N-Methyltyramine
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Preferred IUPAC name
4-[2-(Methylamino)ethyl]phenol | |
Other names
Methyl-4-tyramine; 4-Hydroxy-N-methylphenethylamine; p-(2-Methylaminoethyl)phenol
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Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChemSpider | |
ECHA InfoCard
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100.006.120 |
PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
C9H13NO | |
Molar mass | 151.209 g·mol−1 |
Appearance | colorless crystalline solid |
Density | 1.03 g/mL |
Melting point | 130 to 131 °C (266 to 268 °F; 403 to 404 K) |
Boiling point | 271 °C (520 °F; 544 K) (183-185 °C at 9mm; 135 °C at 0.05 mm) |
moderately soluble in water | |
Hazards | |
Flash point | 120 °C (248 °F; 393 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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N-Methyltyramine (NMT), also known as 4-hydroxy-N-methylphenethylamine, is a human trace amine[1][2] and natural phenethylamine alkaloid found in a variety of plants.[3] As the name implies, it is the N-methyl analog of tyramine, which is a well-known biogenic trace amine with which NMT shares many pharmacological properties. Biosynthetically, NMT is produced by the N-methylation of tyramine via the action of the enzyme phenylethanolamine N-methyltransferase in humans[1][2] and tyramine N-methyltransferase in plants.[4]
Occurrence
N-methyltyramine seems to be quite widely distributed in plants.[3][5]
NMT was isolated as a natural product for the first time, from germinating barley roots, by Kirkwood and Marion in 1950. These chemists found that 600 g of barley, after germination and 10-day growth, yielded 168 mg of N-methyltyramine.[6] Since barley, via its conversion to malt, is used extensively in the production of beer, beer and malt have been examined by several groups of investigators for the presence of NMT. Citing a 1965 study by McFarlane,[7] Poocharoen reported that beer contained ~ 5–8 mg/L of NMT.[8] The NMT content of various malts and malt fractions was extensively studied by Poocharoen himself, who also provided a good coverage of related literature up to 1983. This researcher found a mean concentration of NMT in raw barley[9] of ~ 5 μg/g; in green malts (i.e. barley that had been soaked in water for 2 days then germinated for 4 days), the mean concentration was ~ 21 μg/g, and in kilned malts (i.e. green malts that had been heated in a kiln for 1–2 days) the mean concentration was ~ 27 μg/g. When only green malt roots were examined, their mean content of NMT was ~ 1530 μg/g, whereas the mean level in kilned malt roots was ~ 1960 μg/g.[8]
Studies of
NMT is found in bitter orange, Citrus aurantium, and a concentration of ~ 180 μg/g has been reported from an extract made from the ripe fruit, although the method by which this extract was prepared is not very clearly described.[13]
Chemistry
Synthesis
NMT has been synthesized in a number of ways. One of the earliest syntheses is that reported by Walpole, who made it by the following sequence of steps: (i) acetylation of 4-methoxyphenethylamine with acetic anhydride; (ii) methylation of the amide using Na/methyl iodide; (iii) cleavage of the methyl ether to the phenol using HI; (iv) hydrolysis of the N-acetyl group with aqueous HCl. Walpole also described an alternative, but similar sequence of reactions leading to NMT, beginning with the conversion of 4-methoxyphenethylamine to its benzenesulfonamide, which was then N-methylated and de-protected.[15]
A different method for making NMT was given by Corti, who prepared it by the thermal decarboxylation of N-methyltyrosine (ratanhin), by heating the amino-acid in fluorene at 250 °C. Although N-methyltyrosine occurs naturally, it was made by the methylation of tyrosine using dimethyl sulfate.[16]
NMT was also made by Kirkwood and Marion starting from 4-methoxyphenethylamine, but this was first converted to the imine with benzaldehyde, followed by methylation with dimethyl sulfate; the product was converted to N-methyl-4-methoxyphenethylamine, and finally de-O-methylated with HBr to give N-methyltyramine.[6]
Common Salts
N-methyltyramine hydrochloride, C9H13NO.HCl: m.p. 148.5 °C; highly soluble in water and in ethanol.[15]
N-methyltyramine hydrogen oxalate, C9H13NO.C2H2O4: m.p. 250 °C; very poorly soluble in water.[15]
Basicity
The apparent (see original article for discussion) pKas for protonated N-methyltyramine are 9.76 (phenolic H) and 10.71 (ammonium H).[17]
Pharmacology
NMT is a
Subcutaneous administration of 10 mg/kg of the HCl salt of NMT to mice enhanced the release of norepinephrine (NE) from the heart by 36% over control, measured after 2 hours. For comparison, the same dose of tyramine hydrochloride caused a release of NE of 50% over control in this assay.[21] A qualitatively similar decrease in the NE content of rat heart after treatment with NMT was observed by Camp.[20]
Without giving many experimental details, Evans et al. reported that NMT increased blood pressure in rats, inhibited electrically-induced contractions of the guinea-pig ileum, relaxed
NMT has been found to be a potent stimulant of gastrin release in the rat, with an [[ED50]] of ~ 10 μg/kg.[22] These researchers used a bio-assay-guided isolation procedure to show that NMT was the constituent of beer that was responsible for producing enhanced gastrin release, which in turn raises gastric acid secretion. For comparative purposes, they also tested tyramine and N,N-dimethyltyramine (hordenine) in their assay, finding that 83 nM/kg (corresponding to 12.5 μg/kg of NMT) of each compound enhanced gastrin release by ~ 58% for NMT, ~ 24% for tyramine, and ~ 60% for hordenine.
In order to test the indications from earlier studies that, like tyramine itself, NMT produced most of its pharmacological effects by stimulating
Since NMT is one of the constituents of bitter orange,
NMT is a competitive substrate for MAO.[25]
It is known to be a stimulator of pancreatic secretions in rats.[26]
NMT has been shown to be an
Pharmacokinetics
The pharmacokinetics of NMT have been studied in rabbits and mice using drug that had been
Toxicology
LD50 of HCl salt of NMT (mouse; i.p.) = 227 mg/kg.[18] Another acute toxicity study of NMT (under the Sterling-Winthrop company code "WIN 5582") found it to have an LD50 = 275 mg/kg, after intravenous administration to mice.[30]
See also
References
- ^ PMID 19948186.
- ^ PMID 15860375.
- ^ a b T. A. Smith (1977). "Phenethylamine and related compounds in plants." Phytochemistry 16 9 – 18.
- ^ Tyrosine metabolism - Reference pathway Archived 2019-07-26 at the Wayback Machine, Kyoto Encyclopedia of Genes and Genomes (KEGG)
- ^ T. A. Stewart and I. Stewart (1970) Lloydia 33 244-254.
- ^ a b S. Kirkwood and L. Marion (1950) J. Am. Chem. Soc. 72 2522-2524.
- ^ W. D. McFarlane (1965). "Tyrosine derived amines and phenols in wort and beer." Proc. Europ. Brew. Conv. 387.
- ^ a b B. Poocharoen (1983), Ph. D. Thesis, Oregon State University. http://ir.library.oregonstate.edu/xmlui/handle/1957/27227
- ^ The level of NMT in ungerminated barley is generally negligible, but rises as germination (the first part of the "malting" process) proceeds.
- ^ B. A. Clement, C. M. Goff and T. D. A. Forbes (1998). "Toxic amines and alkaloids from Acacia rigidula." Phytochemistry 49 1377-1380.
- ^ B. A. Clement, C. M. Goff and T. D. A. Forbes (1997) Phytochemistry 46 249-254.
- ^ a b C. S. Evans, E. A. Bell and E. S. Johnson (1979) Phytochemistry 18 2022-2023.
- ^ B. C. Nelson et al. (2007) J. Agric. Fd. Chem. 55 9769-9775.
- PMID 24374199.
- ^ a b c G. S. Walpole (1910) J. Chem. Soc., Trans. 97 941-999.
- ^ U. A. Corti (1949) Helv. Chim. Acta 32 681-686.
- ^ T. Kappe and M. D. Armstrong (1965) J. Med. Chem. 8 368-374.
- ^ a b W. H. Hartung (1945) Ind. Eng. Chem. 37 126-137.
- ^ A. J. Hjort (1934) J. Pharmacol. Exp. Ther. 101-112.
- ^ a b B. J. Camp (1970) Am. J. Vet. Res. 31 755-762.
- ^ J. W. Daly, C. R. Creveling and B. Witkop (1966) J. Med. Chem. 9 273-280.
- ^ Y. Yokoo et al. (1999) Alcohol & Alcoholism 34 161-168. http://alcalc.oxfordjournals.org/content/34/2/161.full.pdf+html
- ^ H. Koda et al. (1999) Jpn. J. Pharmacol. 81 313-315.
- ^ J. Mercader, E. Wanecq, J. Chen and C. Carpene (2011) J. Physiol. Biochem. 67 443-452.
- ^ W. Kemmerling (1996) Z. Naturforsch. C 51 59-64.
- PMID 19298333.)
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: CS1 maint: multiple names: authors list (link - PMID 15860375.
- ^ L. Lindemann et al. (2005) Genomics 85 372-385.
- ^ H. Hai, Z.-G. Guo and J.-M. Wang (1989) Zhougguo Yao Li Xue Bao (Acta Pharmacologica Sinica) 10 41-45. http://www.chinaphar.com/1671-4083/10/41.pdf
- ^ A. M. Lands and J. I. Grant (1952). "The vasopressor action and toxicity of cyclohexylethylamine derivatives." J. Pharmacol. Exp. Ther. 106 341-345.