Study On Extraction, Separation And Purification Technology Of Coumarin From Melilotus

Melilotus (sweet clover) has been used as forage and green manure for a long history, but its development of medicinal value has not been concerned untill foreign products show good therapeutic effects and a broad market prospect. It provides references for developing Melilotus into a kind of domestic pharmaceutical product. The subject used Melilotus which was rich in China as raw materials and a variety of separation and purification technologies as means to determine a safe, economical and effective extraction, separation and purification process of coumarin from sweet clover.Firstly, using the ultrasonic extraction and high performance liquid chromatography to analysis coumarin content in Melilotus was studied. This method was stable, fast and accurate, and it could be used for determination the coumarin content in raw sweet clover, as well as the future production control and product quality control. By measuring the coumarin content in yellow sweet clover at different stages of flowering period, the paper identified the best time to harvest sweet clover which was rich in coumarin was the full flowering period.Secondly, the process of solvent extraction coumarin from sweet clover was studied. Using the single factor exploration and orthogonal design as the method, and using the extraction rate of coumarin, yield of dry extract and coumarin content in dry extract as index, the optimal extraction process was determined as following:extracting 2 times with 1:14 solid-liquid ratio and 50% ethanol solution at 30℃for 30 min each time. After this process, the extraction rate of coumarin was 1.090%.Thirdly, the purification process of coumarin from sweet clover extracts was studied. Using the retention rate of coumarin and the coumarin content in products as index, coumarin was purification by using two-phase solvent extraction, macroporous adsorption resin combined with crystallization. The optimal two-phase solvent extraction process was as follows:extracting the 0.2 mg/mL concentrated solution adding 10% NaCl with 1/3 times amount of ethyl acetate for 3 times. The optimal macroporous adsorption resin combined with crystallization process was as follows:using 3.0 BV/h flow rate and 3.0 mg/mL sample solution to passthrough HPD300 resin screened out, and using 5.0 BV 50% ethanol solution to elute, concentrating and low-temperature crystallization of eluate. After this process, the coumarin purity of the samples increased to 97%, and recovery of coumarin was more than 85%.Lastly, the thermodynamics and kinetics of purification of coumarin from Melilotus with HPD300 resin were studied. Using the thermodynamic models, dynamic models to analysis the experimental datas, the results showed that the process of adsorption was fitted well with Langmuir equation, pseudo-second kinetic equation and intra-particle diffusion model. The process was a spontaneous, exothermic physical adsorption process and the rate of adsorption process was under the control of intra-particle diffusion.