Study On The Interaction Of Black Rice Anthocyanins With Three Proteins

Black rice anthocyanins (BRA) which extracted from black rice, are bioactive compounds that possess various biological effect, such as, antioxidant, anti-tumor and other biological activities. The main anthocyanin component is cyaniding-3- glucoside. Black rice anthocyanins have been widely used in the food industry, while protein is one of the most important nutrients in our foods, and they have important functional characteristics.So the study of the interaction between black rice anthocyanin and protein is very important.The mechanism of the binding between BRA and ?-LG/Cs were studied by UV-Vis absorption spectroscopy, fluorescence spectroscopy, and molecular docking studies. The results showed that the binding of BRA to ?-LGand BRA to Cs were all static quenching.Then the binding constants, the number of binding sites and binding distance were calculated, the effect of the proteins to BRA' characteristics was studied. The results showed that static quenching exits between BRA and ?-LG/Cs by the formation of BRA-?-LG/BRA-Cs complex. The hydrophobic interaction force played major role in the binding of BRA to P-LG, the interacton between BRA and Cs was driven mainly by hydrogen bonds. The interaction between BRA and protein not only affected the secondary structure of protein, but also affected the characteristics of BRA. The anti-oxidative capacity of BRA and ?-LG/Cs were not superimposed. It was found that proteins masked the free radical scavenging potential of BRA. The combination of Cs and BRA played a role in protecting against light and temperature, the effect of P-LG on the photostability and thermostability of BRA was not obvious.The mechanism of the binding between BRA and BSA were studied by fluorescence spectroscopy, UV-Vis absorption spectroscopy, circular dichroism and molecular docking studied. The-results showed that static quenching is the main cause of black rice anthocyanins fluorescence quenching of BSA, thermodynamic parameters calculated resulted indicated that hydrogen bonding and/or van der Waals forces were the main force in the binding of BRA to BSA. The molecular docking results showed that cyanidin-3-O-glucoside mainly binds to the domain III of BSA. UV Vis spectra,synchronous fluorescence spectra, circular dichroism results showed that BRA changed the secondary structure of BSA, but did not change the microenvironment of the tryptophan and tyrosine. The effect of antioxidant capacity caused by the interaction between BRA and BSA were studied by DPPH method. It showed that the antioxidant capacity of BRA declined, maybe due to the hydroxyl groups in the B ring of BRA took part in the combination with BSA.