Comparison of Antioxidant Evaluation Assays for Investigating Antioxidative Activity of Gallic Acid and Its Alkyl Esters in Different Food Matrices

Abstract

The addition of antioxidants is one of the strategies to inhibit lipid oxidation, a major cause of lipid deterioration in foods leading to rancidity development and nutritional losses. However, several studies have been reported that conventional antioxidant assays, e.g., TPC, ABTS, FRAP, and ORAC could not predict antioxidant performance in several foods. This study aimed to investigate the performance of two recently developed assays, e.g., the conjugated autoxidizable triene (CAT) and the apolar radical-initiated conjugated autoxidizable triene (ApoCAT) assays to predict the antioxidant effectiveness of gallic acid and its esters in selected food models in comparison with the conventional antioxidant assays. The results indicated that the polarities of the antioxidants have a strong impact on antioxidant activities. In addition, different oxidant locations demonstrated by the CAT and ApoCAT assays influenced the overall antioxidant performances of the antioxidants with different polarities. To validate the predictability of the assays, the antioxidative performance of gallic acid and its alkyl esters was investigated in oil-in-water (O/W) emulsions, bulk soybean oils, and roasted peanuts as the lipid food models. The results showed that only the ApoCAT assay could be able to predict the antioxidative performances in O/W emulsions regardless of the antioxidant polarities. This study demonstrated that the relevance of antioxidant assays to food models was strongly dependent on physical similarities between the tested assays and the food structure matrices.

Sinapic Acid and its Derivatives Increase Oxidative Stability in Different Model Lipid Systems

“…This lack of correlation was also reported by Phonsatta et al [49] in their study of the antioxidant activities of gallic acid and its alkyl esters in different food matrices. Moreover, it has been hypothesized that in these solvents, less polar substances might be selfaggregated by the hydrophobic effects.…”

Concept, mechanism, and applications of phenolic antioxidants in foods

“…Phenolic antioxidant (AH) can provide a H-atom to the free radical substrate and produce a non-radical substrate (RH, ROH, or ROOH) species and antioxidant free radical (A * ) as shown in Figure 6. (Lu, Nie, Belton, Tang, Nie, Belton, Tang, & Zhao, 2006;Phonsatta et al, 2017;Rajan & Muraleedharan, 2017).…”

Evaluation of Antioxidant Activity and Interaction with Radical Species Using the Vesicle Conjugated Autoxidizable Triene (VesiCAT) Assay

“…Despite their artificiality, the azo initiators were applied because they are easy to use and they can induce a constant, fast, and temperature‐controlled rate of peroxidation in liposome membrane. The method was developed with two different radical generators, AAPH (hydrophilic), and AMVN (lipophilic), because they can generate radical flux at different regions in liposomal system, which is strongly suspected to influence the antioxidant response . Regarding to the expression of results, the calculation of the AUC, characterized by clear starting and ending points, exploits both inhibition time and degree of oxidation.…”

“…This nonlinear trend (also known as cut off effect) of antioxidant behaviors was observed in many cases when experiments were carried out in emulsified systems . The results measured through AAPH‐induced oxidation with conventional peroxide analysis (Figure ) or found in the literature perfectly matched the results we obtained through VesiCAT assays, which confirmed the high accuracy of this newly developed methodology. Yet, more insight could be provided by calculating the VesiCAT value ratio between AAPH and AMVN assays (AAPH/AMVN and AMVN/AAPH) for each antioxidant, representing how the reactivity with oxidant species in the different regions (aqueous or membrane) contributes to the antioxidant response of the molecule.…”

“…The method was developed with two different radical generators, AAPH (hydrophilic), and AMVN (lipophilic), because they can generate radical flux at different regions in liposomal system, which is strongly suspected to influence the antioxidant response. [18,21] Regarding to the expression of results, the calculation of the AUC, characterized by clear starting and ending points, exploits both inhibition time and degree of oxidation. Thus, unlike the other antioxidant capacity assessing methods (the reaction rate with free radicals, the inhibition time, the antioxidant concentration necessary to achieve 50% inhibition, etc.…”