Isolation and structural characterization of four diastereomeric lignan glycosides from Abies holophylla and their neuroprotective activity

Abstract

Diastereomers are a type of a stereoisomer and they are often isolated as a mixture due to their similar physical properties. Through HPLC technique, we isolated four stereoisomeric lignan glycosides, holophyllosides A–D (1–4), from the trunk of Abies holophylla Maxim. which were first isolated as a mixture 25 years ago. The planar structures of 1–4 were characterized by conventional 1D and 2D NMR data analysis and their stereochemistry was determined via empirical comparison of their 13C NMR chemical shifts and 3JH-H coupling constants with the reported values, enzymatic hydrolysis followed by LC-MS analysis, and ECD experiment. Of the four stereoisomers isolated, only compounds 1, 3, and 4 showed moderate neuroprotective activity by inducing NGF secretion in C6 cells whereas 2 did not. This study highlights again the stereochemical importance of molecules in their biological and pharmaceutical application. © 2020 Elsevier Ltd