Three-liquid-phase extraction of diosgenin and steroidal saponins from fermentation of Dioscorea zingibernsis C. H. Wright

Diosgenin is an important starting material in the steroidal hormone industry. The yield of diosgenin obtained from the fermentation of Dioscorea zingibernsis C. H. Wright (DZW) by Trichoderma harzianum is higher than that typically obtained from acid hydrolysis. In this paper, the extraction of steroids in the culture broth was studied. A novel three-liquid-phase system (TLPS) consisted of petroleum ether, ethanol, ammonium sulphate and water was used to separate diosgenin and steroidal saponins in the culture broth. The partition behaviors of various steroidal saponins, diosgenin and glucose were investigated. From this, an optimized TLPS was obtained, which composed of 30% ethanol (w/w), 17% (NH4)2SO4 (w/w) and 40% (w/w) petroleum ether. In the optimized TLPS, almost all of the diosgenin was extracted into the top phase giving a recovery of 97.24%, whereas the steroidal saponins were mainly extracted into the middle phase, with recoveries of zingibernsis newsaponin, deltonin and diosgenin-diglucoside reaching almost 100%. The recoveries of trillin and diosgenin-triglucoside were 96.03% and 98.82%, respectively. Glucose tended to remain in the bottom phase, giving a recovery of 72.01%. The three-liquid-phase extraction (TLPE) successfully resulted in the simultaneous separation of diosgenin, untransformed steroidal saponins and glucose.