Tetrodotoxin derivatives in puffer fish.

Analysis of puffer fish tissue extracts by a fluorometric tetrodotoxin analyzer revealed the presence of three tetrodotoxin derivatives besides tetrodotoxin. The derivatives were isolated and identified as tetrodonic acid, 4-epitetrodotoxin and anhydrotetrodotoxin on the basis of mass spectral and 1H NMR measurements. The lethal potencies of 4-epitetrodotoxin and anhydrotetrodotoxin to mice by i.p. injection were 710 and 92 mouse units/mg, respectively.