Reactive oxygen species (ROS) and free radical chain reactions (ROS)

Reactive oxygen species (ROS) are highly reactive oxygen-containing molecules, such as superoxide and hydrogen peroxide, that are generated as natural byproducts of cellular metabolism (Sies et al., 2017). They play dual roles in biology, serving as critical signaling molecules in low concentrations but causing significant damage when produced in excess (Finkel, 2011). Free radical chain reactions occur when ROS interact with cellular components like lipids, proteins, and DNA, leading to a self-propagating cycle of molecular destruction known as oxidative stress (Halliwell & Gutteridge, 2015). This process is a central driver in the pathophysiology of various conditions, including cancer, atherosclerosis, and neurodegenerative diseases like Alzheimer's (StatPearls, 2023). Pharmacological strategies to address ROS involve the use of antioxidants and radical scavengers, such as edaravone or N-acetylcysteine, which aim to neutralize these species or bolster endogenous defense mechanisms (PubChem, 2024). However, therapeutic success has been limited by the challenge of selectively targeting harmful ROS without disrupting the essential oxidative signaling required for normal cell function and immune defense (Nature Reviews Drug Discovery, 2020). Furthermore, the non-specific nature of many antioxidants often results in poor bioavailability at the site of radical generation, such as the mitochondrial matrix (Murphy & Hartley, 2018). Consequently, modern research is shifting toward site-specific scavengers and the modulation of specific ROS-generating enzymes like NADPH oxidases to achieve better clinical outcomes (Lambeth, 2004).

Other names

ROSOxidative stressFree radicalsReactive oxygen metabolitesOxygen radicalsReactive oxygen intermediates

Antioxidant drugs function by directly scavenging reactive species, donating electrons to neutralize free radicals, or activating the Nrf2-mediated antioxidant response element (ARE) to upregulate endogenous protective enzymes such as superoxide dismutase and catalase.