Pharmacological Studies of Physiologically Active Substances Isolated from Marine Organisms

Abstract

The present review mainly focusses on our recent pharmacological and biochemical studies on bioactive substances isolated from marine organisms. We have shown for the first time that 9-methyl-7-bromoeudistomin D, a derivative of eudistomin D isolated from a marine tunicate, acts on Ca-induced Ca release channels of sarcoplasmic reticulum at low concentrations and that maitotoxin, a dinoflagellate toxin activates voltage-independent Ca channels, thus producing a highly enhanced Ca influx. In the course of our survey of marine bioactive substances, peptide toxins (geographutoxin I and II, striatoxin, eburnetoxin and tessulatoxin) and 62-membered lactones (zooxanthellatoxin-A and-B) have been isolated from cone shells and dinoflagellates, respectively, and these marine toxins change dramatically the plasma membrane permeability of Na⁺ or Ca²⁺. From sea sponge we have isolated unique substances such as xestoquinone and purealin, which stimulate skeletal actomyosin ATPase by affecting the myosin heads directly. Furthermore goniodomin A, a macrolide from a dinoflagellate has been shown to cause modulation of actomyosin ATPase activity mediated through conformational