The antioxidant activity of natural and synthetic compounds was evaluated using five in vitro methods: ferric reducing/antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydradzyl (DPPH), oxygen radical absorption capacity (ORAC), oxidation of an aqueous dispersion of linoleic acid accelerated by azoinitiators (LAOX), and oxidation of a meat homogenate submitted to a thermal treatment (TBARS). All results were expressed as Trolox equivalents. The application of multivariate statistical techniques suggested that the phenolic compounds (caffeic acid, carnosic acid, genistein and resveratrol), beyond their high antioxidant activity measured by the DPPH, FRAP and TBARS methods, showed the highest ability to react with the radicals in the ORAC methodology, compared to the other compounds evaluated in this study (ascorbic acid, erythorbate, tocopherol, BHT, Trolox, tryptophan, citric acid, EDTA, glutathione, lecithin, methionine and tyrosine). This property was significantly correlated with the number of phenolic rings and catecholic structure present in the molecule. Based on a multivariate analysis, it is possible to select compounds from different clusters and explore their antioxidant activity interactions in food products.
Despite the increase in the use of natural compounds in place of synthetic derivatives as antioxidants in food products, the extent of this substitution is limited by cost constraints. Thus, the objective of this study was to explore the synergism on the antioxidant activity of natural compounds, for further application in food products. Three hydrosoluble compounds (x 1 = caffeic acid, x 2 = carnosic acid, and x 3 = glutathione) and three liposoluble compounds (x 1 = quercetin, x 2 = rutin, and x 3 = genistein) were mixed according to a "centroid simplex design". The antioxidant activity of the mixtures was analyzed by the ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) methodologies, and activity was also evaluated in an oxidized mixed micelle prepared with linoleic acid (LAOX). Cubic polynomial models with predictive capacity were obtained when the mixtures were submitted to the LAOX methodology (ŷ = 0
The diet and plasma lipid patterns associated with lipid oxidation susceptibility in rats fed different doses of polyunsaturated fatty acids (n‐3 PUFA) from fish oil were evaluated. Wistar rats were assigned into three groups and received diets containing 8% soybean oil (SOY), 4% soybean oil + 4% fish oil (SOY‐FISH) and 8% fish oil (FISH) for 21 days. Linoleic, oleic and α‐linolenic acids in SOY diets were substituted by myristic, palmitic, palmitoleic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in SOY‐FISH and FISH diets reducing the n‐6/n‐3 ratio and increasing the peroxidability index (PI). Increased dietary EPA and DHA were observed in SOY‐FISH and FISH plasma at the expense of linoleic and arachidonic acid levels. Saturated fatty acids, which were significantly different between the three diets (P < 0.01), were found at the same concentration in the plasma (P = 0.23). No changes were observed in oxidative stress as measured by the concentration of thiobarbituric acid reactive substances (TBARS) expressed in brain homogenates. However, TBARS concentration in the plasma of the SOY‐FISH group was higher than the other two groups (P = 0.02). The major differences between these three groups were the n‐3 PUFA content (0.4, 1.8 and 3.2 g/100 g diet) and the saturates/polyunsaturates ratio (0.3, 0.5 and 0.8) for SOY, SOY‐FISH, and FISH groups, respectively. Thus, n‐3 PUFA intake from fish oil only when followed by a decrease in saturated/polyunsaturated fatty acids ratio increased oxidative susceptibility in rats measured by plasma TBARS concentration. PRACTICAL APPLICATIONS Because fish oil intake is associated with risk reduction for cardiovascular disease, individuals are taking supplements containing a high dose of fish oil. However, there is no scientific consensus if the intake of a high dose of fish oil could increase the oxidative stress. Thus, more studies are necessary to assure the safety of this kind of supplementation.
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