Tannins and Related Compounds. CXVII. Isolation and Characterization of Three New Ellagitannins, Lagerstannins A, B and C, Having a Gluconic Acid Core, from Lagerstroemia speciosa (L.) PERS
Lagerstannins A (6), B (11) and C (8), ellagitannins having a gluconic acid core, have been isolated from the fruits and leaves of Lagerstroemia speciosa (L.) PERS. (=L. flos-reginae RETZ.)(Lythraceae). On the basis of chemical and spectroscopic evidence, their structures were established as 2,3;4,6-bis-O-(S)-hexahydroxydiphenoyl-D-gluconic acid (6), 2,3,5-O-(S, R)-flavogallonyl-4,6-O-(S)-hexahydroxydiphenoyl-D-gluconic acid (11), and 5-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl-D-gluconic acid (8), respectively. Furthermore, the structure of an ellagitannin, punigluconin, previously isolated from the bark of Punica granatum L., was revised as 2,5-di-O-galloyl-4,6-O-(S)-hexahydroxy-diphenoyl-D-gluconic acid (10), based on spectral re-examination.