Review of methods to determine antioxidant capacities

Antioxidant capacity is related with compounds capable of protecting a biological system against the potentially harmful effect of processes or reactions involving reactive oxygen and nitrogen species (ROS and RNS). These protective effects of antioxidants have received increasing attention within biological, medical, nutritional, and agrochemical fields and resulted in the requirement of simple, convenient, and reliable antioxidant capacity determination methods. Many methods which differ from each other in terms of reaction mechanisms, oxidant and target/probe species, reaction conditions, and expression of results have been developed and tested in the literature. In this review, the methods most widely used for the determination of antioxidant capacity are evaluated, presenting the general principals, recent applications, and their strengths and limitations. Analysis conditions, substrate, and antioxidant concentration should simulate real food or biological systems as much as possible when selecting the antioxidant capacity method. The total antioxidant capacity value should include methods applicable to both lipophilic and hydrophilic antioxidants, with regards the similarity and differences of both hydrogen atom transfer and electron transfer mechanism. The methods including various ROS/RNS also have to be designed to comprehensively evaluate the antioxidant capacity of a sample.