Synthesis of 7-methoxyapigeninidin and its fungicidal activity against Gloeocercospora sorghi.

In the structure of sakuranetin, which was isolated as a phytoalexin from the rice plant, the methoxy group at C-7 has been shown to be important for its high activity. Apigeninidin was isolated as a phytoalexin from sorghum, but it had no methoxy group at C-7. We prepared 7-methoxyapigeninidin and compared its fungicidal activity with that of apigeninidin. The 7-methoxyapigeninidin showed higher activity against sorghum fungi than apigeninidin, suggesting that the methoxy group at C-7 was important for the high fungicidal activity.