INHIBITION OF ACETYLCHOLINESTERASE BY A PSEUDOZOANTHOXANTHIN-LIKE COMPOUND ISOLATED FROM THE ZOANTHID PARAZOANTHUS-AXINELLAE (O-SCHMIDT)

An ethanolic extract from a zoanthid crust coral Parazoanthus axinella e was lethal to mice and crabs and exhibited anticholinesterase activi ty. The isolation of several AChE inhibitors with the aid of RP-HPLC i s described. The most abundant of the inhibitors present in the P. axi nellae extract was identified as pseudozoanthoxanthin or an almost ide ntical compound which belongs to the chemically well-characterized ser ies of tetrazacyclopentazulene natural pigments from the genera Parazo anthus, Epizoanthus, Zoanthus and Palythoa. The inhibitor has a mel. w t of 242 and acts as a competitive inhibitor with a K-i of 4 mu M. The inhibitor exhibited a strong blue fluorescence. In vivo action of cru de extract and the isolated inhibitor showed a typical picture of syst emic acetylcholinesterase inhibition. Atropinization of experimental a nimals prior to injection of the inhibitor almost entirely neutralized its activity.