title: Photochemical transformation of the thyroid hormone levothyroxine in aqueous solution.
abstract: OBJECTIVE
  The direct aqueous photolysis of the thyroid hormone levothyroxine (T(4)) has been studied.
  
  
  RESULTS
  One of the major photoproducts, i.e., 4-[4-(2-amino-2-carboxy-ethyl)-2,6-diiodo-phenoxy]-penta-2,4-dienoic acid (P1), was isolated by liquid chromatography and structurally assigned by mass spectrometric (MS) and nuclear magnetic resonance spectroscopic methods. The identity of a second major product, i.e., 3,5-diiodo-L: -thyrosine (P3), was confirmed through access to a commercially available standard. Furthermore, the structures of three additional transformation products are proposed on the basis of data obtained by high-resolution MS analyses. UV absorption spectra were determined for T(4) and the two photoproducts P1 and P3. Disappearance quantum yields were calculated for T(4) (ϕ = 0.014 at pH 12) and P3 (ϕ = 0.024 at pH 12 and ϕ = 0.010 at pH 8.5), whereas the compound P1 was found to be stable under the studied conditions (T(1/2) = 600 min).
  
  
  CONCLUSIONS
  The results indicate that solar UV light may have a significant impact on the fate of T(4) in the aquatic environment.
authors.affiliation: Laboratory of Organic Chemistry, Åbo Akademi University, Biskopsgatan 8, 20500 Turku, Finland.
authors.forename: Jesper
authors.initials: J
authors.lastname: Svanfelt
authors.forename: Johan
authors.initials: J
authors.lastname: Eriksson
authors.forename: Leif
authors.initials: L
authors.lastname: Kronberg
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004104:Diiodothyronines / Q000032:analysis / Q000737:chemistry; D004784:Environmental Monitoring; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010782:Photolysis; D013974:Thyroxine / Q000032:analysis* / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D014873:Water Pollutants / Q000032:analysis / Q000378:metabolism; D014876:Water Pollution / Q000032:analysis
chemical_list: D004104:Diiodothyronines; D014873:Water Pollutants; D014867:Water; D013974:Thyroxine