Study On Inhaled Tea Tree Oil Formulations

Tea tree oil (TTO) is an essential oil extracted from the leaves of the Melaleuca alternifolia plant of the Myrtaceae family, which grows in Australia. Now it is widely introduced and planted all over the world, including Guangdong, Guangxi and Yunnan in China from the end of the previous century. TTO has not only strong antimicrobial activity, but also anti-inflammatory, antioxidation, antiviral, anticancer, preventing cough, antitumor, promoting wound healing, adjusting immune etc. It has great medical value. The important composition of TTO is terpenoid, including monoterpene, sesquiterpene etc. Now TTO has been widely applied in chemical industry, food industry, medicine, agriculture, forestry and so on. It is considered to be applied more extensively in the future.The cyclodextrin inclusion complex and nanoemulsions of TTO were prepared in this study. The active gredients of TTO could not release from the inclusion complex to lead to no in vitro antimicrobial effect. The TTO nanoemulsions were the topic of this study. The details involve emulsifier selection, three-phase diagram preparation, property investigation, quality evaluation, pharmacodynamics as follows.1. TTO-β-cyclodextrin inclusion complexThe optimal formulation and preparation method of TTO-β-cyclodextrin inclusion complex was selected with orthogonal test using yield and encapsulation efficiency as the index. The ratio of TTO and β-cyclodextrin wasl:5.6(w/w), the ratio of β-cyclodextrin and water was1:6(w/w), and the time of milling was one hour. Grain size of inclusion complex was detected in the light microscope, and the aerodynamic diameter calculated was1.6μm, and it is suitable for pulmonary drug delivery. Nevertheless, the TTO β-cyclodextrin inclusion complex’s solubility was too poor to do the antimicrobial experiment in vitro. So the water-soluble derivation of β-cyclodextrin, such as HP-β-CD and SBE-β-CD, were investigated to prepare TTO inclusion complex. Unfortunately, the active component in the complex was so few that can’t achieve its available concertration.2. Preparation and property of TTO nanoemulsionsPolyoxyethylene castor oil-35was selected as the suitable surfactant by HLB value method according to nanoemulsions stability The surfactant’s HLB value is12.5. The area of ternary phase diagrams indicated the optimal faormulation of TTO nanoemulsions. And the emulsifying agent/TTO/water system should contain79%water at least and7%TTO at most. TTO nanoemulsions were transparent solution with light blue opalescence, belonging to O/W type emulsion. TTO nanoemulsions were globular and dispersed uniformly in TEM. The mean size of the nanoemulsion was about13.06nm, and the zeta potential was-14.1mV with good stability. TTO is a compound containing many volatile oil, of which the characteristic component is terpinen-4-ol. We setted up the HPLC analysis method to detecte the concertration of terpinen-4-ol. And the method is accurate, simple.3. The in vitro antimicrobial experiment of TTO nanoemulsionsThe result of in vitro antimicrobial experiment showed that TTO nanoemulsions had strong activity against gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii), gram-positive bacteria (Staphylococcus aureus, et al) and fungi (Candida albicans, et al), and MIC of Klebsiella pneumoniae was7.03mg·ml-1, MIC of Escherichia coli was1.76mg·ml-1,MICs of Acinetobacter baumannii, Staphylococcus aureus and Candida albicans all were3.52mg·ml-1.4. The in vivo antimicrobial experiment of TTO nanoemulsionsBased on the growth curve of the bacteria, we knew that Acinetobacter baumannii’s log phase is2-8h and Candida albicans’ log phase is16-28h. The log phase strains were used to induce rats. After reducing the immune function of rats by injecting Cyclophosphamide, we successfully established the model of SD rat pneumonia induced by Acinetobacter baumannii and Candida albicans through respiratory tract. Then the pneumonic rats were treated with TTO nanoemulsions and Benzylpenicillin or Fluconazol, and results showed TTO nanoemulsions had better antimicrobial effct on Candida albicans than Fluconazol, but not as good as Benzylpenicillin on Acinetobacter baumannii.