Provided is a degradation inhibitor that delays the progress of the degradation reaction of 2ccPA and has an excellent stabilization effect by using a carbacyclic phosphatidic acid compound represented by formula (1):




wherein R1 represents hydrogen, alkali metal, alkyl, arylalkyl, or aryl; bonds indicated by solid and dotted lines represent single or double bonds; wavy lines represent single bonds; and when the single bond is adjacent to a double bond, the steric configuration is E-configuration, Z-configuration, or any mixture thereof.