{"id":"eb834256-2bb4-58fd-af55-a600b20b2d9f","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-medium-peroxide-generation","predicate":"increases","statement":"Ascorbate produced peroxide in cell culture medium without requiring cells; accumulation depended on ascorbate concentration, time and serum fraction, and tracked ascorbyl radical detected by EPR.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"b1f694c6-5137-563c-bc80-64e3cdb03915","mechanism_event_label":"The culture liquid itself could turn high-concentration vitamin C into peroxide.","subject":{"id":"38d0c4d9-53d1-5239-bfe3-c1b5e9b79085","slug":"ascorbate","display_name":"L-Ascorbate","entity_type_key":"small_molecule"},"object":{"id":"18a4b880-f4f3-5991-9062-76adbf68e350","slug":"extracellular-peroxide-accumulation","display_name":"Extracellular hydrogen peroxide accumulation","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"b1f694c6-5137-563c-bc80-64e3cdb03915","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:c-reg-medium-peroxide-generation-event","event_type":"biochemical_relationship","label":"The culture liquid itself could turn high-concentration vitamin C into peroxide.","description":"Ascorbate produced peroxide in cell culture medium without requiring cells; accumulation depended on ascorbate concentration, time and serum fraction, and tracked ascorbyl radical detected by EPR.","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":"da9d64bc-69d4-5d97-90a4-8f0ed03e0ac8","slug":"hydrogen-peroxide","display_name":"Hydrogen peroxide","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"17a4b1a5-451a-563f-8f20-2de8f4b0af8e","slug":"ascorbyl-radical","display_name":"Ascorbyl radical","entity_type_key":"chemical_species"},"role":"measured oxidation intermediate","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"899c7ab0-6f81-5b38-a6bd-fbb33d66ac8d","slug":"oxygen","display_name":"Molecular oxygen","entity_type_key":"small_molecule"},"role":"redox substrate","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":""},{"entity":{"id":"18a4b880-f4f3-5991-9062-76adbf68e350","slug":"extracellular-peroxide-accumulation","display_name":"Extracellular hydrogen peroxide accumulation","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Figure 4A–C","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Cell-free medium; catalase-dependent oxygen-electrode peroxide assay and EPR","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"0.2–2 mM ascorbate over 1 h; 2 mM ascorbate with 0.5–10% FBS in serum-dependence experiment.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Pharmacological in-vitro exposure; medium chemistry and peroxide clearance differ from intact tissues. No dietary or clinical anticancer inference. Net accumulation reflects both production and removal; ascorbate can interfere with routine peroxidase assays.","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":"Cell-free; bovine serum-containing medium","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The culture liquid itself could turn high-concentration vitamin C into peroxide.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[c-reg-chen] Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. (2005). https://pubmed.ncbi.nlm.nih.gov/16157892/ DOI: 10.1073/pnas.0506390102","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Extracellular assay medium","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"acbea4dc-0626-51d2-9c99-b392467aea65","evidence_kind":"source_excerpt","locator":"Lines 1257-1269","start_line":1257,"end_line":1269,"excerpt":"### c-reg-medium-peroxide-generation\nAscorbate produced peroxide in cell culture medium without requiring cells; accumulation depended on ascorbate concentration, time and serum fraction, and tracked ascorbyl radical detected by EPR.\nCondition category: normal\nnutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The culture liquid itself could turn high-concentration vitamin C into peroxide.\norganism: Cell-free; bovine serum-containing medium\ntissue_or_cell_type: Extracellular assay medium\nexperimental_model: Cell-free medium; catalase-dependent oxygen-electrode peroxide assay and EPR\nlimitations: Pharmacological in-vitro exposure; medium chemistry and peroxide clearance differ from intact tissues. No dietary or clinical anticancer inference. Net accumulation reflects both production and removal; ascorbate can interfere with routine peroxidase assays.\nexposure: 0.2–2 mM ascorbate over 1 h; 2 mM ascorbate with 0.5–10% FBS in serum-dependence experiment.\ncross_nutrient: false\nevidence_location: Figure 4A–C\n[c-reg-chen] Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. (2005). https://pubmed.ncbi.nlm.nih.gov/16157892/ DOI: 10.1073/pnas.0506390102","model_system":"Cell-free medium; catalase-dependent oxygen-electrode peroxide assay and EPR","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [c-reg-chen] Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. (2005). https://pubmed.ncbi.nlm.nih.gov/16157892/ DOI: 10.1073/pnas.0506390102","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"fa811221-13bd-5c10-adc1-eaf097c7703c","stable_key":"import-cb568d28-484a-5c2e-9fcc-2d780358e514","title":"Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"b7fd83f956abb81855f2ea23199ba14e465cd91f4a2ac560277ec21ddafd7bfc","revision_id":"6cde9bbb-d712-5746-82a6-85b144253efa","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}