significant effect on the stability of anthocyanins.Cu²⁺can reduce the retention of anthocyanins,while Al³⁺can enhance the color of anthocyanins.Fe²⁺and Fe³⁺can significantly reduce the retention of anthocyanins,which is not conducive to the stability of anthocyanins.Besides Fe³⁺,the stability of modified anthocyanins to different metal ions is higher than that of un-modified anthocyanins.The antioxidant activities of anthocyanins before and after modification were compared,such as DPPH free radical scavenging rate,total reducing power and Fe²⁺chelating ability.The results show that the acylation and methylation modification can improve the antioxidant ability of anthocyanins in vitro.The results showed that mulberry anthocyanin itself had no toxic effect on CHO-K1 cells,and the modified anthocyanin could effectively reduce the toxicity of H₂O₂ induced on cells.After H₂O₂ induced,cells would have oxidative stress reaction,which made the content of oxidation products?ROS,MDA?and antioxidant enzymes?SOD,GSH-Px?increased rapidly in vivo.However,the treatment of modified anthocyanin can significantly inhibit the production of oxidation products,increase the content of antioxidant enzymes,effectively reduce the oxidation and lipid peroxidation of cells,which further proves that the modified anthocyanin has a strong ability of antioxidant induction.