New antioxidant C-geranylated flavonoids from the fruit peels of Paulownia catalpifolia T. Gong ex D. Y. Hong

Three new geranylated flavonoids, including two geranylflavones (1, 2) and one geranylflavonol (3), named as paucatalinone C-E, were isolated from the fruit peel of P. catalpifolia T. Gong ex D. Y. Hong. Their structures were determined by means of UV, IR, MS, and NMR techniques. To our known, geranylflavone or geranylflavonol was the first isolation from the genus Paulownia. These isolated geranylated flavonoids displayed good antioxidant effects on DPPH and the senescent human embryonic lung diploid fibroblasts cells (2BS cells) induced by H2O2. The geranyl substituent may be an important factor for the cellular radical-scavenging effect because of its lipophilic character.