Phlomoides molucelloides (Bunge) Salmaki essential oil: a traditional remedy revitalized for modern antimicrobial challenges

Drug-resistant bacteria are a major threat in wound infections, making the search of effective natural alternatives to antibiotics more urgent than ever. Phlomoides molucelloides (Bunge) Salmaki (Lamiaceae) has been used since ancient time in folk medicine for wound healing and joint pain. This study presents a deep characterization of the essential oil (EO) extracted from P. molucelloides, focusing on the identification and quantification of the main chemicals and evaluating its antimicrobial activity. The EO was extracted by means of hydro-distillation method, from the dried aerial parts of P. molucelloides, which were collected from the natural habitat of Kashan region (Iran). The main chemical constituents were identified via gas chromatography–mass spectrometry (GC–MS). Antimicrobial activity was assessed against 11 microorganisms including bacterial and fungal strains, especially those involved in wound and opportunistic infections, using agar diffusion method, and minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MFC/MBC). The extracted EO was white in color, with a yield of approximately 0.23%. The main compounds identified were caryophyllene (14.67%), bicyclogermacrene (10.69%), phthalic acid, decyl isobutyl ester (9.36%), germacrone D (7.95%), and caryophyllene oxide (6.30%). The largest diameter of the inhibition zone (DZI) was observed against Staphylococcus aureus (10.6 + 1.5 mm), while the strongest inhibitory activity was against Bacillus subtilis (MIC > 62.5 μg/mL) and Pseudomonas aeruginosa (MIC ~ 125 μg/mL), comparable to rifampin used as reference. Overall, this study identifies a new chemotype of P. molucelloides in the Kashan region with a unique chemical profile and promising antibacterial activity against those pathogens mainly responsible for wounds and skin infections. These results support the potential use of this essential oil as an alternative strategy for treating and preventing such infections, in line with the historical use in folk/traditional medicine.