Toxins associated with medicinal and edible seaweeds

Toxins associated with medicinal and edible seaweeds are reviewed with an e mphasis on chemistry. The red alga Digenea simplex has been used for the tr eatment of roundworm disease for centuries. Its active principle is kainic acid (1). The related domoic acid (3) is a constituent of another red alga, Chondria armata, used for the same purpose. These compounds known as kaino ids are potent neurotoxins and excitatory amino acids. Kainoids are importa nt tools in neurophysiological research. Domoic acids are also produced by diatoms and were responsible for the shellfish poisonings known as amnesic shellfish poisonings which occurred in Canada in 1987. Caulerpin (13) and C aulerpicin (15) have been described as toxic constituents of edible species of the green algal genus Caulerpa, but evidences in later studies indicate that they have no acute toxicity. Caulerpin, which has a structure related to auxin, promotes plant growth. Caulerpenyne (16), a toxic constituent of Caulerpa taxifolia and other inedible species, has been evaluated for its ecotoxicological effect in the Mediterranean where C. taxifolia bloomed exp losively. Three different classes of compounds have been identified in the poisonings with species in the genus Gracilaria. They are prostaglandin E-2 (17) from G. verrucosa in Japan, aplysiatoxins and related compounds (19-2 3) from G. coronopifolia in Hawaii, and polycavernosides (26-30) from G. ts udai in Guam.