Germany). Ultra-pure water was processed by a Milli-Q purification system
(Millipore, Molsheim, France). The chemical standards of syringin, chlorogenic
acid, isochlorogenic acid A, isochlorogenic acid B, and kaurenoic acid were
purchased from Weikeqi-Biotech Co., Ltd (Chengdu, China). All the standards have
a purity of at least 98% based on HPLC profile. Imipramine was from Yuanye
Bio-Technology Co., Ltd (Shanghai, China) and other reagents came from
Sigma-Aldrich (St Louis, MO).