Study on process optimization and antibacterial activity of Litsea cubeba essential oil

  Objective  This study aimed to optimize the extraction process of Litsea cubeba essential oil and investigate its antibacterial activity and mechanism of action against plant pathogenic fungi.

  Methods  Response surface methodology was employed to optimize the extraction conditions of Litsea cubeba essential oil, including NaCl volume fraction, liquid-solid ratio, and distillation time. The inhibitory effect of Litsea cubeba essential oil on Pythium aphanidermatum was evaluated by the growth rate method, while its physiological and biochemical effects were assessed by measuring fungal mycelium dry weight, MDA content, reducing sugar content, and protective enzyme activities such as catalase, peroxidase, and superoxide dismutase.

  Results  The optimal extraction conditions for Litsea cubeba essential oil were determined as NaCl volume fraction of 2.39%, liquid-solid ratio of 4.8:1 (mL·g⁻¹), and distillation time of 4.94 hours, resulting in an extraction yield of 4.43%. Litsea cubeba essential oil exhibited a potent inhibitory effect on Pythium aphanidermatum, with an EC₅₀ value of 224.4 μg·mL⁻¹. Treatment with Litsea cubeba essential oil reduced fungal mycelium dry weight, increased cell membrane permeability, decreased reducing sugar content in the fungal body, and increased protective enzyme activities.

  Conclusion  The optimized extraction process was stable, feasible, and cost-effective compared to other methods. Litsea cubeba essential oil exerted antibacterial activity by inhibiting mycelial growth, disrupting cell membrane structure, and decreasing protective enzyme activities in the mycelia.