Xanthine

evidence_span

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experimental_model

Recombinant human XDH variants with urate, superoxide and NO assays

exposure

Xanthine, oxygen and inorganic nitrite assays

limitations

The 2023 Fig. 6E corrigendum corrects a displayed panel; authors state data and conclusions are unchanged. Enzyme activity is not a clinical benefit or dietary response.

nutrient_topic

Molybdenum research collection; topical membership is not evidence of a direct dietary effect. · Molybdenum

organism

Homo sapiens protein

plain_language

The purine-breakdown pathway uses a molybdenum enzyme to make urate.

primary_references

[mo-p37713777] Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health? (2023). https://pubmed.ncbi.nlm.nih.gov/37713777/ DOI: 10.1016/j.redox.2023.102864

tissue_or_cell_type

Purified human enzyme

Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17) · lines 742–753

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant human XDH variants with urate, superoxide and NO assays · source_derived_draft · unverified_draft

### mo-xdh-xanthine Recombinant human XDH/XOR catalyzed conversion of xanthine to urate. Condition category: normal nutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect. plain_language: The purine-breakdown pathway uses a molybdenum enzyme to make urate. organism: Homo sapiens protein tissue_or_cell_type: Purified human enzyme experimental_model: Recombinant human XDH variants with urate, superoxide and NO assays limitations: The 2023 Fig. 6E corrigendum corrects a displayed panel; authors state data and conclusions are unchanged. Enzyme activity is not a clinical benefit or dietary response. exposure: Xanthine, oxygen and inorganic nitrite assays evidence_span: {"source_cache": "artifacts/molybdenum-research/37713777.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "30e93ea24784120403bef1dfe72cf46411f1af88946b9cc1cba3d4c45a367bf9", "start_char": 0, "end_char": 1655, "text_sha256": "30e93ea24784120403bef1dfe72cf46411f1af88946b9cc1cba3d4c45a367bf9"} [mo-p37713777] Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health? (2023). https://pubmed.ncbi.nlm.nih.gov/37713777/ DOI: 10.1016/j.redox.2023.102864

evidence_access

Primary abstract

experimental_model

Purified bovine enzyme steady-state kinetics.

limitations

Bovine enzyme evidence; not a clinical urate-lowering trial.

nutrient_topic

Luteolin collection; molecular form, preparation, species, exposure and manipulation remain explicit. · Luteolin / 3′,4′,5,7-tetrahydroxyflavone

plain_language

It interfered with the purine-breakdown enzyme.

primary_references

Inhibition studies of bovine xanthine oxidase by luteolin, silibinin, quercetin, and curcumin. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19388706/ · DOI 10.1021/np8007123

Luteolin: metabolism, immune signaling, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 284–290

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Purified bovine enzyme steady-state kinetics. · source_derived_draft · unverified_draft

## luteolin-xo-inhibition It interfered with the purine-breakdown enzyme. Luteolin competitively inhibited purified bovine xanthine oxidase without time-dependent inhibition. Model: Purified bovine enzyme steady-state kinetics. Limitations: Bovine enzyme evidence; not a clinical urate-lowering trial. Evidence access: Primary abstract Inhibition studies of bovine xanthine oxidase by luteolin, silibinin, quercetin, and curcumin. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19388706/ · DOI 10.1021/np8007123

evidence_access

Primary abstract and repository full-text methods

experimental_model

Purified bovine-milk enzyme, chromatographic product analysis.

limitations

Sulfate was more potent than parent in the study. Not demonstrated human urate lowering or thiopurine toxicity.

nutrient_topic

Myricetin collection; molecular form, preparation, species, exposure and manipulation remain explicit. · Myricetin

plain_language

One enzyme processes both a natural purine and a medication.

primary_references

Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37734263/ · DOI 10.1016/j.biopha.2023.115548

Myricetin: metabolism, immune signaling, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 388–394

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Purified bovine-milk enzyme, chromatographic product analysis. · source_derived_draft · unverified_draft

## myricetin-xo-parent-xanthine One enzyme processes both a natural purine and a medication. Myricetin aglycone inhibited bovine-milk xanthine oxidase-mediated xanthine oxidation. Model: Purified bovine-milk enzyme, chromatographic product analysis. Limitations: Sulfate was more potent than parent in the study. Not demonstrated human urate lowering or thiopurine toxicity. Evidence access: Primary abstract and repository full-text methods Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37734263/ · DOI 10.1016/j.biopha.2023.115548

evidence_access

Primary abstract and repository full-text methods

experimental_model

Purified bovine-milk enzyme, chromatographic product analysis.

limitations

Sulfate was more potent than parent in the study. Not demonstrated human urate lowering or thiopurine toxicity.

nutrient_topic

Myricetin collection; molecular form, preparation, species, exposure and manipulation remain explicit. · Myricetin

plain_language

One enzyme processes both a natural purine and a medication.

primary_references

Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37734263/ · DOI 10.1016/j.biopha.2023.115548

Myricetin: metabolism, immune signaling, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 404–410

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Purified bovine-milk enzyme, chromatographic product analysis. · source_derived_draft · unverified_draft

## myricetin-xo-sulfate-xanthine One enzyme processes both a natural purine and a medication. Myricetin 3′-O-sulfate inhibited bovine-milk xanthine oxidase-mediated xanthine oxidation. Model: Purified bovine-milk enzyme, chromatographic product analysis. Limitations: Sulfate was more potent than parent in the study. Not demonstrated human urate lowering or thiopurine toxicity. Evidence access: Primary abstract and repository full-text methods Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37734263/ · DOI 10.1016/j.biopha.2023.115548

dose

Naringenin, sulfate and glucuronide conjugates

duration

Acute enzyme incubation

evidence_access

Primary PubMed abstract and indexed metadata reviewed. Full-text method details not stated here remain unresolved.

evidence_scope

literature_reviewed; model-specific source-derived curation

experimental_model

Cell-free xanthine oxidase assays

limitations

Luteolin and myricetin species were the potent inhibitors in this study; the weak naringenin result does not establish a clinical 6-mercaptopurine interaction.

nutrient_topic

Naringenin chapter; interacting nutrients, drugs, peptides and proteins retain their experimental settings. · Naringenin

organism

Cell-free xanthine oxidase assays

plain_language

Naringenin and its sulfate/glucuronide metabolites were weak inhibitors of xanthine oxidase in xanthine and 6-mercaptopurine oxidation assays.

primary_references

Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. (2023). https://pubmed.ncbi.nlm.nih.gov/37734263/ DOI: 10.1016/j.biopha.2023.115548

route

In vitro

tissue

Xanthine and 6-mercaptopurine oxidation

Naringenin: mechanism of action and interactions (2026-09-20) · lines 99–108

Original AI-assisted source-specific curation with primary-study citations, model, exposure, route, duration, negative findings and limitations preserved. Not publisher full text. · supports · Cell-free xanthine oxidase assays · source_derived_draft · unverified_draft

## naringenin-xo-weak Naringenin and its sulfate/glucuronide metabolites were weak inhibitors of xanthine oxidase in xanthine and 6-mercaptopurine oxidation assays. Model/species: Cell-free xanthine oxidase assays Tissue/system: Xanthine and 6-mercaptopurine oxidation Exposure: Naringenin, sulfate and glucuronide conjugates Route: In vitro Duration: Acute enzyme incubation Limits: Luteolin and myricetin species were the potent inhibitors in this study; the weak naringenin result does not establish a clinical 6-mercaptopurine interaction. Primary reference: Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites. (2023). https://pubmed.ncbi.nlm.nih.gov/37734263/ DOI: 10.1016/j.biopha.2023.115548 Access: Primary PubMed abstract and indexed metadata reviewed. Full-text method details not stated here remain unresolved.

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_span

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experimental_model

Retrospective natural history in 58 patients; prospective biomarkers in 21 survivors

exposure

MoCD A:41; MoCD B:17

limitations

Severe inherited cofactor defects; not a prevalence study of ordinary nutritional deficiency or a validated population screening threshold.

nutrient_topic

Molybdenum research collection; topical membership is not evidence of a direct dietary effect. · Molybdenum

organism

Homo sapiens

plain_language

The combined pattern reflects failures in two cofactor-dependent pathways.

primary_references

[mo-p35192225] Molybdenum cofactor deficiency: A natural history. (2022). https://pubmed.ncbi.nlm.nih.gov/35192225/ DOI: 10.1002/jimd.12488

tissue_or_cell_type

Neurological course and plasma/urine

trigger_kind

machinery_impairment Imported condition classification; unverified.

Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17) · lines 1158–1169

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Retrospective natural history in 58 patients; prospective biomarkers in 21 survivors · source_derived_draft · unverified_draft

### mo-mocd-biomarkers MoCD-A and MoCD-B patients had elevated plasma/urinary S-sulfocysteine and xanthine, while urate stayed below reference ranges. Condition category: machinery_impairment nutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect. plain_language: The combined pattern reflects failures in two cofactor-dependent pathways. organism: Homo sapiens tissue_or_cell_type: Neurological course and plasma/urine experimental_model: Retrospective natural history in 58 patients; prospective biomarkers in 21 survivors limitations: Severe inherited cofactor defects; not a prevalence study of ordinary nutritional deficiency or a validated population screening threshold. exposure: MoCD A:41; MoCD B:17 evidence_span: {"source_cache": "artifacts/molybdenum-research/35192225.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "ab9083746ef775c196770d3f4d0208378f1796abf1d7056fe5b23f60421032d4", "start_char": 0, "end_char": 1812, "text_sha256": "ab9083746ef775c196770d3f4d0208378f1796abf1d7056fe5b23f60421032d4"} [mo-p35192225] Molybdenum cofactor deficiency: A natural history. (2022). https://pubmed.ncbi.nlm.nih.gov/35192225/ DOI: 10.1002/jimd.12488

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

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experimental_model

Single case during prolonged total parenteral nutrition

exposure

Prolonged parenteral nutrition followed by ammonium molybdate

limitations

Rare single case. The paper reports 300 micrograms/day ammonium molybdate, not 300 micrograms elemental molybdenum. Historical observation, not a general regimen.

nutrient_topic

Molybdenum research collection; topical membership is not evidence of a direct dietary effect. · Molybdenum

organism

Homo sapiens

plain_language

A second molybdenum-dependent pathway was also impaired.

primary_references

[mo-p6795919] Amino acid intolerance during prolonged total parenteral nutrition reversed by molybdate therapy. (1981). https://pubmed.ncbi.nlm.nih.gov/6795919/ DOI: 10.1093/ajcn/34.11.2551

tissue_or_cell_type

Systemic symptoms; plasma and urine

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17) · lines 1132–1143

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Single case during prolonged total parenteral nutrition · source_derived_draft · unverified_draft

### mo-tpn-purines The same patient had low serum urate with increased urinary hypoxanthine and xanthine. Condition category: nutrient_deficiency nutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect. plain_language: A second molybdenum-dependent pathway was also impaired. organism: Homo sapiens tissue_or_cell_type: Systemic symptoms; plasma and urine experimental_model: Single case during prolonged total parenteral nutrition limitations: Rare single case. The paper reports 300 micrograms/day ammonium molybdate, not 300 micrograms elemental molybdenum. Historical observation, not a general regimen. exposure: Prolonged parenteral nutrition followed by ammonium molybdate evidence_span: {"source_cache": "artifacts/molybdenum-research/6795919.publisher-abstract.txt", "locator": "Exact primary publisher abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d2838a46a598539818059c1a1f8295e283334afced15326a6b5ba1a6104cbfd7", "start_char": 0, "end_char": 1820, "text_sha256": "d2838a46a598539818059c1a1f8295e283334afced15326a6b5ba1a6104cbfd7"} [mo-p6795919] Amino acid intolerance during prolonged total parenteral nutrition reversed by molybdate therapy. (1981). https://pubmed.ncbi.nlm.nih.gov/6795919/ DOI: 10.1093/ajcn/34.11.2551

evidence_span

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experimental_model

Recombinant human XDH variants with urate, superoxide and NO assays

exposure

Xanthine, oxygen and inorganic nitrite assays

limitations

Established reaction summarized in the primary article background; this paper directly assayed xanthine-based activity rather than newly establishing the hypoxanthine step.

nutrient_topic

Molybdenum research collection; topical membership is not evidence of a direct dietary effect. · Molybdenum

organism

Homo sapiens protein

plain_language

Hypoxanthine enters the same two-step purine pathway.

primary_references

[mo-p37713777] Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health? (2023). https://pubmed.ncbi.nlm.nih.gov/37713777/ DOI: 10.1016/j.redox.2023.102864

tissue_or_cell_type

Purified human enzyme

Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17) · lines 755–766

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Recombinant human XDH variants with urate, superoxide and NO assays · source_derived_draft · unverified_draft

### mo-xdh-hypoxanthine The primary article describes sequential XOR hydroxylation of hypoxanthine to xanthine and xanthine to urate. Condition category: normal nutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect. plain_language: Hypoxanthine enters the same two-step purine pathway. organism: Homo sapiens protein tissue_or_cell_type: Purified human enzyme experimental_model: Recombinant human XDH variants with urate, superoxide and NO assays limitations: Established reaction summarized in the primary article background; this paper directly assayed xanthine-based activity rather than newly establishing the hypoxanthine step. exposure: Xanthine, oxygen and inorganic nitrite assays evidence_span: {"source_cache": "artifacts/molybdenum-research/37713777.fulltext.txt", "locator": "Exact primary full-text span; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a8092b2aa7328b59f0275dd8a37d2a2dbb5abb2a32236d0cab5fffcc1ddc671d", "start_char": 1061, "end_char": 1244, "text_sha256": "45575621674b6b2e232b2e7b9605ad8e6acde4977d3f22e20abebfcbfa0b4dcb"} [mo-p37713777] Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health? (2023). https://pubmed.ncbi.nlm.nih.gov/37713777/ DOI: 10.1016/j.redox.2023.102864

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_span

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experimental_model

Genetic analysis of four classical-xanthinuria subjects

exposure

XDH nonsense and frameshift variants

limitations

Specific XDH deficiency, distinct from loss of all Moco synthesis or the combined XDH/AOX1 deficiency of MOCOS defects.

nutrient_topic

Molybdenum research collection; topical membership is not evidence of a direct dietary effect. · Molybdenum

organism

Homo sapiens

plain_language

An enzyme-specific genetic defect should not be labeled a shortage of the mineral.

primary_references

[mo-p9153281] Identification of two mutations in human xanthine dehydrogenase gene responsible for classical type I xanthinuria. (1997). https://pubmed.ncbi.nlm.nih.gov/9153281/ DOI: 10.1172/jci119421

tissue_or_cell_type

Duodenal mucosa and genetics

trigger_kind

machinery_impairment Imported condition classification; unverified.

Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17) · lines 1223–1234

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Genetic analysis of four classical-xanthinuria subjects · source_derived_draft · unverified_draft

### mo-xdh-type-i Three type I xanthinuria subjects had confirmed XDH gene defects; one tested nonsense variant lacked duodenal XDH protein despite preserved mRNA. Condition category: machinery_impairment nutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect. plain_language: An enzyme-specific genetic defect should not be labeled a shortage of the mineral. organism: Homo sapiens tissue_or_cell_type: Duodenal mucosa and genetics experimental_model: Genetic analysis of four classical-xanthinuria subjects limitations: Specific XDH deficiency, distinct from loss of all Moco synthesis or the combined XDH/AOX1 deficiency of MOCOS defects. exposure: XDH nonsense and frameshift variants evidence_span: {"source_cache": "artifacts/molybdenum-research/9153281.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "736b96f30570738a8aa1f55f33d1839eef8ce5911ce2c51b221db2e325517a0e", "start_char": 0, "end_char": 1243, "text_sha256": "736b96f30570738a8aa1f55f33d1839eef8ce5911ce2c51b221db2e325517a0e"} [mo-p9153281] Identification of two mutations in human xanthine dehydrogenase gene responsible for classical type I xanthinuria. (1997). https://pubmed.ncbi.nlm.nih.gov/9153281/ DOI: 10.1172/jci119421