Synthesis and characterization of magnetic solid acid Fe3O4@PEI@SO3H and application for the production of diosgenin by alcoholysis of turmeric saponins

•Fe3O4@PEI@SO3H was synthesized and used for the first time to extract diosgenin.•The FTIR, TGA, XRD, XPS, SEM, EDS, VSM, NH3-TPD of characterization for Fe3O4@PEI@SO3H.•The optimal conditions are obtained by single factor test and response surface method.•Catalytic pathways of alcoholysis were studied by LC-MS. The magnetic solid acid, Fe3O4@PEI@SO3H, was synthesized and used as a catalyst to transfer steroid saponins into diosgenin in an alcoholysis approach. The results showed that the magnetic solid acid greatly improved the alcoholysis efficiency for extraction diosgenin from steriod saponins. To optimize the parameters for alcoholysis, such as the mass of the solid acid, solvent volume, the reaction temperature and time, single factor experiments as well as response surface experiment have been performed. Under the optimal conditions, the diosgenin yield obtained by alcoholysis is higher than that of the traditional inorganic acid hydrolysis. And it worth to mention that no waste liquid is discharged. The catalyst is very stable and can be used for three times without obvious mass loss and activity decrease, indicating that the technology of extracting diosgenin from Dioscorea zingiberensis C.H. Wright tuber has a broad prospect in industrial application. [Display omitted]