The antidepressant drug doxepin: A promising antioxidant

Abstract

Objective: Oxidative stress contributes to the pathophysiology of exposure to environmental pollutants and to different free radical generating biochemical reactions in a human system leading to various types of age-related ailments. An antioxidant is a substance capable of preventing or slowing down oxidation of other molecules. Administration of different natural or synthetic antioxidants can ably lead to prevention and attenuation of such stress-induced biochemical alterations. Best examples of natural antioxidants are plant-derived flavonoids. The present study has been designated to determine antioxidant properties in antidepressant compound doxepin which is structurally similar to flavonoid quercetin. Methods: Antioxidant capacity in doxepin was determined with help of several standard conventional procedures such as phosphomolybdenum assay, Ferric ion and cupric ion reducing power assays, ferrous ion chelating activity assay, hydrogen peroxide, and nitric oxide scavenging activity assays. Results: Doxepin showed a stable rise in its antioxidant activity in a dose-dependent manner as determined by ferric as well as cupric ion reducing capacity and by phosphomolybdenum assay. An almost identical observation was noted while determining ferrous ion chelating activity. Furthermore, doxepin showed a strong nitric oxide scavenging activity in all the concentrations used in the study while its hydrogen peroxide scavenging activity was only observed at 500 µg/ml of doxepin. Conclusion: Thus, our study opens up a new vista in search for antioxidants not only from plant sources but also from clinically established pharmaceutical compounds that are already in practical use among patients.