# Bacteriostatic Mechanism of the Ethyl Acetate Extract from the Root of Schisandra propinqua (Wall.) Baill. var. sinensis Oliv (Xiao Xue Teng) Against Staphylococcus aureus

## TL;DR

This study explores how an extract from a traditional Chinese herb inhibits the growth of Staphylococcus aureus by causing oxidative stress and disrupting protein synthesis.

## Contribution

The paper reveals the bacteriostatic mechanism of Xiao Xue Teng against S. aureus for the first time.

## Key findings

- Xiao Xue Teng caused oxidative stress in S. aureus by increasing reactive oxygen species and hydrogen peroxide.
- The extract inhibited protein synthesis by reducing key factors like IF-2 and EF-Tu.
- Cytoplasmic membrane permeability was enhanced, as observed through cellular swelling and shrinkage.

## Abstract

Staphylococcus aureus (S. aureus) is an important pathogen of zoonoses including skin abscesses, pneumonia and sepsis in humans and dermatitis, mastitis, abscesses and arthritis in animals. However, the clinical treatment of staphylococcosis has become increasingly difficult due to the overuse of antibiotics, which has led to the development of antibiotic resistance. Consequently, developing safe antimicrobial strategies to reduce antibiotic resistance has become imperative. Schisandra propinqua (Wall.) Baill. var. sinensis Oliv, a member of the magnoliaceae family, was documented in the Chinese Materia Medica. The root of Schisandra propinqua (Wall.) Baill. var. sinensis Oliv has been used to treat trauma-related injuries, abscesses, carbuncles, and so on. However, the bacteriostatic mechanism against S. aureus in Schisandra propinqua (Wall.) Baill. var. sinensis Oliv has never been reported. This study investigated the bacteriostatic mechanism of the ethyl acetate extract from the roots of Schisandra propinqua (Wall.) Baill. var. sinensis Oliv (Xiao Xue Teng) against S. aureus ATCC 25923. The results showed that Xiao Xue Teng exerted a bacteriostatic effect against Staphylococcus aureus ATCC 25923 by eliciting oxidative stress, disturbing protein synthesis and enhancing cytoplasmic membrane permeability.

Background: The root of Schisandra propinqua (Wall.) Baill. var. sinensis Oliv is a traditional ethnomedicine in China; it was widely used to treat abscesses, sores, carbuncles, rheumatism, and so on. The purpose of this study was to elucidate the bacteriostatic mechanism of the ethyl acetate extract from the root of Schisandra propinqua (Wall.) Baill. var. Sinensis Oliv (Xiao Xue Teng) against Staphylococcus aureus ATCC 25923 (S. aureus ATCC 25923). Methods: Bioactive bacteriostatic constituents in Xiao Xue Teng were identified through Hybrid Quadrupole-TOF LC/MS/MS. The minimum inhibitory concentration (MIC) of Xiao Xue Teng against S. aureus ATCC 25923 was determined using the microbroth dilution method. A time–kill curve analysis was used to evaluate the bacteriostatic effects. SDS-PAGE coupled with nano-liquid NanoLC-ESI-MS/MS, real-time PCR, and scanning electron microscopy (SEM) was used to study the bacteriostatic mechanism of Xiao Xue Teng against S. aureus ATCC 25923. Results: The MIC of Xiao Xue Teng against S. aureus ATCC 25923 was determined to be 15.625 µg/mL. The translation initiation factor (IF-2) and elongation factor (EF-Tu) were significantly decreased in S. aureus ATCC 25923 after treatment with Xiao Xue Teng, while the proteins SodA and AhpC were obviously increased. The intracellular levels of total reactive oxygen species (ROS) and hydrogen peroxide (H2O2) were significantly increased (p < 0.01) after the treatment with Xiao Xue Teng. Concurrently, the activities of SOD, CAT and GSH-Px were significantly increased (p < 0.01). Moreover, cellular swelling and shrinkage were observed using SEM. Conclusions: The bacteriostatic mechanism of Xiao Xue Teng against S. aureus ATCC 25923 was related to eliciting oxidative stress, inhibiting protein synthesis and enhancing cytoplasmic membrane permeability.