Terpenic Profile of the Essential Oil of Symphyopappus Cuneatus (DC.) Sch.Bip. Ex Baker and Its Effects on Antibiotic Resistance in Vitro

The use of medicinal plants in the treatment of infections is a well-established practice in the context of pub-lic health, which has stimulated the exploration of secondary metabolites in the fight against bacterial resis-tance. Symphyopappus cuneatus (Asteraceae) is a botanical species both native and endemic to Brazil. Although numerous biological activities have been described for other species of this genus, the pharmaco-logical potential of S. cuneatus remains unexplored. Therefore, the present study aims to investigate the chemical composition and characterize the antibacterial activity of the essential oil of S. cuneatus (EOSc). The essential oil was extracted from dry leaves of S. cuneatus through hydrodistillation and analyzed by gas chro-matography coupled with mass spectrometry (GC-MS). The Minimum inhibitory concentration (MIC) of EOSc was determined by the broth microdilution method using standard and resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The effects of EOSc on antibiotic resistance were evaluated by associating the antibiotics gentamicin, norfloxacin, and penicillin with a subinhibitory concen-tration (equivalent to MIC/8) of the essential oil. The GC-MS analysis identified 8 constituents, including the terpenes limonene, spathulenol, and a-pinene, as major components. While a significant antibacterial activ-ity was not observed for both strains of P. aeruginosa, the EOSc inhibited the growth of the other bacterial strains, in addition to reducing the MICs of the antibiotics against all tested strains, except when associated with penicillin against S. aureus. Therefore, it is concluded that the EOSc has antibacterial effects and potenti-ates the activity of antibiotics against multidrug-resistant bacterial strains, which is probably due to the pres-ence of bioactive terpenes in its composition.(c) 2023 SAAB. Published by Elsevier B.V. All rights reserved.