Tannins and related compounds. CIII. Isolation and characterization of new monomeric, dimeric and trimeric ellagitannins, calamansanin and calamanins A, B and C, from Terminalia calamansanai (Blanco) Rolfe.

Continuing chemical examinatino on tannins of Combretaceous Plants has led to the isolation of four new ellagitannins, calamansanin and calamanins A, B, and C, together with ten structurally known tannins and related compounds, from the leaves of Terminalia calamansanai (BLANCO) ROLFE. On the basis of chemical and spectroscopic evidence, the structures of calamansanin and calamanin A were established as 1, 6-di-O-galloyl-2, 3-O-(S)-hexahydroxydiphenoyl-4-O-(S)-flavogallonyl-α-D-glucose (11) and 1-O-galloyl-2, 3-O-(S)-hexahydroxydiphenoyl-4, 6-O-(S)-valoneoyl-α-D-glucose (14), respectively, while calamanin B and calamanin C were characterized as dimeric and trimeric ellagitannins 15 and 16, respectively, in which the glucose units are linked through valoneoyl group(s).