Antioxidant Defense System against Oxidative Stress

Oxidative stress results from an imbalance between reactive oxygen and nitrogen species and antioxidant defenses, leading to cellular oxidative damage and contributing to various chronic diseases. This book provides an overview of the integrated antioxidant defense system, including enzymatic antioxidants such as superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx), as well as intrinsic non-enzymatic antioxidants such as glutathione (GSH), uric acid, melatonin, bilirubin, polyamines, and metal-binding proteins. The roles of cysteine and sulfur-containing compounds in maintaining redox balance are also discussed. In addition, natural antioxidants, including carotenoids, polyphenols, flavonoids, quercetin, and garlic-derived compounds, are examined with emphasis on their antioxidant mechanisms and regulation of antioxidant-related gene expression. Collectively, these interconnected systems maintain redox homeostasis and protect cells against oxidative damage.