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1、Anthraquinones ( 蒽 醌 ),Anthraquinones,I. Overview . Classification . Chemical characteristics . Isolation . Spectroscopic methods of Identification,I. Overview,Anthraquinones compounds include anthraquinone derivatives as well as varying degrees of reduction products, such as oxanthranol, anthranol,
2、 anthrone and the dimer of anthrone and so on.,Anthraquinone,Oxanthranol,Anthrone,Anthranol,1, 4, 5, 8 bit of anthraquinone name as -bit 2, 3, 6, 7-bit called -bit 9, 10-bit known as meso-bit.,Anthraquinone compounds distribute in less than 30 branches of higher plants in the natural world and there
3、 are high content of anthraquinone in Polygonaceae, buckthorn Branch, Rubiaceae, legumes, Liliaceae, Scrophulariaceae, and so on. It is also found in the lichen and fungi.,. Classification,1. Natural anthraquinones always have the substituent of hydroxy, hydroxymethyl, methoxy, carboxyl and so on, a
4、nd the vast majority of anthraquinone compounds containing hydroxyl.,. Classification,The anthraquinones in plant can exist in form of liberation or combined with sugar into the form of glycosides. The sugar of anthraquinone glycosides mostly is glucose, in addition to rhamnose, xylose and arabinose
5、.,It refers to the derivatives that have different substituents , -bit. Because the vast majority contain hydroxy, according to the distribution of hydroxy on the backbone of the anthraquinone, hydroxy anthraquinone derivatives can be divided into two categories.,(i) Anthraquinone derivatives,1. Emo
6、din type: Hydroxyl distribute in both sides of the benzene ring, such as rhein, emodin, chrysophanol, rheochrysidin aloe-emodin which are from the rhubarb belong to this category .,Chrysophanol R1=CH3 R2=H Emodin R1=CH3 R2=OH Rheochrysidin R1=CH3 R2=OCH3 Aloe-emodin R1=H R2=CH2OH Rhein R1=H R2=COOH,
7、2. Alizarin type: Hydroxy distribute in the same side of benzene ring, such as the alizarin, purpurin, psedopurpurin and so on .,Alizarin R1=OH R2=H R3=H Purpurin R1=OH R2=H R3=OH Psedopurpurin R1=OH R2=COOH R3=OH,Anthraquinone will be restored to anthranol and its tautomers anthrone in the acidic c
8、onditions. Anthranol, anthrone derivatives generally exist in fresh plants, and these components can be slowly oxidized into anthraquinones.,(ii) Anthranol , anthrone derivatives,For example, in the fresh rhubarb contains anthranol or anthrone, but after storaging for more than two years these compo
9、nents will be no longer tested. Anthranol compounds are also exist in forms of aglycone and glucoside, and the glucoside that have sugar binding the hydroxyl of meso-bit are relatively stable, only after hydrolyzing of sugar to easily oxidized.,(ii) Anthranol , anthrone derivatives,Anthranol-hydroxy
10、lation display strong Sterilization to Penicillium and it can be used as externally applied agent for the treatment of skin disease. For example, chrysarobin can be used for treatment of the scabies (疥疮）.,(ii) Anthranol , anthrone derivatives,Dianthrone derivatives can be seen as combined by two ant
11、hrone compounds. Sennoside A, B, C, D and so on, which are the the main active ingredient of purgation from senna and rhubarb, belong to these type.,Sennoside A,Sennoside B,(iii) Dianthrone derivatives,Sennoside C,Sennoside D,. Chemical properties,1. Acidity Acidity is the important properties for a
12、nthraquinones. The strength regularity of its acidity are as follows: anthraquinones with COOH with more than two -OH with a -OH with more than two -OH with an -OH.,electrophilic conjugative effect,hydrogen bonding,Chemical properties,The solubility of free anthraquinones in the alkaline solution ar
13、e as follows: with COOH or two -OH are soluble in NaHCO3 solution; with a -OH are soluble in Na2CO3 solution with two or more -OH are soluble in 1% NaOH solution with an -OH can only dissolve in 5% NaOH solution. So, we can isolate free anthraquinones base on the nature and amount of OH / COOH Its c
14、alled “pH gradient extraction method”,2. Color reaction,Borntragers reaction After the addition of alkaline solution, the color of the alcohol solution of hydroxy anthraquinone changes from yellow into red - purple. Anthracene, anthrone, the anthraquinone ketones need to be oxidized into anthraquino
15、ne to change color.,(2) React with metal ions Anthraquinone compounds with -hydroxy or o-hydroxy, can form complexes with Pb2+, Mg2+ and other metal ions. The complex form with Mg2+ (usually used magnesium acetate reagents) has a certain color law and can be used for identification.,(2) React with m
16、etal ions If there is only one -OH or -OH or two OH that are not on the same ring structure, the color of the complex is marked orange; if there is a -OH and a nother hydroxy is o-OH , the color is blue to blue-violet; and if another hydroxy is m-OH the color is orange-red to red and p-OH is purple to
