Chelidonic acid is a heterocyclic organic acid with a pyran skeleton.

Chelidonic acid can be prepared in two steps from diethyl oxalate and acetone:[1][2] Chelidonic acid is used to synthesize 4-pyrone via thermal decarboxylation.

[3] Joseph M. A. Probst (1812–1842) discovered the acid in extracts of Chelidonium majus in 1839,[4] and it was first studied by Joseph Udo Lerch (1816–1892) in 1846.

[5][6] It occurs naturally in plants of the Asparagales order.

[7] Potassium chelidonate has been found to be responsible for nyctinasty in some plants; specifically, it has been found to regulate the closing of leaves of Cassia mimosoides at nightfall.