Development of an HPLC method for the characterization and quantification of cardenolides in Strophanthus kombe extracts

Strophanthus kombé Oliv. is a climbing plant, which may be found mainly in Central Africa. Its seeds contain cardenolides exhibiting cardioactive properties. Hence, Strophanthus extracts and isolated cardenolides have been used for treating heart diseases. Thin-layer (TLC) and high performance liquid chromatography (HPLC) are commonly used as analytical tools for quality control [1, 2]. However, these methods have not been updated taking into account novel analytical developments. Latest reports in this context refer to the separation of a known K-strophanthin mixture and characterization of individual compounds by HPLC-MS/MS [3]. Thus, a Strophanthus seed extract was used for method development in the present study. The method was optimized using an RP-HPLC system coupled with DAD (220nm) and MSⁿ. For this purpose, a C18 column (100 × 2.1 mm, 3.5 µm) with a gradient of water-acetonitrile acidifying both eluents with formic acid was evaluated. Separation of more than 20 cardenolides was achieved within 37 minutes. Individual cardenolides were characterized by MSⁿ experiments. Subsequently, the method was transferred to an UHPLC C18 system (50 × 2.1 mm, 1.9 µm) using Chromeleon™ UHPLC Method Speed-Up Wizard allowing reduction of the separation time to 10 minutes. Separation was equivalent to that of the HPLC method. UHPLC method was validated according to ICH guidelines, thus, allowing quantitation of individual compounds. The developed method is straightforward and applicable for the quality control of raw material from S. kombé and pharmaceutical preparations produced therefrom.

References:

[1] Corona GL, Raiteri M. Separation and quantitative determination of K-strophanthin glycosides by thin-layer chromatography. J Chromatogr 1965; 19: 435 – 437

[2] Tittel G. Substitution of animal tests in pharmacy. Pharm Ind 1986; 7: 822 – 836

[3] Grosa G, Allegrone G, del Grosso E. LC-ESI-MS/MS characterization of strophanthin-K. J Pharm Biomed Anal 2005; 38: 79 – 86