Establishment Of A Self-microemulsifying Drug Delivery System Of Propolis Ethanol Extract And Evaluation Its Antibacterial Activity

Propolis,a natural product which has a broad spectrum of antibacterial properties is rich in flavonoids,terpenes,organic acids,alcohols,aromatic aldehydes,fatty acids,and other compounds.Most of the propolis'effective substances are a fat-soluble substance with very low solubility rate in water.Self-microemulsifying drug delivery system?SMEDDS?is often used as a fat-soluble drug carrier further improves the solubility of the fat-soluble drugs in water.It does increases drug absorption and metabolism pathways,improves drug bioavailability,and stability,as well as other notable advantages.This study investigates the effects of traditional extraction method and ultrasonic-assisted method on the extraction efficiency of effective substances in propolis.For the traditional extraction method,these are the optimum conditions:extraction time 6h,ethanol concentration 95%?v/v?,solid-liquid ratio 1:25?w/v?and the extraction temperature 30°C.The orthogonal test results shows that the best single factor combination is A₃B₂C₃D₁,at optimum conditions when ethanol concentration is95%,solid-liquid ratio of 1:30,extraction temperature of 40°C,and for 4h extraction time.The experimental results show that under these conditions,the extraction rate of flavonoids reachesd 98.68%.For the ultrasonic-assisted method,these are the optimum conditions:ultrasonic power 300 W,ethanol concentration 75%?v/v?,and solid-liquid ratio 1:20?w/v?.The extraction time range for the experiment has little effect on the entire extraction.The orthogonal test result shows that the best single factor combination is A₃B₃C₂D₂,at optimum conditions when ethanol concentration is 85%,solid-liquid ratio which is1:24,ultrasonic power at 300 W,and 5 min as the ultrasonic time.It was verified by experiments that the extraction rate of flavonoids reached 8.12%under these conditions.Propolis ethanol extract self-microemulsifying delivery system?PEE-SMEDDS?was established by solubility test,ternary phase diagram and pseudo-ternary phase diagram methods.The experimental results show that the best formula combinations of SMEDDS are:corn oil,Tween 80,and isoamyl alcohol.The optimal formulation ratio is oil phase:mixed surfactant?Tween 80:isoamyl alcohol=9:1?=14:86,the amount of propolis ethanol extract is 15.0g/100gSMEDDS;the stability of Propolis ethanol extract was established for a period of three months period.The PEM-SMEDDS obtained in the experiment showed no change in the self-microemulsifying time,drug loading and average particle diameters within the three months.The appearance of the PEE-SMEDDS was brownish black.The solution was uniform,and no drug precipitation or liquid separation was found,indicating that the prepared propolis alcohol extract SMEDDS was stable.The antibacterial activity of PEE-SMEDDS and PEE-ethanol solution on test bacteria?Escherichia coli,Pseudomonas,Bacillus subtilis,Staphylococcus aureus,Geotrichum candidum,and Pichia pastoris?was determined by the inhibition zone method.The experimental results showed that the antibacterial effect of propolis ethanol extract on fungi was significantly greater than that of bacteria.The inhibition zone of Geotrichum candidum and Pichia pastoris reached 31.99 mm and 43.02 mm respectively.The PEE-SMEDDS exhibited a strong antibacterial activity.The inhibition zone diameters of bacteria;Geotrichum candidum and Pichia pastoris was20.24 mm and 22.02 mm respectively.In addition,the antibacterial activity of PEE-SMEDDS on the test bacteria was significantly lower than that of the propolis extract ethanol solution.Obviously,propolis ethanol extract may be encapsulated in the SMEDDS,and the probability of contact with the enzyme or cell wall becomes smaller,limiting the bacteriostatic efficacy of the propolis ethanol extract.