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

Abstract

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 λmax, 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, λmax's for 1) BOX A were little affected by the solvent, ranging from 295–297 nm; 2) BOX B, less polar solvent yielded λmax's of lower wavelength, with values ranging from 308–313 nm, and 3) MVM, less polar solvent yielded λmax'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. Keywords: Bilirubin oxidation products, BOX A, BOX B, MVM, λmax, Extinction coefficient, Synthesis