Pteriatoxin A (7)

Pteriatoxin B (8) Pteriatoxin C (9)

be pinnatoxin analogs containing a cysteine moiety. The position of duplicate signals in the XH NMR spectrum suggested that pteriatoxins B (8) and C (9) are C-34 epimers, like 2 and 3.

Pteriatoxins A (7), B, and C (8, 9) showed significant acute toxicity against mice with LD99 values of 100 and 8 ^g/kg, respectively. The toxic symptoms of pteriatoxins were also similar to those of pinnatoxins. Extracts from the digestive glands of several species that are closely related to Pinna sp., including P.muricata, P. attenuata, P. atropupurea, and the commonly eaten shellfish At-rina pectinata, all produced the same symptoms of poisoning in mice. Thus, these shellfish may become toxic as a result of feeding on common toxic organisms such as dinoflagellates.

Pinnamine, an Alkaloidal Marine Toxin from Pinna muricata

In a continuation of our work on pinnatoxins, a novel marine alkaloid, pin-namine (10), was isolated from the Okinawan bivalve P. muricata. Pinnamine exhibited acute toxicity against mice, with characteristic toxic symptoms, such as scurrying around and convulsion (LD99 0.5 mg/kg) [17]. The structure of pinnamine (10) was determined to be a unique alkaloid containing a 9-azabicyclo[4.2.1]nonane moiety and a dihydro-y-pyrone ring. The absolute stereostructure was determined by an analysis of the circular dichroism spectrum [18].

The structure and toxic symptoms of pinnamine resemble those of anatoxin-a (11) [19,20], a potent postsynaptic depolarizing neurotoxin known as very fast death factor (VFDF), and atropine [21], a representative suppressor of the

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