Effect of heat-processing on the antioxidant and prooxidant activities of ß-carotene from natural and synthetic origins on red blood cells.

Extraction of bioactives is a cause of structural changes in these molecules. In this work, the bioactivity of commercial natural ß-carotenes, one softly extracted without heat-assistance from Momordica cochinchinensis (BCG), one conventionally extracted from another natural source (BCC), and a synthetic one (BCS), was assessed during an additional heat-treatment mimicking formulation. Their antioxidant activities were evaluated after heat-treatment at different concentrations through hemolysis of horse red blood cells. The thermal 15-cis-isomerization of ß-carotene, characterized by DAD-HPLC, resulted in a 2.5- to 4.8-fold increase in the anti-hemolytic effect but this was undetected in chemical assay, at 4 µM. At 100 µM, BCC lost its antioxidant properties and became pro-oxidant. This effect might be caused by long-chain-oxidized-products of BCC. Results demonstrated that a short heat-treatment improves the bioactivity of ß-carotene but longer treatments made BCC prooxidant, showing that samples that underwent drastic extraction processes could not tolerate additional steps for functional food production.

Tissue antioxidant status differs in spontaneously hypertensive rats fed fish protein or casein.

The present study was designed to determine whether changes in dietary protein source are related to changes in antioxidant status determined by enzyme activities of catalase, superoxide dismutase (SOD), gluthatione peroxidase (GSH-Px) and gluthatione reductase (GSSG-Red) and lipid peroxidation levels in various tissues. Spontaneously hypertensive rats (SHR; 5 wk old) were fed diets containing 20% casein or fish protein for 2 mo. Feeding the fish protein diet lowered blood pressure and reduced plasma total cholesterol levels and SOD activity in all tissues except muscle compared with the casein diet. Feeding fish protein also enhanced GSH level and GSH-Px activity in liver and heart, accompanied by lower lipid peroxidation. In kidney, however, the lower catalase activity in rats fed fish protein was associated with an enhancement in lipid peroxidation. Plasma and VLDL + LDL lipid peroxidation was unaffected by dietary proteins. In conclusion, the fish protein diet did not play a relevant role in plasma antioxidative defense status but increased it in liver and heart compared with the casein diet. Fish protein attenuated the development of hypertension and also decreased plasma total cholesterol concentration. Thus, it enhances protection against cardiovascular diseases.

Very high alpha-tocopherol diet diminishes oxidative stress and hypercoagulation in hypertensive rats but not in normotensive rats.

BACKGROUND: Oxidative stress is closely related to cardiovascular diseases, such as atherosclerosis. Increasing dietary antioxidants, such as alpha-tocopherol, may prevent these diseases. However, in some pathologies, such as hypertension, oxidative stress is enhanced, thus alpha-tocopherol requirements may be raised. MATERIAL/METHODS: In eleven-week-old spontaneously hypertensive rats and normotensive Wistar Kyoto rats, we investigated the effects of a four-week very high alpha-tocopherol dietary enrichment (1,200 mg/kg diet, VH) on blood pressure, resistance to free radical aggression, and VLDL+LDL resistance to lipid peroxidation. Platelet aggregation and plasma lipid profile were also investigated. RESULTS: With either diet, hypertensive rats were more protected against oxidative stress than normotensive rats. Their capacity to withstand free radical aggression was better, and their VLDL+LDL particles were less sensitive to lipid peroxidation. In either group, the VH diet did not modify blood pressure values when resistance to free radical aggression was increased, but not the resistance of VLDL+LDL to lipid peroxidation. With the control diet, platelet aggregation was faster and higher in hypertensive rats vs. normotensive rats. It was decreased with the VH diet in hypertensive rats but increased in normotensive rats, when compared to their respective controls. Whatever the diet, plasma triacylglycerol, phospholipid and cholesterol concentrations were lower in hypertensive than in normotensive rats. Only cholesterol concentrations were diminished with the VH diet in hypertensive rats, but not in normotensive rats. CONCLUSIONS: These results indicate that very high alpha-tocopherol dietary amounts decrease cardiovascular risk in hypertensive rats with high oxidative stress, but have less effect on normotensive rats.