Direct analysis of alkaloids in natural Cinchona bark and commercial extracts using time-of-flight secondary ion mass spectrometry†
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used for the first time to characterize Cinchona alkaloids in natural Cinchona bark and commercial Cinchona extracts. ToF-SIMS analysis of quinine (Qn), a major Cinchona alkaloid, provides significant molecular fragments, which can be used in the fast qualitative screening of Qn and related compounds in small amounts of Cinchona bark and extract. Conventional approaches for natural product analysis such as bark are time-consuming and typically require large amounts of samples and significant amounts of organic solvents for extensive liquid extraction as well as liquid chromatography for analyte separation from the matrix before detection. In this study, it is demonstrated that ToF-SIMS can be used for the direct analysis and fast qualitative screening (less than 10 minute analysis time) of Cinchona alkaloids. It is also a greener approach than chromatography-based approaches because it uses less sample material and no organic solvents. Before ToF-SIMS analysis, the bark surface topography and roughness were analyzed using 3D laser microscopy. ToF-SIMS results in this study were validated by complementary high performance liquid chromatography-MS results. This work shows the potential of ToF-SIMS in the screening of pharmaceutically relevant compounds that are present in natural samples such as bark and extracts.