Study On Supercritical CO₂ Fluid Extraction,Antioxidant And Antibacterial Activity Of Essential Oils From Flower Buds Of ’Jiaohong No.1’ Magnolia Wufengensis

Magnolia wufengensis is a rare ornamental tree species unique to China.It has been introduced and planted as an important resource for the development of poverty alleviation industry.However,the current application of M.wufengensis is limited to landscape greening.Carrying out M.wufengensis essential oils extraction process,antioxidant and antibacterial activity research will help to provide technical support and theoretical basis for establishing A feasible extraction process system as well as exploring its potential as an antioxidant and antibacterial agent.So as to expanding its application and thus enhance its economic value.In this study,flower buds of‘Jiaohong No.1’were used as the raw material.Single factor experiment and response surface analysis method were used to optimize the process parameters of essential oils extracted by supercritical CO₂fluid extraction.In addition,qualitative and quantitative analysis of essential oils that extracted from flower buds in shade drying,sun drying,oven 55℃drying and freeze drying was carried out by using gas chromatography-mass spectrometry.At the same time,identified and evaluated the antioxidant and antibacterial activities of four kinds of essential oils from flower buds dried by different methods.The main experimental results were as follows:1.Single factor experiments determined that the appropriate level value of each factor was extraction temperature 45℃,extraction pressure 40 MPa and dynamic extraction time 90 min.On this basis,response surface method was used to optimize the optimal extraction parameters of the essential oils extracted by supercritical CO₂fluid extraction from shade-dried flower buds of M.wufengensis.The optimal extraction parameters were extraction temperature 47℃,extraction pressure 40.7 MPa,and dynamic extraction time 102 min.And the verification value of essential oils’extraction yield was basically consistent with the predicted value.The influence intensity of each factor on the extraction yield was:extraction temperature>dynamic extraction time>extraction pressure,and interaction between each two factors was not significant（P>0.05）.2.Taking the optimal parameters optimized by response surface method as the extraction conditions,the supercritical CO₂fluid extraction yields of essential oils from four dried buds were significantly different（P<0.01）,among which freeze-dried flower buds had the highest essential oils extraction yield（2.736±0.138%）,followed by sun-dried（1.864±0.025%）and oven 55℃dried（1.68±0.007%）,and the essential oils extraction yield of shade-dried flower buds was the lowest（1.217±0.014%）.3.A total of 49 components were identified from four kinds of dried flower buds’essential oils by automated mass spectral deconvolution and identification system combined with retention index.26components were identified from freeze-dried flower buds,among which relative content ofγ-sitosterol（27.84%）and 4H-xanthalongia（27.09%）was the highest.Furthermore,20,20 and 30 species were identified by sun-dried,oven 55℃dried and shade-dried ones respectively,the highest relative content compositions wereγ-sitosterol（32.56%,28.01%,24.39%）and hydrocarbons（37.42%,27.82%,29.73%）.4.Measured by DPPH radical scavenging method,ABTS radical scavenging method and reduction capacity method,the essential oils from four different kinds of dried flower buds all had antioxidant activity,and the strength of antioxidant activity were freeze-dried>shade-dried>sun-dried>oven 55℃dried,freeze-dried buds has the potential to be antioxidant agent.5.Measured by filter paper diffusion method and microbroth dilution method,the essential oils from four different kinds of dried flower buds all had broad-spectrum antibacterial properties,and the strongest inhibitory effect was on Staphylococcus aureus.Furthermore,There were no significant correlations between bacterial species,whether Gram-positive bacteria or Gram-negative bacteria.And among essential oils extracted from four different kinds of dried flower buds,freeze-dried one had the strongest antibacterial activity,freeze-dried buds has the potential to be antibacterial agent,especially anti Staphylococcus aureus.