Study On Antioxidant Activity,Antibacterial Activity And Mechanism Of Sesamol

Food spoilage bacteria is one of the important reasons that cause the change of food sensory properties,the reduction and loss of nutritional value and commodity value,which directly affects food safety and human health.At present,adding preservatives is widely used as a simple and effective means.Compared with chemical preservatives,natural preservatives are favored by more people because of their high safety and less side-effects.Therefore,it is great significance to find effective preservatives from natural resources as a substitute for inhibiting food spoilage.In this paper,sesamol,a natural plant source,was selected as the main research object,and its antioxidant activity,antibacterial activity and mechanism were studied in depth.The purpose is to provide a theoretical basis for developing new natural food preservatives.(1)Study on antioxidant activity of sesamol: the free radical scavenging ability of DPPH and ABTS and the protective effect of site-specific and non-site-specific hydroxyl radical mediated 2-deoxy-D-ribose degradation were measured,the result showed that: for DPPH free radical,IC50 of sesamol was 9.39 μg/m L,which is superior to the IC50 of VE(1.61μg/m L).For ABTS free radical,IC50 of sesamol was 31.19 μg/m L,less than the IC50 of VE(119.42 μg/m L).And the protective effect of sesamol on site-specific 2-deoxy-D-ribose degradation by hydroxyl radical was better than the non-site-specific;Through the determination of iron reduction and total reduction ability,the results showed that the reduction ability is very strong;The protection test of oxidative damage of macromolecule DNA and protein showed that sesamol also had obvious protective effect on the Fe2+ and AAPH induced DNA oxidative damage,and sesamol also showed strong protective effect on AAPH induced BSA oxidative damage,but had no protective effect on Cu2+ induced BSA oxidative damage,even promotes its oxidative damage;By determinating the lipidperoxidation capacity,it showed that sesamol had strong ability to inhibit the lipid peroxidation,and at the same concentration(0.02%),the inhibition ability: sesamol>VE>BHT.(2)Study on antibacterial activity of sesamol: the antibacterial ability of 8 kinds of food spoilage bacteria was tested,its results showed that the diameter of their inhibition zone all was more than 20 mm,of which E.coli had the best bacteriostatic ability and the diameter of inhibition zone was 24.7 mm;The MIC and MBC of 8 kinds of food spoilage bacteria were determined,its results showed that the MBC of 8 kinds of bacteria was 2.5 mg/m L,while the MIC for E.coli and P.aeruginosa was 1.25 mg/m L,and the MIC for the other 6 kinds of bacteria was 2.5 mg/m L;The effects of sesamol on growth curve and cell death rate of S.aureus and E.coli were studied,and its results showed that sesamol could obviously delayed the arrival of the logarithmic phase and increased the number of death of the bacteria.(3)Study on the antibacterial mechanism of sesamol: the morphology of spoilage bacteria cells was observed by SEM,and it showed that cells appeared deformation,collapse and rupture,indicating that sesamol could destroy cell structure and make it unable to maintain normal morphology;The relative conductivity,protein content in the supernatant of food spoilage bacteria and bacterial lethal rate were tested,and they showed that after the treatment with sesamol(2MIC),the relative electrical conductivity of S.aureus and E.coli increased by 56.29%,39.16% respectively,protein content increased by 22.14 μg/m L and22.44 μg/m L respectively,the number of dead cells also increased significantly,these results show that sesamol may cause membrane damage,changes of membrane permeability;The division cycle of bacterial cells were detected by flow cytometry,which showed that sesamol may have effect on the replication of DNA preparation period,and make the cell can not get into the DNA replication period,this phenomenon is also very good explanation sesamol can delay the logarithmic growth period of bacteria;Further analyzed the factors that influence cell division and cell growth by gel electrophoresis assay,it showed that sesamol had no direct effect on DNA,but it probably influenced the synthesis of bacterial protein;The amount of ROS produced in E.coli was detected by DCFH-DA fluorescence staining,which showed that the intracellular ROS content increased after the treatment of sesamol,indicatingthat sesamol could accelerate the oxidative damage by causing ROS accumulation in E.coli,resulting in the death of bacteria.In conclusion,sesamol,a natural substance in sesame oil,not only has strong antioxidant activity,but also has strong antibacterial activity on food spoilage bacteria.The versatility,non-toxicity and stability of sesamol determines its profound potential for development.This paper provide a solid theoretical foundation for its development and utilization as a new natural food preservatives.