Antioxidant activity (AA) measures a substance’s ability to counteract free radicals—unstable molecules that cause oxidative damage to cells, proteins, and DNA. This property is vital in health sciences, food preservation, and cosmetics, where oxidative stress leads to aging, spoilage, or disease progression. AA is commonly assessed through chemical and physicochemical methods that monitor either the speed or completeness of reactions between antioxidants and oxidants. These methods fall into three major categories: oxygen consumption, formation of oxidation products, and free radical scavenging.
Oxygen consumption-based methods, such as the Rancimat test, evaluate oxidative stability by measuring how long a sample—typically an oil—can resist oxidation under heat and airflow. Oximetry tracks oxygen depletion in real time and is especially useful in emulsified or aqueous systems. These tests provide valuable kinetic data on oxidation resistance.
Oxidation product-based assays detect the by-products of oxidative damage. The TBARS test measures malondialdehyde, a marker of lipid peroxidation, while protein carbonyl assays indicate oxidative degradation of proteins—important for evaluating biological samples or processed foods. Conjugated diene assays offer early detection of lipid oxidation by monitoring UV absorbance at 233 nm.
Free radical scavenging assays are widely used due to their sensitivity and ease. DPPH and ABTS measure the antioxidant’s ability to quench specific radicals through colorimetric shifts. ORAC evaluates antioxidant protection over time using fluorescence decay, making it biologically relevant. FRAP assesses an antioxidant’s reducing power by measuring its ability to convert ferric (Fe³⁺) to ferrous (Fe²⁺) ions.
Each method highlights different antioxidant mechanisms—electron donation, hydrogen transfer, or radical neutralization. Because antioxidant behavior varies with structure and environment, combining multiple assays ensures accurate profiling. Recent advances in automation and microfluidics now allow high-throughput, multi-assay platforms for more efficient and standardized antioxidant testing.Methods for Measuring Antioxidant Activity
