Synthesis and Characterization of Molecularly Imprinted Polymers for the Selective Extraction of Triterpenoid Saponin From Centella asiatica Crude Extracts

Asiaticoside (AS) and madecassoside (MS) are two key triterpenoid saponin compounds found in Centella asiatica. Despite their structural similarities, they exhibit distinct biological activities. AS is known for its anti-inflammatory properties and its effectiveness in treating rheumatoid arthritis, while MS is recognized for its ability to promote wound healing and significantly improve burn scars. Additionally, AS is widely utilized in the cosmetics industry due to its antioxidant and moisturizing properties. Currently, separating and purifying these two compounds simultaneously using existing methods is challenging. This study focuses on synthesizing molecularly imprinted polymers (MIPs) through precipitation polymerization with AS as the template. By optimizing various preparation parameters, such as the molar ratios of functional monomers, porogens, and cross-linking agents, high selectivity was achieved. The maximum adsorption capacity reached 19.16 mg/g, with an imprinting factor of 2.86. The MIPs were characterized using techniques like scanning electron microscopy (SEM), TA, Brunauer-Emmett-Teller (BET) adsorption, and Fourier-transform infrared (FT-IR). Their effectiveness was assessed through static and dynamic adsorption, desorption, and reusability tests. When applied in molecularly imprinted solid-phase extraction (MISPE) of crude extracts from C. asiatica, the recovery of AS was 39.90%, and its purity increased by 3.01 times, whereas the purity of MS improved by 6.51 times. These findings indicate that the preparation of MIPs is cost-effective, highly selective, reproducible, and user-friendly, making it a promising method for enriching and isolating AS from complex mixtures.