Separation rule of oleanane and ursane pentacyclic triterpenoids isomers from nature plants by coordination chromatography.

Many of oleanolic and ursolic pentacyclic triterpenoid isomers generally coexist. There is a small difference in their structures. Based on coordination chromatography theory, a reversed-phase high-performance thin-layer chromatography (HPLC) method has been investigated for improving the isomers' resolution by adding suitable agents in mobile phase, and the separation rule was summarized. With the calculation analysis, the space sizes of isomers were in the range of 3.77-5.65 Å. The total minimum energy in the inclusion of guest and β-CD had the biggest reduction, compared with the energy in the simple mixture of guest and β-CD (such as "asiaticoside-B" and "β-CD," from 196.4406 to 95.0670 kJ mol(-1)). So, β-CD (the cavity space size is in the range of 6.00-6.50 Å) and its derivatives were selected as the suitable agents. The experiment results showed that the resolution might be improved by adding the hydrophilic β-CD derivatives in mobile phase, such as Glu-β-CD, when the isomer structures carry big hydrophilic groups.