| The heartwood of Dalbergia odorifera T. Chen is a traditional precious Chinese herbal medicines, is also a valuable spice, with the high economic value. With the long-term use of the heartwood, the resource of Dalbergia odorifera T. Chen has been scarcity. However, its leaves, as a renewable resource, can slowdown the over-exploitation. In the present paper, a high efficient and easy method was developed for the extraction of essential oil from its leaves. Then, GC-MS was used to analyze the component of the essential oil and the relative content of each component. On such basis, the antibacterial activities of the essential oil were evaluated against the common pathogens. At the same time, its antioxidant capabilities were detected in terms of1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO) scavenging,(3-carotene-linoleic acid bleaching and reducing power assays. The results as follow,1. The extration condition was developed for the essential oil of Dalbergia odorifera T. Chen’s leaves with steam distillation method:Solid-liquid ratio of1:20, soaked for5h, distillation for20h at150℃. Upper oils, dissolved in anhydrous ether and dried over sodium sulfate anhydrous. Extraction rate1.30±0.03%.2. GC-MS methods to determinate the chemical component from Dalbergia odorifera T. Chen’s leaves and the results of chemical component analysis:Chromatographic conditions:Rtx-WAX capillary column (30×0.25mm; film thickness0.25mm), starting from70℃, the temperature was raised to200℃at10℃/min and held for3min, then raised to240℃at2℃/min and held to the complete. The injector temperature was set at250℃. Helium was the carrier gas at a flow rate of1.0ml/min. The injection volume was0.2μl with a flow controlled by a linear model and split injection with a ratio of1:10.MS conditions:Injector and detector transfer line temperatures were set at200℃and240℃, respectively, and the electronic energy of70eV (m/z=50-600).The main components of the essential oil on the chemical classification should be hexadecanoic acids and phytol acid, involving n-Hexadecanoic acid53.49%,9E)-9-Hexadecenoic acid11.97%and Phytol3.31%.3. Antibacterial capabilities of the essential oil. The results were as follows:1) Through the studies on the antibacterial activity, it was found that the essential oil has good inhibitory activities against Gram-positive bacteria(Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis) and Fungi(Candida albicans, Aspergillus niger), especially Candida albicans; whereas not the Gram-negative bacteria(Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa). The essential oil could inhibit the bacteria in the Gram-positive bacteria biofilm, rather well, but poor inhibitory effects to Gram-negative bacteria. Then, the killing curve reflects the antibacterial effect of the essential oil within the concentration-dependent and time-dependent relationship.2) There is no linear relationship between bacterial biofilm inhibition activities and concentration of essential oil.3) The essential oil can contribute to the biofilm surface bacteria died off, thereby reducing the density of bacteria within the bacterial biofilm surface per unit area, which will help the body’s immune system to remove the biofilm survive remained cell.4. Antioxidant activities of the essential oil. The results were as follows:The results revealed that the essential oil has relatively strong free radical scavenging capability, followed by a clear ability against peroxy radicals. Reducing power assays showed that the essential oil has both strong capabilities of hydrogen atom transferring and hydroxyl radical scavenging, in terms of DPPH, nitric oxide (NO) scavenging, β-carotene-linoleic acid bleaching and reducing power assays. The corresponding IC50value were1.015,1.153,1.93and1.113mg/ml, respectively. |
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