[C.I. 75530]. (-)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)-1,4-naphthoquinone; the major red dye derived from alkanet; used as an astringent, and in cosmetics and foods; can be used as an indicator: red at pH 6.8, changing to purple at pH 8.8 and blue at pH 10.0; also used as a fat stain. Syn: anchusin.