Woodfruticosin (woodfordin C), a new cyclic dimeric hydrolyzable tannin having an inhibitory activity toward deoxyribonucleic acid (DNA) topoisomerase II, has been isolated from the leaves of Woodfordia fruticosa KURZ (Lythraceae) along with three known flavonol glycosides and three known flavonol glycoside gallates. The structure of woodfruticosin (woodfordin C) was determined by the use of two-dimensional nuclear magnetic resonance (2-D NMR) spectroscopy including heteronuclear multiple quantum coherence (HMQC) and heteronuclear mucltiple bond connectivity (HMBC) techniques. Detailed analyses of the proton and carbon-13 NMR (¹H-and ¹³C-NMR) spectra of six known flavonoids were performed.