PROBLEM TO BE SOLVED: To provide a calpain activity inhibitor with excellent safety, which includes a plant-derived constituent as an active constituent and can be utilized for preventing and treating various diseases caused by the excessive activation of calpain.SOLUTION: As a result of performing zealous research about the calpain activity inhibition action of various plant-derived constituents, one or more kinds of plants selected from plants belonging to Theaceae Camellia or the solvent extracts of the plants, particularly, Camellia sinensis (tea) or the solvent extract thereof is remarkably excellent in calpain activity inhibition action.
