Acute toxic effects in mice of an extract from the marine algae Gonyaulax monilata.

Unialgal cultures of Gonyaulax monilata were cultured and harvested. A modified Westphall procedure was used to prepare an extract which did not contain saxitoxin, the gonyautoxins and structurally related toxins. The extract was administered i.p. to young adult, male CD-1 mice and produced: sedation, abdominal constriction, fecal clumping in the perianal area, ataxia, tremors, cyanosis, loss of reflexes, convulsions and death (LD50 = 2.28 mg/kg). Gross and microscopic pathology in the treated mice included: acute active hyperemia of the viscera, multifocal areas of necrosis of the musculature of the intestinal wall and diaphragm and the presence of cytoplasmic vacuoles in the peripheral margins of the acinar portion of the pancreas. Clinical pathology of the mice which survived 24 hr included significant elevation in the levels of serum lactic dehydrogenase, glutamic pyruvic and glutamic oxaloacetic transaminases. Some of these mice also had significantly decreased white blood cell counts. The extract administered orally produced similar signs without the abdominal constriction and convulsions (median lethal oral dose = 6.73 mg/kg). Gross pathology findings included extensive and severe congestion of the abdominal visceral organs. Vehicle control mice were normal. In conclusion, G. monilata, previously reported as nontoxic in homeotherms, yields an extract which contains a water soluble glycosidic substance(s) which is lethal to mice.