Abstract: The reaction of esterase (EST) isozyme, glycogen (Gn) and total protein (TPr) of snails to the extracts of Nerium indicum Mill, Pterocarya stenoptera DC and Rumex japonicum Houtt was studied. EST electrophoresis shows EST is an important antidotal enzyme system and reacts strong to environment. EST changes greatly during the whole treating period and can be viewed as pathological index of toxicity. Extracts can decrease glycogen content greatly. Many factors can affect the glycogen metabolism in snails. The decrease may be due to their effects to liver, alimentary canal or enzyme. Extracts can also decrease protein content, but not so greatly as to glycogen. It shows that energy metabolism abnormity is the major reason for the molluscicidal activities of extracts. The biochemical mechanism needs further research. The molluscicidal activity was explored from microcosmic aspect. The research will provide theoretical foundation for constructing artificial phytocoenos against snails.

Key words: Nerium indicum Mill, Pterocarya stenoptera DC, Rumex japonicum Houtt, active components