Synthesis and characterization of SO 3 H-functionalized silica solid acid catalyst and application for the production of diosgenin

In this work, thiol-functionalized silica SiO 2 -Pr-SH (Pr = −(CH 2 ) 3 ) was synthesized by self-hydrolysis of 3-mercaptopropyltrimethoxysilane (MPTMS) with the average particle sizes up to 1.9 μm. Then sulfonic acid-functionalized SiO 2 -PrSPr-SO 3 H was prepared by the 1,3-Propanesultone grafted onto SiO 2 -Pr-SH and used as solid acid catalysts for alcoholysis of total saponins in Dioscorea zingiberensis C. H. Wright (DZW) to the production of diosgenin. The as-prepared solid acid was fully characterized with FT-IR, Raman, TGA, BET, FESEM, EDS, elemental mapping, XPS, and XRD, respectively. The solid acid quantity, solvent dosage, extraction temperature, and time were studied by single-factor experiments. The maximum yield of diosgenin was calculated to be 16.73% relative to 0.1 g total saponins, which was higher than the sulfuric acid hydrolysis method. Importantly, it is an efficient alcoholysis approach for the production of diosgenin from total saponins and the prepared solid acid can be recycled in the reaction medium. The possible alcoholysis products and reaction mechanism were proposed on the basis of LC-MS results. This work not only provides a new solid acid for the production of diosgenin from DZW but also gives a beneficial synthetic reference for the preparation of high-activity SO 3 H-functionalized catalysts based on the organosilane. Graphical abstract SO 3 H-functionalized silica as an efficient solid acid catalyst for the production of diosgenin from Dioscorea zingiberensis C. H. Wright