POST-GRADUATE STUDENTS

Hoodia gordonii is a popular weight loss product highly susceptible to adulteration, which highlights the need for rapid and simple quality control methods for authentication of raw material and products. High performance thin layer chromatography analysis was used to authenticate raw material. Quantitative high performance thin layer chromatography analysis as well as near infrared, mid-infrared and Raman spectroscopy combined with chemometric techniques were used to develop alternative quantification methods of P57 (the perceived active ingredient of H. gordonii) in raw material and/or products. The concentration of P57 determined with liquid chromatography coupled to mass spectrometry was used as reference data to develop calibration models based on the partial least squares projections to latent structures regression algorithm for the infrared spectra. The performance of each calibration model was evaluated according to the correlation coefficient (R2) and root mean square error of prediction. The high performance thin layer chromatography system produced good separation of compounds including that of the P57 band. Quantitative determination for P57 resulted in linear calibration curves with good correlation coefficient (R2) values of 0.9706-0.9993. For the near infrared spectroscopy data the projections to latent structures model with 2nd derivative pre-processing predicted P57 content with an R2 value of 0.9629 and an root mean square error of prediction of 0.03%. Pre-processing of the Raman data with orthogonal signal correction yielded a projections to latent structures model with an R2 value of 0.9986 and a root mean square error of prediction of 0.004%. The qualitative and quantitative high performance thin layer chromatography analyses provided a chemical fingerprint technique for authentication and confirmation of the presence of P57 in H. gordonii raw material and products as well as for quantification of P57. The parameters of the calibration models demonstrated that both near infrared and Raman spectroscopy shows potential to rapidly quantify P57 in H. gordonii raw material. As H. gordonii is one of the most widely consumed anti-obesity products of natural origin it is worrying that key aspects such as pharmacokinetic and biopharmaceutical aspects have not been sufficiently investigated. The in vitro transport of pure P57 as well as P57 from crude plant extracts across excised porcine intestinal and buccal tissue was investigated using a Sweetana-Grass diffusion apparatus. In addition to using buffer as transport medium, in vivo conditions were mimicked with the use of saliva and simulated intestinal fluid. The apparent permeability coefficient and flux values were calculated and statistically analysed. Pure P57 was transported to a much lower rate and extent than P57 from the crude extract across porcine intestinal tissue. P57 was transported across the buccal mucosa when applied in the form of a crude plant extract but no transport could be detected when P57 was applied in the pure form. The transport of P57 across intestinal and buccal mucosal tissues is significantly affected on exposure to conditions simulating the in vivo situation.