The Study Of In Vitro Antibacterial And Antioxidant Activities Of Plant Essential Oils From Labiatae

With the proposal of the concept of"no antibiotic"in feed and the requirement of the Ministry of agriculture that antibiotics should not be added to feed in 2020,the era of using antibiotics as feed additives has become a thing of the past.Therefore,the search for a new green and healthy alternative to feed additives has attracted more and more researchers’attention.In this study,10 essential oils of Labiatae plants were extracted by steam distillation,and its main chemical components were analyzed.At the same time,and their antioxidant activities and the bacteriostatic effect and stability against feed spoilage bacteria were studied.The results are as follows:1.DPPH（1,1-diphenyl-2-trinitrophenylhydrazine）scavenging experiment and FRAP method were used to determine the antioxidant activity of 10 plant essential oils.The results showed that the scavenging rate of essential oils to DPPH·was significantly related to the concentration of essential oils.The ability to scavenging DPPH·of essential oil of Ocimum basilicumLinn.was optimal,its IC₅₀<1μg/mL and its FRAP was most maximum.The IC₅₀of essential oil of Mosla chinensis Maxim.、Thymus mongolicus Ronn.and Origanum vulgare Linn.is also significantly lower than other essential oils and has higher FRAP value,indicating that it has strong antioxidant capacity.The total antioxidant capacity and free radical scavenging capacity of ten plant essential oils were consistent.2.The main chemical components of 10 plant essential oils were analyzed by GC-MS（gas chromatography-mass spectrometry）,and the categories of chemical components were briefly counted.The chemical components of 10 plant essential oils are mainly composed of small molecules of terpenes,phenols,aldehydes and ketones,and contain a small amount of alcohols and their oxides.For example,thymol and p-cymene are the main components of the essential oil of Mosla chinensis Maxim.and Thymus mongolicus Ronn..In addition,the carvacrol are also major in essential oil of Mosla chinensis Maxim.,and the essential oil of Thymus mongolicus Ronn.contains more p-cymene,too.The main components of essential oil of Thymus mongolicus Ronn.are thymol,p-Cymene andγ-terpinene;the main chemical components of essential oil of Ocimum basilicumLinn.are linalool,trans-α-bergamotene,eugenol and so on.All 10 plants belong to Labiatae,and their chemical compositions are similar,which also reflects the consistency of their basic sources.3.The antimicrobial activities of ten essential oils were determined by filter paper method and broth dilution method.The results showed that the essential oil of Mosla chinensis Maxim.、Thymus mongolicus Ronn.and Origanum vulgare Linn.had a good inhibitory effect on Staphylococcus aureus,Escherichia coli,Bacillus subtilis and Salmonella enteritidis.The minimum inhibitory concentration（MIC）was 1μL/mL～2μL/mL,and the minimum bactericidal concentration（MBC）was 2μL/mL～4μL/mL,and also had a certain inhibitory effect on Aspergillus niger.Perilla essential oil has the best inhibitory effect on Aspergillus niger,but the inhibitory effect on four tested bacteria is not ideal.In this study,essential oil of Mosla chinensis Maxim.and Perilla frutescens（Linn.）Britt.were compounded in a ratio of 1:1,and it was found that their inhibitory effect on Aspergillus niger was enhanced,while the inhibitory effect on four tested bacteria was still obvious.It can be said that this compound essential oil showed"1+1>2"in antibacterial effect.4.The bacteriostatic stability of essential oil was discussed by different temperature,pH and UV irradiation time.The results showed that ten kinds of essential oils had different temperature range（50℃～90℃）,different pH（pH=6～pH=8）and different UV irradiation time（10 min～30 min）.The results showed that the bacteriostatic effect of ten essential oils was stable under different temperature,pH and UV time.In this study,the chemical components of 10 kinds of plant essential oils were comprehensively analyzed,and their antibacterial and antioxidant effects were compared.It was found that the 1:1 combination of essential oil of Mosla chinensis Maxim.and Perilla frutescens（Linn.）Britt.was superior to other plant essential oils in all aspects,and had great development potential,which could provide reference value for the application of essential oils in feed additives in the future.