Phytochemical Analysis and Biological Activities of Essential Oils from Leaves and Stems of Dicranopteris pedata (Houtt.) Nakaike

Dicranopteris pedata (Houtt.) Nakaike (family Gleicheniaceae) is a widespread fern species commonly found in tropical and subtropical areas and has long been employed in folk remedies for its various therapeutic properties. This study aimed to evaluate the phytochemical profiles and the cytotoxic, antibacterial, and biofilm-formation inhibition activities of essential oils from D. pedata leaves and stems, as well as their synergistic interactions with conventional antibiotics. A total of 48 and 40 components were identified by GC-FID and GC-MS, respectively, accounting for 96.6% and 95.2% of the leaf essential oil (LEO) and stem essential oil (SEO). The main constituents were linalool, hexadecanoic acid, (E)-β-ionone, cyclohexadecanolide, (2Z,6E)-farnesol, γ-decalactone, n-nonanal, cis-linalool oxide (furanoid) and α-terpineol. The antibacterial activity was tested by microbroth dilution assays against four bacterial strains (Gram-positive: Staphylococcus aureus and Bacillus subtilis; Gram-negative: Pseudomonas aeruginosa and Escherichia coli). LEO showed a more potent antibacterial activity than SEO against the tested bacterial strains, with MIC values ranging from 20.00 to 640.00 μg/mL. In checkerboard assays, both LEO and SEO revealed strong synergistic activity with chloramphenicol or streptomycin against Pseudomonas aeruginosa. The EOs also exhibited inhibitory effects on the formation of Staphylococcus aureus biofilm, with IC50 values of 31.53 ± 4.53 μg/mL and 62.20 ± 9.36 μg/mL for LEO and SEO, respectively. Furthermore, the MTT assay revealed that LEO exhibited lower IC50 values (36.86 ± 1.97 to 67.34 ± 5.07 μg/mL) against HepG2, HCT-116, A-549, and MCF-7 cells, indicating greater cytotoxicity than SEO. Overall, both LEO and SEO exhibited antibacterial, antibiofilm and cytotoxic potential in these in vitro assays, with LEO generally outperforming SEO; however, further in vivo studies are needed before pharmaceutical or food-preservative use.