Brominated precursors of Tyrian purple (C.I. Natural Violet 1) from Plicopurpura pansa, Plicopurpura columellaris and Plicopurpura patula

Tyrian purple (C.I. Natural Violet 1) and its precursors have enjoyed much attention as various species of gastropods of the Muricidae family. However, few investigations have concerned the dye's precursors, namely Plicopurpura columellaris and Plicopurpura patula. Derivatization and NMR revealed that the purple pigment in Plicopurpura pansa is 6,6′-dibromoindigo. 1H and 13C NMR enabled tyrindolinone (6-bromo-2,2-bis-methylsulfanyl-1,2-dihydro-3H-indol-3-one), a methanethiol adduct of tyrindoleninone from P. pansa, to be identified. GC/MS was used to identify the precursors of C.I. Natural Violet 1 from P. pansa, P. columellaris and P. patula. Tyrindoleninone (6-bromo-2-methylsulsulfanyl-3H-indol-3-one) was present in the milk and the hypobranchial gland of P. pansa only whereas an indole derivative, 6-bromoindalin-2-one (6-bromo-1,3-dihydro-2H-indole-2-one), was present in the hypobranchial gland of P. patula and P. columellaris but not in P. pansa.