UV light absorption parameters of the pathobiologically implicated bilirubin oxidation products, MVM, BOX A, and BOX...

The formation of the bilirubin oxidation products (BOXes), BOX A ([4-methyl-5-oxo-3-vinyl-(1,5-dihydropyrrol-2-ylidene)acetamide]) and BOX B (3-methyl-5-oxo-4-vinyl-(1,5-dihydropyrrol-2-ylidene)acetamide), as well as MVM (4-methyl-3-vinylmaleimide) were synthesized by oxidation of bilirubin with H₂O₂ without and with FeCl₃, respectively. Compound identity was confirmed with NMR and mass spectrometry (MS; less than 1 ppm, tandem MS up to MS⁴). UV absorption profiles, including λ_max, and extinction coefficient (ε; estimated using NMR) for BOX A, BOX B, and MVM in H₂O, 15% CH₃CN plus 10 mM CF₃CO₂H, CH₃CN, CHCl₃, CH₂Cl₂, and 0.9% NaCl were determined. At longer wavelengths, λ_max's for 1) BOX A were little affected by the solvent, ranging from 295-297 nm; 2) BOX B, less polar solvent yielded λ_max's of lower wavelength, with values ranging from 308-313 nm, and 3) MVM, less polar solvent yielded λ_max's of higher wavelength, with values ranging from 318-327 nm. Estimated ε's for BOX A and BOX B were approximately 5- to 10-fold greater than for MVM.