Studies On Extraction, Separation And Properties Of Curcuminoids

Curcuma is a perennial herb, which belongs to turmeric genus of Zingiberaceae family, and is widely cultivated in the south-eastern and south-western part of China. It is a traditional Chinese medicine, and always used as both culinary and medicinal material with the function of dispelling wind and activating blood, regulating Qi to disperse, adjusting menstruation and analgesia. As a major active component of curcuma, curcuminoid is a kind of natural pigment and widely used in the food industry with high security. Due to its remarkable properties of anit-oxidation, anti-tumor, anti-inflammatory and free radicals, curcuminoid has been broadly applied to cancer treatment. It can improve the uniformity, permeability and durability of textile fabrics in printing and dyeing industry. As an additive in cosmetics, curcuminoid demonstrates good activity of anti-oxidation and whitening.This thesis made a systematic and comprehensive study on the extraction, purification, chromatographic separation and determination, properties of solution, thermal and photo-stability of curcuminoids.Our main work as follows:1. Extraction, separation, purification and identification of curcuminoidsThis chapter investigated the optimal method of ultrasonic extraction of curcuminoids by orthogonal experiment, as well as optimized the separation conditions of curcuminoids by thin layer chromatography (TLC). Three curcuminoids were seperated, prepared and then characterized by UV-Vis, IR and NMR. The results showed that the optimal extraction conditions of curcuminoids can be stated as follows:85% (V:V) ethanol solution adding 1.5% (w%) SDS as extraction solvent, the ultrasonic extraction was repeated twice under different ratios of solid to liquid (1:10 and 1:8 respectively) in dark for 40 minutes. The extraction rate of curcuminoids was as high as 11%. The optimium seperating solvents of curcuminoids for TLC was the mixtures of chloroform and methanol in the ratio of 40:1. Three compounds were identified as curcumin, demethoxycurcumin and bisdemethoxy- curcumin.2. HPLC analysis of curcuminoidsThe High performance liquid chromatography (HPLC) separation of curcuminoids was investigated by changing of composition and ratio of the mobile phase, as well as the concentration of acetic acid (ion promoter) and the wavelength monitored. The effective seperation method and content determination of curcuminoids were carried out. Furthermore, the precision, reproducibility and recoveries of samples were estimated. The results indicated that the best chromatographic condition for the separation of the curcumin, demethoxycurcumin and bisdemethoxycurcumin was as follows:with the temperature of 35℃, acetonitrile-water 50:50 (V:V) containing 0.5% acetic acid as mobile phase with the flow rate of 1 mL/min, UV detection wavelength 425 nm. Under above condition, the total contents of curcuminoids from sample S-1 and S-2 were 58.3% and 95.9%, respectively. The method was proven to be of high precision, reproducibility and recoveries and easy to be operated.3. Research on properties of curcuminoidThe changes of UV-Vis and fluorescence spectra of curcuminoid solution at different pH and polar solvents were researched. In addition, DSC, TG and TG-FTIR were utilized to characterization of its thermal property and thermolysis products. The results showed that the maximal absorption wavelength and absorbence remained more or less constant in aqueous solution with pH ranging from 1 to 9, but increased significantly when pH was more than 9. Fluorescence intensity of curcuminoid in acidic and weak base solutions was greater than those with pH more than 9, and the corresponding emission wavelength was smaller than in the strong alkaline medium. The maximum UV-Vis absorbance intensity was obtained in the moderate polarity tetrahydrofuran (THF) solution. When the polarity of solvents was less than THF, the absorbance intensity decreased with increasing polarity of solvents, but it was opposite when the polarity of solvents was more than THF. The strongest fluorescence intensity was also obtained with THF as solvent, and the change laws was similar to UV-Vis absorbance intensity. The melting and thermal decomposition point of curcuminoid was determined to be at 175℃and 247℃, repectively, and the weight loss rate was as high as 62.5% at 420℃. Via TG-FTIR analysis, CO2 was the main decomposition products when curcuminoid was heated to 300℃. The themal decomposition product was residual phenolic hydroxyl group at 400℃, and curcuminoid almost completely degraded at 500℃.4. Study on photo-stability of curcuminoidThe systematic researches about photo-stability of curcuminoid under different lighting conditions and mediums were carried out by UV-Vis. The curcuminoid solutions were analyzed pre and post light exposure by HPLC. Results showed that curcuminoid in ethanol solution was stable under the conditions of indoor lighting, UV irradiation and dark; Be excessively exposured to strong sunlight would cause degradation; The lower concentration of curcuminoid, the more prominent degradation effect was; Citric acid, BHT andβ-CD were less helpful for the stability of curcuminoid. Degradation of curcuminoid was significantly lowered in emulsion, the most stable form of curcuminoid was saved as powders.The analysis of HPLC showed:The degradation rates of curcumin, demethoxycurcumin and bisdemethoxycurcumin were 69.5%,51.4% and 21.2%, separately, after exposure to sunlight for 5 days, which demonstrated that bisdemethoxycurcumin was the most stable compound, while the curcumin was the most unstable compound among curcuminoids. The major degradation products of curcuminoids were ferulic acid and vanillin.