Magnetism-directed selective transformation of ginsenosides via Fe3O4 nanozyme catalysis: Mechanism and green process development

: Background Fe 3 O 4 , as a peroxidase-mimicking metal nanozyme, has garnered broad attention across multiple disciplines. Ginsenosides, the primary bioactive constituents of the Araliaceae family, possess diverse pharmacological activities. Studies indicate that rare ginsenosides exhibit superior potency compared to their conventional counterparts. However, highcost and technical challenges of converting conventional ginsenosides into rare ones significantly limit their availability. Objective To fabricate a magnetic nanozyme for the highly selective conversion of the major ginsenoside Rb1 into the rare ginsenoside CK, and to elucidate the structure-activity relationship governing the product specificity. Methods Single-core Fe 3 O 4 nanoparticles were synthesized via a coprecipitation method, and their surfaces were subsequently modified with oleylamine/oleic acid to yield superparamagnetic iron oxide (SPIO) with weakened magnetism. Ginsenoside transformation was achieved using a standard emulsification procedure combined with ultrasonication and heating. Response surface methodology (RSM) was employed to optimize the transformation conditions. Product profiles were quantified by high-performance liquid chromatography (HPLC), and the adsorption mechanism was investigated through molecular dynamics (MD) simulations. Results Conversion experiments demonstrated that highly magnetic Fe 3 O 4 specifically converted Rb1 into a single product, the rare ginsenoside CK. In contrast, weakly magnetic SPIO produced a mixture predominantly composed of rare ginsenosides F2, CK, and Rh2. Response surface methodology (RSM) optimization yielded a maximum conversion rate of 77.54% at 49.53 ˚C, 3.35 h, and 28.48 kHz ultrasonic frequency. Molecular dynamics (MD) simulations further indicated that Fe 3 O 4 exhibited strong glycosyl binding competitiveness, preferentially adsorbing the glycosyl chain at the C-20 position of ginsenoside via chemisorption, potentially involving Fe–C coordination bond formation. Conclusion Tuning the magnetic strength of Fe 3 O 4 nanozymes enables the selective transformation of Rb1 into CK, providing a promising green and efficient strategy for the scalable production of rare ginsenosides.