Abstract
Nineteen stilbene derivatives (I-XIX), of which five are novel cis-stilbenes, have been obtained from a rhubarb of low quality (commercial name : ?? ?? ??, Imo-Daio). Based on chemical and spectroscopic evidence, these compounds have been characterized as rhapontigenin (I), rhaponticin (II), rhapontigenin 3'-O-β-D-glucopyranoside (III), rhaponticin 6"-O-gallate (IV), rhaponticin 2"-O-gallate (V), rhaponticin 2"-O-p-coumarate (VI), piceatannol (VII), piceatannol 3-O-β-D-glucopyranoside (VIII), piceatannol 3'-O-β-D-glucopyranoside (IX), piceatannol 3'-O-β-D-xylopyranoside (X), piceatannol 3-O-β-D-(6"-O-galloyl) glucopyranoside (XI), desoxyrhaponticin (XII), desoxyrhaponticin 6"-O-gallate (XIII), 3, 4', 5-trihydroxystilbene 4'-O-β-D-(6"-O-galloyl) glucopyranoside (XIV), cis-3, 3', 5-trihydroxy-4'-methoxystillbene 3-O-β-D-glucopyranoside (XV), cis-3, 3', 5-trihydroxy-4'-methoxystilbene 3-O-β-D-(6"-O-galloyl) glucopyranoside (XVI), cis-3, 5-dihydroxy-4'-methoxystibene 3-O-β-D-glucopyranoside (XVII), cis-3, 3', 5-trihydroxy-4'-methoxystilbene 3-O-β-D-(2"-O-galloyl) glucopyranoside (XVIII) and cis-3, 3', 5-trihydroxy-4'-methoxystibene (XIX).
