Essential Oil of Melaleuca ericifolia Sm.: Chemical Composition, Enantiomeric Distribution, and Antimicrobial, Antioxidant, and Anticholinesterase Activities

Melaleuca ericifolia Sm., commonly known as paperbark, is a shrub or small tree native to Australia that has been introduced and cultivated in various regions worldwide due to its adaptability and diverse applications. In the present study, the chemical composition and biological activity of the essential oil isolated from this species are investigated. The essential oil was extracted through steam distillation. The qualitative and quantitative chemical composition of the essential oil was determined by gas chromatography. The enantiomeric distribution was determined using two enantioselective chromatographic columns. Antimicrobial activity was determined using the broth microdilution method against four Gram-negative bacilli, a Gram-positive bacillus, three Gram-positive cocci, one fungus and one yeast. The antioxidant activity was determined using ABTS and DPPH assays. Anticholinesterase activity was determined using a spectrophotometric method. The forty-seven compounds identified accounted for 99.74% of the overall composition. Oxygenated monoterpenes were the most representative group in terms of number of compounds (fourteen) and in terms of relative abundance (72.50%). The most abundant constituents were 1,8-cineole (61.85 ± 1.46%), limonene (11.23 ± 0.16%), α-terpineol (7.99 ± 0.10%), α-pinene (4.97 ± 0.17%) and β-pinene (3.71 ± 0.17%). Five pairs of enantiomers were identified in the essential oil from leaves of Melaleuca ericifolia. The essential oil presented MICs of 2000 and 4000 μg/mL against Candida albicans and Aspergillus niger, respectively. The antioxidant activity was weak with a SC50 of 2 mg/mL in the ABTS assay. The essential oil exhibited moderate anticholinesterase activity, with an IC50 of 73.6 ± 1.0 µg/mL. This study provides the first comprehensive analysis of the chemical composition and biological activities of the essential oil isolated from leaves of Melaleuca ericifolia Sm. cultivated in the Americas. Furthermore, the enantiomeric distribution and antioxidant and acetylcholinesterase inhibitory activities of this essential oil are reported for the first time.