Recovery of lotus (Nelumbo nucifera Gaertn.) seedpod flavonoids using polar macroporous resins: The updated understanding on adsorption/desorption mechanisms and the involved intermolecular attractions and bonding.

Macroporous resins have been employed in the effective recovery of flavonoids from plants. In this study, S8 polar resins were used to recover flavonoids and procyanidins from lotus seedpods. Adsorption kinetics, isotherms, and thermodynamics studies revealed that the adsorption process involved physico-chemical interactions, including flavonoid-resin and flavonoid-flavonoid electrostatic interactions, π-π aromatic stacking, moderate and strong hydrogen bonding, and repulsive forces. These forces worked complementarily in adsorption, except for the repulsive force, which opposed the adsorption. Further, adsorption temperature determined the adsorption behavior, with multilayer adsorption enhancing adsorption capacity. In dynamic desorption tests, an acetone/water/acetic acid mixture (58.77: 39.34: 1.89) designed by the D-optimal design method was able to desorb 95.57% and 89.85% of total flavonoids and procyanidins, respectively, using less than two bed volumes of solvent. Ultra-performance liquid chromatography triple-time of flight/mass spectrometry (UPLC-TOF/MS) analysis showed that 26 flavonoids, including 5 procyanidins, were detected after the recovery.