Noscapine (NC)

Noscapine is a benzylisoquinoline alkaloid from plants of the Papaveraceae family, without painkilling properties. This agent is primarily used for its antitussive (cough-suppressing) effects. The lactone ring is unstable and opens in basic media. The opposite reaction is presented in acidic media. The bond C1-C3' is also unstable. This is the bond connecting the two optically active carbon atoms. In aqueous solution of sulfuric acid and heating it dissociates into cotarnine (4-methoxy-6-methyl-5,6,7,8-tetrahydro-[1,3]dioxolo[4,5-g]isoquinoline) and opic acid (6-formyl-2,3-dimethoxybenzoic acid). When noscapine is reduced with zinc/HCl, the bond C1-C3' saturates and the molecule dissociates into hydrocotarnine (2-hydroxycotarnine) and meconine (6,7-dimethoxyisobenzofuran-1(3H)-one). Noscapine's antitussive effects appear to be primarily mediated by its sigma receptor agonist activity.