Photostability of biliverdin bound to smectite, clay mineral

Biliverdin, the precursor of bilirubin, was adsorbed onto the synthetic clay mineral, smectite, in a mixed solution of benzene and methyl alcohol (7:3 v/v) to form a biliverdin-smectite conjugate. The adsorption of biliverdin to smectite followed the Freundlich equation with an adsorption coefficient of 1.0. The water-soluble conjugate had a green color with the absorbance maxima at 679 and 378 nm. The biliverdin-smectite conjugate became photostable in water to irradiation with UV, although the biliverdin in benzyl alcohol was rapidly decolorized.