Biliverdin dihydrochloride was found responsible for cytoprotection. It was also found to induce tolerance to cardiac allografts. Biliverdin hydrochloride may regulate the cellular heme degradation process by occupying the heme binding site on heme oxygenase which would prevent access of the substrate to the catalytic site of the enzyme.
Lemberg, R.; Lockwood, W.H.; Legge, J.W. Coupled oxidation of ascorbic acid and haemoglobin. Studies on the formation of bile pigments from choleglobin and verdohaemochromogen and on their isolation from erythrocytes. Biochem J. 1941, 35, (5), 363-379.
Emilio Rodriguez Garay.; Beatriz Noir.; Marcelo Royer. Biliverdin pigments in green biles. Biochimica et Biophysica Acta (BBA) - General Subjects. 1965, 100, (2), 411-417.