Trigonelline

Trigonelline is an alkaloid with chemical formula C₇H₇NO₂. It is a zwitterion formed by the methylation of the nitrogen atom of niacin (vitamin B₃). Trigonelline is a product of niacin metabolism that is excreted in the urine of mammals.^[1]

Trigonelline

Names
Preferred IUPAC name 1-Methylpyridin-1-ium-3-carboxylate
Other names Nicotinic acid N-methylbetaine Coffearine Caffearine Gynesine Trigenolline
Identifiers
CAS Number	535-83-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:18123 Y
ChEMBL	ChEMBL350675 Y ChEMBL489961 Y
ChemSpider	5369 Y
ECHA InfoCard	100.007.838
PubChem CID	5570
UNII	3NQ9N60I00 Y
CompTox Dashboard (EPA)	DTXSID2026230
InChI InChI=1S/C7H7NO2/c1-8-4-2-3-6(5-8)7(9)10/h2-5H,1H3 Y Key: WWNNZCOKKKDOPX-UHFFFAOYSA-N Y InChI=1/C7H7NO2/c1-8-4-2-3-6(5-8)7(9)10/h2-5H,1H3 Key: WWNNZCOKKKDOPX-UHFFFAOYAV
SMILES O=C([O-])c1ccc[n+](c1)C
Properties
Chemical formula	C7H7NO2
Molar mass	137.138 g·mol−1
Melting point	230 to 233 °C (446 to 451 °F; 503 to 506 K) (monohydrate)[contradictory] 258–259 °C (hydrochloride)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Trigonelline occurs in many plants. It has been isolated from the Japanese radish^[2] (Raphanus sativus cv. Sakurajima Daikon), fenugreek seeds (Trigonella foenum-graecum, hence the name),^[3] garden peas, hemp seed, oats,^[4] potatoes, Stachys species, dahlia,^[5] Strophanthus species,^[6] and Dichapetalum cymosum.^[7] Trigonelline is also found in coffee.^[8] Higher levels of trigonelline are found in arabica coffee.

Holtz, Kutscher, and Theilmann have recorded its presence in a number of animals.^[9]

Chemistry

Trigonelline crystallizes as a monohydrate from alcohol in hygroscopic prisms (m.p. 130 °C or 218 °C [dry, dec.]). It is readily soluble in water or warm alcohol, less so in cold alcohol, and slightly so in chloroform or ether. The salts crystallize well, the monohydrochloride, in leaflets, sparingly soluble in dry alcohol. The picrate forms shining prisms (m.p. 198−200 °C) soluble in water but sparingly soluble in dry alcohol or ether. The alkaloid forms several aurichlorides: the normal salt, B•HCl•AuCl₃, is precipitated when excess of gold chloride is added to the hydrochloride, and, after crystallization from dilute hydrochloric acid containing some gold chloride, has m.p. 198 °C. Crystallized from water or very dilute hydrochloric acid, slender needles of B₄•3 HAuCl₄ (m.p. 186 °C) are obtained.

When trigonelline is heated in closed tubes with barium hydroxide at 120 °C, it gives rise to methylamine, and, if treated similarly with hydrochloric acid at 260 °C creates chloromethane and nicotinic acid (a form of vitamin B₃). Trigonelline is a methyl betaine of nicotinic acid.^[10]

References

1. Merck Index, 11th Edition, 9606.
2. Kuroda, Rei; Kazumura, Kimiko; Ushikata, Miki; Minami, Yuji; Kajiya, Katsuko (2018). "Elucidating the Improvement in Vascular Endothelial Function from Sakurajima Daikon and its Mechanism of Action: A Comparative Study with Raphanus sativus". Journal of Agricultural and Food Chemistry. 66 (33): 8714–8721. doi:10.1021/acs.jafc.8b01750. PMID 30037222. S2CID 51712881.
3. Ouzir, Mounir; El Bairi, Khalid; Amzazi, Saaïd (2016). "Toxicological properties of fenugreek (Trigonella foenum graecum)". Food and Chemical Toxicology. 96: 145–154. doi:10.1016/j.fct.2016.08.003. PMID 27498339.
4. Schulze and Frankfurt, Ber., 1894, 27, 709.
5. Schulze and Trier, Zeit. physiol. Chem., 1912, 76, 258.
6. Thoms, Ber., 1891, 31, 271, 404.
7. Rimington, Onderstepoort J., 1935, 5, 81.
8. Gorter, Annalen, 1910, 372, 237; cf. Polstorff, Chem. Soc. Abstr., 1910, ii, 234; Palladino, ibid, 1894, ii, 214; 1895, i, 629; Graf, ibid, 1904, i, 915; Nottbohm and Mayer, Zeit. Unters. Lebensmitt., 1931, 61, 429.
9. Zeit. Biol., 1924, 81, 57.
10. Anderson Henry, Thomas (1949). The Plant Alkaloids (4th ed.). Philadelphia: The Blakiston Company. pp. 7–8.