{"id":"bdbea035-977a-54c3-adff-5eb03bd0074d","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-tocopherol-radical-recycling","predicate":"reduces-radical-and-regenerates","statement":"Aqueous ascorbate reduced bilayer alpha-tocopheroxyl radical back to alpha-tocopherol in oxidizing soybean phosphatidylcholine liposomes; the reported apparent bimolecular rate constant was about 2 × 10^5 M^-1 s^-1 under those conditions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"3d5833d6-2ae0-5937-b938-944c21efdaf4","mechanism_event_label":"Vitamin C recycled the vitamin E radical back into vitamin E across this artificial membrane-water interface.","subject":{"id":"38d0c4d9-53d1-5239-bfe3-c1b5e9b79085","slug":"ascorbate","display_name":"L-Ascorbate","entity_type_key":"small_molecule"},"object":{"id":"40a6525a-76b8-576e-b73d-1e11aecf5f8d","slug":"alpha-tocopherol","display_name":"Alpha-tocopherol","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"3d5833d6-2ae0-5937-b938-944c21efdaf4","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-tocopherol-radical-recycling-event","event_type":"biochemical_relationship","label":"Vitamin C recycled the vitamin E radical back into vitamin E across this artificial membrane-water interface.","description":"Aqueous ascorbate reduced bilayer alpha-tocopheroxyl radical back to alpha-tocopherol in oxidizing soybean phosphatidylcholine liposomes; the reported apparent bimolecular rate constant was about 2 × 10^5 M^-1 s^-1 under those conditions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"da1a7137-08f2-5a36-8bb6-377fbd32e327","slug":"vitamin-c","display_name":"Vitamin C","entity_type_key":"chemical_species"},"role":"nutrient context","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ec585435-0fdf-5f6f-97d9-6fff230d405e","slug":"alpha-tocopheroxyl-radical","display_name":"Alpha-tocopheroxyl radical","entity_type_key":"chemical_species"},"role":"electron-accepting substrate","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"40a6525a-76b8-576e-b73d-1e11aecf5f8d","slug":"alpha-tocopherol","display_name":"Alpha-tocopherol","entity_type_key":"small_molecule"},"role":"regenerated product","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"2f77ef6d-3ecd-5a80-9ca3-3cbea403d9fc","slug":"phosphatidylcholine","display_name":"Phosphatidylcholine","entity_type_key":"lipid"},"role":"liposome material","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"38d0c4d9-53d1-5239-bfe3-c1b5e9b79085","slug":"ascorbate","display_name":"L-Ascorbate","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Primary abstract radical accessibility and kinetic result","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Soybean L-alpha-phosphatidylcholine liposomes undergoing Fe(III)-triethylenetetramine-initiated peroxidation; EPR, optical and polarographic measurements","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Aqueous ascorbic acid described as physiological concentration in abstract (exact dose unavailable); bilayer alpha-tocopheroxyl radical detected at 10^-8–10^-7 M.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Membrane composition, radical initiator and assay conditions determine kinetics; no human clinical benefit or universal membrane rate is established.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin C research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-c","display_name":"Vitamin C","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Glycine max lipid preparation; cell-free","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Vitamin C recycled the vitamin E radical back into vitamin E across this artificial membrane-water interface.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[c-reg-scarpa] Formation of alpha-tocopherol radical and recycling of alpha-tocopherol by ascorbate during peroxidation of phosphatidylcholine liposomes. An electron paramagnetic resonance study. (1984). https://pubmed.ncbi.nlm.nih.gov/6089911/ DOI: 10.1016/0304-4165(84)90070-9","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Artificial liposomes","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"734ea076-c784-5c19-bf25-fcd604d7cafe","evidence_kind":"source_excerpt","locator":"Lines 1201-1213","start_line":1201,"end_line":1213,"excerpt":"### c-reg-tocopherol-radical-recycling\nAqueous ascorbate reduced bilayer alpha-tocopheroxyl radical back to alpha-tocopherol in oxidizing soybean phosphatidylcholine liposomes; the reported apparent bimolecular rate constant was about 2 × 10^5 M^-1 s^-1 under those conditions.\nCondition category: normal\nnutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Vitamin C recycled the vitamin E radical back into vitamin E across this artificial membrane-water interface.\norganism: Glycine max lipid preparation; cell-free\ntissue_or_cell_type: Artificial liposomes\nexperimental_model: Soybean L-alpha-phosphatidylcholine liposomes undergoing Fe(III)-triethylenetetramine-initiated peroxidation; EPR, optical and polarographic measurements\nlimitations: Membrane composition, radical initiator and assay conditions determine kinetics; no human clinical benefit or universal membrane rate is established.\nexposure: Aqueous ascorbic acid described as physiological concentration in abstract (exact dose unavailable); bilayer alpha-tocopheroxyl radical detected at 10^-8–10^-7 M.\ncross_nutrient: true\nevidence_location: Primary abstract radical accessibility and kinetic result\n[c-reg-scarpa] Formation of alpha-tocopherol radical and recycling of alpha-tocopherol by ascorbate during peroxidation of phosphatidylcholine liposomes. 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