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Two related phenolic antioxidants with opposite effects on vitamin E content in low density lipoproteins oxidized by ferrylmyoglobin: consumption vs regeneration.
Arch Biochem Biophys. 1995 Nov 10; 323(2):373-81.AB

Abstract

Endogenous alpha-tocopherol of low density lipoprotein (LDL) particles exposed to ferrylmyoglobin (iron in the form of FeIV = O) vanishes as a function of myoglobin concentration. After alpha-tocopherol depletion, subsequent heavy lipid peroxidation is prevented by caffeic and p-coumaric acids, i.e., phenolic acids present in foods and beverages, by a mechanism involving the one-electron transfer reaction between the phenols and the ferrylmyoglobin, with formation of metmyoglobin and the corresponding phenoxyl radicals from caffeic and p-coumaric acids, as previously discussed. Caffeic acid delays alpha-tocopherol consumption when present before oxidation challenging and restores alpha-tocopherol when added halfway during the reaction. Conversely, p-coumaric acid accelerates the rate of alpha-tocopherol consumption when added either before or during the oxidation reaction. In LDL enriched with alpha-tocopherol, caffeic acid induces an inhibition period of oxidation longer than that expected from the sum of discrete periods characteristic of the phenolic acid and alpha-tocopherol. Surprisingly, p-coumaric acid decreases the peroxidation chain rate. Similar effects of these phenolic acids on alpha-tocopherol consumption were observed in a Triton X-100 micellar system, i.e., in the absence of a peroxidation chain reaction. Results suggest that caffeic acid acts synergistically with alpha-tocopherol, extending the antioxidant capacity of LDL by recycling alpha-tocopherol from the alpha-tocopherol radical (i.e., alpha-tocopheroxyl radical). By contrast, the phenoxyl radical from p-coumaric acid (produced by electron-transfer reaction between phenolic acid and ferrylmyoglobin) oxidizes alpha-tocopherol. However, in spite of alpha-tocopherol consumption, the exchange reaction recycling p-coumaric acid can still afford an antioxidant protection to LDL on basis of the chain-breaking activity of p-coumaric acid. These results emphasize the biological relevance of small structural modifications of phenols on the interaction with alpha-tocopherol in LDL. The significance of these results in the context of atherosclerosis is discussed.

Authors+Show Affiliations

Laboratório de Bioquímica, Faculdade de Farmácia, Universidade de Coimbra, Portugal.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

7487101

Citation

Laranjinha, J, et al. "Two Related Phenolic Antioxidants With Opposite Effects On Vitamin E Content in Low Density Lipoproteins Oxidized By Ferrylmyoglobin: Consumption Vs Regeneration." Archives of Biochemistry and Biophysics, vol. 323, no. 2, 1995, pp. 373-81.
Laranjinha J, Vieira O, Madeira V, et al. Two related phenolic antioxidants with opposite effects on vitamin E content in low density lipoproteins oxidized by ferrylmyoglobin: consumption vs regeneration. Arch Biochem Biophys. 1995;323(2):373-81.
Laranjinha, J., Vieira, O., Madeira, V., & Almeida, L. (1995). Two related phenolic antioxidants with opposite effects on vitamin E content in low density lipoproteins oxidized by ferrylmyoglobin: consumption vs regeneration. Archives of Biochemistry and Biophysics, 323(2), 373-81.
Laranjinha J, et al. Two Related Phenolic Antioxidants With Opposite Effects On Vitamin E Content in Low Density Lipoproteins Oxidized By Ferrylmyoglobin: Consumption Vs Regeneration. Arch Biochem Biophys. 1995 Nov 10;323(2):373-81. PubMed PMID: 7487101.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Two related phenolic antioxidants with opposite effects on vitamin E content in low density lipoproteins oxidized by ferrylmyoglobin: consumption vs regeneration. AU - Laranjinha,J, AU - Vieira,O, AU - Madeira,V, AU - Almeida,L, PY - 1995/11/10/pubmed PY - 1995/11/10/medline PY - 1995/11/10/entrez SP - 373 EP - 81 JF - Archives of biochemistry and biophysics JO - Arch Biochem Biophys VL - 323 IS - 2 N2 - Endogenous alpha-tocopherol of low density lipoprotein (LDL) particles exposed to ferrylmyoglobin (iron in the form of FeIV = O) vanishes as a function of myoglobin concentration. After alpha-tocopherol depletion, subsequent heavy lipid peroxidation is prevented by caffeic and p-coumaric acids, i.e., phenolic acids present in foods and beverages, by a mechanism involving the one-electron transfer reaction between the phenols and the ferrylmyoglobin, with formation of metmyoglobin and the corresponding phenoxyl radicals from caffeic and p-coumaric acids, as previously discussed. Caffeic acid delays alpha-tocopherol consumption when present before oxidation challenging and restores alpha-tocopherol when added halfway during the reaction. Conversely, p-coumaric acid accelerates the rate of alpha-tocopherol consumption when added either before or during the oxidation reaction. In LDL enriched with alpha-tocopherol, caffeic acid induces an inhibition period of oxidation longer than that expected from the sum of discrete periods characteristic of the phenolic acid and alpha-tocopherol. Surprisingly, p-coumaric acid decreases the peroxidation chain rate. Similar effects of these phenolic acids on alpha-tocopherol consumption were observed in a Triton X-100 micellar system, i.e., in the absence of a peroxidation chain reaction. Results suggest that caffeic acid acts synergistically with alpha-tocopherol, extending the antioxidant capacity of LDL by recycling alpha-tocopherol from the alpha-tocopherol radical (i.e., alpha-tocopheroxyl radical). By contrast, the phenoxyl radical from p-coumaric acid (produced by electron-transfer reaction between phenolic acid and ferrylmyoglobin) oxidizes alpha-tocopherol. However, in spite of alpha-tocopherol consumption, the exchange reaction recycling p-coumaric acid can still afford an antioxidant protection to LDL on basis of the chain-breaking activity of p-coumaric acid. These results emphasize the biological relevance of small structural modifications of phenols on the interaction with alpha-tocopherol in LDL. The significance of these results in the context of atherosclerosis is discussed. SN - 0003-9861 UR - https://www.unboundmedicine.com/medline/citation/7487101/Two_related_phenolic_antioxidants_with_opposite_effects_on_vitamin_E_content_in_low_density_lipoproteins_oxidized_by_ferrylmyoglobin:_consumption_vs_regeneration_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0003986185700574 DB - PRIME DP - Unbound Medicine ER -