2,2-Diphenyl-1-picrylhydrazyl is widely used as a stable free radical in antioxidant research. It is commonly employed in the DPPH assay, a method to evaluate the free radical scavenging activity of various compounds, particularly in food, cosmetics, and pharmaceuticals. This chemical reacts with antioxidants, leading to a color change from purple to yellow, which can be measured spectrophotometrically to determine antioxidant capacity. Its stability and ease of use make it a valuable tool in assessing the efficacy of natural and synthetic antioxidants. Additionally, it is utilized in studies involving oxidative stress and the development of antioxidant-rich products.