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Green solvent extraction techniques development and metabolite profiling in medicinal plants
Author
Teo, Chin Chye
Supervisor
Tan, Swee Ngin
Yong, J. W. H. (Jean W. H.)
Abstract
Stringent quality control for medicinal plant production is important for raising the standards of complementary alternative medicine. In plant sample preparations, the extraction method is carefully chosen in order to extract the desired metabolites prior to the analytical process. The bioactive secondary metabolites are traditionally extracted as markers in chemical standardization for quality control. This dissertation focussed on developing a useful platform linking the primary and secondary metabolite profiling for enhanced quality control in herbs used for complementary alternative medicine.
Furthermore, the metabolite profiling obtained could provide a plausible mechanistic understanding of key plant metabolic pathways. Complementary analytical techniques and data analysis tools were used to develop the platform. The key highlights in the investigations are the development of a low cost and green solvent pressurized hot water extraction (PHWE) and microwave-assisted extraction (MAE) methods to extract bioactive compounds from selected medicinal plants. Compared to the conventional methods, their advantages include shorter extraction process, higher extraction efficiency and minimal solvent consumption. Simultaneously, the key primary metabolites were profiled by various analytical techniques to study the biosynthesis of terpenes, alkaloids and flavonoids in selected medicinal plants. The metabolite profiling was studied using the Principal Component Analysis (PCA) to assess the quality of medicinal plants grown under Good Agriculture Practice (GAP) conditions.
The dissertation is organized into three sections. The first section (Chapter 1-2) provided the relevant literature reviews of medicinal plants and the recovery of bioactive compounds by various extraction techniques. The improved methodology for the analyses of plant metabolites, with the emphasis of green solvent PHWE and MAE techniques and metabolite profiling, were discussed.
Chapter 3-6 focused on the development of green solvent methods in order to extract the bioactive compounds from Gastrodia (TCM herb used for treatment of epilepsy) and Stevia (traditional herb used for treatment of diabetes) under different GAP cultivation conditions. These compounds were successfully extracted from the botanicals using ultra-pure water at optimized conditions (Chapter 3-4). Their extraction efficiencies were found to be comparable to the reflux method using ultrapure water. Concurrently, an approach based on the optimized green solvent methods, HPLC-UV chemical fingerprints and PCA was developed to evaluate the quality of Stevia grown under different GAP controlled greenhouse soil and in vitro cultivation conditions (Chapter 4). The primary metabolite profiling for Stevia, Coptidis (TCM herb used for treatment of fever), and Scutellaria (TCM herb used for treatment of bacterial infection) of different origins were accomplished using the GC-MS and 1D 1H NMR analysis (Chapter 5). A metabolomics approach was developed to understand the key metabolic pathways in these herbs. Furthermore, Chapter 6 provided the results of the primary and secondary metabolite profiling, and also the linkage of the metabolite profiling with PCA in order to assess the quality of different medicinal plants.
The final section (Chapter 7) provided some insights on the successful applications of the two green solvent methods and the metabolite profiling for the quality control of medicinal plants. Future works proposed include the “scaling-up” of the green extraction techniques, exhaustive metabolite profiling development by complex analytical systems and biotechnology manipulations for bioactive compounds accumulation in plants are discussed.
Furthermore, the metabolite profiling obtained could provide a plausible mechanistic understanding of key plant metabolic pathways. Complementary analytical techniques and data analysis tools were used to develop the platform. The key highlights in the investigations are the development of a low cost and green solvent pressurized hot water extraction (PHWE) and microwave-assisted extraction (MAE) methods to extract bioactive compounds from selected medicinal plants. Compared to the conventional methods, their advantages include shorter extraction process, higher extraction efficiency and minimal solvent consumption. Simultaneously, the key primary metabolites were profiled by various analytical techniques to study the biosynthesis of terpenes, alkaloids and flavonoids in selected medicinal plants. The metabolite profiling was studied using the Principal Component Analysis (PCA) to assess the quality of medicinal plants grown under Good Agriculture Practice (GAP) conditions.
The dissertation is organized into three sections. The first section (Chapter 1-2) provided the relevant literature reviews of medicinal plants and the recovery of bioactive compounds by various extraction techniques. The improved methodology for the analyses of plant metabolites, with the emphasis of green solvent PHWE and MAE techniques and metabolite profiling, were discussed.
Chapter 3-6 focused on the development of green solvent methods in order to extract the bioactive compounds from Gastrodia (TCM herb used for treatment of epilepsy) and Stevia (traditional herb used for treatment of diabetes) under different GAP cultivation conditions. These compounds were successfully extracted from the botanicals using ultra-pure water at optimized conditions (Chapter 3-4). Their extraction efficiencies were found to be comparable to the reflux method using ultrapure water. Concurrently, an approach based on the optimized green solvent methods, HPLC-UV chemical fingerprints and PCA was developed to evaluate the quality of Stevia grown under different GAP controlled greenhouse soil and in vitro cultivation conditions (Chapter 4). The primary metabolite profiling for Stevia, Coptidis (TCM herb used for treatment of fever), and Scutellaria (TCM herb used for treatment of bacterial infection) of different origins were accomplished using the GC-MS and 1D 1H NMR analysis (Chapter 5). A metabolomics approach was developed to understand the key metabolic pathways in these herbs. Furthermore, Chapter 6 provided the results of the primary and secondary metabolite profiling, and also the linkage of the metabolite profiling with PCA in order to assess the quality of different medicinal plants.
The final section (Chapter 7) provided some insights on the successful applications of the two green solvent methods and the metabolite profiling for the quality control of medicinal plants. Future works proposed include the “scaling-up” of the green extraction techniques, exhaustive metabolite profiling development by complex analytical systems and biotechnology manipulations for bioactive compounds accumulation in plants are discussed.
Date Issued
2011
Call Number
QD63.E88 Teo
Date Submitted
2011