Abstract:

The effect of microwave-assisted extraction on chemical components of Litsea cubeba oil and its antimicrobial
activity were studied. Litsea cubeba oil was extracted by either steam distillation extraction (SD) or microwave-assisted
steam distillation extraction (MASD), and analyzed by gas chromatography-mass spectrometry (GC-MS) for qualitative
analysis of chemical components. The in vitro antimicrobial activity of Litsea cubeba oil was determined by filter paper
method, and its underlying mechanism was explored. There were significant differences in the contents of neral (SD-LCO:
14.82%, MASD-LCO: 11.50%, the same order below), geranial (17.95%, 13.90%), limonene (10.80%, 5.57%), α-terpineol
(5.70%, 9.05%), cineole (7.11%, 12.88%) and linalool (8.44%, 12.65%) in Litsea cubeba oil extracted by SD and MASD.
Chemical transformation of monoterpenes was promoted under microwave irradiation. The results of antimicrobial assay
showed that Litsea cubeba oil displayed high antimicrobial activity. The antimicrobial activity of Litsea cubeba oil against
Aspergillus niger and Rhizopus was better than that against Escherichia coli and Staphylococcus aureus, and its minimal
inhibitory concentration (MIC) against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Rhizopus were 3.12,
6.25, 1.56 and 3.12 mg/mL, respectively. Litsea cubeba oil could destroy the cell membrane structure and increase cell
membrane permeability, thus inhibiting the growth of microorganisms.

Key words: Litsea cubeba oil, microwave, chemical transformation, antimicrobial activity