title: Formulation and stabilization of riboflavin in liposomal preparations.
abstract: A study of the formulation of liposomal preparations of riboflavin (RF) with compositional variations in the content of phosphatidylcholine (PC) and their entrapment efficiency (26-42%) have been conducted. Light transmission characteristics of the liposomal preparations have been determined to evaluate their effect on the amount of light passing through the system to initiate a photochemical reaction. Dynamic light scattering (DLS) and atomic force microscopy (AFM) have been used to study the physical characteristics of liposomes. The liposomal preparations of RF have been subjected to photolysis using visible light and the apparent first- order rate constant, kobs, for the degradation of RF have been determined. The values of kobs (1.73-2.29×10(-3)min(-1)) have been found to decrease linearly with an increase in PC concentration in the range of 12.15 to 14.85 mM. Thus, an increase in PC concentration of liposomes leads to an increase in the stability of RF. RF and its main photoproduct, lumichrome (LC), formed in liposomes have been assayed by a two-component spectrometric method at 356 and 445 nm using an irrelevant absorption correction to compensate for the interference of liposomal components. The fluorescence measurements of RF in liposomes indicate excited singlet state quenching and the formation of a charge-transfer complex between RF and PC. It results in electron transfer from PC to RF to cause photoreduction and stabilization of RF.
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super Highway, Gadap Road, Karachi 74600, Pakistan.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Ahmad
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super Highway, Gadap Road, Karachi 74600, Pakistan; HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi 75270, Pakistan. Electronic address: adeelarsalan@hotmail.com.
authors.forename: Adeel
authors.initials: A
authors.lastname: Arsalan
authors.affiliation: HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi 75270, Pakistan.
authors.forename: Syed Abid
authors.initials: SA
authors.lastname: Ali
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super Highway, Gadap Road, Karachi 74600, Pakistan.
authors.forename: Muhammad Ali
authors.initials: MA
authors.lastname: Sheraz
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super Highway, Gadap Road, Karachi 74600, Pakistan.
authors.forename: Sofia
authors.initials: S
authors.lastname: Ahmed
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super Highway, Gadap Road, Karachi 74600, Pakistan.
authors.forename: Zubair
authors.initials: Z
authors.lastname: Anwar
authors.affiliation: HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi 75270, Pakistan.
authors.forename: Iqra
authors.initials: I
authors.lastname: Munir
authors.affiliation: HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi 75270, Pakistan.
authors.forename: Muhammad Raza
authors.initials: MR
authors.lastname: Shah
mesh_terms: D002626:Chemistry, Pharmaceutical; D002855:Chromatography, Thin Layer; D000067493:Dynamic Light Scattering; D007700:Kinetics; D008027:Light; D008081:Liposomes / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D010782:Photolysis / Q000528:radiation effects; D012256:Riboflavin / Q000737:chemistry*
chemical_list: D008081:Liposomes; D012256:Riboflavin
keywords: Fluorescence quenching; Kinetics; Liposomal formulation; Photolysis; Riboflavin; Stabilization