Himbacine molecule, tubular 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 for the acetylcholine receptor M2. The atoms are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red).