Enrichment and separation of steroidal saponins from the fibrous roots of Ophiopogon japonicus using macroporous adsorption resins

Abstract

In this study, a simple and effective strategy for the enrichment of total steroidal saponins (TSS) from the fibrous roots of Ophiopogon japonicus (L. f.) Ker-Gawl. (FROJ) using macroporous adsorption resin was systematically developed. XAD-7HP resin was selected from six macroporous resins for further study because of the highest static adsorption and desorption capacities. The static adsorption of TSS on XAD-7HP resin fitted well to the Langmuir isotherm model and pseudo second-order kinetic model; the thermodynamics test showed that the adsorption process was spontaneous and exothermic. The dynamic tests on XAD-7HP resin columns demonstrated that the breakthrough volume was 16 bed volume (BV), and 6 BV of 80% ethanol was suitable for dynamic desorption. In a lab scale-up separation under optimal dynamic conditions, the content of TSS in the resin-enrichment fraction increased from 1.83% in the crude extracts to 13.86% by 7.59-fold with a recovery yield of 82.68%. Three steroidal saponins were obtained from the resin-enrichment fraction, and showed protective effects against oxidized low-density lipoprotein (ox-LDL) induced human umbilical vein endothelial cell (HUVEC) injury. Overall, these results suggested that XAD-7HP resin chromatography was an effective strategy for the large scale enrichment of TSS from FROJ, which showed the potential for functional food and pharmaceutical application.