Photochemistry of Bilirubin Dipyrrinone Subunits

Dominik Madea,^1) Jiří Janoš,^2) Taufiqueahmed Mujawar,^1) Aleš Dvořák,^3) Lucie Muchová,^3) Petra
 Čubáková,^4^) Miroslav Kloz,^4^) Petr Slavíček,^2) Jakub Švenda,^1) Libor Vítek,^3) Petr Klán^1)

                                                 ^

^1) Department of Chemistry and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A8, 625
                      00 Brno, Czech Republic, email: dominik.madea@seznam.cz

 ^2) Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, 16628
  Prague 6, Czech Republic.^3) Institute of Medical Biochemistry and Laboratory Diagnostics, 1^st
    Faculty of Medicine, Charles University, Na Bojišti 3, 121 08 Praha 2, Czech Republic.^ 4)
Institute of Physics of the Czech Academy of Sciences, ELI Beamlines, Za Radnicí 835, 252 41 Dolní
                                      Břežany, Czech Republic


Bilirubin (BR) is an essential metabolite formed by the catabolism of heme. Phototherapy with
blue-green light can be applied to reduce high concentrations of BR in blood, especially in the
neonatal period.[1] In our work, we studied the photochemistry of both bilirubin dipyrrinone
subunits (1 and 2, prepared as the corresponding methyl esters) by steady-state and transient
spectroscopies.[2,3] Bilirubin subunits represent useful models to study of the complex
photochemistry of bilirubin. Both subunits undergo efficient reversible photoisomerization (Φ[ZE] ~
Φ[EZ] ~ 0.15–0.30), furthermore, E-1 undergo lumirubin-type photorearrangement to form a
seven-membered ring system. The cyclization process is significantly less efficient (Φ[c] ~
0.001–0.07), but is strongly wavelength-dependent.

The photochemistry of bilirubin dipyrrinone subunits and its biological properties are discussed
and compared to those of bilirubin.

[1] Vítek, L.; Ostrow, J. D. Curr. Pharm. Des. 2009, 15, 2869.

[2] Madea, D. et. al. J. Org. Chem. 2020, 85, 13015.

[3] Janoš, J.; Madea, D. et. al. J. Phys. Chem. A. 2020, 124, 10457.