2,3,5,7-Tetrahydroxy-1,4-naphthalenedione
# 2,3,5,7-Tetrahydroxy-1,4-naphthalenedione

2,3,5,7-Tetraahydroxy-1,4-naphthalenedione, also called 2,3,5,7-tetrahydroxynaphthoquinone or spinochrome B, is an organic compound with formula C $_{10}H$ $_6O$ $_4,$ 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 °C.

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, C $_{10}H$ $_2O$ $_2(CH$ $_3COO)_4,$ that crystallizes from methanol as yellow needles that melt at 157 °C.

