Profiling Hoodia Extracts by HPLC with Charged Aerosol Detection and Electrochemical Array Detection and Pattern Recognition

Hoodigosides are oxypregnane steroidal glycosides abundant in Hoodia gordonii and related plants native to the deserts of southwestern Africa. These plants, used traditionally to ease hunger, enjoy wide use today in dietary supplements purported to suppress appetite and aid in weight loss. Presented are two approaches to profile Hoodia related products. First, Hoodia extracts were analyzed by HPLC with charged aerosol detection. Eight hoodigosides isolated from dried plant material were separated within 15 min on a solid core enhanced C8 analytical column. With low-nanogram sensitivity, the charged aerosol detector responds uniformly to all non-volatile species including the target analytes, degradation products and impurities that may not possess a chromophore. Second, Hoodia extracts were analyzed by gradient HPLC with an online electrochemical array detector that responds to redox active compounds such as polyphenols. Each of the sixteen sensors in the electrochemical array detects analytes at a unique potential to yield picogram on-column sensitivity for diverse compounds that vary widely in redox properties. The chromatograms resulting from this voltammetric approach often clearly resolve co-eluting compounds. These two techniques provide complementary data that were used to quantify known compounds. The complex patterns of both known and unknown compounds revealed by the detectors were also interrogated by pattern recognition software to support inferences on product quality, authenticity, adulteration, or origin. Limits of detection, linear and dynamic range, precision, and pattern recognition results are compared for the two approaches.