Spectroscopic evaluation of the interaction of myoglobin with biomedically relevant compounds.

Reported here is an investigation of the redox behavior of myoglobin (Mb) in the presence of several bioactive compounds with biomedical relevance. These include the well-known Pt(II) drug, cisplatin, oxoplatin (a Pt(IV) compound representative for a newer-generation drugs based on platinum), capric acid, fenbufen, plumbagin and fisetin. These molecules were selected based on their structural diversity and documented biological effects, such as anti-inflammatory, chemotherapeutic, or antioxidant properties. The study aimed to evaluate how these compounds affect the structural and redox properties of Mb, particularly in terms of their capacity to bind to the protein and modulate its oxidation state. Spectroscopic and computational methods (UV-Vis absorption, fluorescence, NMR, molecular docking and molecular dynamics) were used to monitor binding and modifications of the redox state of the Mb in reactions such as autoxidation, nitrite-induced autoxidation, and peroxide-induced damage. These experiments are designed to parallel previous findings with similar experiments on hemoglobin with small molecules of biomedical/therapeutic relevance. While some compounds induced minimal or no spectral changes - suggesting limited interaction or redox impact, others displayed distinct redox effects, with plumbagin promoting oxidation while fisetin exerted a stabilizing, protective influence on the oxygenated form of myoglobin. These findings suggest that plumbagin may act as pro-oxidant by promoting myoglobin oxidation, whereas fisetin interacts with Mb in a manner that stabilizes the oxygenated form and mitigates oxidative conversion. The observed variability highlights the complex nature of small molecule-protein interactions and underlines the importance of assessing individual compound behavior in biochemical systems.