SURFACTANT MEDIATED EXTRACTION OF TRITERPENES AND THEIR DIRECT HPLC ANALYSIS FROM THE MICELLAR SYSTEM

Abstract

The pentacyclic triterpenes oleanolic acid (OA) and ursolic acid (UA) in Salvia triloba are attractive ingredients for cosmetic and pharmaceutical formulations. These triterpenoids are constitution isomers and differ only in the position of one methyl group in their chemical structures. Therefore it is difficult to achieve a baseline separation by standard RP-HPLC systems. Another challenge is that the complex plant contains a large variety of similar compounds. To achieve precise results for the target molecules, these compounds should be removed prior to analysis. Due to the large application of these two triterpenes, a fast quantification method is favored. If the triterpenes are extracted with aqueous two-phase systems, the target substances are enriched in a surfactant-rich phase. For this application, it is desirable to develop a method that is capable of quantifying both triterpenes directly by RP-HPLC without additional purification steps. The optimal chromatographic conditions for pure substances as well as for crude surfactant-containing extracts were accomplished on a Nucleodur C18 ISIS column by isocratic elution with methanol/water/acetic acid/triethanolamine (90:10:0.04:0.02 v/v) as the mobile phase and a column temperature of 10°C. The flow rate was 0.6 mL/min, and the detection wavelength was 210 nm. With these parameters, a baseline separation was achieved and the calibration curve showed a very good linearity (R2 > 0.999 for OA and UA) within the test range. The method is simple, rapid, and reliable for the quantification of crude extracts from plant material.