Comprehensive guide to trigonelline (N-methylnicotinic acid) — the second most abundant alkaloid in coffee. Biosynthesis via CTgS1/CTgS2 enzymes, NAD-derived pathway, roasting conversion to niacin (vitamin B3), species variation, and health benefits.
Trigonelline (N-methylnicotinic acid) is a major alkaloid in coffee seeds, constituting 1–3% of the dry weight of raw beans. Along with caffeine, it is one of the most abundant bioactive compounds in coffee [3][4][5][6].
Trigonelline is present in all parts of coffee plants, with particularly high concentrations in young fruits and the pericarp of developing fruits [3][6]. During roasting, trigonelline undergoes thermal degradation, converting to nicotinic acid (niacin, vitamin B3) and other metabolites that contribute to the taste and aroma of coffee beverage [3][8].
The biosynthetic pathway of trigonelline shares interesting parallels with caffeine biosynthesis. Both involve N-methyltransferase enzymes belonging to the motif B' methyltransferase family, highlighting an evolutionary connection between these two major coffee alkaloids [1][6].
Recent research has elucidated the key enzymes responsible for trigonelline synthesis. In 2014, Mizuno et al. characterized two trigonelline synthases (CTgS1 and CTgS2) from Coffea arabica, confirming their role in catalyzing the conversion of nicotinic acid to trigonelline using S-adenosyl-L-methionine as methyl donor [1].
Beyond its role in coffee flavor and aroma, trigonelline has attracted significant scientific interest for its potential health benefits, including neuroprotective effects, anti-diabetic activity, antioxidant properties, and prevention of kidney stone formation [2][5][7][10].
The major biosynthetic pathway from NAD to trigonelline in Coffea plants [3][6]
High trigonelline biosynthesis activity found in young fruits and in the pericarp of developing fruits [3]
Conversion of nicotinic acid to trigonelline is catalyzed by trigonelline synthase (N-methyltransferase) belonging to motif B' methyltransferase family [1][6]
Coffee Trigonelline Synthase 1 (CTgS1) Coffee Trigonelline Synthase 2 (CTgS2)
Nicotinic acid + S-adenosyl-L-methionine (SAM) → Trigonelline + S-adenosyl-L-homocysteine (SAH)
First characterization of trigonelline synthase genes from Coffea arabica [1]
7.5 for both enzymes [1]
Nicotinate is the specific methyl acceptor for CTgSs [1]
No activity detected with:
CTgSs have strict substrate specificity [1]
| Enzyme | Km (Nicotinic Acid) | Km (SAM) |
|---|---|---|
| CTgS1 | 121 μM | 68 μM |
| CTgS2 | 184 μM | 120 μM |
Both caffeine synthases and trigonelline synthases belong to the motif B' family of methyltransferases, a group of novel plant methyltransferases with motif B' instead of motif B [1][6].
This high homology explains why the trigonelline biosynthesis genes were initially discovered as "caffeine synthase homologous genes" before their actual function was characterized through recombinant enzyme studies [1].
Significant differences between the two major coffee species
| Parameter | Coffea arabica | Coffea canephora (Robusta) | Reference |
|---|---|---|---|
| Trigonelline (% dry weight) | 1-3% | 1-3% | [3][5] |
| Mean trigonelline (g/100g) | 0.49 ± 0.20 | 0.22 ± 0.14 | [4] |
| Nicotinic acid (g/100g) | 0.03 ± 0.01 | 0.02 ± 0.00 | [4] |
| Correlation with caffeine | Not directly correlated; both accumulate during fruit development but independently regulated [1] | ||
The production of nicotinic acid (niacin) during roasting varies from 0.160 to 0.400 mg/g in roasted coffee [8].
During roasting, trigonelline undergoes thermal decomposition to form nicotinic acid (niacin) [3][8]
increase in nicotinic acid content compared to raw beans [8]
0.160-0.400 mg/g in roasted coffee [8]
Trigonelline degradation also produces:
The trigonelline content of raw beans appears to be a deciding factor for niacin production during roasting [8]
Implications: The effects of growing and processing conditions on trigonelline content would be expected to have a bearing on flavor differences in roasted coffee [8].
Principal component analysis of 38 commercial roasted and ground coffees using chemical composition parameters [9]
Kahweol/Cafestol ratio Decreasing ratio indicates higher robusta proportion
Caffeine/Kahweol ratio Increasing ratio indicates higher robusta proportion
Nicotinic acid was useful for assessing roasting degree, while trigonelline showed variability between species but was less discriminative than the thermostable diterpenes and caffeine [9].
Recent evidence from 2023-2025 reviews
Contributes to neuroprotective effects alongside caffeine and chlorogenic acids [2][10]
Moderate evidenceTrigonelline has been found to have antidiabetic properties, contributing to glucose homeostasis [2][10]
Moderate evidenceTrigonelline prevents the formation of kidney stones [5][7]
Emerging evidenceDuring roasting, trigonelline is partially converted to nicotinic acid, making coffee beverages a significant source of vitamin B3 [3][8]
EstablishedTrigonelline indirectly contributes to the formation of flavor-forming compounds in coffee during roasting [3]
Established"Trigonelline, on the other side, has been found to lower oxidative stress by increasing antioxidant enzyme activity and scavenging reactive oxygen species. It also prevents the formation of kidney stones." [5][7]
Mizuno K., Matsuzaki M., Kanazawa S., et al. (2014). Biochem Biophys Res Commun 452(4):1060-6 [1]
First characterization of CTgS1/CTgS2; >95% identity between CTgS1/2; 82% homology with CCS1; Km values 121/184 μM; optimal pH 7.5; strict substrate specificity for nicotinate.
View Abstract(2025). Frontiers in Nutrition 12:1690881 [2]
Trigonelline (1-3% dry mass) as second major alkaloid; neuroprotection; anti-diabetic effects; multi-target mechanisms with caffeine and CGAs.
View ArticleAshihara H. (2014). ScienceDirect Chapter [3]
1-3% dry weight; NAD → nicotinamide → nicotinic acid → trigonelline pathway; high activity in young fruits; roasting conversion to niacin and aroma compounds.
View ChapterMakiso M.U., et al. (2024). Food Sci Nutr 12(2):734-764 [5][7]
Trigonelline lowers oxidative stress via antioxidant enzyme activity; ROS scavenging; prevents kidney stone formation.
View ArticleAshihara H. (2016). Nat Prod Commun 11(7):1047-54 [6]
Key enzymes are N-methyltransferases of motif B' family; pathway summary; transgenic approaches for alkaloid modification.
View Abstract(1963). Nature 197:1321 [8]
Classic paper demonstrating trigonelline → niacin conversion during roasting; 10× increase; 0.16-0.40 mg/g niacin in roasted coffee; trigonelline content as deciding factor.
View ArticlePeer-reviewed sources and authoritative references cited in this research
* Additional references available in the complete Publications Database. All sources are peer-reviewed.