Turbotoxins A and B, Novel Diiodotyramine Derivatives from the Japanese Gastropod Turbo marmorata

Bioassay-guided separation of the aqueous ethanol extract of the viscera of the Japanese gastropod Turbo marmorata resulted in the isolation of two toxins, turbotoxins A and B. Their structures were determined by spectral analysis and confirmed by organic synthesis to be diiodotyramine derivatives. Turbotoxins A and B exhibited acute toxicity against ddY mice, with LD99 values of 1.0 and 4.0 mg/kg, respectively. The structure–toxicity relationships of turbotoxins were examined, and it was proved that the iodine atoms and trimethylammonium groups are important for its acute toxicity. Turbotoxin A inhibits acetylcholinesterase with an IC50 of 28 μM.