| As a widely used tropinoid alkaloid,scopolamine possesses many biological activities.At present,it is mainly extracted from Flos Daturae.Due to the unstable properties of scopolamine,it is often transformed into scopolamine hydrobromide by freezing crystallization in production,which is beneficial to the separation and purification as well as the protection of its optical activity.However,several problems have not been resolved during the freeze crystallization process,such as long crystallization time and low yield.Therefore,the development of a rapid,efficient and new-style crystallization method is of great significance for the production of scopolamine.In this study,with scopolamine as the research object,the specific influence of electromagnetic field on its crystallization process was investigated,the mechanism of electromagnetic induced crystallization was discussed,the quality of crystals obtained under electromagnetic field was evaluated,and the electromagnetic induced crystallization process was optimized.The research results are described as follows:(1)The magnetic field has a beneficial effect on the crystallization of scopolamine:With the parameters of crystallization induction time,crystal growth rate,crystal purity and recovery rate as indicators,the effects of magnetic field on the crystallization process of scopolamine were investigated from three aspects,namely,the direction of magnetic field,the strength of magnetic field and the crystallization solvent.It was found that magnetic field can shorten the induction time,increase the growth rate,purity and recovery of crystal.(2)The hydrogen bond between scopolamine and the solvent was broken by the magnetic field:Quantum chemistry was used to simulate the lowest energy conformation of scopolamine and different solvents,and to calculate the most stable form when scopolamine and solvents combine in different proportions.Then,magnetic field was used to investigate the physical properties of the solution,and it was found that magnetic field could increase the absorbance,decrease the surface tension,decrease the solubility and decrease the viscosity and density of the solution.It was speculated that magnetic field breaks the intermolecular hydrogen bond and reduces the intermolecular interaction between solute and solvent,as well as solvent and solvent.Thus,the physical properties of the solution were changed,accelerating the formation of nucleation and the growth of crystal.(3)The quality of scopolamine hydrobromide crystal was improved by magnetic field:The quality of scopolamine hydrobromide crystal was evaluated by using modern analytical instruments.Firstly,the infrared spectrogram indicated that the chemical structure of scopolamine hydrobromide did not change under the magnetic field.Secondly,the DSC thermal analyzer was used to explain the decrease of crystal melting process,increase of melting point and melting enthalpy,which indicated that the crystal arrangement was more regular and compact under the magnetic field.Scanning electron microscopy showed that the magnetic field has a "compression effect" on the crystal.The polarimeter indicated that the crystal has a higher optical rotation under magnetic field.(4)The optimal crystallization process of scopolamine induced by electromagnetic was obtained:The process of electromagnetic induced crystallization was optimized.On the basis of investigating the influence of solvent type,solution concentration,temperature,addition amount of hydrobromic acid,magnetic field strength and magnetization time on the crystallization process,the temperature,concentration and amount of hydrobromic acid were selected as factors with the purity and recovery as indexes,and then three factors three levels of response surface experiments were performed.Under the optimum process conditions including the concentration of 98 mg/mL,adding amount of 1:1.1 hydrobromide,temperature of 15?,the crystal purity and recovery of scopolamine hydrobromide was 99.22% and 84.14%,respectively. |
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