[Transformation pathways in methanol of echinacoside, a principal effective ingredient of Cistanches Herba]

Echinacoside (ECH) is one of the active ingredients in Cistanche Herba and the principal effective component of Memoregain© as well. Moreover, a new agent namely Naoqing Zhiming tablet, derived from ECH has been licensed for clinical trials. However, the knowledge regarding the stability of is limited, till now, initiating a significant barrier for its further development along with the clinical trials. Herein, we aim to in depth characterize the transformation pattern of ECH in methanol. When ECH was stored in methanol, two primary products (P1 and P2) could be observed in HPLC chromatogram. A home-made automated fraction collector was configured via employing two 2-phase/6-port electronic valves to prepare P1 and P2. Following ¹H-NMR and LC-MS/MS assays, P1 and P2 were unambiguously identified as acteoside and cistanoside A, respectively. Moreover, the existences of cis-ECH, cis-acteoside, and cis-cistanoside A were claimed after careful analysis of the ¹H-NMR spectra of ECH, P1 and P2. Above all, the primary transformation pathways of ECH in methanol included methylation as well as hydrolysis, and mild transformation could also be initiated by cis/trans- configuration transferring for the caffeoyl group. The findings obtained in current study are envisioned to provide useful insight for the further development of ECH and the impurity detection of Naoqing Zhiming tablet. Moreover, the automated fraction collector configured in current study is able to serve as a versatile tool for the collection of signals-of-interest within phytochemical evaluations and impurity isolation.