Uniformly-sized, molecularly imprinted polymers for (−)-epigallocatechin gallate, -epicatechin gallate and -gallocatechin gallate by multi-step swelling and polymerization method

Uniformly-sized, molecularly imprinted polymers (MIPs) for (−)-epigallocatechin gallate (EGCg), -epicatechin gallate (ECg) and -gallocatechin gallate (GCg) were prepared by a multi-step swelling and polymerization method using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and cyclohexanol as a porogen. Molecular recognition abilities of the obtained MIPs were evaluated in liquid chromatography using a mixture of ethanol and water, or ethanol as the eluent. Each MIP gave the highest molecular recognition ability for the respective template molecule. In addition, (−)-EGCg and -ECg had the same configuration (2R,3R) at positions 2 and 3, and therefore resulting in high cross reactivity each other. However, (−)-GCg, which has different configuration at position 2 with (−)-EGCg and -ECg, showed low cross reactivity with them. On the other hand, those MIPs showed no molecular recognition against (−)-epigallocatechin and -epicatechin, which have no gallate group at position 3. These results indicate that the MIPs prepared can recognize configuration at position 2 and a gallate group at position 3. Furthermore, the MIP for (−)-GCg could be successfully used for isolating (−)-EGCg and -ECg from green tea extract.