Trapanin A (6), a trimeric hydrolyzable tannin, and trapanin B (7), a tetrameric hydrolyzable tannin, were isolated from the leaves of Trapa japonica (Trapaceae), and their structures were determined on the basis of spectroscopic and chemical data. The following tannins were also isolated from the leaves : cornusiin C (8) (trimer); cornusiin A (3), camptothin B (4) and cornusiin D (5) (dimer); gemin D (1), tellimagrandin I (2), pedunculagin, casuarictin and casuarinin (monomer).
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Hatano et al. (1990) studied this question.