Paralytic toxicity of ribbon worms ("himomushi" in Japanese), identified as undescribed
species of the genus Cephalothrix, found on the surface of the shells of cultured
oysters in Hiroshima Bay, Hiroshima Prefecture was examined between April 1998 and
December 2001. The toxicity study showed that all of specimens were found to contain
toxins with strong paralytic action in mice; the highest toxicity (as tetrodotoxin,
TTX) was 25,590 mouse units (MU) per gram for whole body throughout the monitoring
period. The main toxic component of this himomushi toxin (HMT) was isolated from a
pooled specimen (390 g; total toxicity 2,897,000MU) by a method that consisted of
treatment with activated charcoal, chromatography on Bio-Gel P-2 and Bio-Rex 70 (H+
form), and finally crystallization from an acidified methanolic solution. The recrystallized
toxin showed a specific toxicity of 3520MU/mg. This toxin showed (M+H)+ and (M+H-H(2)O)+
ion peaks at m/z 320 and 302, respectively, by electrospray ionization-mass spectrometry
(ESI-MS). The absorption band at 3353, 3235, 1666, 1612 and 1076 cm(-1) were observed
in infrared spectrum of this toxin. This spectrum was indistinguishable from that
of TTX. The 1H-NMR spectrum for the recrystallized toxin was the same as that for
TTX. The pair of doublets centered at 2.33 (J=10.0Hz) and 5.48 ppm (J=10.0Hz) which
are characteristic of TTX, were shown to be coupled by double irradiation. Furthermore,
by gas chromatography-mass spectrometry (GC-MS) of the alkali-hydrolyzate of this
toxin indicated the presence of quinazoline skeleton (C9-base) specific to TTX.