'Methylamine irisolidone' (=5,7-dihydroxy-6-methoxy-3-(4-methoxyphenyl)-8-[(methylamino)methyl]-4H-[1]benzopyran-4-one), a new compound, is a structurally modified kakkalide with good water solubility. In this study, we investigated its effect on hypoxia/reoxygenation (H/R) injury in cultured rat cardiac myocytes. The results showed that methylamine irisolidone could significantly inhibit lactate dehydrogenase (LDH) release, enhance the mitochondrial membrane potential, decrease intracellular calcium (Ca(2+)) associated with the attenuation of reactive oxygen species (ROS) generation, reduce contents of malondialdehyde (MDA), and increase the activity of superoxide dismutase (SOD) after H/R in a dose-dependent manner. The present study demonstrated that methylamine irisolidone can directly protect cardiomyocytes against H/R injury, primarily as a result of reduction of the intracellular Ca(2+) overload coincident with an attenuation of ROS generation and ROS-mediated lipid peroxidation, which may contribute to the preservation of mitochondrion function and antioxidant against H/R injury.