Study On The Antioxidation Of Lycopene,?-carotene,and Delphinidin And Pelargonidin On Quantum Chemistry

Carotenoids and phenols are two common natural and effective antioxidants.They are widely distributed in fruits and vegetables,almost daily food consumed by ordinary people.Among them,lycopene and beta carotene are the two major carotenoids,and the delphinidin and pelargonidins are two common species of anthocyanins.They have high efficiency in scavenging free radicals.It also has a good performance in preventing cancer and tumor,improving immunity and preventing cardiovascular diseases.The study of the mechanism and activity of scavenging free radicals can be used to guide the method of determining antioxidant capacity of antioxidants and provide some reference for the application of antioxidant in natural plants in the future.In this experiment,the mechanism of the reaction of lycopene,beta carotene,delphinidin ? pelargonidins and free radicals was studied in detail in combination with the quantum chemical density functional theory and in vitro antioxidant evaluation method.By calculating the transition state of four kinds of phytochemicals,superoxide anion radical and hydrogen peroxide free radical,the specific process and mechanism of reaction were studied and the value of reaction enthalpy was calculated to judge the active site.The results of the study are as follows:The configuration of lycopene,beta carotene,delphinidin,pelargonidins was optimized by using density functional theory B3LYP/ 6-311+G(d,p)basis set.According to the structural parameters such as bond length and dihedral angle,their activity was analyzed,and the dissociation energy of chemical bond was calculated.The results showed that the C4' site length of lycopene and beta carotene was the longest,followed by C5 locus.The dissociation energies of lycopene and beta carotene C4 are 65.57 Kcal/mol and 65.43 Kcal/mol,respectively,according to the dissociation energies of hydrocarbon bonds.It is the site of the most prone to hydrogen atom transfer reaction.The O-H bonds of C4' and C3 positions in the pigment and Geranium pigment were longer and more active,which were 0.96923 and 0.96541 respectively.This is also consistent with the dissociation of hydrogen and oxygen bonds.The most active site in the gas phase is C3 locus,and the C4' site is the most active in the solvent.The reaction process of lycopene,beta carotene,delphinidin,pelargonidins with superoxide anion radicals and hydroperoxide free radicals was calculated by using the density functional B3LYP/6-31+G(D,P)base group,and a PCM solvent model was used to calculate the single point energy at the level of 6-311++G(D,P).The results showed that lycopene and beta carotene tended to complete the radical scavenging reaction through the RAF reaction mechanism.The scavenging effect of superoxide anion is not ideal,and the reaction with superoxide anion is easier to occur in the benzene solution,and the reaction with the hydrogen peroxide free radical is more easily carried out in aqueous solution.The C4' locus and C3 locus of delphinidin,pelargonidins are the active sites for scavenging free radicals,which are consistent with the results of bond dissociation.The antioxidant capacity of lycopene is stronger than that of beta carotene,and the scavenging free radical of the delphinidin is slightly higher than that of pelargonidins.The scavenging ability of lycopene,beta carotene,delphinidin,pelargonidins on superoxide,DPPH and ABTS radicals was measured in vitro.The results showed that lycopene was stronger than beta carotene,and that delphinidin was stronger than that of pelargonidins.