Determination of Anthracene in Plant Extracts by Colorimetry
Plant extractsMost of the anthraquinones and their glycosides are yellow or orange red, and the hydroxyanthraquinones can dissolve in alkali solution and appear red or purple red;anthracenolAnd dimeric quinone and alkali do not appear red, only yellow, need to be oxidized to hydroxyanthraquinone before it interacts with alkali to appear red; hydroxyanthraquinones can react with methanol solution of magnesium acetate due to different structures. Orange, red, blue, purple and other colors can be determined according to this property.
1. Drawing the standard curve
After phosphorus pentoxide dried 24h emodin (or rhein, 1,8- = hydroxyanthraquinone) reference appropriate amount, with lye (Imol/L sodium hydroxide solution or a mixed solution with 2% ammonium hydroxide solution) or 0.5% a 1% magnesium acetate methanol solution bandwidth evaluation, scanning at 500~ 550nm wavelength, the absorbance measured at the maximum absorption wavelength, absorbance concentration to draw a standard curve, linear range of 4~ 24ug/ml.
2. Determination of free anthraquinone
Take an appropriate amount of drug powder or its preparation powder (approximately equivalent to free anthraquinone 1.5mg) and add ether (or chloroform) to dissolve, or use a Soxhlet extractor to reflux until the extract is colorless. The ether is evaporated, the residue is dissolved with methanol, and the magnesium acetate methanol solution is added to bandwidth evaluation; or the ether extract is moved into the separation funnel, extracted with lye and bandwidth evaluation, colorimetric determination, and the content is calculated according to the standard curve.
3. Determination of total anthraquinone
(1) After hydrolysis, extract an appropriate amount of the test product (approximately equivalent to 1.5mg of total anthraquinone), use acid solution (1-7.5mol/L sulfuric acid solution or 1.5-6mol/L hydrochloric acid solution) for 20-30ml, water bath reflux for 1-2h, so that the bound anthraquinone glycoside is hydrolyzed, the quinone is free, and then extracted with ether (or chloroform), and the filtered drug residue and filter paper are dried at 50 ° C and then extracted with ether reflux. The extract is colorless in the Soxhlet extractor, combined with the ether solution, and determined by the free anthraquinone determination method.
For samples containing reduced anthrone glycosides (such as sennoside), according to the principle that they can be oxidized by ferric chloride and hydrolyzed into oxidized anthraquinone glycosides by acid, an appropriate amount of the sample is weighed, 30 ml of water is added for ultrasonic treatment for 1-30 minutes (to improve the efficiency of dissolution and extraction, and to greatly shorten the dissolution and extraction time), 20ml of 10.5% ferric chloride solution is added, 20-60 minutes is refluxed, and 1-3 ml of hydrochloric acid is added for 30 minutes.
Anthraquinones and alkali after color, hydrogen peroxide can not make it fade, and other colored substances can be oxidized by its fading, alkali extract containing interfering components, plus a small amount of 1% hydrogen peroxide solution, heated in a boiling water bath 4min oxidation, cooling, bandwidth evaluation, colorimetric determination.
(2) Extract first and then hydrolyze, take an appropriate amount of the test product, and addmethanol(Or ethanol, chloroform, etc.), for the extract containing tetraquinone, ultrasonic treatment for 30 minutes to dissolve. For the original plant medicine powder preparation containing anthraquinone, it should be extracted in a Soxhlet extractor until the extract is colorless, the methanol is recovered to dryness, the residue is hydrolyzed with acid, and the ether (or chloroform) is extracted and determined according to law.
