Antioxidant properties of C-60 flavonoid conjugates were computationally examined via their O-H bond dissociation enthalpies (BDEs) and ionization energies (IEs) using two-layer ONIOM and PM6 methods, respectively. Eight ONIOM((RO)B3LYP/6-311++G(2df,2p):PM6) models were evaluated by computing BDE(O-H)s of a series of polyphenol. Synthetic mechanism of C-60 flavonoid conjugates was also explored via the potential energy surfaces of reaction between C-60 and malonate flavonoid derivatives (chalcone, flavone and flavanone) at the B3LYP/6-31G(d)//PM6. Antioxidant activities of C-60 flavonoid conjugates were discussed via hydrogen atom transfer, single electron transfer mechanisms and the effect of C-60 on the BDE(O-H) s and IEs of these compounds. (C) 2016 Elsevier B.V. All rights reserved.