Efficient alcoholysis of total saponins in D. zingiberensis C. H. Wright with novel magnetic solid acids through a cleaner approach

From the perspective of full utilization of biomass, a clean approach for the production of diosgenin from total saponins in Dioscorea zingiberensis C.H. Wright (DZW) was realized by preliminary separation and extraction. An alcoholysis approach was adopted to obtain diosgenin using a novel magnetic solid acid Fe 3 O 4 @SiO 2 -Pr-S-Pr-SO 3 H Pr = -(CH 2 ) 3 -) as the catalyst. The prepared solid acid has been fully characterized. The single factor methodology was used to optimize the process parameters. The optimum conditions were: 0.50 g Fe 3 O 4 @SiO 2 -Pr-S-Pr-SO 3 H, 6.0 mL ethanol, the reaction temperature 120 ℃, reaction time 7.0 h and the maximum yield of diosgenin was 24.18% which are higher than conventional hydrolysis with 1.5 M sulfuric acid indicating the high catalytic activity of the solid acids. In addition, the solid acid had good reusability. The LC-MS technique was applied to analyze the main steroidal saponins in total saponins and possible mechanisms and pathways of hydrolysis and alcoholysis processes. Alcoholysis by an as-prepared magnetic solid acid is clearly excellent in high efficiency and reusability. It is a promising strategy for the green production of diosgenin through a cleaner approach.