Research on the optimization, key chemical constituents and antibacterial activity of the essential oil extraction process of Thuja koraiensis Nakai

Thuja koraiensis Nakai is a kind of precious economic tree species with fragrance, ornamental and medicinal functions. The essential oil has the satisfactory antibacterial activity. In this paper, the essential oil from the branches and leaves of Thuja koraiensis Nakai was studied by optimization of extraction process, and the optimized parameters mainly include solid-liquid ratio, NaCl concentration, distillation time, storage conditions, etc. Which provided technical scientific basis for the development and utilization of Thuja koraiensis Nakai. The essential oil from the branches and leaves of Thuja koraiensis Nakai was extracted by steam distillation, and the single factor experiment was carried out. The extraction process of the essential oil from the branches and leaves of Thuja koraiensis Nakai was optimized by response surface methodology. The chemical constituents were analyzed by GC-MS. The antibacterial activity of the essential oil was detected by filter paper and plate coating methods. Thuja koraiensis Nakai showed that when the material-to-liquid ratio was 50 g/400 ml, the NaCl concentration was 6.0%, the distillation time was 5 h,the storage condition was dry branch, the oil content was the highest. The response surface optimization method showed that material-to-liquid ratio was 7.8804 ml/g, distillation time was 2.23 h, NaCl concentration was 6.56%, under such condition, the yield was 1.1712%. The chemical constituents of the essential oil were analyzed by GC-MS (gas chromatography-mass spectrometry), and 45 compounds were detected, accounting for 96.03% of the total number. The bacteriostatic activity was detected by filter paper method. The results showed that the essential oil of Thuja koraiensis Nakai had antibacterial effect on three strains (Staphylococcus aureus, Bacillus subtilis and Escherichia coli), among them, the diameter of bacteriostatic circle against S. aureus, B. subtilis and E. coli was 10.00 mm, 15.20 mm and 9.86 mm. The minimum inhibitory concentration (MIC) of the branches and leaves of Thuja koraiensis Nakai to S. aureus was 5 μg/ml, to B. subtilis was 0.625 μg/ml and to E. coli was 2.50 μg/ml. The highest extraction yield of essential oil from the branches and leaves of Thuja koraiensis Nakai by steam distillation was 1.30%. A total of 45 compounds were identified from the essential oils of Thuja koraiensis Nakai, among which carverol acetate was the highest. The essential oil from the branches and leaves of Thuja koraiensis Nakai has obvious antibacterial effect and great development potential, for example, making insect repell0ents, fungicides, essential oil soaps, so it is recommended to collect and use it.