title: Effect of nicotinamide on the photolysis of cyanocobalamin in aqueous solution.
abstract: The photolysis of cyanocobalamin by visible light in the presence of nicotinamide at pH 1.0-7.0 has been studied. The second-order rate constants for the bimolecular interaction of these vitamins have been determined which vary from 9.50 x 10(-3) (pH 1.0) to 1.25 x 10(-3) M(-1) min(-1) (pH 7.0). The rate-pH profile indicates a gradual slow decrease in rate in the pH range 1-3 followed by a relatively fast decrease in the pH range 3-7. The protonated form of cyanocobalamin appears to be more susceptible to photolysis than the non-ionised form. Cyanocobalamin photolysis leads to the formation of hydroxocobalamin at pH 1.0-7.0.
authors.affiliation: Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Karachi, Karachi 75270, Pakistan. a12345@emirates.net.ae
authors.forename: Iqbal
authors.initials: I
authors.lastname: Ahmad
authors.forename: Izhar A
authors.initials: IA
authors.lastname: Ansari
authors.forename: Tehmina
authors.initials: T
authors.lastname: Ismail
mesh_terms: D002855:Chromatography, Thin Layer; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009536:Niacinamide / Q000737:chemistry*; D010777:Photochemistry; D012996:Solutions; D014805:Vitamin B 12 / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D012996:Solutions; D014867:Water; D009536:Niacinamide; D014805:Vitamin B 12