Trigonelline

Trigonelline is a naturally occurring alkaloid classed chemically as the N-methylbetaine of nicotinic acid, meaning it is niacin with a methyl group added to the ring nitrogen, giving a stable internal salt or zwitterion. It forms in plants and in the body from niacin through the action of a nicotinate N-methyltransferase, which transfers a methyl group from the cofactor S-adenosylmethionine, and it is regarded as a product of niacin metabolism ^[2]. As such it sits at the junction of vitamin B3 chemistry and the wider metabolism of NAD, the essential cofactor built from niacin.

The compound is distributed widely across the plant kingdom. It is especially abundant in the seeds of fenugreek, Trigonella foenum-graecum, the source of its name, and in coffee beans, with arabica generally richer than robusta. During coffee roasting trigonelline is partly broken down, yielding niacin along with volatile compounds that contribute to coffee's aroma and flavour; it also occurs in foods such as peas, oats, potatoes and hemp seed. It is a water-soluble crystalline solid.

Most modern research on trigonelline has centred on metabolic health. It is one of the constituents credited with fenugreek's traditional use in glucose control, and reviews describe antidiabetic actions that include supporting insulin secretion, improving glucose tolerance and insulin sensitivity, and lowering oxidative stress ^[2][4]. Laboratory work has shown it can protect vascular endothelial cells against high-glucose injury by limiting oxidative damage and mitochondrial dysfunction ^[3]. Beyond diabetes, it has been studied as a neuroprotective agent in models of Alzheimer's and Parkinson's disease, stroke and depression ^[2]. A prominent recent finding is that trigonelline behaves as a natural NAD precursor; in worms, mice and human muscle cells it is taken up and converted into NAD by way of the Preiss-Handler pathway, raising NAD levels, improving mitochondrial function and, in animals, enhancing muscle strength during ageing, while low blood trigonelline was associated with human sarcopenia ^[1].

Trigonelline is not an approved medicine. It is consumed as a normal component of foods and beverages and is available in fenugreek extracts and as an isolated ingredient in some dietary supplements, where much of the interest reflects the NAD-boosting and metabolic research rather than established clinical use.

As a dietary constituent it is generally regarded as well tolerated, and its safety at the levels found in food and coffee is long established; however, controlled human trials of isolated trigonelline are limited, so its effects and safety as a concentrated supplement are still being characterised ^[2].

As a normal component of coffee and fenugreek it has a long dietary history and appears well tolerated. Isolated high-dose supplement safety is less established. It may lower blood sugar, so caution if combining with glucose-lowering drugs.