Preparation Of Centella Asiatica Total Glycosides Microcapsules And Sustained-release Crea

Titrated extract of centella asiatica（TECA）are extracted from the dry grass of Centella asiatica and are effective components of triterpene saponins,mainly including active components such as madecassoside and asiaticoside.A number of clinical studies and animal experiments have found that TECA has effects of anti-inflammatory,promoting wound healing,preventing scar hyperplasia,and resisting skin aging.It also has effects on the treatments of scleroderma,traumatic burns,surgical trauma,keloids,and pigmentation.Its external preparation in the dermatology clinical application is asiaticoside cream ointment whose half-life is short.3 to 4 times daily is needed for the continuous treatment of 3 to 6 months,and the local pruritus and irritation during use of the drug can occur occasionally,which can seriously affect the patient’s normal work and life.Therefore,it is necessary to prepare sustained-release preparations of TECA in order to delay the release of drugs and prolong the action time,thereby reducing the frequency of drug administration and adverse reactions to improve patient compliance.In recent years,microcapsules have attracted more and more attention in the application of sustained-release preparations of Chinese medicine as a new type of drug-loading preparation.Both the stability and the safety as well as the controlled and sustained-release have been manifested with obvious advantage.Biocompatibility of natural polymer material gelatin was used to encapsulate TECA through the means of pharmaceutical preparations in this topic and its in vitro release and stability were studied.Then it was prepared into a cream,in order to obtain a stable quality asiaticoside sustained release cream.The main research content is as follows:1.Establishment of Analytical Method for TECAQualitative and quantitative analysis methods for thin layer chromatography（TLC）,ultraviolet spectrophotometry（UV）,and high performance liquid chromatography（HPLC）were established for the major components of TECA,madecassoside and asiaticoside.These methods are accurate,reliable and fast,which provide an effective analytical method for the preparation process and quality evaluation of TECA microcapsules and their creams.Among these methods,the TLC can quickly identify the active components of TECA,the determination of TECA content by UV method was 74.29%,the contents of madecassoside and asiaticoside were determined as 55.59%and 16.76%by HPLC,respectively.2.Pre-design study of TECA prescriptionThe physical and chemical properties of TECA were studied,which laid a foundation for the study of the preparation of TECA microcapsules and its cream.The results of the equilibrium solubility measurement showed that both the pH 6.8 phosphate buffer and the 20%ethanol physiological saline can be used as vehicles for the release of TECA in vitro.The investigation of the basic properties of powders revealed that the angle of repose of TECA was at 40.11° and the fluidity was not good.The measurement of bulk density showed that the porosity was 27.33%,which was relatively loose.According to the curve of critical relative humidity,the ambient humidity should be less than 65%during storage and preparation process of TECA.According to the results of the accelerated stability test,the TECA was stable with light and temperature,and the stability was poor under a high humidity environment at 80℃.The interaction between TECA and possible excipients was studied by TLC.The results showed that the combination of TECA and stearic acid,glyceryl monostearate,white vaselin,and glycerol did not change the synergy.3.Preparation of TECA microcapsules and its quality evaluationThe determination methods for the optimization indicators involved in the preparation process of the microcapsules were established,including the encapsulation efficiency,particle size,cross-linking degree,and swelling degree.Gelatin was used as the microcapsule material to prepare TECA microcapsules by single coagulation method.（1）Single factor test determined that the oil phase was light liquid paraffin,emulsifier Span-80 concentration was 0.02g/mL,emulsification time was 10 min,emulsification temperature was 55℃,curing agent was 1%Genipin solution whose amount was 5 mL,curing time was 180 min.Gelatin concentration,core/wall ratio,and stirring speed had a great influence on the encapsulation efficiency and particle size of the microcapsules.（2）Central composite design-response surface method（CCD-RSM）was adopted,and the total evaluation OD of the encapsulation rate（Y1）and the particle size（Y2）was used as an evaluation index,and the gelatin concentration（X₁）,the core/wall ratio（X₂）,and the stirring speed（X₃）were used as independent variable to optimize process,which yields the quadratic polynomial fitting regression equation:OD=0.5903-0.0997X₁-0.0787X₂+0.11 75X₃+0.0053X₁X₂+0.0026X₁X₃+0.0009X₂X₃+0.0441X₁2-0.0103X₂2-0.1147X₃2,and it determined the optimum process conditions are:the gelatin concentration was 7.03%,the core/wall ratio was 0.18,and the stirring speed was 656.59 r·min^-1.The optimal process was verified through tests.The average encapsulation efficiency of the three batches of TECA microcapsules was 72.6%,the average particle size was 30 μm.They were evenly distributed and the morphology was plump.（3）The in vitro drug release characteristics were investigated.It could be observed from the cumulative drug release curve that TECA had good sustained-release properties after microencapsulation.The accelerated stability test confirmed that the obtained TECA microcapsules have reduced hygroscopicity and improved stability.4.Preparation of TECA microcapsule cream and in vitro drug releaseThe cream was prepared from TECA microcapsules.The O/W formulation matrix was used.The appearance color,paste viscosity and spreadability were used as evaluation indicators.The optimal preparation process was determined by orthogonal test:Prescription matrix ratio was 5g of stearic acid,7.5g of light liquid paraffin and 6.75g of glycerol,emulsifier ratio was 2.5g of glyceryl monostearate,0.08g of sodium lauryl sulfate,the stirring speed was 600 r·min^-1,Through preliminary quality evaluation,the in vitro drug release of TECA microcapsules cream was observed and showed a significant sustained release effect.