title: Phenol group in pyridoxamine acts as a stabilizing element for its carbinolamines and Schiff bases.
abstract: Pyridoxamine (PM), a natural derivative of vitamin B(6) , possesses a high biological and biomedical significance by virtue of its acting as enzyme cofactor in amino acid metabolism and as inhibitor in the nonenzymatic glycation of proteins. Both types of processes require the initial formation of a Schiff base. In this work, we used NMR spectroscopy to study the formation mechanism for a Schiff base between PM and formaldehyde (FA). This allowed the Schiff base and an intermediate carbinolamine (CA) to be detected. The Schiff base was found to be in isomeric equilibrium with a hemiaminal (HE) form. The formation equilibrium constants for the CA and HE over the pD range of 6.0-13.0 were determined and compared with those for the reaction between 4-picolylamine (PAM) and formaldehyde (FA). The comparison revealed a strong influence of the phenol group on the equilibrium constant. Based on the results, the phenol group in PM is a key structural element towards stabilizing the resulting carbinolamine and Schiff base.
authors.affiliation: Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Departament de Química, Universitat de les Illes Balears, Ctra Valldemosa km 7.5, ES-07122 Palma de Mallorca.
authors.forename: Catalina
authors.initials: C
authors.lastname: Caldés
authors.forename: Bartolomé
authors.initials: B
authors.lastname: Vilanova
authors.forename: Miquel
authors.initials: M
authors.lastname: Adrover
authors.forename: Francisco
authors.initials: F
authors.lastname: Muñoz
authors.forename: Josefa
authors.initials: J
authors.lastname: Donoso
mesh_terms: D005557:Formaldehyde / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D019800:Phenol / Q000737:chemistry; D011733:Pyridoxamine / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry*; D014803:Vitamin B Complex / Q000737:chemistry*
chemical_list: D012545:Schiff Bases; D014803:Vitamin B Complex; D005557:Formaldehyde; D019800:Phenol; D011733:Pyridoxamine