Theoretical Study on the Prooxidant Activity of α- and β-Lapachones in Aqueous Media

Abstract

The prooxidant activities of α- and β-lapachones were studied in aqueous media using density functional theory. Although these compounds are well-known prooxidants and have applications as alternatives in the treatment of tumor cells, little is known about the reaction mechanisms involved. The prooxidant activity of α- and β-lapachones considered their reduced forms; they are hydronaphthoquinones $H_2{Q}_{\alpha }$ and $H_2{Q}_{\beta }$, whereas the single electron transfer mechanism was considered in the reduction reaction where oxygen, hydrogen peroxide, copper, and iron were substrates. Two reaction routes were identified for the prooxidant activities of H₂Q_α and H₂Q_β: The first considered that the metals were not present in the reduction reactions of oxygen and hydrogen peroxide and obtained reaction rates of 10⁶–10⁷ M⁻¹ s⁻¹; the second considered that the metals copper and iron were present in the reduction reactions and the reaction rates were limited by diffusion. Understanding the reaction mechanism involved in the prooxidant activity of α- and β-lapachones and the physiological importance of these molecules could be employed to comprehend the anticancer properties of compounds in which prooxidant activity is involved.