Abstract
A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method was developed to separate and determine betulinic acid (BA), oleanolic acid (OA) and ursolic acid (UA) in traditional Chinese medicines (TCMs). Three pentacyclic triterpene acids were baseline seperated in the buffer (pH 9.0) of 6% (v/v) methanol containing 10 mmol L-1 disodium tetraborate, 10 mmol L-1 sodium dihydrogen phosphate, 50 mmol L-1 sodium dodecylsulfate, 15 mmol L-1 2-hydroxypropyl-β-cyclodextrin within 15 min. The good linear relationships between the peak area and concentration were obtained in the ranges of 16.5-330 µg mL-1, 18-360 µg mL-1 and 19.5-390 µg mL-1 for BA, OA and UA, respectively. Compared with high performance liquid chromatography with γ-CD as chiral mobile phase additive (CMPA-HPLC), CD-MEKC has better analytical efficiency for three acids, and the analytical time (15 min) was shorter than that of CMPA-HPLC (80 min).
Highlights
Triterpenoids, such as betulinic acid (BA), oleanolic acid (OA) and ursolic acid (UA), existing in traditional Chinese medicines (TCMs) in the form of free acids or aglycones for triterpenoid saponins,[1] possess important pharmacological properties
It can be seen that the effective mobilities difference between BA and OA was large, and the effective mobilities difference between OA and UA was almost zero when the Sodium dodecylsulfate (SDS) concentration approached to 10 mmol L-1
The limits of detection (LOD) and limits of quantitation (LOQ) under the proposed cyclodextrin-modified micellar electrokinetic chromatographic (CD-micellar electrokinetic chromatography (MEKC)) conditions were determined at a signal-to-noise ratio (S/N) of 3 and 10, respectively
Summary
Triterpenoids, such as betulinic acid (BA), oleanolic acid (OA) and ursolic acid (UA), existing in traditional Chinese medicines (TCMs) in the form of free acids or aglycones for triterpenoid saponins,[1] possess important pharmacological properties. The only difference between them is the position of the methyl group on the ring E. The main analytical methods of triterpenoids in TCMs are gas chromatography (GC),[9,10,11] high-performance liquid chromatography (HPLC),[12] capillary zone electrophoresis (CZE)[13,14] and micellar electrokinetic chromatography (MEKC).[15] the resolution of OA and UA was not satisfied by common HPLC or MEKC due to their similar molecular structures. Gas chromatography-mass spectrometry (GC-MS) via a time-consuming derivatisation reaction has already been used to identify OA and UA,[16] and liquid chromatography-electrospray/atmospheric pressure chemical mass spectrometry (LC-ESI/APCI-MS) can be employed to identify BA17 and UA,[18] as the triterpenoids have weak chromophores
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