Spinochrome B (2,3,5,7-tetrahydroxynaphthoquinone) is an organic compound with formula , formally derived from 1,4-naphthoquinone through the replacement of four hydrogen atoms by hydroxyl (OH) groups.
Spinochrome B occurs naturally as pigment in the shell and spines of sea urchins such as the Japanese dull red species aka-uni (Pseudocentrotus depressus), the greenish-black murasaki-uni (Heliocidaris crassispina), and the brown bafun-uni (Strongylocentrotus pulcherrimus). It is soluble in methanol and crystallizes as bright red needles that sublime above 200 ðC.
The compound gives a greenish yellow solution when treated with sodium hydroxide, a green solution with ferric chloride, and a green precipitate with lead acetate. It forms a fourfold acetate ester, ()<sub>4</sub>, that crystallizes from methanol as yellow needles that melt at 157 ðC.