Undescribed Phenolic Glycosides from Syzygium attopeuense and Their Inhibition of Nitric Oxide Production

AbstractFour undescribed phenolic glycosides including three stilbene derivatives (1 and 3) and sodium salt of 3 (2), and a chalcone glycoside (4), together with thirteen known compounds (5–17) were isolated from the leaves of Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry. Their chemical structures were elucidated to be (Z)‐gaylussacin (1), 6′′‐O‐galloylgaylussacin sodium salt (2), 6′′‐O‐galloylgaylussacin (3), 4′‐O‐[β‐D‐glucopyranosyl‐(1→6)‐glucopyranosyl]oxy‐2′‐hydroxy‐6′‐methoxydihydrochalcone (4), gaylussacin (5), pinosilvin 3‐O‐β‐D‐glucopyranoside (6), myricetin‐3‐O‐(2′′‐O‐galloyl)‐α‐L‐rhamnopyranoside (7), myricetin‐3‐O‐(3′′‐O‐galloyl)‐α‐L‐rhamnopyranoside (8), myricetin‐3‐O‐α‐L‐rhamnopyranoside (9), quercitrin (10), myricetin‐3‐O‐β‐D‐glucopyranoside (11), myricetin‐3‐O‐β‐D‐galactopyranoside (12), quercetin 3‐O‐α‐L‐arabinopyranoside (13), myricetin‐3‐O‐2′′‐O‐galloyl)‐α‐L‐arabinopyranoside (14), (+)‐gallocatechin (15), (−)‐epigallocatechin (16), and 3,3’,4’‐trimethoxyellagic acid 4‐O‐β‐D‐glucopyranoside (17) by the analysis of HR‐ESI‐MS, 1D and 2D NMR spectra in comparison with the previously reported data. Compounds 1–3, 5, and 6 significant inhibition of NO production in LPS‐activated RAW264.7 cells, with IC50 values ranging from 18.37±1.38 to 35.12±2.53 μM, compared to a positive control (dexamethasone) with an IC50 value of 15.37±1.42 μM.