In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET-PT and SPLET, for
mono-substituted Indole-3-Carbinols were calculated in gas-phase and water. Results show that elec-
tron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP)
and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation
enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent
effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with
the indolic NAH bond length after electron abstraction, R(NAH+
), and the partial charge on the indolyl
radical nitrogen atom, q(N). Furthermore, calculated IP and PA values for mono-substituted Indole-3-Car-
binols show linear dependence on the energy of the highest occupied molecular orbital (EHOMO) of studied
molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in
water.
کلید واژگان :
Antioxidant Indole-3-Carbinol Substituent effect Solvent effect Reaction enthalpy HOMO
