Auxiliary Therapeutic Role of Cholinergic Agents: Mechanistic Insights into the Antioxidant Behavior of Alzheimer's Disease Drugs

Repurposing of existing drugs toward new therapeutic use(s) has become an emergent area of research in current times. In this context, the antioxidant behavior of eight cholinergic drugs used in the treatment of Alzheimer's disease (AD) was investigated theoretically. The low bond dissociation enthalpy values in all of the compounds advocated for the hydrogen atom transfer mechanism toward the observed antioxidant behavior. The kinetic study for the reaction of the drugs with hydroperoxyl radicals indicated an indirect reaction path owing to the presence of preand postreaction complexes. In some cases, the rate constant for the H-abstraction reaction (k = 2.8 x 10(3) L mol(-1) s(-1)) is found to be close to that of a well-known nonphenolic antioxidant, alpha-terpinene (k = 4.3 x 10(3) L mol(-1) s(-1)). Quantification of charge transfer character among the drugs with DNA bases and molecular docking calculations confirmed the groove binding model and predicted the drugs to be safe from DNA damage. A theoretical evaluation of the mechanistic details governing the antioxidant property along with the proven stress reversal ability of these AD drugs provided new insights to design and develop more efficient drugs with dual therapeutic potential.