ANTIOXIDANT PROPERTIES OF FOLIC ACID: A DFT STUDY
Keywords:folic acid, antioxidant, density functional theory, HAT, SET.
Antioxidant activity of folic acid (FA) was investigated via two main antioxidant mechanisms: hydrogen atom transfer (HAT) and single electron transfer (SET) at the DFT/B3LYP/6-311G(d,p) level of theory. The characterizing thermochemical properties such as bond dissociation enthalpies (BDEs), ionization energy (IE) and electron affinity (EA) were calculated in the gas phase. Analyses of HOMOs distribution shows that the postions which easily donate electrons to free radicals are essentially found at C ring, while the positions which easily accept electrons (LUMOs) from radicals are mainly situated at B ring. The lowest BDE values equal to 76.5 and 80.1 kcal/mol are obtained at C19-H and C9–H position, respectively. It is showed that FA represents a potential antioxidant via HAT mechanism. In addition, the IE and EA values calculated in the gas phase are equal to 5.45 eV and 1.87 eV, respectively. This result shows that FA has higher ability to donate electrons into free radicals, while the ability to receive electrons is quite weak. Finally, the HAT reaction between FA and reactive radical like HOO• was also calculated at the same level of theory. This provides more insight into its mechanism on free radicals scavenging.
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