Biochemistry and analytical chemistry are fundamental to understanding the complex processes within living systems, especially concerning cellular health and disease. This article provides a comprehensive overview of oxidants, antioxidants, and oxidative stress, key concepts that bridge biochemistry and analytical chemistry by involving chemical reactions, molecular structures, and methods for assessing cellular damage.
The Role of Oxidants and Reactive Metabolites in Biochemistry
In biochemistry, oxidants are substances that gain electrons, causing other compounds to lose electrons (oxidation). They often exist as free radicals—atoms, molecules, or fragments with one or more unpaired electrons capable of independent existence. These highly reactive species can be electroneutral, anionic, or cationic. Alongside free radicals, other highly reactive metabolites (RM) or reactive oxygen/nitrogen species (ROS/RNS) are formed, often more toxic than their precursors.
Reactive metabolites are crucial in both physiological and pathological processes. They can originate from internal sources like phagocytes, mitochondria, peroxisomes, and reactions involving xanthine oxidase, or external sources such as cigarette smoke, radiation, and environmental pollution.
Reactive metabolites are formed through:
- Homolytic cleavage of covalent bonds (e.g., by radiation).
- Oxidation of a compound by losing an electron.
- Reduction of a compound by accepting an electron.
Reactive Oxygen Species (ROS) Explained
Reactive oxygen species (ROS) encompass both oxygen radicals (e.g., hydroxyl radical, superoxide anion radical) and non-radicals (e.g., hydrogen peroxide, hypochlorous acid, singlet oxygen, ozone). These are potent oxidizing agents, readily converting into radicals or directly causing damage.
- Superoxide Anion Radical (O₂•⁻): A product of physiological processes (e.g., in neutrophils during phagocytosis) or
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