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Record Information
Version5.0
StatusDetected and Quantified
Creation Date2005-11-16 15:48:42 UTC
Update Date2023-02-21 17:15:16 UTC
HMDB IDHMDB0000873
Secondary Accession Numbers
  • HMDB00873
Metabolite Identification
Common Name4-Methylcatechol
Description4-Methylcatechol, also known as homocatechol or toluene-3,4-diol, belongs to the class of organic compounds known as catechols. Catechols are compounds containing a 1,2-benzenediol moiety. Outside of the human body, 4-Methylcatechol is found, on average, in the highest concentration within a few different foods such as coffee and cocoa powders and in a lower concentration in beers. 4-Methylcatechol has also been detected, but not quantified in eggplants. This could make 4-methylcatechol a potential biomarker for the consumption of these foods. Recent studies have suggested that a lack of brain-derived neurotrophic factor (BDNF) in the limbic system may cause neuropathic pain (PMID:22198556 ). It is both a substrate and a suicide inhibitor of catechol 2,3-dioxygenase (PMID:15006807 ). 4-Methylcatechol is a metabolite of homoprotocatechuic acid (PMID:4974346 ). 4-Methylcatechol is known to induce the production of BDNF.
Structure
Data?1676999716
Synonyms
ValueSource
1,2-Dihydroxy-4-methylbenzeneChEBI
2-Hydroxy-4-methylphenolChEBI
3,4-DihydroxytolueneChEBI
4-Methyl-1,2-benzenediolChEBI
4-Methyl-1,2-dihydroxybenzeneChEBI
4-MethylpyrocatecholChEBI
HomocatecholChEBI
HomopyrocatecholChEBI
p-MethylcatecholChEBI
p-MethylpyrocatecholChEBI
Toluene-3,4-diolChEBI
1-Methyl-3,4-dihydroxybenzeneHMDB
4-Methyl-pyrocatecholHMDB
4-MethylcateholHMDB
4-MetylcatecholHMDB
5-MethylcatecholHMDB
Chemical FormulaC7H8O2
Average Molecular Weight124.1372
Monoisotopic Molecular Weight124.0524295
IUPAC Name4-methylbenzene-1,2-diol
Traditional Name4-methyl-1,2-benzenediol
CAS Registry Number452-86-8
SMILES
CC1=CC(O)=C(O)C=C1
InChI Identifier
InChI=1S/C7H8O2/c1-5-2-3-6(8)7(9)4-5/h2-4,8-9H,1H3
InChI KeyZBCATMYQYDCTIZ-UHFFFAOYSA-N
Chemical Taxonomy
Description Belongs to the class of organic compounds known as catechols. Catechols are compounds containing a 1,2-benzenediol moiety.
KingdomOrganic compounds
Super ClassBenzenoids
ClassPhenols
Sub ClassBenzenediols
Direct ParentCatechols
Alternative Parents
Substituents
  • P-cresol
  • M-cresol
  • Catechol
  • 1-hydroxy-4-unsubstituted benzenoid
  • 1-hydroxy-2-unsubstituted benzenoid
  • Toluene
  • Monocyclic benzene moiety
  • Organic oxygen compound
  • Hydrocarbon derivative
  • Organooxygen compound
  • Aromatic homomonocyclic compound
Molecular FrameworkAromatic homomonocyclic compounds
External Descriptors
Ontology
Physiological effectNot Available
Disposition
Biological locationRoute of exposureSource
Process
Role
Physical Properties
StateSolid
Experimental Molecular Properties
PropertyValueReference
Melting Point65 °CNot Available
Boiling Point247.70 °C. @ 760.00 mm Hg (est)The Good Scents Company Information System
Water Solubility24900 mg/L @ 25 °C (est)The Good Scents Company Information System
LogP1.37HANSCH,C ET AL. (1995)
Experimental Chromatographic Properties

Experimental Collision Cross Sections

Adduct TypeData SourceCCS Value (Å2)Reference
[M-H]-Not Available121.8http://allccs.zhulab.cn/database/detail?ID=AllCCS00002102
Predicted Molecular Properties
PropertyValueSource
Water Solubility37.9 g/LALOGPS
logP1.02ALOGPS
logP1.88ChemAxon
logS-0.52ALOGPS
pKa (Strongest Acidic)9.55ChemAxon
pKa (Strongest Basic)-6.2ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count2ChemAxon
Hydrogen Donor Count2ChemAxon
Polar Surface Area40.46 ŲChemAxon
Rotatable Bond Count0ChemAxon
Refractivity35.06 m³·mol⁻¹ChemAxon
Polarizability12.82 ųChemAxon
Number of Rings1ChemAxon
BioavailabilityYesChemAxon
Rule of FiveYesChemAxon
Ghose FilterNoChemAxon
Veber's RuleNoChemAxon
MDDR-like RuleNoChemAxon
Predicted Chromatographic Properties

Predicted Collision Cross Sections

PredictorAdduct TypeCCS Value (Å2)Reference
DarkChem[M+H]+125.96931661259
DarkChem[M-H]-122.57531661259
AllCCS[M+H]+124.25732859911
AllCCS[M-H]-121.58732859911
DeepCCS[M+H]+124.32830932474
DeepCCS[M-H]-120.49630932474
DeepCCS[M-2H]-157.7930932474
DeepCCS[M+Na]+133.3330932474
AllCCS[M+H]+124.332859911
AllCCS[M+H-H2O]+119.432859911
AllCCS[M+NH4]+128.832859911
AllCCS[M+Na]+130.132859911
AllCCS[M-H]-121.632859911
AllCCS[M+Na-2H]-123.632859911
AllCCS[M+HCOO]-125.932859911

Predicted Kovats Retention Indices

Underivatized

MetaboliteSMILESKovats RI ValueColumn TypeReference
4-MethylcatecholCC1=CC=C(O)C(O)=C12692.8Standard polar33892256
4-MethylcatecholCC1=CC=C(O)C(O)=C11137.4Standard non polar33892256
4-MethylcatecholCC1=CC=C(O)C(O)=C11279.1Semi standard non polar33892256

Derivatized

Derivative Name / StructureSMILESKovats RI ValueColumn TypeReference
4-Methylcatechol,1TMS,isomer #1CC1=CC=C(O[Si](C)(C)C)C(O)=C11294.6Semi standard non polar33892256
4-Methylcatechol,1TMS,isomer #2CC1=CC=C(O)C(O[Si](C)(C)C)=C11288.2Semi standard non polar33892256
4-Methylcatechol,2TMS,isomer #1CC1=CC=C(O[Si](C)(C)C)C(O[Si](C)(C)C)=C11366.3Semi standard non polar33892256
4-Methylcatechol,1TBDMS,isomer #1CC1=CC=C(O[Si](C)(C)C(C)(C)C)C(O)=C11539.6Semi standard non polar33892256
4-Methylcatechol,1TBDMS,isomer #2CC1=CC=C(O)C(O[Si](C)(C)C(C)(C)C)=C11529.2Semi standard non polar33892256
4-Methylcatechol,2TBDMS,isomer #1CC1=CC=C(O[Si](C)(C)C(C)(C)C)C(O[Si](C)(C)C(C)(C)C)=C11851.5Semi standard non polar33892256
Spectra

GC-MS Spectra

Spectrum TypeDescriptionSplash KeyDeposition DateSourceView
Experimental GC-MSGC-MS Spectrum - 4-Methylcatechol GC-EI-TOF (Non-derivatized)splash10-014i-1930000000-6225053efa0739efca3d2017-09-12HMDB team, MONA, MassBankView Spectrum
Experimental GC-MSGC-MS Spectrum - 4-Methylcatechol GC-EI-TOF (Non-derivatized)splash10-014i-1930000000-6225053efa0739efca3d2018-05-18HMDB team, MONA, MassBankView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (Non-derivatized) - 70eV, Positivesplash10-00di-4900000000-2d8d69f64905f6f9396e2017-07-27Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (2 TMS) - 70eV, Positivesplash10-0udj-3940000000-d5331c4c752130a850842017-10-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (Non-derivatized) - 70eV, PositiveNot Available2021-10-12Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (TMS_1_1) - 70eV, PositiveNot Available2021-11-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (TMS_1_2) - 70eV, PositiveNot Available2021-11-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (TBDMS_1_1) - 70eV, PositiveNot Available2021-11-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (TBDMS_1_2) - 70eV, PositiveNot Available2021-11-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - 4-Methylcatechol GC-MS (TBDMS_2_1) - 70eV, PositiveNot Available2021-11-06Wishart LabView Spectrum

MS/MS Spectra

Spectrum TypeDescriptionSplash KeyDeposition DateSourceView
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol Quattro_QQQ 10V, Positive-QTOF (Annotated)splash10-0a6r-1900000000-9045a710867168d6cc512012-07-24HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol Quattro_QQQ 25V, Positive-QTOF (Annotated)splash10-004i-9000000000-0e20b47a091c0b3e39ab2012-07-24HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol Quattro_QQQ 40V, Positive-QTOF (Annotated)splash10-004i-9000000000-0e20b47a091c0b3e39ab2012-07-24HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol , negative-QTOFsplash10-00di-0900000000-7db9fcc9e56ad8a390802017-09-14HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 40V, Negative-QTOFsplash10-014j-9200000000-f6f538341319fcc5433b2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 20V, Negative-QTOFsplash10-00di-0900000000-97cd131a887e2f8701862021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 10V, Positive-QTOFsplash10-014i-9000000000-6981a2924f054e884c5c2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 35V, Negative-QTOFsplash10-00di-0900000000-0aaf237b7039ed11a1d72021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 40V, Positive-QTOFsplash10-0553-9000000000-fe5754c269058c591feb2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 20V, Positive-QTOFsplash10-0006-9000000000-c1c0f17738a12823f96d2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 10V, Negative-QTOFsplash10-00di-2900000000-e5f3b6d9329514c202a82021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 20V, Negative-QTOFsplash10-00di-1900000000-d5abc716689493ede24f2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 10V, Negative-QTOFsplash10-00di-0900000000-6bd82a87c9fe3a5ac3f72021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - 4-Methylcatechol 40V, Negative-QTOFsplash10-03dj-9000000000-5833215eaa6163ad44f42021-09-20HMDB team, MONAView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 10V, Positive-QTOFsplash10-004i-0900000000-efa52ff0e22aa918c8322017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 20V, Positive-QTOFsplash10-004i-2900000000-1813508ce877db8f3b512017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 40V, Positive-QTOFsplash10-0v00-9200000000-42f7207a63d63607822f2017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 10V, Negative-QTOFsplash10-00di-0900000000-965e88496dc55d1d3a082017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 20V, Negative-QTOFsplash10-00di-1900000000-528bea85898c5bbee9742017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 40V, Negative-QTOFsplash10-05fu-9400000000-25d222489152bbee48942017-06-28Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 10V, Positive-QTOFsplash10-056r-2900000000-f83a6dc29f504d8a27ea2021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 20V, Positive-QTOFsplash10-004i-9400000000-f09039303c5f740d5e992021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 40V, Positive-QTOFsplash10-0gdi-9000000000-5a1ebbe40df7d21e329f2021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 10V, Negative-QTOFsplash10-00di-0900000000-ee9e9b8403f62cfc7fdf2021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 4-Methylcatechol 20V, Negative-QTOFsplash10-00di-2900000000-5af433d114ee67df4fda2021-09-22Wishart LabView Spectrum

NMR Spectra

Spectrum TypeDescriptionDeposition DateSourceView
Experimental 1D NMR1H NMR Spectrum (1D, 600 MHz, H2O, experimental)2012-12-04Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 100 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 100 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 1000 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 1000 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 200 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 200 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 300 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 300 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 400 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 400 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 500 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 500 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 600 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 600 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 700 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 700 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 800 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 800 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 900 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 900 MHz, D2O, predicted)2021-09-24Wishart LabView Spectrum
Experimental 2D NMR[1H, 13C]-HSQC NMR Spectrum (2D, 600 MHz, H2O, experimental)2012-12-05Wishart LabView Spectrum

IR Spectra

Spectrum TypeDescriptionDeposition DateSourceView
Predicted IR SpectrumIR Ion Spectrum (Quadrupole Ion Trap, ESI+, Adduct: [M+Na]+)2022-02-11FELIX labView Spectrum
Predicted IR SpectrumIR Ion Spectrum (Quadrupole Ion Trap, ESI-, Adduct: [M-H]-)2022-02-11FELIX labView Spectrum
Predicted IR SpectrumIR Ion Spectrum (Predicted IRIS Spectrum, Adduct: [M-H]-)2023-02-03FELIX labView Spectrum
Predicted IR SpectrumIR Ion Spectrum (Predicted IRIS Spectrum, Adduct: [M+H]+)2023-02-03FELIX labView Spectrum
Predicted IR SpectrumIR Ion Spectrum (Predicted IRIS Spectrum, Adduct: [M+Na]+)2023-02-03FELIX labView Spectrum
Biological Properties
Cellular LocationsNot Available
Biospecimen Locations
  • Blood
  • Feces
  • Urine
Tissue LocationsNot Available
Pathways
Normal Concentrations
BiospecimenStatusValueAgeSexConditionReferenceDetails
BloodDetected but not QuantifiedNot QuantifiedAdult (>18 years old)BothNormal details
BloodExpected but not QuantifiedNot QuantifiedNot AvailableNot Available
Normal
      Not Available
details
FecesDetected but not QuantifiedNot QuantifiedAdult (>18 years old)Both
Normal
details
FecesDetected but not QuantifiedNot QuantifiedAdult (>18 years old)Both
Normal
details
FecesDetected and Quantified7.814 +/- 1.128 nmol/g wet fecesAdult (>18 years old)Both
Normal
details
FecesDetected and Quantified14.339 nmol/g wet fecesAdult (>18 years old)Both
Normal
details
UrineDetected and Quantified1.8 +/- 1.2 umol/mmol creatinineAdult (>18 years old)Both
Normal
details
UrineDetected but not QuantifiedNot QuantifiedAdult (>18 years old)BothNormal details
Abnormal Concentrations
BiospecimenStatusValueAgeSexConditionReferenceDetails
FecesDetected but not QuantifiedNot QuantifiedAdult (>18 years old)Both
Colorectal cancer
details
UrineDetected and Quantified3.6 +/- 1.5 umol/mmol creatinineAdult (>18 years old)Male
Smoking
details
UrineDetected but not QuantifiedNot QuantifiedAdult (>18 years old)BothBladder cancer details
Associated Disorders and Diseases
Disease References
Colorectal cancer
  1. Goedert JJ, Sampson JN, Moore SC, Xiao Q, Xiong X, Hayes RB, Ahn J, Shi J, Sinha R: Fecal metabolomics: assay performance and association with colorectal cancer. Carcinogenesis. 2014 Sep;35(9):2089-96. doi: 10.1093/carcin/bgu131. Epub 2014 Jul 18. [PubMed:25037050 ]
Smoking
  1. Carmella SG, La Voie EJ, Hecht SS: Quantitative analysis of catechol and 4-methylcatechol in human urine. Food Chem Toxicol. 1982 Oct;20(5):587-90. [PubMed:6890513 ]
Associated OMIM IDs
DrugBank IDDB04120
Phenol Explorer Compound ID704
FooDB IDFDB008861
KNApSAcK IDC00002660
Chemspider ID9564
KEGG Compound IDC06730
BioCyc IDNot Available
BiGG IDNot Available
Wikipedia Link4-Methylcatechol
METLIN ID5834
PubChem Compound9958
PDB IDNot Available
ChEBI ID17254
Food Biomarker OntologyNot Available
VMH ID4MCAT
MarkerDB IDNot Available
Good Scents IDrw1205021
References
Synthesis ReferenceLiang, Zesheng; Zhang, Ying; Wu, Baojun; Zhang, Mingsen; Wang, Xiu'en. Preparation of 4-methylcatechol with good yield and selectivity. Faming Zhuanli Shenqing Gongkai Shuomingshu (2001), 6 pp.
Material Safety Data Sheet (MSDS)Download (PDF)
General References
  1. Baba S, Furuta T, Horie M, Nakagawa H: Studies on drug metabolism by use of isotopes XXVI: Determination of urinary metabolites of rutin in humans. J Pharm Sci. 1981 Jul;70(7):780-2. [PubMed:7264927 ]
  2. Alanko J, Riutta A, Holm P, Mucha I, Vapaatalo H, Metsa-Ketela T: Modulation of arachidonic acid metabolism by phenols: relation to their structure and antioxidant/prooxidant properties. Free Radic Biol Med. 1999 Jan;26(1-2):193-201. [PubMed:9890654 ]
  3. Carmella SG, La Voie EJ, Hecht SS: Quantitative analysis of catechol and 4-methylcatechol in human urine. Food Chem Toxicol. 1982 Oct;20(5):587-90. [PubMed:6890513 ]
  4. Glasser G, Graefe EU, Struck F, Veit M, Gebhardt R: Comparison of antioxidative capacities and inhibitory effects on cholesterol biosynthesis of quercetin and potential metabolites. Phytomedicine. 2002 Jan;9(1):33-40. [PubMed:11924762 ]
  5. Ridder L, Briganti F, Boersma MG, Boeren S, Vis EH, Scozzafava A, Veeger C, Rietjens IM: Quantitative structure/activity relationship for the rate of conversion of C4-substituted catechols by catechol-1,2-dioxygenase from Pseudomonas putida (arvilla) C1. Eur J Biochem. 1998 Oct 1;257(1):92-100. [PubMed:9799107 ]
  6. Capasso R, Evidente A, Schivo L, Orru G, Marcialis MA, Cristinzio G: Antibacterial polyphenols from olive oil mill waste waters. J Appl Bacteriol. 1995 Oct;79(4):393-8. [PubMed:7592132 ]
  7. Okuta A, Ohnishi K, Harayama S: Construction of chimeric catechol 2,3-dioxygenase exhibiting improved activity against the suicide inhibitor 4-methylcatechol. Appl Environ Microbiol. 2004 Mar;70(3):1804-10. [PubMed:15006807 ]
  8. Shen Y: In vitro cytotoxicity of BTEX metabolites in HeLa cells. Arch Environ Contam Toxicol. 1998 Apr;34(3):229-34. [PubMed:9504968 ]
  9. Graefe EU, Veit M: Urinary metabolites of flavonoids and hydroxycinnamic acids in humans after application of a crude extract from Equisetum arvense. Phytomedicine. 1999 Oct;6(4):239-46. [PubMed:10589442 ]
  10. Fukuhara K, Ishikawa K, Yasuda S, Kishishita Y, Kim HK, Kakeda T, Yamamoto M, Norii T, Ishikawa T: Intracerebroventricular 4-methylcatechol (4-MC) ameliorates chronic pain associated with depression-like behavior via induction of brain-derived neurotrophic factor (BDNF). Cell Mol Neurobiol. 2012 Aug;32(6):971-7. doi: 10.1007/s10571-011-9782-2. Epub 2011 Dec 25. [PubMed:22198556 ]
  11. Scheline RR: Drug metabolism by intestinal microorganisms. J Pharm Sci. 1968 Dec;57(12):2021-37. doi: 10.1002/jps.2600571202. [PubMed:4974346 ]