What is the main toxic alkaloid in Laburnum, the golden chain tree? Cytisine.
Laburnum is a small tree or shrub in the pea family, Fabaceae, famed for its long, hanging clusters of yellow flowers. Those flower chains account for names such as golden chain tree, golden chaintree, and goldenchain tree. The plant's attractive appearance can obscure the danger posed by its toxic seeds and other tissues.
Cytisine is the principal toxin associated with Laburnum. It is a quinolizidine alkaloid and a nicotinic acetylcholine-receptor agonist, meaning it can overstimulate nerve and muscle signaling. Poisoning may cause drowsiness, vomiting, staggering, convulsions, coma, and potentially death, although fatalities are uncommon.
Cytisine is not unique to Laburnum. It also occurs in related or otherwise connected legume genera including Cytisus, Sophora, Genista, Thermopsis, Anagyris, and Retama. The compound has an unexpected medical history: because it acts on nicotine receptors, cytisine has been studied and used in some countries as an aid to smoking cessation. That medicinal use does not make Laburnum safe to ingest.