Study On The Combined Antibacterial Activity Of Essential Oils From Origanum Vulgare L. And Houttuynia Cordata T.

With the continuous improvement of safety awareness,people's demand for safe and efficient natural bacteriostatic substances is getting higher and higher.Essential oil has attracted more and more attention because of its good bacteriostatic activity and safety,and it is a natural antimicrobial substance with broad application prospects.In this study,Origanum vulgare L.and Houttuynia cordata T.(OVEO and HCEO)were extracted by steam distillation.Identification of main components of OVEO and HCEO by GC-MS.The antimicrobial activity of OVEO and HCEO were studied by using Staphylococcus aureus,Klebsiella pneumoniae,Escherichia coli,Salmonella enteritidis and Salmonella paratyphoid?as experimental strains.Then the combined antimicrobial concentration of OVEO and HCEO were determined by chessboard method.The bacteriostatic mechanism of OVEO and HCEO were investigated.The results are as follows:1.The main components in OVEO are thymol(24.73%),?-cymene(23.56%)and 4-isopropylbenzoic acid(12.06%),etc.;The main components in HCEO are 4-terpenol(15.65%),methyl n-nonone(13.38%)and 1,1-dimethoxy decane(11.69%),etc.;2.The minimum inhibitory concentration of O.vulgare L.essential oil to S.aureus is0.625?L/m L,MIC are 1.25?L/m L to K.pneumoniae,E.coli,S.enteritidis and S.paratyphoid?,and the minimum inhibitory concentration of H.cordata T.essential oil to five kinds of experimental strains are 5?L/m L.When OVEO and HCEO are used together,the mixture of OVEO and HCEO with 0.313?L/m L and 0.313?L/m L respectively can inhibit S.aureus,which is the minimum inhibitory concentration(MIC_combination)when they are combined.The MIC_combination of OVEO and HCEO are 0.625?L/m L and 0.313?L/m L for the other four experimental strains,and the fractional inhibitory concentration indices for the five strains were 0.563,showing partial synergistic effect.3.It was observed by scanning electron microscopy that after the combination of OVEO and HCEO,five kinds of bacterial cells were sunken and broken,some of them were completely broken and agglomerated,and the cell morphology was destroyed.The essential oil compounded with OVEO and HCEO can lead to the leakage of alkaline phosphatase between the cell membrane and cell wall of five kinds of strains,which indicates that the essential oil destroys the cell wall of the test strains.The essential oil compounded with OVEO and HCEO lead to the leakage of nucleic acids,active proteins and potassium ions in the cell of bacterias,which indicates that the essential oil can cause the change of the permeability and integrity of the bacterial membrane.With the increase of the concentration of the essential oil,the membrane potential and the activity of succinate dehydrogenase decreased,indicating that the complex essential oils had an effect on the respiration of five experimental strains.4.The area of bacterial biofilms formed by bacterias were significantly reduced after treat with the combination of OVEO and HCEO.The results showed that the combination of OVEO and HCEO had inhibitory effects on the five bacterial biofilms.Crystal violet staining test also confirmed that the compound essential oils had an inhibitory effect on the formation of bacterial biofilm and could remove mature biofilm.