Nedyalka V. Yanishlieva

Antioxidant activity and mechanism of action of thymol and carvacrol in two lipid systems

The autoxidation of purified triacylglycerols of lard and sunflower oil (TGL and TGSO) containing 0.02, 0.05, 0.10 and 0.20% thymol and carvacrol was studied at ambient temperature. The results obtained with the inhibited lipid systems (thymol - TGL; carvacrol - TGL; thymol - TGSO and carvacrol - TGSO) showed that thymol had the highest antioxidant effectiveness and activity during TGSO oxidation. Thymol and carvacrol participated in one side reaction during inhibited TGL oxidation, and thymol took part in two side reactions during TGSO oxidation. Carvacrol molecules did not participate in side reactions during TGSO oxidation. Thymol and carvacrol contributed to chain initiation to a higher degree during TGSO oxidation than during TGL oxidation. Thymol radicals did not participate in chain propagation during TGL and TGSO oxidation. Carvacrol radicals took part in one reaction of chain propagation in both lipid systems. In general, during autoxidation of lipids at ambient temperature, thymol is a more effective and more active antioxidant than carvacrol. Both antioxidants differ in the mechanism of their inhibiting action which depends on the character of the lipid medium. Thymol is a better antioxidant in TGSO than in TGL, whereas the activity of carvacrol in the two lipid systems does not differ significantly.

Antioxidants in Food : Practical Applications

Part 1 Antioxidants and food stability: The development of oxidative rancidity in foods Inhibiting oxidation Measuring antioxidant activity. Part 2 Antioxidants and health: Cardiovascular disease and nutritional phenolics Antioxidants and anti-tumour properties Predicting the bioavailability of antioxidants in food: the case of carotenoids. Part 3 Natural antioxidants: Introducing natural antioxidants Sources of natural antioxidants: oilseeds, nuts, cereals, legumes, animal products and microbial sources Sources of natural antioxidants: vegetables, fruits, herbs, spices and teas. Part 4 Practical applications: Regulation of antioxidants in food Use of natural antioxidants in food products Preparation of natural antioxidants Natural antioxidant functionality during food processing.

Antioxidants in food

ion Electron

Antioxidative activity of extracts from selected species of the family Lamiaceae in sunflower oil

Abstract The kinetics of peroxide accumulation during oxidation of sunflower oil at 100 °C in the presence of different concentrations of hexane, ethyl acetate and ethanol extracts of Melissa officinalis L., Mentha piperita L., Mentha spicata L., Ocimum basilicum L., Origanum vulgare L. and Saturejae hortensis L. have been studied. It has been established that the extracts from Ocimum basilicum L. and Origanum vulgare L. do not improve the oxidation stability of sunflower oil. The ethanol extracts from the other four spices have proved to be the most active in retarding the autoxidation process. The strongest action has been exhibited by the ethanol extracts from Saturejae hortensis L., followed by the ethanol extracts from Mentha piperita L. and Melissa officinalis L. The stabilization factor F for the ethanol extracts (0.1–0.5%) from Saturejae hortensis L. is 1.8–2.3. It is higher than F for 0.02% butylated hydroxytoluene BHT (F = 1.2). From a practical point of view (yield and stabilization factor), the direct ethanol extract from Saturejae hortensis L. should be recommended as the most suitable antioxidant for the stabilization of sunflower oil.

N-3 fatty acids for human nutrition: stability considerations

Currently there is great interest in dietary n-3 fatty acids to promote health. The food industry aims to produce food products enriched in α-linolenic acid (Ln), eicosapentaenoic acid (EPA) and/or docosahexaenoic acid (DHA) to reduce some of the physiological effects of linoleic acid (L), the major polyunsaturated fatty acid in our diet. However, the goal is hampered by the susceptibility of the n-3 fatty acids to oxidation. As a result the sensory and nutritional quality of such foods deteriorates. Lipid scientists therefore have to find a way to stabilise these fatty acids. Innovative technologies to protect n-3 polyunsaturates using antioxidants, adequate preparation, refining and packaging of the oil are needed. In this paper we review the inherent stability and the stabilisation of these nutritionally valuable polyunsaturated fatty acids.

Effect of an Ethanol Extract from Summer Savory (Saturejae hortensisL) on the Stability of Sunflower Oil at Frying Temperature

The effect of the ethanol extract from Saturejae hortensis L on the oxidative and thermal processes occurring in sunflower oil during its high-temperature treatment (180°C) was investigated. The changes during simulated deep fat frying were monitored by determination of the oxidation stability at 100°C, as well as by determination of unchanged triacylglycerols. It was established that the addition of 1 and 5 g kg-1 ethanol extract from S hortensis L leads to a decrease in the oxidative and thermal changes in the oil. The ethanol extract from S hortensis L improved the oxidative stability of sunflower oil even after 50 h at 180°C and it inhibited the oxidative processes more than the thermal processes under these conditions.

Antioxidative effectiveness of some natural antioxidants in sunflower oil

Sunflower oil has been oxidized at 25 and 100°C in the presence and in the absence of 0.01,0.02 and 0.05% 3,4-dihydroxybenzoic acid, caffeic acid, esculetin and fraxetin. 3,4-Dihydroxybenzoic acid shows no antioxidative activity at either temperature. Esculezin possesses a relatively low effectiveness at 100°C (stabilization factorF=1.3 for 0.05% esculetin), and at 25°C it does not improve the oxidative stability. Sunflower oil is more easy to stabilize at 100°C:F=3.0 for 0.05% fraxetin, andF=1.9 for 0.05% caffeic acid. Native sunflower oil is much more difficult to stabilize than are its kinetically pure triacylglycerols.

Accumulation of lead, zinc and cadmium in plant seeds growing in metalliferous habitats in Bulgaria

Seeds from some plants were collected from metalliferous region in Bulgaria. In this area the concentrations of lead, cadmium and zinc in soil were 3500 mg kg−1, 280 mg kg−1 and 30 mg kg−1, respectively. Plants accumulate heavy metal ions in their seeds selectively. It appears that peanut and corn seeds accumulate mainly Pb (5.2–9.6 mg kg−1), pea seeds accumulate mainly Cd (1.0–1.2 mg kg−1 l), and wheat seeds accumulate mainly Zn (59.4–73.2 mg kg−1). This shows that the accumulation of heavy metals in the seeds of plants from some polluted regions may reach dangerous levels, especially if they are used as forage or food.

Effects of chain transfer and recombination/disproportionation of inhibitor radicals on inhibited oxidation of lipids

The kinetics of inhibited oxidation of lipids was studied by computer simulation to evaluate the contributions of the recombination/disproportionation of inhibitor radicals and chain transfer to retardation effects. The influence of inhibitor regeneration on the induction periods and inhibited oxidation rate was demonstrated.

Action of 1-(11-Selenadodecyl)-glycerol and 1-(11-Selenadodecyl)-3-Trolox-glycerol Against Lipid Peroxidation

The antioxidant action on lipid peroxidation of the synthesized selenium compounds 1-(11-selenadodecyl)-glycerol (SeG) and 1-(11-selenadodecyl)-3-Trolox-glycerol (SeIrG, where Trolox=6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid) was investigated. We compared the reactivity of the selenium compounds toward peroxyl radicals and their inhibitory effect on lipid peroxidation, induced by several kinds of initiating species such as azo compounds, metal ions, and superoxide/nitric oxide in solution, micelles, membranes, and rat plasma. SeTrG, but not SeG, scavenged peroxyl radicals. SeG reduced methyl linoleate hydroperoxides in organic solution and in methyl linoleate micelles oxidized by ferrous ion (Fe2+)/ascorbic acid. In rat plasma SeG and SeTrG decreased the formation of lipid hydroperoxides generated by hydrophilic azo compounds. SeG and SeTrG spared α-tocopherol (α-TOH) consumption in multilamellar vesicle membranes oxidized by hydrophilic or lipophilic initiators, and only SeTrG spared α-TOH in superoxide/nitric oxide oxidized membranes. In rat plasma oxidized by radical initiators (either hydrophilic or lipophilic) or superoxide/nitric oxide, SeTrG suppressed α-TOH consumption, but SeG had no effect. The two selenium-containing compounds showed inhibitory effects on lipid peroxidation that depended on their structure, the medium where they acted, and the oxidant used.