第十章天然药物化学实验 12 alcohol solution,05%magnesium acetate methanol solution 4.Experimental procedures 1.Extraction and Isolation of Anthraquinone from Rheum palmatum L. The dried and finely ground plant material (5g)of Rheum palmatum L.is hydrolyzed with 20%H2SO(60 ml)at water bath for 2 hours (operating in 250 ml round bottom flask),hydrolyzed material is obtained after vacuum filtration(washed to neutral with water)and air drying Dried hydrolyzed material is extracted with ethyl ether(25 ml)at room temperature about 2-3 days.The ethyl ether extraction is subjected to separation over a silica gel column and eluted with a petrolum ether-EtOAc gradient solvent system (7:3.-200 ml). Eluents are collected with test tubes,5~7ml per fraction.The fractions are defined by the results of TLC(silica gel,developing solvent:petrolum ether-EtOAc 7:3).Each fraction then is evaporated and obtains pure compounds.Column chromatography operation is as follows: The ethyl ether extraction is adsorbed onto 0.5~1.0 g silica gel (200~300 mesh)in evaporating dish and the solvent is evaporated at water bath,thus obtained sample silica gel.Dry column-packing method:silica gel (30 g.200-300 mesh)is added to the chromatography column,then sample silica gel is packed on the top,some silica gel and absorbent are placed on the top of the sample oprevent washing the sample n mess when adding solvent on the top..●●●●●●●●●●●●● 2.Chemistry detection reactions (1)Borntrager's reaction Sample eluent and1%alizarin alcohol solution each 2 ml are added 2 ml%NaOH at test tube.respectively.shake and then standing.observe color changes. (2)Magnesium acetate test Taking a drop of sample eluent and 1%alizarin alcohol solution are added on the same filter paper strip (3x10 cm),and then 0.5%magnesium acetate methanol solution is sprayed on this strip.observe color changes after heated at 80C about 5min. 5.Ouestions 1.What are the principles of extraction and isolation of anthraquinones from Rheum palmatum L.? 2.Try to write extraction and isolation flow chart of anthraquinone aglycons. 3.What about the Rf values of five anthraquinone aglycons when they are separated by silica gel thin-layer chromatography and developed with petroleum ether:ethyl acetate (7:3).and why?第十章 天然药物化学实验 12 alcohol solution, 0.5% magnesium acetate methanol solution. 4. Experimental procedures 1. Extraction and Isolation of Anthraquinone from Rheum palmatum L. The dried and finely ground plant material (5 g) of Rheum palmatum L. is hydrolyzed with 20% H2SO4 (60 ml) at water bath for 2 hours (operating in 250 ml round bottom flask), hydrolyzed material is obtained after vacuum filtration (washed to neutral with water) and air drying. Dried hydrolyzed material is extracted with ethyl ether (25 ml) at room temperature about 2-3 days. The ethyl ether extraction is subjected to separation over a silica gel column and eluted with a petrolum ether-EtOAc gradient solvent system (7:3, ~200 ml). Eluents are collected with test tubes, 5~7 ml per fraction. The fractions are defined by the results of TLC (silica gel, developing solvent: petrolum ether-EtOAc 7:3). Each fraction then is evaporated and obtains pure compounds. Column chromatography operation is as follows: The ethyl ether extraction is adsorbed onto 0.5~1.0 g silica gel (200~300 mesh) in evaporating dish and the solvent is evaporated at water bath, thus obtained sample silica gel. Dry column-packing method: silica gel (30 g, 200~300 mesh) is added to the chromatography column, then sample silica gel is packed on the top, some silica gel and absorbent cotton are placed on the top of the sample to prevent washing the sample in a mess when adding solvent on the top. 2. Chemistry detection reactions (1) Bornträger’s reaction Sample eluent and 1% alizarin alcohol solution each 2 ml are added 2 ml 1% NaOH at test tube, respectively, shake and then standing, observe color changes. (2) Magnesium acetate test Taking a drop of sample eluent and 1% alizarin alcohol solution are added on the same filter paper strip (3×10 cm), and then 0.5% magnesium acetate methanol solution is sprayed on this strip, observe color changes after heated at 80 about 5 min. ℃ 5. Questions 1. What are the principles of extraction and isolation of anthraquinones from Rheum palmatum L.？ 2. Try to write extraction and isolation flow chart of anthraquinone aglycons. 3. What about the Rf values of five anthraquinone aglycons when they are separated by silica gel thin-layer chromatography and developed with petroleum ether: ethyl acetate (7:3), and why?