Study on the Secondary Metobolites of Paulownia coreana

Paulownia coreana Uyeki (Scrophulariaceae), a deciduous species indigenous to Korea and also called as Korean Paulownia, has been extensively used in the wood industry and folk medicines [1]. However, its secondary metobolites and bioactivities have little been investigated. In our work, 22 compounds were isolated and purified from 70% aqueous acetone extracts of P. coreana leaves, outer bark, inner bark and fruits by repeated Sephadex LH-20 column chromatography and TLC. Structures of the 22 isolated compounds were elucidated through extensive spectroscopic techniques and sorted as 8 flavonoids, (+)-catechin (1), (-)-epicatechin (2), naringenin (3), taxifolin (4), apigenin (5), luteolin (6), kaempferol (7) and quercetin (8), 3 flavonoids glycosides, apigenin-7-O-β-D-glucopyranoside (9), apigenin-7-O-β-D-glucuronopyranoside (10), and apigenin-7-O-[β-D-glucuronopyranosyl-(1→2)-O-β-D-glucuronopyranoside] (11), 6 phenolic acids, ρ-hydroxybenzoic acid (12), vanillic acid (13), gallic acid (14), cinnamic acid (15), ρ-coumaric acid (16) and caffeic acid (17), and 5 phenylpropanoid glycosides, verbascoside (18), isoverbascoside (19), cistanoside F (20), campneoside II (21) and isocampneoside II (22). Among these compounds, isocampneoside II (22) was a new epimeric phenylpropanoid glycoside and compounds 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 20 and 22 were isolated for the first time in the genus of Paulownia [2]. Acknowledgements: Natural Science Foundation of Tianjin (09JCYBJC15800), China Postdoctoral Science Foundation and Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China are gratefully acknowledged. We are also thankful to Dr. Ji-Sook Ryu, Central Lab of KNU, for measuring the NMR spectra. Reference: [1] Kim TO (1994) Korean Plants. Teaching Press. Seoul. [2] Si CL (2006) Doctoral dissertation submitted to Kangwon National University. Korea.