G-1168

Investigation of the Antibacterial Activity of Essential Oil, Hydroalcoholic Extract, and Green-Synthesized Gold Nitrate (Au) Nanoparticles from Satureja bachtiarica Bunge Aqueous Extract against Staphylococcus aureus, Escherichia coli, and Pseudomonas ae

Hadi Ebrahimi ¹ ℗, Nazanin Mohammadi ¹, Seyed Abdolmajid Khosravani ² ©, Asghar Sharifi ², Seyed Sajjad Khoramrooz ², Mohammad Malekzadeh ³, Damoun Razmjoue ⁴   

 
Abstract

Introduction: Nanotechnology, focusing on the design and production of materials at a scale of 1 to 100 nanometers, enables the modification of molecular properties of materials, leading to extensive applications in biological sciences. Gold nanoparticles, due to their unique properties such as biocompatibility and antimicrobial activity, have garnered significant attention. The increasing microbial resistance to chemical antibiotics has posed challenges to the treatment of infectious diseases. Consequently, the use of plant-based compounds and nanoparticles as potential alternatives has been investigated. Biosynthetic methods for nanoparticle synthesis are preferred over chemical methods due to their environmental compatibility, cost-effectiveness, and ease of implementation. Satureja bachtiarica, a plant native to southern and southwestern Iran, is recognized for its medicinal properties. This study evaluates the antibacterial activity of essential oil, hydroalcoholic extract, and gold nanoparticles synthesized from the aqueous extract of Satureja bachtiarica against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Methods and Materials: Essential oil extraction was performed using a Clevenger apparatus, and hydroalcoholic extract preparation was conducted at the Medicinal Plants Research Center, Yasuj University of Medical Sciences. Gold nanoparticles were synthesized by mixing 0.5 mL of aqueous plant extract with 9.5 mL of a 1 mM HAuCl4 solution. The synthesized nanoparticles were characterized using UV-Vis spectroscopy, TEM, FTIR, XRD, and EDS techniques. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and zone of inhibition (ZOI) were determined for the three studied bacteria using the standard microdilution method and agar well diffusion assay. Data were analyzed using SPSS version 26, employing descriptive statistics (mean and standard deviation) and analytical tests (analysis of variance). Results: Analysis of the essential oil revealed thymol as the primary component. Gold nanoparticles were synthesized in spherical shapes with an average size of 23 nanometers. The results indicated that the MIC, MBC, and ZOI of Satureja bachtiarica essential oil for Staphylococcus aureus were 37.5–75 µL/mL, 150–300 µL/mL, and 15–16.3 mm, respectively; for Escherichia coli, 75–150 µL/mL, 150–300 µL/mL, and 13.5–14.5 mm; and for Pseudomonas aeruginosa, 75–150 µL/mL, 150–300 µL/mL, and 11.8–13 mm. Statistically significant differences (P-value 0.01) were observed between groups. The hydroalcoholic extract showed no significant inhibitory effect, whereas the essential oil and gold nanoparticles exhibited potent inhibitory effects against both Gram-positive and Gram-negative bacteria. Conclusion and Discussion: The essential oil and gold nanoparticles synthesized from Satureja bachtiarica demonstrate significant antibacterial activity, suggesting their potential as alternatives or complements to chemical antibiotics in treating infections. These findings highlight the potential of medicinal plants and nanotechnology in addressing antibiotic resistance.

Keywords: Satureja bachtiarica, Nanoparticles, Hydroalcoholic Extract, Green-Synthesized, Essential Oil