Extraction Purification And Antimicrobial Activity Of Phytosterol From Corn Silk

Corn silk is one of traditional Chinese herbs, which contains a variety ofbiologically active ingredients, such as saponin, flavonoids, polysaccharide, vitamin C,phytosterols, amino acids and vitamin E etal. And it has a certain pharmacologicalactivities and diet therapy efficacy. Phytosterol is a kind of compounds with similarcyclic alcohol structure and has obvious hypolipidemic, antioxidant, anti-inflamatoryand anti-cancer functions. To improve the corn silk sterol yield and explore itsantimicrobial activity, extraction purification and antimicrobial activity werediscussed.To improve corn silk sterol yield, Ultrasonic and microwave assisted extractionprocess for corn silk sterol was optimized by response surface method, and establishcorresponding regression model. Based on single factor tests, effects of ultrasonictime, ultrasonic power, solid-liquid rate and microwave time on yield of corn silksterol. By Box-behnken experimental design, the optimum extraction parameters wereas follows: ultrasonic time of55min, ultrasonic power of200W, solid-liquid ratio of1:40g/mL and microwave time of16min respectively. Under these conditions,phytosterol extraction rate of0.76%was obtained. In order of most significance, itgoes solid-liquid ratio, ultrasonic time, microwave time and ultrasonic power.Through five verification tests, extraction yield of corn silk sterol was0.76%, whichis consistent with predicted value basically.The combination of ultrasonic and microwave assisted extraction was better thansingle ultrasonic assisted extraction and microwave assisted one by comparison ofdifferent extraction methods.To remove the impurites, macroporous resin was used to purification process ofcorn silk sterol. Among five types of resins of S-8, D101, AB-8, D3520and NKA-9,adsorption and desorption rates of AB-8were highest and it is suitable for purification.The purification process parameters of corn silk sterol with macroporous resintechnique were as follows: macroporous resin type of AB-8, macroporous resin massof2.50g (sample volume of30mL), sample concentration of0.20mg/mL, desorptionliquid ratio of1:5(95%ethanol:chloroform) through four-factor three-level orthogonalexperiment design. Under these conditions, corn silk sterol yield reached86.32%.Corn silk sterol extract before and after purification were qualitatively analysizedby thin layer chromatography. The results showed that corn silk sterol extract beforeand after purification contained phytosterol compounds and mainly was β-sitosterol.And mixture of petroleum ether and diethyl ether was better than other solvent asdeveloping solvent. Retardation factor (Rf) value of the components of corn silk sterolextract were between0.40and0.80. Corn silk sterol extract contained campesterol,stigmasterol and sitosterol by combination Gas chromatography and mass spectrometry (GS-MS) analysis.Inhibition effects of corn silk sterol extract on bacteria and molds wereinvestigated by filtering paper method. The results showed that corn silk sterolcertainly inhibited the tested bacteria and molds, and more stronger inhibition effectsagainst Staphylococcus aureus, Shigella, Mucor and Penicillium. Among them, thestrongest inhibition effects against Staphylococcus aureus and Mnimal inhibitioncontent (MIC) of corn silk sterol extract was1.5mg/mL.In order to explore the inhibition mechanism, effects of corn silk sterol onmicrobial cell membrane permeability, protein content and ability of using reducingsugar were investigated by detection of electrical conductivity value, coomassiebrilliant blue method, and color-developing method of3,5-dinitrosalicylic acid (DNS)in microbial suspension added phytosterol. The results showed that microbialelectrolyte appeared leakage, permeability of microbial cell membrane changed,microbial protein content decreased and protein synthesis velocity was restrained,consumption velocity of reducing sugar slowed down and the ability of usingreducing sugar decreased when corn silk sterol was added into microbial suspension.Corn silk sterol reduced nitrite content in vitro test and possesed a certainscavenging action to nitrite compounds. When corn silk content was2.0mg/mL, thescavenging rate reached78%.