Separation and Bioactive Assay of 25R/S-Spirostanol Saponin Diastereomers from Yucca schidigera Roezl (Mojave) Stems

In order to find a simple, generic, efficient separation method for 25R/S-spirostanol saponin diastereomers, the liquid chromatographic retention behaviors of C(12) carbonylation and C(12) unsubstituted 25R/S-spirostanol saponin diastereomers on different stationary phases (C(8), C(18), C(30) columns) and different mobile phases (MeOH-1% CH(3)COOH and CH(3)CN-1% CH(3)COOH) were investigated. A C(30) column was firstly found to offer the highest efficiency for the separation of this kind of diastereomers than C(8) and C(18) columns. Meanwhile, the analysis results indicated that both CH(3)CN-1% CH(3)COOH and MeOH-1% CH(3)COOH eluate systems were selective for C(12) unsubstituted 25R/S-spirostanol saponin diastereomers, while MeOH-1% CH(3)COOH possessed better selectivity for C(12) carbonylation ones. Using the abovementioned analysis method, six pairs of 25R/S-spirostanol saponin diastereomers 1a–6a and 1b–6b from Yucca schidigera Roezl (Mojave) were isolated successfully by using HPLC on C(30) column for the first time. Among them, three pairs were new ones, named as (25R)-Yucca spirostanoside E(1) (1a), (25S)-Yucca spirostanoside E(1) (1b), (25R)-Yucca spirostanoside E(2) (2a), (25S)-Yucca spirostanoside E(2) (2b), (25R)-Yucca spirostanoside E(3) (3a), (25S)-Yucca spirostanoside E(3) (3b), respectively. Moreover, 3a, 5a, 6a, 3b–6b showed strong inhibitory activities on the growth of SW620 cell lines with the IC(50) values of 12.02–69.17 μM.