Theoretical elucidation of DPPH radical-scavenging activity difference of antioxidant xanthones

As naturally occurring polyphenols, xanthones are rather active in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. By means of quantum chemical calculation, we reveal that the activity difference of xanthones can be elucidated by their different O-H bond dissociation enthalpies (BDEs) and can be further explained in terms of electronic effect and intramolecular hydrogen bond effect of substituents. The unique structure of xanthones enables them to be promising antioxidants with advantages of rather low O-H BDE and relatively high ionization potential.