Urinary excretion of alpha- and beta-isomers of biliverdin-IX in humans

Abstract

The distribution and relative proportions of the four isomers of alpha-, beta-, gamma- and delta-biliverdin-IX were investigated using urinary samples from seven healthy adults. The biliverdins from samples were adsorbed on talc, and the adsorbed biliverdins were then soaked in a solution of methanol and concentrated sulfuric acid for derivation to the dimethyl esters. The esters were passed to a reversed-phase cartridge for clean-up, then quantitated by HPLC on a reversed-phase column. The analyses revealed that the biliverdins in 24-h urine were comprised of 6.4 +/- 2.5 nmol alpha- and 9.3 +/- 5.4 nmol beta-isomers. The HPLC analyses suggested the presence of a delta-isomer in a much smaller amount, but no gamma-isomer was detected. The identifications of alpha- and beta-isomers were performed with co-chromatography and absorption spectra.