Selective Preparation Of Glabridin And Gastrodin By Molecularly Imprinting Technique

Glabridin, a isoflavan, is one of the most important bioactive compound in G. glabra L. and its content is about0.2%. This compound is widely used in pharmaceutical and cosmetics industry due to its biological activities and unique skin whitening effect. Gastrodin is the main active compound in Gastrodia elata Bl. and its content is about1.97%. Gastrodin has sedative and anticonvulsant actions, neuroprotective effect, antioxidant and free radical scavenging activities. Due to its pharmaceutical activities, this compound is commonly used in medicines and health produncts to relieve headache. The complex matrices of herbs and the low content of glabridn and gastrodin make traditional preparation methods tedious, time-consuming and inefficiency. Therefore, developing a new method with high efficiency to selectively obtain glabridin and gastrodin is very necessary.Molecualrly imprinting is a technique to produce molecularly imprinted polymers (MIPs) progammed to recognize a target molecule, which named template. Due to MIPs have many outstanding advantages such as high affinity to the template, excellent stability in harsh chemical environment, ease of preparation and repeated usage, these polymers have been widely used in chromatogramphic separation, biosensors, enzyme mimic catalyst, artificial antibodies, etc. and shows great application potential in separation and preparation of bioactive compounds in traditional Chinese medicines. In present study, the preparation processes of glabridin MIPs and gastrodin MIPs have been optimized and the performance of these MIPs as selective materials to prepare glabridin and gastrodin have been investigated.1. Selective preparation of glabridin by molecularly imprinting techniqueMIPs with high selectivity and affinity to glabridin were designed based on the screening results of the library of non-imprinted polymers (NIPs). The NIP library contained48polymers that were polymerized with the combinations of different functional monomers, cross-linkers, and porogenic solvents. The distribution coefficient (k) was used to estimate the affinity of NIPs to glabridin. The corresponding MIPs of the best three NIPs were prepared. After evaluating the imprinting effect and selectivity of the three MIPs, the performance of the best MIP as solid-phase extraction sorbent was investigated. Glabridin with percent recovery of83was obtained from the extract of Glycyrrhiza glabra L.(G. glabra L.) residues by molecularly imprinted solid-phase extraction (MISPE). Thus, this material can be successfully used for the extraction and purification of glabridin from G. glabra L. residues.2. Selective preparation of gastrodin by molecularly imprinting techniqueMIPs with high selectivity and affinity to gastrodin in water were designed using allyl2,3,4,6-tetra-O-acetyl-glucopyranoside (TAGL) and1,2,3,4,5-pentafluoro-6-vinylbenzene (PFVB) as novel functional monomers. Binding characterization of pre-polymerization complexes was researched by nuclear magnetic resonance (NMR) and the MIPs were characterised by scanning electron microscopy (SEM). The properties involving adsorption isotherm, adsorption kinetics and selective recognition capacity were evaluated. The MIP/TAGL exhibited good site accessibility in which it only took30min to achieve adsorption equilibrium and highly selective recognition for the template. Furthermore, the performance of the MIP/TAGL as solid phase extraction material was investigated in detail and hot water at50℃served as the eluting solvent. Pure gastrodin with the recovery of76.6%was obtained from the aqueous extract of Gastrodia elata roots. Due to water was used in the loading and eluting process, this polymer was an environment-friendly material with high selectivity to gastrodin.