Imprinting-based smart syringe: A fast, efficient, and selective approach for extraction of methyl gallate from Caesalpinia pulcherrima extract

Abstract

A simple, facile, quick, highly selective, and efficient extraction protocol for a medicinal compound methyl gallate (MG) is developed for the first time using molecularly imprinted-based solid phase extraction (MISPE). Density functional theory (DFT) was employed to calculate the binding energies of the complex of MG with the functional monomer in the gas and in the implicit solvent to evaluate the best combination of the functional monomer, crosslinker, and porogen for MG. Decisively, the synthesis of a molecularly imprinted polymer (MIP) and its respective non-imprinted polymer (NIP) was conducted using methacrylamide (MAAm) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a crosslinker, and methanol as a porogen. The polymers were characterized by SEM, FT-IR, BET, and TGA, while the adsorption properties of MG-MIP/NIP were evaluated by batch rebinding experiments. Theoretical modeling was done by Langmuir, Freundlich, Scatchard analysis, LF-isotherm, and kinetic models. The MG-MIP appeared to have a higher binding capacity towards MG compared to the corresponding NIP: 57.6 mg/g compared to only 17.6 mg/g rendering an imprinting factor 3.3. Moreover, in competitive recognition studies, the synthesized MG-MIP showed good selectivity towards MG compared to its structural analogs, confirming the presence of MG-specific imprinting sites. In competitive recognition tests and real-sample analysis, HPLC was used to determine the concentration of MG and the analogous compounds. Furthermore, the volume and elution times of the washing solvent (DI water) and elution solvent (acetonitrile) were optimized. Finally, MG-MISPE frits were successfully designed for selective enrichment of MG from Caesalpinia pulcherrima methanolic extract using a syringe, PTFE membrane, and MG-MIPs. Hence, MG-MISPE is a promising alternative of traditional extraction methods for selective extraction and enrichment of MG from complex plant matrices. The approach has potential to be applied to any compound of interest.