| It is well known that conventional extraction techniques, including solvent extraction, Soxhlet extraction, heat-reflux extraction, et al., often involves large solvent consuming, long extraction time, low extraction rate or low percentage impurity clearance. It was also reported that microwave-assisted extraction and supercritical fluid extraction had been employed to extract the active compounds from TCMs. But these methods both need sophisticated equipments (microwave oven or supercritical fluid extraction system) and high cost. Therefore, developing a simple and low-cost extraction method is still in great needs nowadays.As an important form of electromagnetic wave, infrared radiation (IR) has wavelengths between about 750 nm and 1 mm. IR has been widely employed as heat resource for health care due to its high penetration ability. Infrared can also be used in cooking and heating food as it predominantly heats the opaque, absorbent objects, rather than the air around them. The high efficiency of the infrared heater is achieved by matching the wavelength of the infrared heater to the absorption characteristics of the material.In this study, we focused on developing a new extraction method for separation and determination of active compounds in TCMs (Traditional Chinese Medicine) using the commercial infrared bulb as infrared radiation source. The infrared-assisted extraction of combined with modern chromatographic methods, were applied for separation and qualition of different kinds of target compounds such as phenolic acids, diterpenoids, alkaloids and volatile oils from TCMs.In chapter 1, an infrared-assisted extraction (IRAE) method was developed and coupled with high-performance liquid chromatography (HPLC) for simultaneous determination of four phenolic acids and four diterphenoids in radix Salviae Miltiorrhizae (Chinese name Danshen). The extraction conditions of IRAE were optimized using orthogonal design, and the optimal conditions were as follows: extraction time of 15 min; extraction solvent of 70%(v/v) methanol in water solution, and solid/liquid ratio of 0.1:15 (g/mL). Under the optimized chromatographic conditions, all the target compounds were well separated with high resolution. Good linearity (r>0.9994) was observed over the concentration ranges investigated, and intra-day and inter-day precision were high. Recoveries of the eight compounds were from 96.90%-104.30% and relative standard deviations (RSD) were below 2.5%. By using this IRAE method, with a much shorter extraction time, the determined amounts of the eight active components of Danshen were comparable with or even higher than those extracted with conventional heat-reflux extraction and ultrasound-assisted extraction methods. The IRAE method was further established by simultaneous quantification of the four phenolic acids and four diterpenoids in Danshen from different geographic origins.In chapter 2, the developed IRAE-HPLC method, was employed to determination of indigo and indirubin in leaves of Isatis indigotica Fort. (Chinese name Daqingye). This newly developed and optimized infrared-assisted extraction (IRAE) method was compared with ultrasound assisted extraction (UAE), Soxhelt extraction (SE) and microwave-assisted extraction (MAE) in terms of extraction amounts of these two active components. Besides the influence factors mentioned in chapter 1, we also investigated the effect of different infrared power on the extraction results. The optimal conditions were as follows:extraction reagent of trichloromethane; power of infrared lamp of 275W; extraction time of 20 min; liquid/solid ratio 20 mL/0.1g. Under the optimized chromatographic conditions, indigo and indirubin were well separated with high resolution. Good linearity (r>0.9996) was observed over the concentration ranges investigated, and intra-day and inter-day precision were high. Recoveries of these two compounds were above 96.0% and relative standard deviations (RSD) were below 2.0%. The results showed that the amounts of indigo extracted by IRAE were a little higher than that extracted by other three extraction methods, while for indirubin, the amount obtained by MAE reached the highest.In chapter 3, we employed, for the first time, a novel strategy for extracting essential oil compounds from cumin with nitrogen purge-solvent free-infrared assisted-solid phase microextraction (IRAE-SPME) coupled with gas chromatography mass spectrometry (GC-MS). Some parameters, including SPME fiber coating and irradiation time, were optimized. The optimal conditions were as follows:SPME fiber coating of 75μm CAR/PDMS; power of infrared lamp of 275W; irradiation time of 2 min.28 volatile substances was obtained by GC-MS and the results showed the method is simple, rapid and solvent-free.Since the use of microwave radiation for organic synthesis has been widely reported, we were interested in that whether the infrared radiation could be applied to the organic synthesis. So, in chapter 4, a simple method for synthesis of methyl salicylate using infrared radiation has been developed. The results showed that using infrared radiation for simple organic reactions is practicable.In summary, the main contributes of this dissertation is that we initially investigated the feasibility of extraction active components from TCMs with infrared radiation. The developed methods were successfully applied to separation and analysis of phenolic acids, diterpenoids, alkaloids and volatile oils from different plant materials. We also established a method to synthesis of methyl salicylate using new infrared radiation. We aimed at exploring and finding out new techniques in sample preparation of plant material analysis, so that more breakthroughs can be obtained in the quality control research study of TCMs.
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