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.

Yanping Wu,Hong Gao,Yina Huang,Yan Jiang,Huayi Qi,Jinrong Bai,Kai Zhong

doi:10.3390/molecules21081084

Abstract

Recently, we reported that a novel phenolic compound isolated from Cedrus deodara, 3-p-trans-coumaroyl-2-hydroxyquinic acid (CHQA), exhibits a potent antioxidant activity. The present study aimed to evaluate the antibacterial activity of CHQA against eleven food-borne pathogens and to elucidate its mechanism of action against Staphylococcus aureus. The results from minimum inhibitory concentration (MIC) determinations showed that CHQA exhibited moderate inhibitory effects on all of the tested pathogens with MIC values ranging from 2.5–10 mg/mL. Membrane potential measurements and flow cytometric analysis demonstrated that CHQA damaged the cytoplasmic membrane of S. aureus, causing a significant membrane hyperpolarization with a loss of membrane integrity. Moreover, CHQA induced an increase in membrane fluidity and conformational changes in membrane protein of S. aureus, suggesting that CHQA probably acts on the cell membrane by interactions with membrane lipid and protein. Transmission electron microscopic observations further confirmed that CHQA disrupted the cell membrane of S. aureus and caused severe morphological changes, which even led to leakage of intracellular constituents. These findings indicated that CHQA could have the potential to serve as a natural antibacterial agent to control and prevent the growth of pathogens in food and in food-processing environments.

Highlights

Food-borne diseases are one of the most important issues that continue to be a major concern for the food industry and consumers worldwide, even in well-developed countries [1,2]
One-way analysis of variance and Duncan0 s multiple range tests were performed to determine significant differences (p < 0.05) between the means on SPSS 19.0 software(IBM Co., Armonk, NY, USA). This is the first report on the antibacterial activity and mechanism of action of coumaroyl-2-hydroxyquinic acid (CHQA)
The results demonstrated that CHQA possessed moderate antibacterial activity against both Gram-positive and Gram-negative bacteria

Summary

Introduction

Food-borne diseases are one of the most important issues that continue to be a major concern for the food industry and consumers worldwide, even in well-developed countries [1,2]. Predominant pathogens causing food-borne diseases include Salmonella sp., Staphylococcus aureus, Clostridium perfringens, Bacillus cereus, Escherichia coli, and Vibrio parahaemolyticus [2,3]. S. aureus is a significant pathogen that can cause a series of food-borne diseases, ranging from mild skin infections to severe and potentially fatal diseases such as endocarditis, osteomyelitis, and pneumonia [4]. It is important to control and prevent the growth of this pathogen in human health [2,5]. It is important to control and prevent the growth of this pathogen in food and in food-processing environments. Logarithmic phase S. aureus cells were harvested by centrifugation at 3000 rpm for 5 min, washed, and resuspended at 1 × 109 CFU/mL in 0.85% sterile saline. The bacterial suspension was incubated with 2 × MIC of CHQA at 37 ◦ C for 3 h. 1 mL of the suspension was incubated with 60 μM propidium iodide (PI) and 10 μM SYTO 9 for 15 min in the dark at room temperature

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