The objective of the present invention is to provide: an NOX inhibitor and an NF&kgr;B inhibitor, each having excellent activity; and a prophylactic or therapeutic agent for diseases associated with NOX or NF&kgr;B, which utilizes the NOX inhibitor or the NF&kgr;B inhibitor. In order to achieve this objective, a specific methoxyflavone is used.本發明之課題為提供具有優良作用之NOX抑制劑及NFκB抑制劑、及利用其之起因於NOX或NFκB之疾病的預防或治療劑。因此,係使用特定之甲氧基黃酮。