Antibacterial And Antioxidant Activities Of The Formulating Essential Oil From Freesia Hybrida Red River^? Flowers

According to the statistics,the number of patients worldwide who die from microbial infections is about 16 million each year,accounting for about one-third of the total number of deaths.In the past few years,the problem of microbial resistance caused by the abuse of antibiotics has become more and more serious.Since 1987,None new types of antibiotics have been found for over 30 years.Researchers are beginning to look for natural products with bactericidal activity,and plant essential oils are gaining more and more attentions as emerging natural antibacterial and therapeutic drugs.Bacterial resistance to antibiotics is due to the fact that the composition of antibiotics is relatively simple,while the chemical components contained in single essential oils range from 10 to more than 400,making it difficult for bacteria to develop drug resistance.In this study,Freesia hybrida was used as the research object to study the antibacterial activity of plant flower essential oil.It is a kind of bulbous herb from Iridaceae,which was introduced to Europe from South Africa in the late 18th century.Freesia hybrida has many varieties,rich floral flavor and high single yield.It is a good material for extracting essential oils thus.However,the research on the preparation and efficacy of essential oils of Freesia hybrida plants has rarely been reported.Therefore,the studying of the antibacterial and antioxidative effects of the essential oil of Freesia hybrida will lay foundations for the further application and development of essential oil.Due to the high price of natural plant essential oils,the laboratories usually use formulating essential oils to study their health-promoting effects.In this study,the essential oil of Freesia hybrida was extracted by steam distillation and organic solvent co-extraction methods,GC-MS（gas chromatography-mass spectrometry）was used to determine the volatile oil composition and content of essential oils.The antibacterial activity of the essential oil agansist bacteria（Escherichia coli,Bacillus subtilis,Staphylococcus aureus,Staphylococcus epidermidis）and fungi（Canidia albican,Saccharomyces cerevisiae,Sporothrix schenckii,Trichophyton rubrum）was analyzed by antibacterial and antibacterial susceptibility test.The minimum inhibitory concentration（MIC）of the essential oil was determined by the constant broth dilution method,the minimum bactericidal concentration（MBC）of the essential oil was determined through plate coating.The stability of the essential oil（acid-base,temperature and ultraviolet）was explored by means of diffusion on a filter paper agar plate.In addition,the oxidation resistance of the essential oil was analyzed by DPPH method.Scanning electron microscopy was used to observe the morphology variations of the bacteria after treatment with the essential oil,and the contents of the cells were measured by the full-wavelength microplate reader.The results showed that:1.57 were identified from 59 components which were detected in the essential oil extracted from Red River^?,and the identified components accounted for 97.78%of the total peak area of the volatiles,The main chemical components were linalool,terpineol,geraniol,etc,which have been reported to have antibacterial properties,and thus Freesia essential oil is a good material for studying the antibacterial action of plant essential oils.2.By measuring the diameter of the inhibition zone,it was found that the formulated essential oil according to Freesia hybrida had antibacterial effect on the eight tested microorganisms（Escherichia coli,Bacillus subtilis,Staphylococcus aureus,Staphylococcus epidermidis,Canidia albican,Saccharomyces cerevisiae,Sporothrix schenckii,Trichophyton rubrum）.Among them,the antibacterial effect of fungi was better than that of bacteria.In general,the formulated essential oil had a certain broad-spectrum bactericidal effect and the potential as a new fungicide.3.The minimum inhibitory concentration（MIC）of the formulated essential oil against Escherichia coli,Bacillus subtilis,Staphylococcus aureus,Staphylococcus epidermidis,Canidia albican,Saccharomyces cerevisiae,Sporothrix schenckii,Trichophyton rubrum was 0.25%,0.10%,0.125%,0.125%,0.10%,0.10%,0.10%,0.025%,respectively.The minimum bactericidal concentration（MBC）was 0.40%for Staphylococcus epidermidis;0.25%for Bacillus subtilis,Candida albicans and Saccharomyces cerevisiae;0.125%for Sporothrix schenckii;0.05%for Trichophyton rubrum.In contrast,a concentration of 0.4%formulated essential oil resulted in relatively less clones of Escherichia coli and Staphylococcus aureus.4.The absorbance of the cell extracts indicated that the preparation of the formulated essential oil could increase the permeability of the cell membrane,causing the membrane structure of the cell to be destroyed,and the cell was eluted and discharged.Scanning electron microscopy showed that the cell membrane was shrunken and inwardly depressed,the treatment of essential oil might destroy the cell surface.At the same time,some of the cell contents were leaked out,causing multiple cells to gather together,indicating that the cell structure was significantly damaged.5.The stability of bacteriostatic effect showed that the formulated essential oil according to Freesia hybrida had UV stability and thermal stability,but its antibacterial effect could be influenced by external acid and alkali.6.DPPH free radical scavenging ability indicated that Freesia formulated essential oils could be used as a chronic antioxidant.The scavenging ability of free radicals gradually increased with the increase of the amount of essential oils added to the perfume.