Online monitoring of catechin compounds transformation by the stationary phase of star phenylalanine cyclodextrin polymer.

The active ingredients of natural products represent a critical source for innovative drug discovery. However, the poor stereochemical stability and transformation of stereoisomers during storage directly influence therapeutic efficacy and safety. Therefore, the development of new chiral stationary phases (CSPs) with high chiral and structural selectivity is imperative for reliable quality control of natural products. Here, a star phenylalanine cyclodextrin (CD) polymer, Star-Phe-CD, was designed and synthesized. It features a CD parent nucleus, with Phe-derivatized CD as the sidechain monomers. Subsequently, a mixed-mode Sil-Star-Phe-CD CSP was fabricated with Star-Phe-CD as the chiral ligand, which exhibited significant fluorescence enhancement effects and multiple mixed-mode chromatographic retention mechanisms. The Sil-Star-Phe-CD CSP exhibits exceptional shape selectivity and stereoselectivity towards structurally similar analytes, demonstrating outstanding stereoseparation selectivity for analytes with rigid structures or multiple benzene rings with αlansoprazole = 1.90 and αatropine = 1.55, respectively. Coupled with LC-MS analysis, an online approach was established to simultaneously separate two pairs of catechin epimers and monitor their epimerization process. Molecular docking studies revealed the mechanism of chiral recognition, which relies on the cooperative effects of diverse intermolecular interactions, including hydrogen bonding, π-π interactions, and hydrophobic interactions. These interactions are crucial for recognizing structurally similar stereoisomers in complex systems.