**Author details**

method knowing that many kinds of antioxidants and radicals are present. Four general sources of antioxidant have been identified: (i) enzymes (superoxide dismutase, gluthatione peroxidase), (ii) large molecules (albumin, ferritin), (iii) small molecules (phenols, ascorbic acid, carotenoids) and (iv) and some hormones (estrogen, melatonin). Many kinds of free radicals can be found, for example O2▪-, HO▪, NO▪, RO(O)▪, LO(O)▪. Moreover, the stability, the selectivity of the radicals and the reaction mechanisms can be also different. Thus, it is possible that no single method may be able to express the antioxidant capacity of different antioxidants taken independently or in a mixture [18]. Previous studies demonstrated that it is not appropriate to use one-dimensional methods to evaluate the antioxidant activity of multifunctional food such as fruits and vegetables, since they contain a large diversity of

The determination of antioxidant activity in the food matrix needs a sample preparation to extract the active molecules and then an accurate method of measurement and an expression of the results. (i) During sample preparation, precautions must be taken to avoid the loss of antioxidants due to the drastic conditions of extraction. A determination of all food constitu‐ ents is necessary because a certain interference with antioxidants can occur. Antioxidant capacity values should only be compared where the method, the solvent and the analytical conditions are similar [38]. Indeed, some authors underlined that there is an effect of the solvent used for the extraction or used to solubilize antioxidants on the result of the antioxidant activity evaluation [39-42]. This is due to interference of the reaction mechanism and the solvent [38]. (ii) The method to measure the antioxidant activity must be chosen according to the nature of the active molecules present in the samples. Some methods described in part 3 are more appropriate for some kinds of antioxidants. For example the DPPH method is more adequate to lipophilic systems. Moreover, several assays must be carried out to determine a value of antioxidant activity. (iii) Results of antioxidant activity measurement can be expressed as EC50 (quantity of antioxidant necessary to assure 50% depletion of free radicals), tEC50 (time to reach 50% depletion of free radicals), tEC50 (time to reach 50% depletion of free radical) or AE (antiradical efficiency defined as the inverse of the product between EC50 and tEC50). Thus, taking these 3 parameters into account can be relevant to have a more comprehensive evalu‐

The determination of the antioxidant capacity by in vivo methods is not always feasible but it appears interesting because it simulates an environment closer to that really happening in biological systems. Methods using HAT reactions will be preferred to SET reactions because peroxyl radicals used in HAT assays are the predominant free radicals found in lipid oxidation and biological systems. To elucidate a full profile of antioxidant capacity against various ROS, the development of different methods specific for each ROS/ RNS may be needed. [18] proposed a comparison of different in vitro methods; conclusions given that ORAC, TRAP and LDL are considered to be the most biologically relevant assays [18] because the antioxidant capacity measured reflects closer the in vivo action of the antioxidants. So, it appears clearly that the antioxidant activity determination needs a standardization of the procedure used and a combination of at least two or three methods. The use of only one method does not reflect the antioxidant activity of food raw material due the variability of the molecules that act as

natural antioxidants.

88 Biotechnology

ation of antioxidant activity [38].

antioxidant.

Irina Ioannou\* , Hind Chaaban, Manel Slimane and Mohamed Ghoul

\*Address all correspondence to: irina.ioannou@univ-lorraine.fr

Lorraine University – ENSAIA, Vandoeuvre Cedex France, France
