Plant Extracts Inhibit the Formation of Hydroperoxides and Help Maintain Vitamin E Levels and Omega-3 Fatty Acids During High Temperature Processing and Storage of Hempseed and Soybean Oils

Oxidative stability of hempseed and soybean oils, was evaluated after heating at 180 °C, followed by a subsequent 14-day storage at 38 °C. Natural plant extracts (Rosemary, Sage, and Thyme) were added to oils, to evaluate the carry-over stabilizing potential. Heated oils exhibited a relatively faster (P < 0.05) onset of lipid oxidation, as depicted by the analysis of the peroxides and aldehydes formed during the lipid oxidation process, with hempseed oil being more susceptible to lipid oxidation than soybean oil. There were notable losses in ω-3 PUFA and ω-6-GLA during storage of heat treated hempseed oil (P < 0.05). Moreover, peroxide values measured from hempseed oil remained low after high-temperature heating but progressed at a relatively greater rate than that observed in soybean during storage (P < 0.05). The addition of different plant extracts to oils did not prevent oxidation due to heating, but effectively inhibited the generation of hydroperoxides during subsequent storage (P < 0.05). This stabilizing effect was attributed to retention of tocopherols, in particular, γ-tocopherol. PRACTICAL APPLICATION: This research demonstrates the use of plant extracts like rosemary, sage and thyme, for improving the shelf-life and nutritional stability of hempseed and soybean oil. We demonstrate the deterioration of fatty acid profiles and vitamin E levels in the oil on heating and subsequent storage, and show the efficacy of using plant extracts in slowing down these deteriorations. This research will be applicable in food industries using or producing oils for use in food during cooking, and also as dressing on already processed food products.

Omega-3 polyunsaturated fatty acids improve the antioxidative defense in rat astrocytes via an Nrf2-dependent mechanism

BACKGROUND

Neuronal tolerance to hypoxia and nutrient defficiency highly depends on GSH levels and antioxidant enzyme activity in astrocytes. Omega-3 polyunsaturated fatty acids (ω-3PUFA) enhance antioxidant defence in different cells. The aim of present study was to investigate if ω-3PUFA improve antioxidant status in astrocytes.

METHODS

Rat primary astrocytes were incubated for 24h with DHA and EPA (30μM), then lysed, fractioned and fatty acids were determined by gas chromatography. GSH and protein thiols were assayed by enzymatic methods. Glutamate cysteine ligase (GCL), glutathione synthetase (GS), glutathione peroxidase 4 (GPx4) and Nrf2 protein expression was validated by Western blot. Intracellular ROS level using H₂DCF-DA, and Nrf2 activation by ELISA were measured.

RESULTS

Incubation of cells with DHA doubled DHA, not EPA content in the membranes, and incubation with EPA increased both fatty acids content compared to control. However, both ω-3PUFAs reduced ROS generation in dose-dependent manner in basal condition and in H₂O₂-treated cells, and significantly increased GSH, GCL and GPx4 levels. The thiols level was higher only in DHA-treated cells. DHA and EPA activated Nrf2 in a dose-dependent manner but p38MAPK-Nrf2 activation was found only in DHA-enriched astrocytes.

CONCLUSION

Both ω-3PUFA improved the antioxidant defense in astrocytes via an Nrf2-dependent mechanism, however, upstream pathways of Nrf2 activation may depend on proportion of DHA to EPA incorporated into membrane phospholipids. These results suggest that enrichment of astrocytes with ω-3PUFA may better protect neurons during harmful conditions.