Effective adsorption of salvianolic acids with phenylboronic acid functionalized polyethyleneimine-intercalated montmorillonite

It is important to separate salvianolic acids from Danshen owing to their significant therapy-related activities of cardiovascular and cerebrovascular diseases. In this study, phenylboronic acid functionalized polyethyleneimine-intercalated montmorillonite (PAPIM) was successfully synthesized via intercalation and amidation to capture salvianolic acid A (SAA), salvianolic acid B (SAB) and rosmarinic acid (RA) effectively. Adsorption of three salvianolic acids kinetically follows a pseudo-second-order model. The maximum adsorption capacities can be determined to be 1.285, 0.692 and 1.154 mmol/g for SAA, SAB and RA by Langmuir adsorption model, respectively. Comprehensive factors of function groups of adsorbents and structure of phenolic acids result in the affinity order of adsorbent for phenolic acids: SAA > SAB > RA > other phenolic acids with simple structure. Different dominant processes lead to different adsorption thermodynamics of three salvianolic acids. It is found that the adsorption mechanism includes covalent bond, electrostatic interaction, hydrogen bond and π-π stacking interaction. Remarkably, boronic acid affinity and electrostatic interaction play the important role in the selective adsorption process, which is verified by density functional theory (DFT) calculations. This work highlights that PAPIM is a promising adsorbent to realize effective separation of salvianolic acids and provides an alternative potential strategy to selective separate certain compound with multiple synergetic interactions.