Antioxidant properties of 34 alkaloids of natural origin: a density functional theory study

The antioxidant properties of 34 plant alkaloids in gas phase, ethanol and water have been evaluated using density functional theory (DFT). The computations have been made according to three different single electron mechanisms: (1) H-atom transfer (HAT); (2) electron transfer followed by H⁺ transfer (SET-PT); and (3) sequential H⁺-loss electron transfer (SPLET). As a result, the highest antioxidant activity was established for evodiamine. Global reactivity in terms of hardness/softness has been calculated also, as well as Fukui indices of local reactivity. Structural aspects related to H, electron and proton loss have been regarded in sufficient details. In terms of global softness, palmatine, dehydroevodiamine and chelerythrine have been determined as the most reactive molecules, whereas C7 atom of evodiamine has been found to be the most reactive atom. All the findings are in agreement with the recent experimental and theoretical studies on alkaloid antioxidant activity and can be compared with the results for ascorbic acid, which was used as a reference compound.