Research on the Composition and Antioxidant and Antibacterial Activities of Elsholtzia Essential Oil
Antibiotic resistance has become a major challenge in the 21st century. The American Infectious Diseases Association has identified six types of drug-resistant bacteria, including Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli, as extremely harmful. Patients are at high risk of disability and death after infection, and there is currently no treatment plan available. Aromatherapy is a type of medication that has the effect of dispersing surface pathogens and relieving surface symptoms, commonly used for respiratory infections. Essential oils extracted from aromatic drugs can exert strong antibacterial activity by dissolving cell walls and bacterial membranes, causing bacterial contents to leak. In addition, researchers have found that plant essential oils can alleviate antibiotic resistance and are effective substances for killing drug-resistant strains.
Elsholtzia ciliata (Thunb.) Hyland It belongs to the category of aromatic surface relieving drugs and is a herbaceous plant in the family Lamiaceae, belonging to the genus Elsholtzia. It can be used as a whole herb for medicinal purposes, with a pungent taste and a slightly warm nature. It has the effects of sweating, removing dampness, and promoting diuresis and reducing swelling. Modern research has shown that Elsholtzia ciliata essential oil (ECEO) contains components such as phenylpropanoids, flavonoids, phenols, and terpenes, and has various biological activities such as antibacterial, anti influenza, anti insect, and antioxidant properties. Previous studies have shown that ECEO has strong antibacterial effects on Escherichia coli and Bacillus subtilis. In addition, Elsholtzia extract can reduce oxidative stress and inflammation levels in J774A. 1 cells. However, there are currently few literature reports on the prevention and delay of antibiotic resistance by ECEO. Therefore, this study will evaluate the chemical composition, antioxidant capacity, and antibacterial activity of ECEO, providing reference for the comprehensive development of Elsholtzia essential oil.

 

Seven compounds were identified from Elsholtzia essential oil through GC-MS analysis, with the main components being thymol (79.17%) and 4-isopropyl-3-methylphenol (12.35%). FTIR analysis revealed that the essential oil of Elsholtzia contains functional groups such as hydroxyl and double bonds. Yang et al. also indicated that the main component of Elsholtzia essential oil is thymol. The antioxidant results indicate that Elsholtzia essential oil has strong DPPH scavenging ability and β – carotene bleaching ability, which may be related to the phenolic substances in Elsholtzia essential oil. Research has shown that the benzene ring on thymol, the main component of Elsholtzia essential oil, contains hydrogen donating hydroxyl groups that can exert free radical scavenging ability, thereby inhibiting DNA damage caused by oxidative stress and enhancing its antioxidant capacity.
Elsholtzia essential oil has a certain inhibitory effect on sensitive and drug-resistant bacteria, and has strong inhibitory effects on Pseudomonas aeruginosa, Shigella dysentery, Candida albicans, and Aspergillus flavus. Researchers have found that Elsholtzia essential oil has strong antibacterial effects on Pseudomonas aeruginosa, Escherichia coli, and methicillin-resistant Staphylococcus aureus, which is similar to our research results. Research has shown that thymol can reduce the biofilm synthesis of methicillin-resistant Staphylococcus aureus, causing disruption of bacterial cell membrane permeability and electrolyte imbalance, thereby achieving antibacterial effects. This may be the reason why Elsholtzia essential oil exhibits strong antibacterial properties. There are currently reports indicating that plant essential oils can inhibit animal inflammation caused by Pseudomonas aeruginosa. In this article, Elsholtzia essential oil effectively improved pneumonia caused by Pseudomonas aeruginosa infection in mice, and prevented and delayed the occurrence of pneumonia caused by repeated infection of levofloxacin resistant Pseudomonas aeruginosa, indicating that Elsholtzia essential oil has the potential to treat drug-resistant Pseudomonas aeruginosa infection and provide a basis for the development of natural drug product alternatives in antibiotic resistant infections.

In summary, Elsholtzia essential oil has good antioxidant and inhibitory effects on sensitive and drug-resistant bacteria, and has good medical application prospects, which can become a new potential source of natural anti infective drugs.