Chemical Composition and Evaluation of the Antibacterial, Synergistic Antibacterial, Antioxidant and Cytotoxic Activities of the Essential Oil of Macrothelypteris torresiana (Gaudich.) Ching

In this study, we evaluated the chemical composition, antioxidant, cytotoxic, and antibacterial activities of the essential oil extracted from the aerial parts of Macrothelypteris torresiana (Gaudich.) Ching (MT-EO), as well as its synergistic antibacterial effect in combination with commercial antibiotics. Fifty-seven compounds were identified in MT-EO, representing 97.9% of the total oil content. The compounds bicyclogermacrene (12.9%), spathulenol (11.9%), β-elemene (5.7%), and hexyl hexanoate (5.0%) were detected as the main constituents. The microdilution and checkerboard assays were used to evaluate the antibacterial and synergistic properties of the essential oil. It was found that MT-EO possessed bactericidal activity against all tested bacteria, with MIC values between 0.625 to 1.250 mg/mL, which was the same as MBCs. Additionally, synergistic effects were detected in both M. torresiana essential oil -chloramphenicol and -streptomycin combinations. Besides, according to the MTT test, MT-EO possessed broad-spectrum cytotoxicities on various cell lines with IC50 values ranging from 15.12 ± 0.96 to 47.07 ± 1.96 μg/mL, including the MCF-7, A-549, HCT-116, HepG2, and LO2 cell lines. Furthermore, MT-EO showed moderate antioxidant activities in DPPH, ABTS, and FRAP assays, with IC50 values of 434.5 ± 9.6 and 98.1 ± 1.1 μg/mL, and Trolox equivalent of 97.11 ± 3.37  μmol Trolox × g-1, respectively.