A Survey of Determination Methods of Aloe – emodin in Aloe Vera Extract
Aloe emodin, also known as aloe vera diarrhea. Orange needle crystal (from toluene). Melting point 223 ℃ ~ 224. Soluble in hot ethanol, benzene, and ether in the yellow. In the ammonia and sulfuric acid [f] was crimson, is anthraquinone compounds, acid solution f} 1 is reduced to produce anthralin and its tautomers of anthrone llI. It is widely found in Liliaceae Aloe, beans Cassia, Polygonaceae plant rhubarb, with anti-bacterial, anti-inflammatory, insecticide, anti-cancer, anti-aging effect. And aloe vera, rhubarb, cassis, etc. have medicinal value, so this article refer to Zeng Yunjin literature on a variety of aloe emodin detection methods were reviewed for rapid and sensitive detection of aloe emodin (aloe-emodin) to provide a reference.
Keywords: aloe emodin (aloe-emodin) aloe extract
1 aloe emodin (aloe-emodin) content determination method
1.1 High-Performance Liquid Chromatography
1), set the 25mL volumetric flask, add methanol diluted to the mark, shake, ultrasonic treatment 15min, take the supernatant 5mI clam lOmL volumetric flask, add methanol diluted to the scale, made of samples Solution. Mobile phase: methanol – 0.1% perchloric acid (6: 4); flow rate: lmI / rain determination wavelength 254nm. The aloe-emodin was 0.03%; the aloe extract contained aloe-emodin (aloe-emodin) with aloe-emodin (aloe-emodin) Emodin) for O. 32%. The use of aloe vera products should be based on practical application of aloe emodin (aloe-emodin) content indicators. The method was applied to the determination of aloe-emodin in aloe products, which was simple, rapid, sensitive and reproducible. It could be used as a method to control the quality of aloe vera products. Prescription and other first to take compound alone capsule content of about 50mg, accurately weighed, add methanol 20mL, ultrasonic extraction 30min, constant volume 25mL, filtration, precision absorption continued filtrate 10mL plus 60% iron chloride lmL, hydrochloric acid 6mI, water bath reflux 4h Cold, plus phenolphthalein indicator l drops, drop concentrated ammonia solution to the solution becomes light red.
At this time to produce red iron hydroxide precipitation, 50mL in methanol volume, shake. The amount of about lOmL, centrifugal precipitation 3rain. The Precise amount of supernatant 5mL water bath evaporated, let cool, dissolved in methanol and volume 5mL, filter capsule hydrolyzate. Another fine absorption of aloe juice 20mI, according to the above method plus reagent refluxing and volume 5mL, filtered by the juice hydrolyzate. The hydrolyzate was taken as the mobile phase at the wavelength of 287nm with methanol: water (70:30) and determined by the external standard method. The linear range of aloe-emodin is O. 04-0.4 g, in which the concentration has a good linear relationship with the peak area (r = 0.9999). The average recovery of aloe-emodin was 102.5% and RSD was 3.6%. (200minx4.5ram, 51xm) was used to determine the content of aloe-emodin in aloe juice, and the contents of aloe-emodin were determined by reversed phase high-performance liquid chromatography (HPLC) 45) as the mobile phase, flow rate hnL / rain, detection wavelength of 225nm, column temperature of 3O ℃. Linear range: 0.0066tzg ~ 0.066 ~ g, r = 0.9997; recovery rate of 100.05%, RSD1.28%. Ma Jingjun et al  through the comparative test to explore the aloe vera aloe emodin (aloe-emodin) extraction method, the HP [C method for simultaneous determination of aloe vera aloe emodin (aloe-emodin) and aloe vera content of the method was And finally established the chromatographic conditions for the determination of aloe-emodin and aloe vera in aloe vera by HPLC. Mobile phase: methanol-water (70:30); flow rate 1. OmL / min; the measurement wavelength was 293 nm. The results showed that the extraction efficiency of methanol was better than that of 50% methanol, and the ultrasonic extraction was complete for 30 min.
1.2 Thin layer scanning method
Deng Yuqiong accurate measurement of the amount of 20mL, placed in the separatory funnel, with carbon tetrachloride sub-extraction 3 times, each 2OraL, combined carbon tetrachloride liquid, in the rotary evaporator evaporated, with methanol solution and Capacity to lmL, for point sample use. The sample solution was spotted on a silica gel chromatography plate with ethyl acetate-methanol monohydrate (100: 5: 1) as developing solvent, developed, removed, dried and developed with 10% potassium hydroxide methanol solution. The scanning conditions were as follows: the wavelength was 490 nm, the reference wavelength was 690 nm, the linearizer was SX = 3, the slit was 0.4 mm x 5.0 mm, and the scanning was performed. The results showed that aloe-emodin was 1.70Ixg / mL, the RSD was 1.34%, the recovery was 98.44% and RSD was 0.64%. The above tests show that thin-layer scanning is a method of high sensitivity, quick and easy operation.
1.3 Spectrophotometric method
1.3.1 Fluorescence spectrophotometry. The applicable conditions for the determination of aloe-emodin were determined by fluorescence spectrophotometry. In the 10mL colorimetric tube followed by 2mL0.5too1. L NaC1 solution, 2 mL Tris-HCI buffer solution, ImL ethanol, a volume of O. Img / mL aloe-emodin ethanol solution was used to scan the fluorescence spectra of aloe-emodin at ex / em = 470 / 540nm and pH = 7.0. The linear range Is 1.0 to 8.1 p. G / mL, the detection limit was 0.0311 ~ g / mL, the precision of the method was 2.18%, and the content of aloe-emodin in the samples of Semen Cassia, serum and urine samples was successfully determined.
Huang Liying et al. (4) Determination of aloe-emodin in aloe vera capsule by fluorescence spectrophotometry. The hex and hem of aloe-emodin were determined in Hac-NaAc buffer at pH 5.76 and in the presence of sodium dodecyl sulfonate (SDS) surfactant. The results showed that the concentration of aloe vera was 1.0×10-6_2.5×10 ~ mol / L, which was linear with its fluorescence intensity. The detection limit was 2 × 10 mol / L. The kex and hem of aloe-emodin were 460 nm and 550 nm, respectively, and had strong fluorescence, while no fluorescence was observed in hex and hem systems at 387 nm and 533 nm, respectively. Fluorescence method is used for the quantitative analysis of the matter. The advantage is that the sensitivity is higher than that of UV-visible spectrophotometry. Compared with the literature, the detection limit is lower than that of the literature. At the same time, the selectivity is good and the interference is small The application of the method is not as broad as UV-visible spectrophotometry because many substances themselves do not fluoresce.
1.3.2 UV-Vis spectrophotometry Huang Liying et al [ll] According to the dual wavelength principle, respectively, in the determination of wavelength 255nm and 376nm, the reference wavelength 355nm and 475nm determination of aloe emodin (aloe-emodin) and aloe glycoside content. Aloe-emodin (aloe-emodin) in 2. OOxlO ~ -5. OOxlO mol / L concentration range and optical density (D) was linear, r = O. 9995; aloe vera in 2. OOxlO ~ 6. OOxlO mol / L concentration range and a linear relationship with D, r = -0.9998. The single-wavelength Uv method can not directly measure aloe-emodin and aloe vera, respectively, and interfere with each other because the absorption spectra of the two components overlap each other . Applications such as absorption of a dual-wavelength method, the measurement can eliminate mutual interference problems. Determination of aloe-emodin (aloe-emodin), the choice of D and D, 255nm is aloe-emodin (aloe-emodin) a characteristic absorption peak, and aloe glycoside D and D, equal, AD = D = KC1, D = KC1 and aloe-emodin (aloe-emodin) concentration was proportional to the concentration of △ A, the elimination of aloe glycoside absorption, The same determination of aloin glycosides, the choice of determination of wavelength 355nm, the reference wavelength of 475nm, the elimination of aloe verticillin interference. Aloe vera slices of the juice of its aloe emodin (aloe-emodin), aloe vera glycosides content> aloe vera, aloe whole leaf> aloe vera gel. The two-wavelength spectrophotometric method is fast, simple and accurate. It can be used to determine the two components in aloe samples without separation. [Abstract] According to the absorption spectra of two substances, aloe-emodin (aloe-emodin) glycosides as the standard to join the components, in the aloe-emodin (aloe-emodin) and another absorption wavelength of 361.4nm and 480.9nm Standard addition assay was performed. Aloe-emodin and aloe-emodin concentrations were in the range of 0 1 xlO mol / L. The relative standard deviation (n = 6) of aloe-emodin and aloe-emodin in aloe vera were less than 2%. In this paper, the dual wavelength standard addition method proposed by the principle of standard addition method and dual wavelength absorption method is used to combine the two to improve the selectivity without reducing the sensitivity.
(1) According to the spectral characteristics of aloe-emodin and aloe-emodin, 350 ~ 450nm was used as the determination wavelength range. The aloe-alan and aloe-emodin were determined by multi-wavelength linear regression spectrophotometry. Emodin) content. Determination of the absorbance value of the sample solution in the measurement wavelength interval nm, the establishment of the regression equation A/aloe vera rhubarb = C aloe vera alga glycosides, aloe vera yellow + an aloe vera yellow, aloe vera and aloe emodin (aloe-emodin) The recoveries were 97.4% ~ 102.5%, 97.5% -100.7%, RSDs were 0.22% ~ 0.89%, 0.35% ~ 0.82%, respectively When the two do not interfere with each other. The method is simple, reliable and reproducible, which provides a new method and important basis for the further development and utilization of aloe resources and quality control.
Gengmei et al. Used the method of simultaneous determination of aloin and aloe-emodin by the good addition of aloe-emodin and aloe-emodin. In the case of adding only ammonia water, respectively, aloe vera and aloe emodin (aloe-emodin) working curve; in the case of adding ammonia and sodium periodate solution, for aloe vera and aloe emodin of the other two work curve. The samples were measured in the same two conditions, respectively, and the absorbance was measured. The amount of aloe-emodin and aloe-emodin were determined by solving the simultaneous equations of four working curves. The lower limit of determination of aloe vera was 0.0024mg / mL, and the lower limit of aloe-emodin was O. O006mg / mL. The relative standard deviation of the sample analysis is less than 7%, and the recovery rate is 99% to 101%.
1.4 electrochemical analysis
The anthraquinone structure in the aloe-emodin molecule has electrochemical activity, and the determination of aloe-emodin can be achieved by detecting the high sensitivity of electrochemical detection. Both the voltammetry and the polarography are analyzed by a current (voltage) or potential-time curve obtained from the electrolysis process. The difference between them is that the polarized electrode used in the voltammetry is a solid electrode or a liquid electrode that can not be renewed on the surface, and the polarographic method uses a droplet electrode that can be updated periodically.
1.4.1 Polarographic method Zou Hong et al. Studied the electrochemical behavior of aloe-emodin by single-sweep polarography. In the 5% NaCO + 5% NaOH (9 + 1) base solution, aloe-emodin produced two oscillon polarographic peaks at a 0.84 V (P) and 0.97 V (P) The The range of linearity was 0.11 ~ 2.4mg / L and 3.0 ~ 28.6mg / L, the detection limit was 0.06mg / L, the aloe-emodin could be determined. In this paper, the electrochemical behavior of aloe-emodin in aqueous solution was studied, and the mechanism of electrode reaction was put forward. The single-sweep polarographic analysis of aloe-emodin was established, and the aloe-emodin (rhubarb) Aloe-emodin) content, the results are good. The scavenging effect of aloe-emodin on superoxide free radicals was also investigated.
There is a quasi-reversible dual proton double electron transfer process in a good proton source system, and the aloe-emodin content of aloe-emodin can be established by using this characteristic. Determination of electrochemical method. Chen et al.  studied the electrochemical properties of aloe-emodin on glassy carbon electrodes, established differential pulse voltammetry with its content determination, and optimized the measurement conditions. The reduction peak current of aloe-emodin was determined by differential pulse voltammetry in the phosphate buffer solution at pH 4.0, and the mixture was enriched by open-circuit stirring for 2 min. In the 5 × 10 a 2×10. Mol / L, the differential pulse voltammetric peak current of aloe-emodin has a good linear relationship with its concentration, and the detection limit is 3×10-Smol / L. Differential pulse voltammetry uses the method of adding pulse voltage to eliminate the capacitance current and Faraday current distortion and effectively eliminates the influence of impurities in supporting the electrolyte, with high sensitivity characteristics. The method has good reproducibility and can directly measure the content of aloe-emodin in aloe vera, and can realize the determination of aloe-emodin.
1.4.3 adsorption on carbon paste electrode voltammetry Li Li refused to put a solution of dissolved oxygen as the oxidant, carbon paste electrode (CPE) adsorption catalytic voltammetric determination of anthraquinone-based drugs method. The mechanism of the catalytic voltammetric peak was studied by linear sweep voltammetry, cyclic voltammetry, and potentiostat electrolysis. Experiments show that aloe-emodin can effectively absorb and enrich the surface of CPE. In the process of cathodic potential scanning, aloe-emodin is reduced to anthrahydroquinone compounds and then oxidized to dissolved aloe-emodin in solution by dissolved oxygen, followed by Restore, thus forming a catalytic cycle. And aloe-emodin on the mercury electrode produces a reversible redox reaction, and no catalytic reaction is observed. In the 0.56 mol / L NH-NHCl (pH8.9) buffer solution, aloe-emodin produced a sensitive catalytic voltammetry peak at a 0.60 V (vs. SCE) The method was applied to the determination of aloe-emodin in rhubarb of Chinese medicine, which was consistent with the results of high-performance liquid chromatography. Adsorption of organic compounds on CPE and other solid electrodes The catalytic voltammetry has high sensitivity and is non-toxic to the electrode, showing a different reaction mechanism with mercury electrodes. It has important implications for pharmacology, pharmacodynamics, drug toxicity, clinical medicine, and biochemistry.
1.4.4 1.5-order differential anodic stripping voltammetry Lin Xinhua  studied aloe-emodin (aloe-emodin) in 0.1mol / L Hac (pH2.89) to support the electrolyte, glass carbon electrode for the work The adsorption voltammetric behavior of the electrode. The results showed that aloe-emodin had a quasi-reversible double electron transfer process, and its peak current ID and peak potential Ep were related to the pH value of the solution. At the same time, a new method for the determination of content by 1.5 – step differential anodic stripping voltammetry was established. At a 0.80 V (VS.SCE) potential, a sensitive differential anodic stripping peak, the peak potential Ep is 0.38 V, the peak current Ip and the concentration of aloe emodin (aloe-emodin) in 2 .0 × 1O ~ 8.0×10-6mol / L in a linear relationship between the minimum detection limit of 1.0×10 ~ mol / L. The method is simple, sensitive, less interference, and can be used for the direct determination of aloe-emodin in different varieties of aloe.
At present, the aloe-emodin (aloe-emodin) determination of many methods, but the results are very different, such as Zeng Xiaoying using high-performance liquid measured l0 times aloe vera whole leaves containing aloe-emodin 0.004%; 1000 times aloe Juice contains aloe-emodin (aloe-emodin) is O. 03%; aloe extract contains aloe-emodin (aloe-emodin) is O. 32%. Ma Jingjun and other 171 with high-performance liquid phase measured Aloe vera aloe vera emodin (aloe-emodin) content of 365.5mg / kg. The contents of aloe-emodin in aloe vera juice were determined by reversed-phase high-performance liquid chromatography (HPLC). The results of different batches were 0.1331 p, g / mL, 0.1112 I ~ g / M [, o. 0865 txt / mL, 0.0717 Ix / mL, O. 0614p, g / mL. Fluorescence method is more sensitive than UV spectrophotometry, good selectivity, less interference, but because many substances themselves do not fluoresce, so the application of fluorescence method is not as broad as UV spectrophotometry. Zou Hong et al. [Duo hospital electrochemical method to determine the content of aloe-emodin (aloe-emodin), this method has a high sensitivity, can achieve a trace of aloe emodin (aloe-emodin) determination, but because of its professional Strong is not easy to accept, so use lighter. It can be seen that the method of determination of aloe-emodin content is systematically studied to find out the method of eliminating systematic error, to evaluate the comparability of the results obtained by different analytical methods, to determine the quantitative analysis of various analytical methods , It is necessary to select the appropriate analytical method for the instruments and reagents to guide the analyst’s accuracy and accuracy of the results.
Aloe-emodin (aloe-emodin) has been widely used in medicine, food, health products and cosmetics. Therefore, it is of great significance to study the development and utilization of aloe emodin (aloe-emodin), which contains aloe vera emodi, rhubarb and cassia seed.
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