Antioxidative Bromoindole Derivatives from the Mid-Intestinal Gland of the Muricid Gastropod Drupella fragum

Three new bromoindoles, 6-bromo-5-hydroxyindole (1), 6-bromo-4,5-dihydroxyindole (2), and 6-bromo-4,7-dihydroxyindole (3), were isolated from the midintestinal gland of the muricid gastropod Drupella fragum. The structures of 2 and 3 were elucidated mainly by NMR spectroscopic analyses of their acetyl derivatives, whereas the structure of 1 was established by spectroscopic methods and total synthesis. Antioxidative activity for compounds 1−3 was evaluated by the POV method, and compound 1 was found to have as strong an antioxidative potency as BHT.