Antioxidant Activity,antibacterial Activity And Mechanism Of Action Of The Eugenol And Isoeugenol

In recent years,there have been many studies on the antioxidant and antibacterial of plant extracts,and it has been found that essential oils have good antioxidant and antibacterial activity.However,not only the essential oils iteself are complex,but the interactions among them are not clear.With the mature of extraction technology,and the deep understanding of main components,its antibacterial and antioxidant research has become a hot issue.Eugenol,as the main component of volatile oil clove,was confirmed to have a good effect on antioxidant and antibacterial.But there are few reports on the antioxidant activity and antibacterial activity of eugenol derivatives.In order to mak e full use of eugenol and its derivatives,we explored eugenol and isoeugenol systematically through a series experiments.In this paper,eugenol and isoeugenol were used as the research objects,and the similarities and differences of antioxidant and antibacterial activities were studied.The antibacterial mechanism of isoeugenol was also discussed.The main contents and results are as follows:1)Through the comparison between eugenol and isoeugenol,we studied its ability of free radical scavenging,iron reduction,reducing grease peroxidation,and protection of protein and DNA oxidative damage from eugenol and isoeugenol.The results showed that both eugenol and isoeugenol show strong ability to scavenge free radical(DPPH,ABTS),to reduce iron and to inhibite oxidation of oil.Besides,they also have the protective effect on DNA oxidative damage.But when referring to protein oxidative damage,both eugenol and isoeugenol were show promote oxidation.2)The antimicrobial activity of eugenol and isoeugenol to several pathogens was studied by assay of inhibition zone,MIC and MBC,growth curve drawing and flow cytometry.The results showed that both eugenol and isoeugenol could inhibite 7 pathogens strongly;The assay of MIC and MBC showed that isoeugenol had a stronger inhibitory effect than eugenol.The growth curve showed that eugenol could delay the logarithmic phase at low concentration and inhibit bacterial growth at high concentrations,even leading bacteria death,as well as isoeugenol.The results of flow cytometry indicate that the bacteria mortality of isoeugenol is higher than eugenol,which demonstrated that the bacteriostasis of isoeugenol is more outstanding.3)Escherichia coli and Listeria monocytogenes were used as test materials,and isoeugenol was used as the research material to explore its antibacterial mechanism.The effect of isoeugenol on the cell wall and membrane was studied by the determination of bacterial conductivity,scanning electron microscopy and PI fluorescence staining.The results showed that isoeugenol could destroy the cell wall and membrane,even leading to the change of cell membrane permeability.The effect of isoeugenol on the metabol ism of the cells was observed by DCFH-DA fluorescence staining.The results showed that isoeugenol could induce the increase of intracellular reactive oxygen and accelerate the oxidative damage,which could result in cell death.The effects of isoeugenol o n the protein and nucleic acid in the cells were studied by SDS-PAGE and agarose gel electrophoresis.The results showed that isoeugenol could affect the synthesis of proteins and DNA,but the experiment of gel retardation found that isoeugenol had no dire ct effect on DNA.The effect of isoeugenol on the apoptosis of bacterial cells was detected by AnnexinV method.It was found that isoeugenol had no effect on bacterial cell apoptosis.In conclusion,various studies show that the antibacterial mechanism of isoeugenol is the result of multiple effects.