Antibacterial activity and membrane-disruptive mechanism of 3-p-trans-coumaroyl-2-hydroxyquinic acid, a novel phenolic compound from pine needles of Cedrus deodara, against Staphylococcus aureus
Background and aims: Food-borne diseases, provoked by food pathogens, are important causes of morbidity and mortality worldwide.It is still necessary to search for more efficient antimicrobials to prevent the growth of pathogenic and spoilage microorganisms in food.Natural phenolic products are primary sources of antimicrobial agents as safer food preservative.Recently, we have reported that a novel phenolic compound, 3-p-trans-coumaroyl-2-hydroxyquinic acid (CHQA), isolated from Cedrus deodara, exhibits a potent antioxidant activity, whereas its antibacterial activity has not been reported yet.The present study was aimed to evaluate the antibacterial activity of CHQA against several food-borne pathogens, and elucidate its mechanism of action against Staphylococcus aureusby determining the effects of CHQA on membrane potential, membrane integrity,membrane fluidity, membrane protein as well as cell morphology.Methods: The minimum inhibitory concentrations (MICs) of CHQA against eleven food-borne pathogenswere determined by broth microdilution method to evaluate its antibacterial activity.The effect of CHQA on the membrane potential of S.aureus was assessed by measuring the fluorescence intensity of the membrane potential-sensitive fluorescent probe bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC4(3)).Flow cytometric analysis coupled with LIVE/DEAD BacLight bacterial viability kit was performed to investigate the effect of CHQA on the membrane integrity of S.aureus cells.Meanwhile, the alterations in membrane fluidity of S.aureus cells after CHQA treatment were evaluated by measuring the fluorescence polarization values of 1,6-diphenyl-l,3,5-hexatriene (DPH).The interaction of CHQA with the membrane protein of S.aureus cells was investigated by determining the effect of CHQA on the fluorescence spectra of the Phe residues of membrane protein.Moreover, the morphology and intracellular alterations in S.aureus cells under CHQA treatment were directly observed with transmission electron microscope.Results: The results from MIC determinations showed that CHQA exhibited moderate and consistent inhibitory effects against both Gram-negative and Gram-positive bacteria with the MIC values ranging from 2.5-10 mg/mL.Membrane potential measurements revealed that CHQA caused a significant hyperpolarization of S.aureus cytoplasmic membrane in a dose-dependent manner.Flow cytometric analysis further demonstrated that CHQA exposure induced damages on cell membrane of S.aureus by a loss of membrane integrity.Additionally, CHQA caused a significant increase in membrane fluidity, suggesting that CHQA probably acts on the cell membrane by interactions with membrane lipid.The Fluorescence experiments indicated that CHQA could quench the fluorescence of Phe residues of membrane proteins, thus indicating that CHQAchanged the conformation and structure of S.aureus cell membrane protein.Transmission electron microscopic observations confirmed that CHQA disrupted the cell membrane of S.aureus and caused severe morphological changes, which even led to leakage of intracellular constituents.Conclusions: The antibacterial activity of CHQA against S.aureus was achieved by damaging the cytoplasmic membrane with a significant membrane hyperpolarization, a loss of membrane integrity as well as severe morphological change.Furthermore, the membrane-disruptive action of CHQA could be partially attributed to the interaction of CHQA with membrane components, such as membrane lipid and membrane protein.These findings indicated that CHQA could have potential to serve as a natural antibacterial agent to control and prevent the growth of pathogens in food and food-processing environment.
Phenolic compound Staphylococcus aureus Antibacterial activity Antibacterial mechanism Membrane damage
Yanping Wu Jinrong Bai Kai Zhong Yina Huang Huayi Qi Yan Jiang Hong Gao
Department of Food Science and Technology, College of Light Industry, Textile and Food Engineering, Department of Public Health, West China Medical School Sichuan University, Chengdu 610041, China Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
国内会议
“科技创新驱动发展食品产业—从研究到应用”研讨会暨2016年四川省食品科学技术学会学术年会
四川自贡
英文
292-304
2016-11-18（万方平台首次上网日期，不代表论文的发表时间）