Himbacine molecule, space-filled model. Himbacine (C22.H35.N.O2), a complex piperidine alkaloid isolated from the bark of Australian magnolias, is a promising lead in Alzheimer's disease research due to its potent muscarinic receptor antagonist property. Himbacine is an alkaloid isolated from the bark of Australian magnolias. Himbacine's specificity for the muscarinic acetylcholine receptor M2, made it a promising starting point in Alzheimer's disease research. The atoms are colour-coded: carbon and hydrogen (white), nitrogen (blue), oxygen (red).