The metabolism of radioactive crustaxanthin (3,3′,4,4′-tetrahydroxy-β-carotene)

Abstract

1. 1. Tritiated crustaxanthin (3,3′,4,4′-tetrahydroxy-β-carotene), presumably labeled in the 4 and 4′-H positions, was prepared from astaxanthin (3,3′-dihydroxy-4,4′-diketo-β-carotene) by reduction with sodium borotritiide (NaB 3 H 4 ). 2. 2. Less than 0·4% of the tritium in crustaxanthin exchanged with water during equilibration in neutral aqueous solution. 3. 3. When 3 H-crustaxanthin was injected intraperitoneally into rats, most of the radioactivity was excreted in the urine as metabolites more polar than crustaxanthin, and a less polar radioactive metabolite was identified in the liver. 4. 4. Vitamin A was not labeled, and water of the urine contained a small but significant amount of tritium 5. 5. In the carp (Cyprinus carpio L.) 3 H-crustaxanthin given by intraperitoneal injection was absorbed efficiently, but was not metabolized to any detectable radioactive compounds. © 1975.