α-tocopherol content in trout oil

Tocopherols in Seafood and Aquaculture Products

Fish products contain various nutritionally beneficial components, namely, ω3-polyunsaturated fatty acids (ω3-PUFA), minerals, and vitamins. Particularly, tocopherols (α-, β-, γ-, and δ-tocopherol) can be provided by seafood and aquaculture products. Hence, this review shows the various aspects of tocopherols in seafood and aquaculture products. For tocopherol determination in these products, HPLC methods coupled with diode array detection in the UV area of the spectrum or fluorescence detection have been shown as sensitive and accurate. These newest methods have helped in understanding tocopherols fate upon ingestion by seafood organisms. Tocopherols pass through the intestinal mucosa mainly by the same passive diffusion mechanism as fats. After absorption, the transport mechanism is thought to consist of two loops. The first loop is dietary, including chylomicrons and fatty acids bound to carrier protein, transporting lipids mainly to the liver. The other is the transport from the liver to tissues and storage sites. Moreover, tocopherol levels in fish organisms correlate with diet levels, being adjusted in fish body depending on diet concentration. For farmed fish species, insufficient levels of tocopherols in the diet can lead to poor growth performance or to nutritional disease. The tocopherol quantity needed as a feed supplement depends on various factors, such as the vitamer mixture, the lipid level and source, the method of diet preparation, and the feed storage conditions. Other ingredients in diet may be of great importance, it has been proposed that α-tocopherol may behave as a prooxidant synergist at higher concentrations when prooxidants such as transition metals are present. However, the antioxidant action of tocopherols outweighs this prooxidant effect, provided that adequate conditions are used. In fact, muscle-based foods containing higher levels of tocopherol show, for instance, higher lipid stability. Besides, tocopherols are important not only from the nutritional point of view but also from the physiological one, since they are involved in many metabolic processes in the human organism. Moreover, synergistic interactions with selenium and ascorbic acid have been reported. It deserves attention that there is evidence tocopherols taken with food can prevent heart disease, while no such evidence was found for α-tocopherol as supplement. From this perspective, eating fish is advisable, since, for instance, a 100 g serving of salmon may provide nearly 14% of recommended dietary allowance.

Role of the raw composition of pelagic fish muscle on the development of lipid oxidation and rancidity during storage

The muscle composition of a pelagic fish species, Atlantic mackerel (Scomber scombrus), has been studied to determine the relationship with its susceptibility to develop lipid oxidation during chilled storage. For such an aim, the initial concentrations of the major components (water, total lipids, protein, and PUFAs) and minor pro-oxidant and antioxidant components (ascorbic acid, α-tocopherol, hemoglobin, total iron, LMW-iron, copper, and zinc) of different batches of mackerel were characterized. For the study, several batches of mackerel were caught during the spring and summer periods. The different batches were subjected to chilled storage, and the onset of lipid oxidation was statistically related with the initial muscle composition. Results showed significant compositional differences among the mackerel lots, especially for the muscle lipid content (2.83-9.50%). In a first step, a Pearson correlation test was used to check the influence of each component on the progress of lipid oxidation. Results showed a significant relationship between shelf life and water and total lipid contents. Multiple regression was performed to reveal the contribution of each component to the susceptibility to lipid oxidation. The model obtained combines the content of PUFAs, total iron, hemoglobin, and ascorbic acid. An accurate prediction of shelf life in terms of rancidity was achieved by the model created (R(2) = 0.9975). These results establish that the levels of endogenous pro-oxidants and antioxidants present in fish muscle together with the polyunsaturated lipids are relevant factors affecting the shelf life of mackerel muscle.

[Olive oil and inhibition of low density lipoprotein oxidation. Role of phenolic compounds]

BACKGROUND

To investigate the protective effect of several olive oils with different phenolic composition on low density lipoprotein susceptibility to oxidation.

PATIENTS AND METHODS

Refined olive oil (phenolic content: 0 mg/l caffeic acid equivalents [CAE]), common olive oil (0.1 and 0.3 mg/l CAE), and virgin olive oil diluted with refined olive oil (0.1 y 0.3 mg/l CAE), were added to isolated low density lipoprotein. Conjugated dienes formation was monitored after copper-mediated low density lipoprotein oxidation.

RESULTS

An increase in the lag time of conjugated dienes formation after copper-mediated low density lipoprotein oxidation was observed linked to olive oil phenolic content (p < 0.0001, ANOVA). Multiple regression analysis showed that phenolics were the most significant antioxidants with 0.1 mg/l--increase in phenolic concentration, adjusted for alpha-tocopherol and beta-carotene, was 72 minutes (95% confidence interval [CI] 64 to 80 min) for common olive oil, and 111 min (CI 95%: 100-123 min) for virgin olive oil. In common olive oil alpha-tocopherol levels were significatively associated with the increase in the lag time (p = 0.003), reaching in virgin olive oil a borderline significant (p = 0.084).

CONCLUSIONS

Olive oil containing phenolics showed more antioxidant effect on low density lipoprotein oxidation than refined olive in relation to its phenolic content. The nature of the phenolic content influences the antioxidant capacity of an olive oil.

Protective effect of olive oil and its phenolic compounds against low density lipoprotein oxidation

The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined) phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025-0.3 mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25-160 mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after adjustment for effects of other antioxidants; alpha-tocopherol also achieved a statistically significant effect. These results indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil.