Thermodynamic and NMR investigations on the adsorption mechanism of puerarin with oligo-beta-cyclodextrin-coupled polystyrene-based matrix

BACKGROUND: Adsorption of puerarin on native resin polystyrene (PS) and oligo-beta-cyclodextrin-coupled matrix (PS-CDP) was studied for interactions between the adsorbents and the adsorbates. The sorption mechanism on PS-CDP was investigated using the isosteric heat approach and nuclear magnetic resonance (NMR) spectroscopy. RESULTS: The equilibrium adsorption data of puerarin on the two matrices PS and PS-CDP (polystyrene-based matrix before and after coupling by oligo-beta-cyclodextrin) in the temperature range 288-318 K were well fitted to the Freundlich adsorption isotherm model. The energetic heterogeneity of the media was observed based on the result that the values of isosteric enthalpy were quantitatively correlated with the fractional loading of puerarin adsorption. The more heterogeneous surface of PS-CDP compared with PS was attributed to the complexation between puerarin and beta-cyclodextrin (beta-CD). NMR studies validated the formation of an inclusion complex puerarin/beta-CD. CONCLUSION: Thermodynamic and NMR studies confirmed that multi-interaction cooperatively governed the isolation of puerarin from aqueous solution on PS-CDP matrix. (c) 2009 Society of Chemical Industry