Thymoquinone provides structural protection of human hemoglobin against oxidative damage: Biochemical studies

Abstract

Hydroxyl radicals (OH.) are one of the most active reactive oxidants recognized for their deleterious effects to cause protein oxidative damage. Thymoquinone, a monoterpene molecule abundantly present in black cumin and known for its pharmacological activities, but its activity against the OH.-induced protein oxidative damage has never been explored. This study determined the therapeutic potential of thymoquinone against OH.-induced oxidative human hemoglobin damage. Novel data demonstrated that thymoquinone provides structural protection of hemoglobin against oxidative damage. Treatment of hemoglobin with OH. induces hypochromicity at 280 and 405 nm, whereas thymoquinone reversed these hypochromic effects. In addition, OH. cause significant reduction in tryptophan fluorescence, however thymoquinone also reversed these damaging effects. Thymoquinone also reduces OH.-induced hydrophobicity and also reduces OH.-induced carbonylation. Moreover, it also inhibits thermal stabilization of OH.-hemoglobin complex. SDS-PAGE of unmodified hemoglobin showed four bands, which disappeared upon OH. treatment and these changes were also retained by thymoquinone. In conclusion, this is the first study that shows the therapeutic potential of thymoquinone against OH.-induced oxidative damage in human hemoglobin.