The human body relies on a complex and efficient antioxidant defense system to protect itself from the harmful effects of reactive oxygen species (ROS), which are unstable molecules that can damage cells, proteins, and DNA through oxidative stress. This defense system comprises both enzymatic and non-enzymatic antioxidants, each playing a crucial role in maintaining cellular health.
Enzymatic antioxidants include key enzymes like catalase, peroxidase, superoxide dismutase (SOD), and glutathione S-transferase (GST). Catalase, for instance, catalyzes the decomposition of hydrogen peroxide, a harmful byproduct of metabolic processes, into water and oxygen, thereby preventing potential cellular damage. Peroxidase enzymes also reduce hydrogen peroxide but are versatile in detoxifying various peroxides. SOD is pivotal in dismutating the superoxide radical, one of the most reactive ROS, into less harmful molecules. Meanwhile, GST plays a significant role in detoxifying endogenous and exogenous compounds by catalyzing the conjugation of glutathione to a wide range of substrates.
Non-enzymatic antioxidants, on the other hand, include small molecules like ascorbic acid (vitamin C), tocopherol (vitamin E), and phenolic compounds, which directly neutralize free radicals. Ascorbic acid is water-soluble and acts primarily in the aqueous environments of the body, scavenging ROS and regenerating other antioxidants. Tocopherol, a fat-soluble vitamin, protects cell membranes from lipid peroxidation, while phenolic compounds, found abundantly in plants, exhibit strong antioxidant activity through their ability to donate electrons to neutralize ROS.
The growing body of research on natural antioxidants, particularly those found in foods, has sparked significant interest in the development of new assays to better measure antioxidant activity and understand their mechanisms of action. This research not only advances our knowledge of how antioxidants function but also has practical implications for developing dietary strategies to enhance antioxidant defenses and improve overall health.
Antioxidant Defense Systems: Enzymatic and Non-Enzymatic Mechanisms in Cellular Protection
