|Title:||Application of chromatographic and chemometrics techniques to enhance chemical analysis of cordyceps sinensis, herba menthae and other Chinese herbal medicines|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Medicinal plants -- China -- Analysis
Materia medica -- China -- Analysis
|Department:||Department of Applied Biology and Chemical Technology|
|Pages:||xxvii, 240 leaves : ill. (some col.) ; 30 cm|
|Abstract:||Chromatographic technique is one of the most common analytical methods applied in many fields of Chemistry. In the past decade, the rapid improvement of computer technology and the chemometrics based methodologies, data processing techniques enhance the development of chromatography to become a more accurate, reliable and user-friendly method in this century. In this research programme, chromatographic studies together with chemometrics and image analysis techniques were applied for qualitative and quantitative analysis of Chinese medicines (CM) including Cordyceps sinensis and Herba Menthae. Cordyceps sinensis is probably the most unusual energizer ever to become popular. Recently, there are a few health food products of Cordyceps sinensis available in the international market. Nucleosides are the main class of active components in Cordyceps sinensis. Thin layer chromatography (TLC) is one of the most commonly used methods for analyzing chemical components of herbal medicine. Since the isocratic elution method cannot be applied successfully in TLC analysis for separating the nucleoside components, the stepwise gradient elution has been developed in this work to separate the eight nucleoside standards with success. To the best of our knowledge, these nucleoside standards have never been completely separated by the TLC technique before. In this way, qualitative and quantitative analysis of the Cordyceps sinensis samples were achieved via the proposed TLC procedure coupled with the scanning densitometric techniques of CAMAG and TLCQA method. Chemical compositions of the Chinese herbs are known only to a small extent owing to their complicated structures. For safety and control purpose, it is desirable to know more about this kind of chemical information. High-performance liquid chromatography - diode array detector (HPLC-DAD) was applied in this work for chemical analysis of nucleosides components of Cordyceps sinensis. The gradient elution method was found to have advantage over the isocratic one. The separation of the constituents within a sample via HPLC is affected by different factors such as the flow rate, pH value, the solvent used and others. The complicated nature of TCM product renders the separation of the chemical components via HPLC a very challenging job. To tackle the problem, combination of chemometric based methods of Heuristic Evolving Latent Projection (HELP) and Simplex with the use of experimental design is a useful tool to optimize peak separation in HPLC experimentation as well as chemical information extraction. Simplex procedure is a search method. Owing to its versatility, it is widely applied in optimizing HPLC separation. It has been shown that the simplex algorithm can provide an efficient search strategy in handling complex chromatographic systems where the effects of several interdependent variables on the separation are difficult to predict. Further, it is useful to obtain guidance and direction to improve results from future experimentation via this approach. The software package MultiSimplex was applied in this work to optimize the HPLC separation of the chemical components of Cordyceps sinensis. Apart from Cordyceps sinensis, Herba Menthae has also been used for thousands of years, for both medicinal and culinary purposes. Herba Menthae is a species cultivated as a source of essential oil and is mainly used as a condiment in foodstuff. The essential oil of the leaves and stems of Herba Menthae are mainly investigated by Gas Chromatography/Mass Spectrometry (GC/MS). Based on comparing the resultant mass spectra with standards available as well as spectra accessed via the electronic data system, different sources of Herba Menthae samples from China were classified. Therefore, in this study, qualitative and quantitative analyses of the Herba Menthae samples were achieved using the GC/MS technique coupled with the Computer Aided Similarity Evaluation (CASE). Beside, a rapid and non-destructive method for analyzing of Herba Menthae according to different cultivation area in China was developed using Near-Infrared Reflectance (NIR) Spectroscopy and GC/MS method was used as reference method in this investigation. Although there were no obvious differences in the raw NIR spectra based on the leave and stem samples, the spectral features were enhanced and differentiated by utilizing a second-derivative algorithm for data processing. It was found that the new approach can be utilized for standardization and quality control of Herba Menthae products. It can also be applied to analyze other herbal medicines.|
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