Extraction Of Essential Oils From Different Spices And Their Insecticidal And Antimicrobial Activities

Plant essential oils are natural products obtained from aromatic plants.In this study,the essential oils from seven different spices were extracted by ultrasonic steam distillation.The main chemical components were identified and analyzed.Meanwhile,the insecticidal activity of the rice weevil,Sitophilus oryzae was determined and the mechanism of fumigant toxicity of plant essential oils on Sitophilus oryzae was preliminarily discussed.The antimicrobial activity of plant essential oils on four food borne pathogens and three food spoilage fungi were compared,which provided a basis for the application of plant essential oils in bacteriostatic,antiseptic and insecticidal applications.(1)Optimization of ultrasonic assisted steam distillation for extraction of clove essential oil by single factor and response surface.The optimum extraction conditions used were as follow: the crushing particle size of 40 mesh,the liquid-to-feed ratio of 7.27 mg/L,the ultrasonic time of 21 min and the extraction time of 3.4 h.Under this condition,the extraction rate of clove oil was12.62% and the extraction rate of cinnamon,anise,peppermint,lemongrass,pepper and camphor were 3.82%,6.17%,2.35%,2.09%,6.93%,2.84%,respectively.At the same time,the main components of seven essential oils of clove,cinnamon,anise,peppermint,citronella,pepper and camphor were identified by GC-MS analysis.The main components of the essential oils were found to be terpenes and phenols,and the composition and content of different essential oils differs significantly.(2)Insecticidal activity and mechanism of seven essential oils against Sitophilus oryzae.In this study,the repellent,contact,and fumigation activities against Sitophilus oryzae of seven essential oils were evaluated.The results showed that at the same concentration,camphor essential oil showed the highest repellent effect and clove essential oil had the strongest contact effect,while clove and cinnamon oils had the highest fumigation mortality rate,followed by anise essential oil;The three preferred essential oils of clove,cinnamon and aniseed showed dose and time dependence on the fumigant toxicity,among which clove oil had the strongest fumigant toxicity,and the LC50 of the 24 h and 48 h was 3.308 and 2.192 ?L/L air,respectively.The fumigation toxicity test of the two main components of the three preferred essential oils showed that eugenol was a more effective component for clove oil,and the LC50 value of the 24 h treatment was 2.907 ?L/L air.The main compounds of cinnamon oil,cinnamaldehyde and methyl salicylate,showed obvious fumigant toxicity.In anise oil,the fumigant toxicity of estragole(LC50 of 5.421 ?L/L air)is stronger than the main component of the anethole(LC50 of 8.230 ?L/L air).It was found that treated with different dosage and time,the carboxylesterase and P450 enzyme activities in Sitophilus oryzae were inhibited,while the GST activity of Sitophilus oryzae was induced.The results of PCR showed that fumigation of clove essential oil resulted in the increase of at least 13 GST genes and 5 P450 genes expression in Sitophilus oryzae,and the increased GST and P450 genes were mainly from GST epsilon and CYP6 families,while most esterase genes expression levels decreased after fumigation,indicating that these enzymes may play an important role in hydrolyzing secondary metabolites of plant essential oils.(3)The antimicrobial activity of seven essential oils.Four bacteria strains Escherichia coli,Salmonella typhimurium,Bacillus subtilis and Staphylococcus aureus and three kinds of bread spoilage fungi Aspergillus niger,Aspergillus oryzae and Aspergillus ochraceus were estimated.The results showed that the seven essential oils showed different degrees of antibacterial activity.The MIC range for the three fungi was 0.0625-2 mg/m L,and the MIC range for the four bacteria was 0.125-4mg/m L.Cinnamon essential oil was found to exhibit the strongest antimicrobial effect,showing the largest zone of inhibition zone(DIZ)and the lowest range of MIC values,followed by clove oil.And the seven essential oils can effectively inhibit the growth of bacteria in the lag phase and exponential phase.Cinnamon and clove essential oil can inhibit the mycelial growth and spore germination of three kinds of bread spoilage fungi.The results of in vivo experiments indicated that these two essential oils had a good antiseptic effect during storage of the bread.