title: The stability of 5-aminolevulinic acid in solution.
abstract: 5-Aminolevulinic acid (ALA) is being assessed for photodynamic therapy of cancer and other diseases worldwide. However, its stability properties in solution are not well understood yet. The breakdown of ALA in pH-buffered solutions was examined in this work. Solutions of ALA in PBS buffered to physiological pH were found to be unstable, leading to a breakdown product that absorbs photons around 278 nm. The ability of the solution to stimulate porphyrin production in cells is gradually lost upon breakdown, though the kinetics for this are different from those for formation of the UV absorbing product. It is likely, therefore, that several chemical pathways contribute to the breakdown of dissolved ALA at physiological pH. Temperature studies of the formation kinetics of the UV absorbing product also indicate that a complex formation process is involved.
authors.affiliation: Department of Pathology, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway. o.b.gadmar@labmed.uio.no
authors.forename: Øystein Bech
authors.initials: ØB
authors.lastname: Gadmar
authors.forename: Johan
authors.initials: J
authors.lastname: Moan
authors.forename: Eldri
authors.initials: E
authors.lastname: Scheie
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Ma
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
mesh_terms: D000622:Aminolevulinic Acid / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012996:Solutions; D014407:Tumor Cells, Cultured
chemical_list: D012996:Solutions; D000622:Aminolevulinic Acid