| Carvacrol is the main component of oregano oil,thyme oil and other plant essential oils.It has broad-spectrum antibacterial activity and natural safety,but its hydrophobicity,high volatility and instability seriously limit its application.Therefore,it is necessary to find a suitable drug delivery system to load carvacrol to improve its hydrophobicity,stability and antibacterial activity.In this paper,carvacrol was used as the research object,and carvacrol was embedded in three preparations of nanoemulsion,film and gel as carriers,aiming to comprehensively evaluate the stability,antibacterial activity,antioxidant activity and cell safety of three carvacrol preparations.The main results are as follows:(1)The carvacrol nanoemulsion prepared by Tween 80 as emulsifier has small mean droplet size,uniform droplet dispersion,good storage stability and centrifugal stability.The content of carvacrol,the content of emulsifier and the shearing time were used as the investigation factors,and the mean droplet size was used as the evaluation index,the optimum formula of carvacrol nanoemulsion was obtained by Box-Behnken response surface method:the content of carvacrol was 5%,the content of emulsifier was 8%,and the shearing time was 7 min.Under this condition,carvacrol nanoemulsion was prepared by high-speed shear of high-pressure homogenizer,and the mean droplet size was 88 nm.The carvacrol nanoemulsion prepared by the optimal formula had good antibacterial activity against S.aureus and E.coli,and its antibacterial effect was better than that of commercial carvacrol aqueous solution and carvacrol.By investigating the bacterial morphology,ROS level,the content of MD A and leakage of bacterial contents,it was found that the bacterial cells treated with carvacrol nanoemulsion shrank,deformed or even ruptured,the ROS level increased sharply,the content of MDA increased,and the leakage of bacterial contents increased significantly.The antioxidant activity of carvacrol nanoemulsion was significantly higher than that of commercial carvacrol aqueous solution and carvacrol.The survival rate of L-02 cells treated with carvacrol nanoemulsion for 24 h was still higher than 80%,indicating that the prepared carvacrol nanoemulsion had good cell safety.(2)The film of carvacrol-SPI was prepared by using soy protein isolate as film-forming material.Through the characterization of the film-forming solution,it was found that SPI can be used as an emulsifier to make the film-forming solution present a stable state.The addition of carvacrol had no significant effect on the content of water in the protein films(p>0.05).As the content of carvacrol increased from 0%to 2.5%,the thickness of the protein films gradually increased,the transparency and brightness gradually decreased,the color of films was yellowish,the TS decreased from 23.90 N/mm to 15.14 N/mm,the EAB increased from 102.72%to 213.25%,the solubility decreased from 54.83%to 43.45%,and the swelling index decreased from 893.88%to 376.47%.The WVP decreased from 0.55 g·mm·h-1·kPa-1·m-2 to 0.34 g·mm·h-1·kPa-1·m-2,and the CA increased from 46.862° to 64.799°.The addition of carvacrol effectively improved the mechanical properties and moisture resistance of the protein films.The carvacrol-SPI films can destroy the integrity of the bacterial cell membrane,resulting in the leakage of macromolecules,increased oxidative stress in the bacteria,and deepened lipid peroxidation,thereby inducing bacterial damage and even death.With the increase of carvacrol content,the DPPH free radical scavenging rate of protein films was also increasing.When the content of carvacrol loaded on the protein films was less than 1.0%,it could promote the growth of L-02 cells.When the content of carvacrol gradually increased,the cell survival rate gradually decreased,but it was still higher than 90%,indicating that carvacrol-SPI films had high biosafety.(3)Carvacrol-KGM-XAN gel was prepared with konjac glucomannan and xanthan gum as matrix.When the mixing ratio of KGM and XAN is 3:7,a stable gel can be formed,and the TS is the largest,Carvacrol-KGM-XAN gel is a kind of thermo-reversible gel.The gel state disappears at higher temperature and forms gel after cooling.With the increase of carvacrol content from 0%to 7.5%,the TS of the gel decreased from 15.64 N/mm to 8.52 N/mm,the EAB increased from 60.23%to 110.58%,the swelling index decreased from 23.55%to 10.89%,and the in vitro degradation rate decreased from 12.19%to 4.54%,while the content of water in the gels did not change significantly(p>0.05).Carvacrol-KGM-XAN gel could effectively inhibit the growth of S.aureus and E.coli,when the content of carvacrol was 7.5%,the gel had the strongest antibacterial activity.With the increase of carvacrol content,the DPPH free radical scavenging rate of the gels gradually increased,when the content of carvacrol was 7.5%,the gel had the highest DPPH free radical scavenging rate,which was 38.76%.The L-02 cells treated with Carvacrol-KGM-XAN gel showed high cell survival rate,indicating that the prepared gel had good cell safety and biocompatibility.In this paper,carvacrol was prepared into three different preparations,and its stability,antibacterial properties,antioxidant properties and cell safety were studied,which provided new ideas for the future application of carvacrol in biomedicine,food packaging and other fields. |
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