Isolation of tunichrome B-1, a reducing blood pigment of the sea squirt, Ascidia nigra.

The tunicates, or sea squirts, are common marine organisms that selectively accumulate metals such as V, Fe, Mo, Nb, in their blood cells. Despite the more than 70 years of interest in the compounds responsible for this accumulation, their extreme lability has eluded attempts to isolate and characterize them. The isolation and structure of the first of these blood pigments tunichrome B-1 from the Ascidia nigra is reported.