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

Hydroxyl radicals (OH center dot) 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 center dot-induced protein oxidative damage has never been explored. This study determined the therapeutic potential of thymoquinone against OH center dot-induced oxidative human hemoglobin damage. Novel data demonstrated that thymoquinone provides structural protection of hemoglobin against oxidative damage. Treatment of hemoglobin with OH center dot induces hypochromicity at 280 and 405 nm, whereas thymoquinone reversed these hypochromic effects. In addition, OH center dot cause significant reduction in tryptophan fluorescence, however thymoquinone also reversed these damaging effects. Thymoquinone also reduces OH center dot-induced hydrophobicity and also reduces OH center dot- induced carbonylation. Moreover, it also inhibits thermal stabilization of OH center dot-hemoglobin complex. SDS-PAGE of unmodified hemoglobin showed four bands, which disappeared upon OH center dot 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 center dot-induced oxidative damage in human hemoglobin. (C) 2021 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.