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Quality control of Hoodia gordonii raw material and products
Hoodia gordonii is a popular weight loss product highly susceptible to adulteration. This highlights the need for rapid and simple quality control methods for authentication of raw material and quantification of the perceived active ingredient, P57, a steroidal glycoside. High performance thin layer chromatography (HPTLC) analysis was used to authenticate raw material and near infrared (NIR) spectroscopy and Raman spectroscopy combined with chemometric techniques were used to attempt the quantification of P57 in raw material. The concentration of P57 determined with liquid chromatography coupled to mass spectrometry (LC-MS) was used as reference data to develop calibration models based on the partial least squares projections to latent structures (PLS) regression algorithm. The performance of each calibration model was evaluated according to the correlation coefficient (R2) and root mean square error of prediction (RMSEP). The HPTLC system produced good separation of compounds including that of the P57 band which was confirmed with preparative TLC. For the FT-NIR spectroscopy data the PLS model with 2nd derivative pre-processing predicted P57 content with an R2 value of 0.9629 and an RMSEP of 0.03%. Pre-processing of the Raman data with orthogonal signal correction (OSC) yielded a PLS model with an R2 value of 0.9986 and an RMSEP of 0.004%. The HPTLC analysis provided a chemical fingerprint for authentication and confirmation of the presence of P57 in H. gordonii raw material and products. The parameters of the calibration model demonstrated that both NIR and Raman spectroscopy shows potential to rapidly quantify P57 in H. gordonii raw material.