Development of Analytical Methodology for Determination of Flavonoids and Other Phenolic Compounds in Waxberry (Myrica rubra ) Product

A rapid ultralsound-assisted hydrolysis, microwave-accelerated derivatization, followed by chromatography--mass spectrometric (GC--MS) analytical method was developed to simultaneously separate, characterize and quantify phenolic compounds in Chinese waxberry products. Both free and conjugate phenolic acids, which are rarely reported previously, were characterized and quantitated for the first time in this study. A baseline separation of the 20 phenolics and aromatic acids was achieved in 35 min with standard calibration curves linear over the concentration range from the detection limits to 25 microglmL. Among the 20 phenolic and aromatic acids identified in Chinese waxberry, the most abundant waxberry phenolic acids (dried weight) are trans-resveratrol (42.20 mg/kg), p-hydroxybenzoic acid (39.55 mg/kg), and o-hydroxycinnamic acid (37.94 mg/kg). The results indicate that the Chinese waxberry can be regarded as a potential source of valuable phenolics for functional food and nutraceutical applications. In this thesis, special attention was paid on the strategies and the tools available to make sample-pretreatment and analytical methods greener. The main principles are to reduce the amounts of reagents needed, to miniaturize and to automate analytical methods, making it possible to reduce dramatically the amounts of energy and time consumed and wastes generated.;In this thesis, the application of ultrasound-assisted hydrolysis significantly accelerated the acidic hydrolyzation of the conjugated phenolics. The optimization study of the hydrolysis was carried out, and the results showed that ultrasonic hydrolysis of 150 min can achieve similar effect as of the 16 hrs with the conventional method. By comparing with conventional acidic hydrolysis, the ultrasonic-assisted hydrolysis is a simpler, more effective, less reagent and timing consumed alternative hydrolysis process, which can also be applied in the analysis of phenolics in other plant-derived foods and in human fluids for their bioavailability and pharmacokinetic studies.;The 20 phenolics and aromatic acids studied were simultaneously derivatized with N,O- bis(trimethylsilyl)trifluoroacetamide (BSTFA) + trimethylchlorosilane (TMCS) in pyridine solution under microwave irradiation. Effects of irradiation time (15-120 s) and power level (240-800 W) in terms of yield, reproducibility, and overall analysis time were systematically investigated and optimized. The derivatization under the irradiation of 800 W microwave for 60 s produced comparable results when compared with the conventional heating process in a sand bath for 4 hrs at 80 °C. The result indicates that microwave-accelerated derivatization successfully shorten the derivatization time and reduced the energy consumption without lossing the derivatization yield and efficiency.