Selective enrichment with click oligo (ethylene glycol) column and TOF-MS characterization of simple phenylpropanoids in the fruits of Forsythia suspensa

To separate samples of complex natural products, highly efficient and selective separation methods should be developed. Herein, a selective enrichment method was developed to separate Forsythia suspensa components with click oligo (ethylene glycol) (OEG) column in reversed phase (RP) mode. In this method, F. suspensa aqueous extract was successfully separated. And three fractions with structure-related compounds were obtained. Fraction I mainly consisted of C-6-C-2 natural alcohols and glycosides, fraction II mostly consisted of lignans, and fraction III mainly consisted of simple phenylpropanoids (SP). Then, the three fractions were separated with ultra-performance liquid chromatography (UPLC). Four more lignans were observed in fraction II, and eight more SP were observed in fraction III than that without OEG column. Fraction III was successively characterized by TOF-MS, 2 acids (caffeic acid and chlorogenetic acid), 26 SP with caffeoyl, and 26 SP with coumaroyl were characterized. The results prove that a valid method has been developed to selectively enrich SP and lignans. And the method combined with UPLC can efficiently separate SP and lignans. Furthermore, the TOF-MS method is effective to confirm the substituents of SP.