How is the oxidative potential of reactive species quenched?

Answer 1

The oxidative potential of reactive species, such as free radicals and reactive oxygen species (ROS), can be quenched through several mechanisms. These strategies often involve the interaction of the reactive species with other molecules that can donate electrons, stabilize the radical, or scavenge the reactive species. Here are some of the key mechanisms:

1. Antioxidants: Molecules such as vitamins C and E, glutathione, and flavonoids can directly neutralize reactive species by donating an electron, thereby reducing the oxidative potential. These antioxidants can stabilize free radicals and prevent them from causing cellular damage.

2. Enzymatic Reactions: Enzymes like superoxide dismutase (SOD), catalase, and peroxidases catalyze the conversion of reactive species to less harmful molecules. For instance:

   • SOD converts superoxide radicals into hydrogen peroxide.
   • Catalase and peroxidases then break down hydrogen peroxide into water and oxygen, thereby reducing its oxidative potential.

3. Metal Ion Chelation: Metal ions can catalyze the production of free radicals through Fenton-type reactions. Chelating agents, such as EDTA or certain phytochemicals, can bind to these metal ions and prevent them from participating in radical-generating reactions.

4. Reaction with Biological Macromolecules: Some inert biological macromolecules (like proteins and enzymes) can also sequester free radicals or reactive species. This could lead to their transformation or enhancement of their stability, keeping them from interacting with more critical cellular components.

5. Formation of Non-reactive Products: Several reactive species can form non-reactive products through reactions with various substrates. For example, hydroperoxides can decompose or react with lipids and proteins, forming less harmful compounds.

6. Physical Processes: Some reactive species may be quenched and neutralized through physical means. For example, UV radiation can help dissipate the energy of excited-state species, reducing their reactivity.

7. Buffering in Biological Systems: Biological systems often contain buffering agents and compartments (like lysosomes) that can help neutralize reactive species and maintain cellular homeostasis.

These pathways exemplify the body's inherent mechanisms to counteract oxidative stress, protect cells from oxidative damage, and maintain redox balance.