title: Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate.
abstract: The xanthine oxidase catalyzed oxidation of hypoxanthine was followed by monitoring the formation of uric acid at 290 nm. Inhibition of xanthine oxidase occurs in aqueous solutions of folic acid methotrexate and aminopterin. These compounds are known to dissociate upon exposure to ultraviolet light resulting in the formation of their respective 6-formylpteridine derivatives. The relative rates of dissociation were monitored spectrophotometrically by determining the absorbance of their 2,4-dinitrophenylhydrazine derivatives at 500 nm. When aqueous solutions of folic acid, aminopterin and methotrexate were exposed to uv light, a direct correlation was observed between the concentrations of the 6-formylpteridine derivatives existing in solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.
authors.affiliation: Department of Chemistry, Seattle University, Washington 98122.
authors.forename: K
authors.initials: K
authors.lastname: Robinson
authors.forename: T F
authors.initials: TF
authors.lastname: Pilot
authors.forename: J E
authors.initials: JE
authors.lastname: Meany
mesh_terms: D000630:Aminopterin / Q000494:pharmacology / Q000528:radiation effects*; D005492:Folic Acid / Q000494:pharmacology / Q000528:radiation effects*; D007700:Kinetics; D008727:Methotrexate / Q000494:pharmacology / Q000528:radiation effects*; D010782:Photolysis; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors; D014466:Ultraviolet Rays; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors*
chemical_list: D005492:Folic Acid; D014969:Xanthine Oxidase; D000630:Aminopterin; D008727:Methotrexate