Structures of alnusiin and bicornin, new hydrolyzable tannins having a monolactonized tergalloyl group.
From the fruit extract of Alnus sieboldiana, a new hydrolyzable tannin, alnusiin (1), was isolated together with five known tannins : tellimagrandin I (6), pedunculagin (7), casuarinin (9), casuariin (10) and 2, 3-O-(S)-hexahydroxydiphenoyl-D-glucose (11). The structure (1) of alnusiin in which a monolactonized tergalloyl group, a rare component unit, bonds to the glucose residue, was elucidated based on spectral analyses including <SUP>1</SUP>H-<SUP>13</SUP>C long-range shift correlation spectroscopy, and chemical methods. Another new hydrolyzable tannin with a related structure, bicornin (21), and six known galloylglucoses as well as six ellagitannins (including oligomers), were isolated from Trapa bicornis fruits and their structures were characterized.
- Ｃｈｅｍ． Ｐｈａｒｍ． Ｂｕｌｌ．
Ｃｈｅｍ． Ｐｈａｒｍ． Ｂｕｌｌ． 37(10), 2655-2660, 1989