Degradation of phenylethanoid glycosides in Osmanthus fragrans Lour. flowers and its effect on anti-hypoxia activity

Yajing Zhao,Zhiwei Ge,Xiaodan Wu,Maiquan Li,Fei Zhou,Baiyi Lu,Tao Xu,Liuquan Zhang

doi:10.1038/s41598-017-10411-0

Abstract

This study was aimed at investigating the chemical stability (the thermal, light and pH stability) of phenylethanoid glycosides (PhGs) in Osmanthus fragrans Lour. flowers, identifying the degradation products of acteoside and salidroside (major PhGs in O. fragrans flowers) by UPLC–QTOF–MS and studying the anti-hypoxia activity of PhGs after degradation. The degradation of PhGs followed first-order reaction kinetics, and the rate constant of acteoside (4.3 to 203.4 × 10−3 day−1) was higher than that of salidroside (3.9 to 33.3 × 10−3 day−1) in O. fragrans flowers. Salidroside was mainly hydrolyzed to tyrosol during storage, and the degradation products of acteoside were verbasoside, caffeic acid, isoacteoside, etc. In a model of cobalt chloride (CoCl2)-induced hypoxia in PC12 cells, the anti-hypoxia ability of PhGs decreased after degradation, which resulted from the reduction of PhGs contents. Particularly, caffeic acid exhibited stronger anti-hypoxia ability than acteoside and could slightly increase the anti-hypoxia ability of degraded acteoside. The results revealed that high temperature, high pH and light exposure caused PhGs degradation, and thus the anti-hypoxia ability of PhGs reduced.

Highlights

Previous studies revealed that the anti-aging and antioxidant activities of O. fragrans flowers were well correlated with phenylethanoid glycosides (PhGs), especially the acteoside[8, 12, 13]
We consider acteoside and PhGs in O. fragrans flowers have the potential ability of anti-hypoxia in PC12 cell
The acteoside content was slightly higher than that determined by Jiang et al.[12], which might be due to the different origin of O. fragrans flowers and/or extraction conditions

Summary

Introduction

Previous studies revealed that the anti-aging and antioxidant activities of O. fragrans flowers were well correlated with phenylethanoid glycosides (PhGs), especially the acteoside ( named verbascoside)[8, 12, 13]. Salidroside can protect PC12 cell from CoCl2-induced hypoxia damage[20, 21]. We consider acteoside and PhGs in O. fragrans flowers have the potential ability of anti-hypoxia in PC12 cell. The objectives of this work were (1) to evaluate the effects of temperature, pH and light on the degradation kinetics of acteoside, salidroside and TPG in O. fragrans flower extracts (OFE); (2) to identify the degradation products of acteoside and salidroside by UPLC–QTOF–MS/MS; (3) to investigate the anti-hypoxia activities of acteoside, salidroside and TPG after degradation

Objectives

Methods

Results