Voltammetric procedure for the determination of oleanolic and ursolic acids in plant extracts

Abstract

In this work, a novel method based on square wave voltammetric determination of pentacyclic triterpenes (oleanolic and ursolic acids) at an unmodified glassy carbon electrode in plant material after chromatographic separation was developed. In a solution of sodium hydroxide, the calibration graphs were linear from 0.02 to 3.0 ng L⁻¹ for oleanolic acid (OA) and ursolic acid (UA) with correlation coefficients (R²) equal to 0.9958 and 0.9963, respectively. The detection and quantification limits were 0.0075 and 0.025 ng L⁻¹ for OA, and 0.0082 and 0.027 ng L⁻¹ for UA, respectively. The separated HPLC fractions of the triterpenes were analyzed by square wave voltammetry (SWV) at a glassy carbon electrode for OA or UA quantification in the extract of flowers of Sambucus nigra L. and OA in the extract of Viscum album L. The obtained contents of OA and UA by the proposed voltammetric method overlapped with those obtained using HPLC coupled with a photodiode array detector (DAD).